TABLE OF CONTENTS INTRODUCTION CHAPTER 1 ROOF SYSTEMS 2

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2 TABLE OF CONTENTS INTRODUCTION I CHAPTER 1 ROOF SYSTEMS 2 Roof Coverings Roof Shingles Retrofit Technique For Shingles Adhesive Under Shingle Tabs Re-Roofing Retrofit Techniques and Products For Re-Roofing Secondary Water Resistance Underlayment New Roof Coverings Composition Shingles 3 Roof Sheathing Roof Sheathing to Roof Framing Members Retrofit Techniques and Products Adhesives Construction Adhesives Structural Foam Installation of Replacement Sheathing Panels 7 Trusses and Rafters Truss or Rafter to Wall Connection Retrofit Techniques and Products Clips and Straps From The Interior From The Exterior During Re-Roof Hurricane Clips and Straps 9 Gable Ends Gable End Bracing Retrofit Techniques and Products Bracing Installation Installing Bracing at Bottom of Gable End Wall Installing Bracing Along the Top Edge of Gable End Wall Connecting the Bottom of Gable End Wall and Top of End Wall Lookout Gable End Overhangs 11 Retrofit Specifications for Roof Systems 11 CHAPTER 2 WALL SYSTEMS 14 Windows Retrofit Techniques and Products Windows Impact Resistant Glass Shutters Permanent Shutters Plywood Shutters Other Temporary Shutters 16

3 Doors Retrofit Techniques and Products Doors Sliding Glass Doors Exterior Doors Frames Hardware 17 Garage doors Retrofit Techniques and Products Garage Doors Replace the Garage Door Protect the Opening Brace the Garage Door Brace the Frame 19 Connectors Connectors 19 Retrofit Specifications for Wall Systems 19 CHAPTER 3 FLOOR AND FOUNDATION SYSTEMS 22 Floor Systems Retrofit Techniques and Products Floors Wall Framing to Floor System Connections 22 Foundation Systems Retrofit Techniques and Products Foundations Floor System to Foundation Connections Piers and Stem Walls Pile Foundations Connectors 23 Retrofit Specifications for Floor and Foundation Systems 24 CHAPTER 4 OTHER DISASTER RESISTANT CONSIDERATIONS Flood Determine Flood Risk Actions Wildfire/Forest Fire Preventive Measures Safe Rooms/Shelters Shelter Size New vs. Existing Home Foundation Types In-ground Shelter Shelter Designs 29

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6 viding secondary water resistance if the roof cover underlayment tears or fails in a high wind event. Roof covering should then be installed in accordance with locally adopted building codes. For shingles, a minimum of 6 roofing nails are required for each shingle. For mechanically attached tiles, a minimum of two #8 screws are recommended Underlayment The underlayment should be two layers of 15-pound or a single layer of 30-pound, roofing felt. To improve its waterproofing capability and its adhesion to the roof deck, hot asphalt can be mopped on the deck before the underlayment is laid in place. The underlayment layer should be installed with roofing nails and 1 -diameter metal tags. These tags help to spread the fastener s load to prevent the nail heads from being ripped through the underlayment. Illustration of underlayment layout. Figure 1.1 When the underlayment is laid out, there should be a 2 overlap between rows and a 4 end lap. Along the overlapping rows and at the end laps, nails should be spaced at 6 oc. The nail spacing in the field of the underlayment should be 12 oc. All nail spacings are minimum spacing. This overlap and nail pattern helps prevent the loss of the underlayment layer in the event of the loss of the roof covering. Figure 1.1 demonstrates the correct technique for installing the underlayment New Roof Coverings Composition Shingles Most shingles are not rated to withstand winds above 60 mph which is well below the minimum hurricane speed of 74 mph. Using six nails per three-tab shingle is a significant improvement in resisting wind uplift over the standard practice of using only four nails per shingle. When installing a new roof, hand tab shingles with additional adhesive. Another detail that can help maintain the shingles during a storm is to begin roofing by attaching a starter course consisting of the top half of a three-tab shingle with the tabs cut off. The tab-less shingle strips are installed along the lower edge of the roof sheathing. The shingle strips in the starter course are attached with six nails per strip, nailed 1/2 from the edge of the sheathing. Then three 1 diameter dabs of roof cement are applied between the starter strip and the first course of shingles. Roof Sheathing Roof Sheathing to Roof Framing Members After Hurricanes Andrew and Hugo, two of the most recent and destructive hurricanes, damaged buildings were examined to determine where and how they failed. These investigations identified significant problems with the attachment of roof sheathing to framing members: (1) staples were not adequate to make this connection, (2) sheathing panels were easily blown off because sheathing fasteners missed the framing members due to poor workmanship, as in Figure 1.2, or (3) there was a total lack of fasteners. Other problems included sheathing that was too thin and nails that were too small, too thin or spaced too far apart. In addition, the connection between roof sheathing panels and framing members can also be weakened by the absence or inadequate installation of panel clips (H clips)

7 Once any sheathing panels are lifted by a hurricane s winds, the entire structure is more vulnerable to damage; the wind can pressurize the attic space and force off more sheathing panels. Roof sheathing is most vulnerable at the eaves, corners and ridge. When sheathing panels are removed, trusses or rafters become exposed and unstable and the entire roof may collapse. This loss of all or a portion of the roof system allows rain to enter the building. Water damage has caused a significant percentage of interior damage in recent storms. Sheathing nails that missed the framing member, after Hurricane Andrew. Figure 1.2 Often it is difficult to determine how well the sheathing is attached to roof framing members. It is only possible to make an evaluation from the attic space. From the inside, it is possible to observe whether the nails miss the framing members, indicating a poor installation. The lack of missed nails, however, does not necessarily indicate a good installation. Nails that missed the roof framing members present the opportunity to estimate nail size and spacing. The size and the spacing of the fasteners are important considerations in determining if a retrofit is required. It is important to recall that staples are not considered acceptable roof sheathing fasteners. If staples are observed to have been used, the sheathing to framing connection must be strengthened. When hurricane winds flow around a building, they exert positive and negative forces on various surfaces. The side of the building facing the wind experiences high positive pressures, while the surface on the opposite side of a corner or edge experiences negative pressures due to wind separation from the building surface. The wind flowing over a change in the surface plane (such as eaves and ridge) causes separation and mini-vorticies. The negative pressure creates uplift or suction on the exterior building surface similar to the forces created by an airplane s wing as it lifts the plane into the sky. The positive force on one side and negative force on the other side of the point of separation create high stress at that point. The result is that his point of high stress is often the site of the first structural failure. To maintain the integrity of the house envelope, it is important that the connections at roof corners and at eaves and ridges be as strong as possible. The attachment of the roof sheathing to the framing members is considered the most important connection to maintain during a hurricane. This connection should be strengthened, (1) if staples are used to attach sheathing panels, (2) if more than 5 percent of the sheathing fasteners miss the framing members, and (3) if the nailing pattern is less than the following Roof Sheathing Nailing Schedule. In general, improving this connection is fairly easy and inexpensive. Because of its importance, retrofitting should be considered if there is any doubt about the condition of the current roof sheathing connection

8 Roof Sheathing Nailing Schedule Spacing of Framing 16" o.c. 24" o.c. Thickness of Sheathing 1/2" nominal 5/8" nominal 8d Common Nails 6" o.c. 4" o.c Retrofit Techniques and Products Adhesives This method may be the best solution for strengthening the sheathing to roof framing connection if the house will not be re-roofed. Two different product types are available: 1. Construction adhesives applied from a tube in a caulking gun 2. Spray-on structural foam products Construction Adhesives The construction adhesives are used to sister (or attach) additional lengths of lumber to the existing roof structural members and roof sheathing. This process requires the purchase and cutting of the lumber to be added and then securing each new piece into place while the adhesive cures to achieve maximum strength. The technique requires cutting several 6 -long 1 x2 blocks of wood. The blocks are installed with a 1/4 bead of construction adhesive applied evenly along the entire 6 length. The blocks are placed on 15 o.c. on both sides of the framing member s length. Refer to Figures 1.3 and 1.4. lllustrations of construction adhesive and blocking installation, Figures 1.3 and

9 Structural Foam Structural foam also can be used to strengthen the sheathing-framing-member connection. Figure 1.5 shows how the foam is sprayed along the length of the framing member at the joint between the member and the sheathing. The application of structural foam on both sides of the framing member, as in Figure 1.6, is similar to a fillet weld that is used in steel construction. The foam undergoes a catalytic reaction and begins curing immediately. Once the foam has cured, it creates a bond between the framing member and the sheathing that has been tested as 2 to 4 times stronger than a mechanically fastened connection. Structural foam connection between framing members and sheathing. Figure 1.5 The structural foam starts as a two-part solution that is sprayed from a specially designed application machine. A spray application allows the product to be applied in areas where it may be difficult to reach the members or to handle a hammer or other tools and equipment. The spray also can be applied continuously or in bursts, which give it even greater flexibility in how and where it is applied. It has been tested at Clemson University to determine its strength against uplift and wind loads. This testing determined that structural foam is suitable for retrofit applications and that significant increases in uplift strength are achieved. Retrofit application of structural foam. Figure

10 Installation of Replacement Sheathing Panels If replacement of roof sheathing is required, the following should be considered. To achieve the greatest strength in the areas of greatest uplift, the corners, ridges and edges of the roof, the sheathing must be installed correctly and with the proper number of nails. Sheathing panels should start with the full four foot width at the eaves and ridges so that there is no sheet less than four feet wide at an edge. Each panel of sheathing should be attached to at least three trusses or rafters. If a row of panels must be installed that is less than four feet in width, this make-up row should be placed in the middle of the roof slope. If a make-up panel less than four feet in length is required within a given row, it should be placed in the middle of a row, not at either end. At the same time, it is important to ensure proper sheathing nail spacing. Trusses and Rafters Truss or Rafter to Wall Connection The connection of the roof assembly to the exterior walls is extremely important. If the wind is able to produce enough uplift on the roof, it can pull the roof off the house. Roof framing members can consist of pre-engineered roof trusses and/or common framed members. All roof-framing members should be secured to the walls by hurricane clips and/or straps, as shown in Figure 1.7. The intersection of the top of the wall and the roof are covered on the interior of the building by the wall finish and on the exterior by the soffit assembly. This makes retrofitting the roof-to-wall connection difficult. There are three approaches to gain access to add hurricane straps to the roof/wall intersection. Potentially several different products can be used. Each manufacturer can offer technical information on uplift load resistance and recommend which products are suitable for retrofit. (see Figure 1.8 for examples of hurricane straps and their applications). Even though the sheathing was torn off at the roof edge, the hurricane straps held the trusses in place (FEMA 1992). Figure Retrofit Techniques and Products Clips and Straps There are three possible ways to gain access to the intersection of the roof to the wall: 1. From the interior 2. From the exterior 3. During re-roofing. Examples of hurricane straps for interior or exterior retrofitting. Figure

11 From the Interior One solution is to remove the covering materials around the top of the interior walls and ceiling. This process will provide access to the trusses and the top plate of the wall. Hurricane straps can be retrofitted, as illustrated in Figure 1.9. The expense of this technique depends on the type of interior finish. Some interior finishes such as plaster or wallpapered walls may be too expensive, invasive and time-consuming to consider making holes in these walls and then repairing after the retrofit is complete. If the interior is wood panels or drywall, however, it may be more economical to remove these materials to gain access to the top of the wall, install the retrofit and repair the access point From the Exterior Example of interior wall and ceiling surface removed and hurricane straps installed. Figure 1.9 Access to roof members and top of the wall also may be gained from the exterior. An examination of the soffit and exterior cladding must be made to determine the cost, invasiveness and time to complete the retrofit. It may be as simple as removing the soffit material to gain access, make the retrofit and replace the soffit. In other cases, some access points may have to be cut through cladding or cladding material may have to be removed and replaced once the retrofit is accomplished. (see Figure 1.10) Wall sections with horizontal and sloped soffits at the roof/wall intersection. Figure During Re-Roof When the sheathing is removed there is greater access to all components of the roof load path. It also is easier to install a greater variety of clips or straps than what the limited access of the attic or soffit may allow. This greater access offers an opportunity to examine the condition of any existing connectors that may be present. If any of these components appear corroded, damaged or incorrectly installed, they should be replaced at this time. This also allows the installation of higher capacity hurricane straps that wrap over the truss

12 Hurricane Clips and Straps There are several manufacturers of hurricane clips and straps and each manufacturer has several products that are available to fit most conditions. It is important to select the clips or straps with maximum uplift and shear capacities that are available. All clips and straps shall be installed in accordance with the manufacturer s specifications and in compliance with the locally adopted minimum building code. Gable Ends Gable End Bracing An unbraced gable end after Hurricane Andrew (FEMA 1992). Figure 1.11 Another major failure point is the collapse of the gable end, as seen in Figure If gable-end framing has not been sufficiently braced during construction, as in Figure 1.12, it can deflect and possibly fail under the strong inward and outward pressures that hurricane winds induce on a house. The collapse of a gable end allows internal pressurization. Wind and water damage may occur once the building envelope has been breached. Gable end failure is caused by inadequate lateral bracing of the top of the gable truss or the bottom of the gable truss Retrofit Techniques and Products Gable End Bracing There are two retrofit options for the bottom chord and one retrofit option for the top chord of the gable end matt: 1. Installing bracing at the bottom of the gable end 2. Strengthening the connection between the bottom of the gable end and the top of the sidewall 3. Installing bracing along the top edge of the gable end. Unbraced trusses at a gable end. Figure Installing Bracing at Bottom of the Gable End Bracing at the bottom of the gable end is a retrofit that provides effective protection against collapse. The top of the gable end is braced by the sheathing, assuming that it is well connected, but the bottom of the gable end may be unbraced. This lack of bracing would make it quite vulnerable to failure. The forces produced by a hurricane on the gable ends can push or pull until the deflection causes failure. Bracing the bottom of the truss to the interior framing members gives the gable end increased strength to resist the inward and outward forces that the winds apply

13 To brace the bottom of the gable end, 2x4 members with a minimum length of 8 are installed perpendicular to the plane of the gable end at 6 o.c. Refer to Figures 1.13 and These bracing members should be connected to the bottom chord of the gable end or to the base of the studs of the gable end with metal connectors and fastened to each of the interior framing members they intersect either the bottom chords of the interior trusses or other framing members. These connections should be made with a minimum of two 16d nails at each intersection. Gable end bracing illustrations. Figures 1.13 and Installing Bracing Along the Top Edge of the Gable End Bracing at the top of the gable end can be achieved in two ways. One method is to use the same technique as described in That is, installing 8 long 2x4 members at 6 o.c. perpendicular to the gable end surface on the underside of the top chord of the trusses. Another method is to install 2x4 blocking at 24 o.c. between the gable end framing and first two interior rafters or truss top chords. The concept behind this more limited approach is that the roof sheathing will provide most of the support and connection along the top of the gable end and the two layers of blocking will reinforce this support Connecting the Bottom of the Gable End to the Top of the End Wall Hurricane gusset angle. Figure 1.15 The last important area to retrofit at the gable ends is the connection between the gable end trusses and the top plate of the end wall below. This is a quick and easy retrofit that requires only a hammer and nails. The bottom chord of the gable-end truss should be attached securely to the top plate below it; there should be no visible gaps as seen in Figure A pair of nails, a minimum of 10d, should be placed 24 o.c. to create a solid connection between the truss and the top plate. This connection will reduce the deflection and possibility of failure of the gable end wall during a hurricane. If the wall construction below the gable-end is masonry instead of wood framing, the same retrofit can be completed using retrofit bolts instead of nails. These bolts are pre-cut threaded rods, supplied with a nut and washer. A 1/2 diameter, 6 length of retrofit bolt can be installed every 4 o.c. To install these bolts, drill a 5/8 diame

14 ter hole and remove the dust from the hole. If the dust is not removed, it will reduce the epoxy s holding capacity. Fill the hole halfway with epoxy, starting at the bottom to avoid air pockets. Insert the retrofit bolt, turning it slowly until it reaches the bottom of the hole. This connection also can be made using hurricane clips or straps to secure the truss to the wall top plate. Clips or straps can be used on both masonry and wood frame construction. Check with the manufacturer of the chosen connector to recommend the appropriate product and installation methods Lookout Gable End Overhangs It is a common building practice to construct the framing for the overhang at a gable end on the ground and to tack it in place at the roof eaves. This overhang commonly is referred to as ladder framed because the framing looks like a ladder before it is attached to the house. Although, this is an economical method of constructing an overhang, it is a poor design in terms of wind resistance. The attachment of the ladder frame to the house is weak. It is designed to resist the gravity loads that it constantly experiences, but it is not designed to resist the uplift forces of a hurricane. Hurricane-force winds can push up the overhangs and pry the sheathing loose along the edge. Once the sheathing along the edge is gone, the entire roof is at risk. A possible solution to this problem is to add new lookouts to create the overhang. During reroofing, the sheathing along the gable edge can be removed and 2x6 members can be retrofitted to create the overhang. The new 2x6 members are placed at 2 o.c. with the 6 face parallel to the sheathing surface. They extend from the second framing member, across the gable end member, and project out the distance of the overhang. To maintain the level of the roof, the roof framing members must be notched to accept the lookout members. Most building codes forbid cutting into the depth of a framing member in the middle third of its span. To accomplish the retrofit and abide by the code, a 2x4 is sistered to the second rafter or the truss. This additional 2x4 is attached only to the second roof framing element

15 Retrofit Specifications for Roof Systems 1. A. Replace Roof Covering Roof covering is to be removed to the decking level. Prior to the application of underlayment, all joints between plywood sheets should be taped with a self-adhering polyethylene or rubberized asphalt underlayment that has a minimum width of 6 inches. This self-adhering product shall be applied in accordance with the manufacturer s instructions for wood application. This product shall have adherence strength suitable so that it remains attached to the roof deck and provides secondary water resistance if the roof cover underlayment tears or fails in a high wind event. A new covering is to be installed in accordance with locally adopted building codes. For shingles, 6 nails are required for each shingle. For mechanically attached tiles, a minimum of two #8 screws are recommended. 1. B. Replace Roof Covering and Re-nail Sheathing Roof covering is to be removed to the decking level and all roof sheathing is to be re-nailed such that fastener spacing does not exceed 6 inches on center using the specifications in accordance with locally adopted building codes. Existing fasteners may be used to satisfy this requirement. Within 4 feet of any gable end, it is recommended that the nail spacing be reduced to 4 inches on center. It is recommended re-nailing be done with 10d common nails. Prior to the application of underlayment, all joints between plywood sheets should be taped with a self-adhering polyethylene or rubberized asphalt underlayment that has a minimum width of 6 inches. This self-adhering product shall be applied in accordance with the manufacturer s instructions for wood application. This product shall have adherence strength suitable so that it remains attached to the roof deck and provides secondary water resistance if the roof cover underlayment tears or fails in a high wind event. Roof covering shall then be installed according to locally adopted building codes. For shingles, 6 roofing nails are required for each shingle. For mechanically attached tiles, a minimum of two #8 screws are recommended. 1. C. Replace Roof Covering and Replace Sheathing Roof covering is to be removed to the decking level and all roof deck is to be replaced in accordance with locally adopted building codes. Nailing of sheathing should follow guidelines given in Option 1A above. Prior to the application of underlayment, all joints between plywood sheets should be taped with a self-adhering polyethylene or rubberized asphalt underlayment that has a minimum width of 6 inches. This self-adhering product shall be applied in accordance with the manufacturer s instructions for wood application. This product shall have adherence strength suitable so that it remains attached to the roof deck and provides secondary water resistance if the roof cover underlayment tears or fails in a high wind event. Roof covering should then be installed in accordance with locally adopted building codes. For shingles, 6 roofing nails are required for each shingle. For mechanically attached tiles, a minimum of two #8 screws are recommended. 1. D. Apply Adhesive to Roof Decking and Rafters For cases where the roof covering is adequate and attic access is available, adhesive can be applied to the underside of the roof sheathing from the attic such that a positive bond between

16 the joists and the sheathing is formed. The applied adhesive shall have a minimum uplift capacity of 250 lb./sq.ft. for an 4x8 ft panel as determined by laboratory testing. This adhering product shall be applied in accordance with the manufacturer s instructions for wood application. Joints between sheathing pieces will also be sprayed with adhesive to prevent water infiltration in the event of roof covering losses. The adhesive should be applied continuously to within at least one foot of the eaves. 1. E. Tie Roof To Walls Most houses in Florida will have roof-wall clips or straps. However, if these connections do not exist, an allowance should be made for installing these connectors and they must be installed according to the requirements of the locally adopted building codes and the manufacturer s installation specifications. Some local building departments may require a licensed engineer to inspect and specify measures for the installation of these connections. If these connectors exist, they do not need to be replaced unless they are in poor condition or improperly installed. 1. F. Brace Gable End of Roof This process is recommended in all homes with gable ends. Bottom chord bracing is described in Sections and of these guidelines. Top chord bracing may be accomplished through the use of properly connected roof sheathing. If the roof sheathing is not strengthened during the retrofit, then additional top cord bracing is recommended as described in Section of these guidelines. Some local building departments may require certification by a Professional Engineer. 1. G. Install Code Compliant Gable End Vent Protection Protection devices must satisfy the impact resistance and pressure standards in SSTD of the Standard Building Code, ASTM E1886 and ASTM E1996 or standards in the South Florida Building Code, Dade County Edition. Shutters must be installed according to the manufacturer s installations specifications. See Retrofit 2B in Chapter 2 for other requirements. 1. H. Protect Skylights with Code Compliant Shutter Devices Protection devices must meet impact resistance and pressure standards in SSTD of the Standard Building Code, ASTM E1886 and ASTM E1996 or standards in the South Florida Building Code, Dade County Edition. All devices must be installed according to the manufacturer s instructions. See Retrofit 2B in Chapter 2 for other requirements. 1. I. Install Code Compliant Impact Resistant Skylights Protection devices must meet impact resistance and pressure standards in SSTD of the Standard Building Code, ASTM E1886 and ASTM E1996 or standards in the South Florida Building Code, Dade County Edition. All devices must be installed according to the manufacturer s instructions. An allowance for repair of surrounding roof during installation of Impact Resistant product should be made. See Retrofit 2B in Chapter 2 for other requirements

17 CHAPTER 2 Wall Systems Building codes categorize all residential buildings as either enclosed, partially enclosed or open. Most buildings are designed and built as enclosed structures. However, perforations in the building envelope made by flying debris can transform an enclosed building into a partially enclosed building. This change in category can almost double the uplift pressure on the roof and the outward pressures on walls. Unprotected windows and doors can be penetrated easily by wind borne debris in hurricane winds, thus allowing entry of damaging water and wind. Protecting openings with impact resistant components can prevent much if this damage. Windows Retrofit Techniques and Products for Windows Unprotected, standard glass windows present the most vulnerable opening in a building s envelope. They can be broken easily by flying debris or destroyed by wind pressure. Once window glass fails, the subsequent pressurization of the structure can cause total destruction of the house. If the house withstands the wind pressure, the interior may still be lost due to water damage. With the exception of impact-resistant polycarbonate glazing or some laminated glass systems, all window glass, whether it is annealed, tempered, wire reinforced or insulated, needs to be protected during a hurricane. There are two main approaches to retrofitting windows to improve their impact resistance or completely protect them from debris and pressure changes. 1. Impact-resistant glass 2. Shutter systems Impact Resistant Glass One possible retrofit is impact-resistant glass systems used in place of standard glass. Impact-resistant glass systems currently are available as complete units, including the frame, and they can be installed in front, behind or as a replacement for conventional windows. These windows are made of a clear polycarbonate glazing and have greater strength than glass. They can withstand hurricaneforce winds and the impact of flying debris. One example of this type of system s strength is the successful missile impact test. To be effective, however, the impact-resistant glass must be installed in a tested high-strength frame according to the manufacturer s specifications. One advantage of using impact-resistant glass is that it is always in place; it does not need to be installed and removed before each storm. It also provides security against crime. If this type of glass is installed in addition to regular windows, it can improve energy efficiency. Impact-resistant glass can also be installed under skylights to maintain the building envelope s integrity if the skylight is damaged

18 Shutters Temporary or permanent shutters are another possible method for protecting windows. A wide variety of shutter systems are available. The most important factors to consider when choosing a shutter system are the level of protection, price, ease of use, value added to the house, discounts in insurance and aesthetics Permanent Shutters Permanent shutters should be installed by trained individuals according to the manufacturer s specifications to ensure the shutters perform as designed and tested. The most important factor to consider when choosing a shutter system is its approval as a system, designed and tested for its resistance to hurricane force wind loads and its impact resistance. Permanent shutters come in many types and styles, such as, Bahama (Figure 2.1), roll downs (Figure 2.2), accordion (Figure 2.3), awning, and colonial. Choosing a style can be based on several criteria, primarily location of the building and cost. If the shutters will cover windows on an upper floor or in a hard-to-reach position, they should be operable from the inside. An accordion shutter. Figure 2.3 A Bahama style shutter. Figure 2.1 A section showing a roll down shutter, mounted in the soffit. Figure 2.2 Roll-down shutters are often the easiest to operate in these conditions. Ease of operation is an important factor to consider because if the shutters are not installed or closed, they will not provide any protection during a storm. The other shutter types, accordion, Bahama, colonial and awning, usually are closed from the outside. Typically, they are used on the ground floor or at easily accessible locations Plywood Shutters One of the least expensive solutions for protecting windows is to construct plywood panels that can be installed when a hurricane warning is issued. The mounting hardware should be pre-installed around each window and each panel should be labeled with its intended location to facilitate installation. While plywood shutters offer the lowest cost protection, they are cumbersome to store and carry. Often more than one person is required to install them. The American Plywood Association has developed standard designs of plywood shutters for masonry and wood construction. For some spans, 2x4s may be needed to strengthen the panels. The recommendations of the APA should be followed to determine the thickness of the plywood panels. FEMA has also developed several details

19 for installation of plywood shutters on wood frame as well as masonry walls. FEMA or APA publications can be used for design and construction of plywood shutters. Both of these organizations also maintain web sites at and These web sites provide information that is useful to the public, builders and inspectors. (refer to Figures 3.16 and 3.17) Other Temporary Shutters In addition to plywood, other temporary shutter systems are available, including steel and aluminum panels (Figure 2.4) and clear polycarbonate panels. The advantage that these systems have over plywood is that they are designed specifically to withstand the impact forces of a hurricane. Usually these panels are corrugated and come in standard widths, allowing them to be joined together to cover wider openings. As with permanent shutters, the panel systems should be tested and rated by the strictest current testing procedures. Storm panels easy to handle and install on preinstalled mounting hardware. Figure 2.4 These systems also may have an installation system that is quicker than attaching the plywood panels. Clear panels can be installed well in advance of the storm s approach and allow light to continue to come through the windows while other preparations inside the house are being made. In general, the same principles for the plywood systems apply to other temporary panel products. They should meet the specific standards for impact resistance, their mounting hardware should be installed well before a storm s impact and they should be labeled for each respective opening. Doors Retrofit Techniques and Products Doors Three items that should be considered when retrofitting door openings are the door, the frame and the hardware. All three items are important in maintaining the strength of the entire door system. Failure of any one would result in a breach of the building envelope and ensuing damage to the residence Sliding Glass Doors Glass doors should be protected by one of the systems discussed in the Windows section. In addition, sliding doors should be mounted securely in their frames so they cannot be pushed in or pulled out under hurricane wind loads. The frame itself should be attached securely to the wall so that it, too, does not fail under load. To ensure that the frame is fully installed, all mounting holes should be used and the condition of the original fasteners should be checked. If any mounting holes are not used or if any of the screws have deteriorated, new screws should be installed

20 If the sliding glass doors are protected by a shutter or a panel, adding fasteners to the frame may not be necessary Exterior Doors Exterior doors must be strong enough to resist the wind loads and impact loads of windborne debris or be protected with a panel or shutter system. Hollow wood doors can fail under the wind and impact loads in a hurricane. Thus, doors should be constructed of solid wood or metal Frames The frames of all exterior doors must be mounted securely to the wall systems. Additional fasteners can be added to strengthen frames as needed. Frames that are attached improperly could fail in a hurricane and allow wind and water penetration. With many doors it may be difficult to determine the frame installation. If possible, pry up a length of door molding. If there is concern or doubt about the frame s installation, add screws around the frame that are long enough to penetrate to the framing members Hardware Hardware is another area that can be retrofitted to improve a door s strength. Every door should have three hinges and a dead bolt security lock. Screws used for the hinges and the strike plate should extend into the framing members, not just into the door frame. This is true for the dead bolt too; the bolt throw should be long enough to extend to the framing members, not just into the door frame, which could split and fail in a storm. The screw lengths and dead bolt throw should have been measured during the house inspection. If either item is too short to extend through the frame, they should be replaced. Screws for the hinges and strike plates can be removed and replaced with longer screws. The dead bolt also can be removed from the door and replaced with a new dead bolt with a longer throw. The hole in the door frame may have to be extended to accommodate the longer throw length. These are small retrofits that can increase the door s strength to withstand a storm and any other unwanted attempts to gain entry to the home. In addition, double doors should have either surface or integral bolts installed that secure the center of the doors to the header framing member and through the door jamb into the subfloor. These retrofits can be completed by checking the bolts length, replacing them if necessary, and extending the hole depth through the door frame and/or threshold. Garage Doors Garage Doors Garage doors serve as additional points of failure and subsequent breaches of the house envelope. Garage doors are vulnerable to hurricane forces for two reasons the relatively long span of opening that they cover and the strength of the materials from which their systems are constructed. Many garage doors are constructed from lightweight materials to conserve weight and expense. Although their lighter weight makes them easier to raise and lower, it also makes them less resistant

21 to the wind and impact forces of a hurricane. Garage door assemblies have three major weaknesses: 1. Deflection under wind loads 2. Track strength and installation 3. Impact resistance. Unbraced garage doors can deflect under the loads applied by hurricane-force winds. Depending on whether the door is on the windward or leeward side of the structure, it will experience positive or negative pressures, respectively. These pressures will push and pull the door out of its track. If the door is not braced to resist these deflections, it may fail and allow the pressurization of the residence s interior. The track is the second system that can fail under a storm s forces. A lightweight or poorly anchored and braced track may torque and twist from the force of the garage door s deflection. A track that failed in this manner is seen in Figure 2.5. As the track is bent out of shape and fails, the door glider wheels will pull out of the track and the door will collapse. The last concern when addressing garage Example of a garage door track failure. Figure 2.5 doors is impact resistance. Many doors are not designed to withstand the impact of wind borne debris created by a hurricane. If the garage door is perforated during a storm, it may allow interior pressurization and water damage. Several retrofit options address these weaknesses: 1. Replace the garage door system 2. Protect the opening 3. Brace the door 4. Brace the frame. These options are described in the following sections Replace the Garage Door One solution is to replace the existing garage door with a system that is designed specifically to withstand both the wind load and impact forces of a hurricane. Though replacing the door is the most expensive option, it also may be the most secure. Such systems are available through do-it-yourself centers or through garage door subcontractors. In order to insure proper installation and to avoid injury, it is recommended that a contractor perform the replacement of overhead garage doors equipped with counter-balance springs Protect the Opening A second option is to construct and install a protective panel system that covers the garage door

22 opening in the same manner that a shutter covers a window. The construction of a garage shutter is identical to the construction and installation for a window, however, the extra span needs to be considered and supported as if it were a large window Brace the Garage Door To brace a garage door, horizontal wood or metal girts are added to the interior surface. The bracing members should be 2x4 lumber and should extend the length of the door. The 2x4 s are attached to the vertical mullions of the garage door, at 2 o.c. in the center of the door panels. (See Figure 2.6 for an example of a braced garage door) Brace the Frame Example of a braced garage door track. Figure 2.6 Several steps are required to strengthen and brace the garage door frame. The first element to be considered is the track itself. The heavier the gauge of the material from which the frame is constructed from, the better. A track with a greater cross-sectional area will resist twisting more than a thinner track. The track thickness can be increased only by replacing the track. A second strengthening element is a web brace on the brackets that connect the track to the wall. Web braces can be welded to these brackets or the brackets can be removed and replaced with brackets that have integral web bracing. The last connection to be considered to strengthen the frame is the attachment of the frame to the garage wall. If the garage door opening is masonry or concrete, the brackets should be installed with expansion anchors to resist pullout. An epoxy adhesive can be used in addition to the expansion anchors to provide even greater resistance. If the house is wood framed, the brackets should be attached to the framing, not just to the interior surface material. In either case, the bolts or screws should be sized according to the manufacturer s recommendations for the specific length and width of the garage door Connectors Connectors are available from a variety of connector manufacturers and there are a many types that can be used in different situations. Retrofitting the wall-framing-to-roof system or the wallframing-to-floor system may include the use of a variety of connectors and anchor bolts. All connectors and anchor bolts shall be installed in accordance with the manufacturer s specifications and in compliance with the locally adopted minimum building code

23 Retrofit Specifications for Wall Systems 2. A. Install Code Compliant Shutters on Windows Shutters must satisfy the impact resistance and pressure standards in SSTD of the Standard Building Code, ASTM E1886 and ASTM E1996 or standards in the South Florida Building Code, Dade County Edition. Shutters must be installed as per the manufacturer s specifications. Other requirements: If the structure is equipped with shutter protection or the equivalent thereof, non-compliance with the one of the above reference standards should be verified before replacement with new products. The contractor will ensure that all local codes, standards and requirements are met. Some local building departments may require obtaining a wind load calculation according to the 1997 Standard Building Code, Section 1606 or the South Florida Building Code, Dade County Edition and stamped by a licensed engineer in the state of Florida. 2. B. Replace Windows with Code Compliant Impact Resistant Products Existing windows shall be replaced with units that satisfy the impact resistance and pressure standards in SSTD of the Standard Building Code, ASTM E1886 and ASTM E1996 or standards in the South Florida Building Code, Dade County Edition. Windows must be installed as per the manufacturer s specifications. Other requirements: The contractor will ensure that all local codes, standards and requirements are met. Some local building departments may require obtaining a wind load calculation according to the 1997 Standard Building Code, Section 1606 or the South Florida Building Code, Dade County Edition and stamped by a licensed engineer in the state of Florida. 2. C. Install Code Compliant Accordion Storm Shutters on Sliding Glass Doors Protection devices must meet impact resistance and pressure standards in SSTD of the Standard Building Code, ASTM E1886 and ASTM E1996 or standards in the South Florida Building Code, Dade County Edition. All devices must be installed according to the manufacturer s instructions. Other requirements: See other requirements for Retrofit 2B above. 2. D. Replace Sliding Glass Doors with Code Compliant Impact Resistant Products Existing sliding glass doors shall be replaced with units that meet impact resistance and pressure standards in SSTD of the Standard Building Code, ASTM E1886 and ASTM E1996 or standards in the South Florida Building Code, Dade County Edition for both impact resistance and pressure requirements. Sliding glass doors must be installed as per the manufacturer s specifications. Other requirements: See other requirements for Retrofit 2B above. 2. E. Replace Garage Doors with Code Compliant Impact Resistant Products Protection devices must meet impact resistance and pressure standards in SSTD of the Standard Building Code, ASTM E1886 and ASTM E1996 or standards in the South Florida Building Code, Dade County Edition. All devices must be installed according to the manufacturer s instructions. Other requirements: See other requirements for Retrofit 2B above

24 2. F. Reinforce Garage Doors Retrofit existing garage door with a post system that can be locked during severe storms and provides positive reinforcement against pressure loads. Brace the garage door frame. Materials and methods used to reinforce garage doors and frame shall be installed per the manufacturer s specifications and in compliance with the locally adopted minimum building code. 2. G. Replace One Entry Door and Shutter Remaining Doors One entry door shall be replaced with an impact resistant product meeting impact resistance and pressure standards in SSTD of the Standard Building Code, ASTM E1886 and ASTM E1996 or standards in the South Florida Building Code, Dade County Edition. All remaining entry doors will be equipped with code compliant shutter devices. All devices must be installed according to the manufacturer s instructions. Other requirements: See other requirements for Retrofit 2B above. 2. H. Replace all Entry Doors with Code Compliant Impact Resistant Products Existing entry doors shall be replaced with units that meet impact resistance and pressure standards in SSTD of the Standard Building Code, ASTM E1886 and ASTM E1996 or standards in the South Florida Building Code, Dade County Edition. Entry doors must be installed as per the manufacturer s specifications. Other requirements: See other requirements for Retrofit 2B above

25 CHAPTER 3 Floor and Foundation Systems Floor Systems The two primary types of floor systems found in residential construction are concrete and off grade wood floors or a combination of the two. Connections between the floor system and the wall system and between the floor system and the foundation system are important for maintaining the integrity of entire structure from the ground up. These connections help resist wind forces from tropical storms, hurricanes or hydrostatic forces from floods and storm surge. Floor and foundation systems are particularly vulnerable to both vertical and lateral hydrostatic forces associated with floods and storm surge from tropical storms and hurricanes. Structures with floor systems not properly connected to the foundation can be lifted off their foundations and result in extensive damage or total destruction Retrofit Techniques and Products Floors Wall Framing to Floor System Connections The retrofit options for this section include installing connectors that tie the wall framing to the floor system. Connectors can be found from a variety of connector manufacturers and there are a multitude of types that can be used in different situations. Retrofitting the wall framing to floor system can include adding new anchor bolts or connectors and can require removing a portion of the wall covering. Whether to approach the problem from the inside or the outside depends on the situation present. All anchors and connectors shall be installed in accordance with the manufacturer s specifications. When dealing with slab on grade systems with wood walls, holes should be drilled through the wall s existing bottom plate into the concrete foundation and properly sized approved anchor bolts should be installed at intervals that comply with the locally adopted minimum building code. A commercial grade epoxy may be used to install the anchor bolts in retrofit applications. The most common anchoring system for wood walls and wood floor systems is the use of metal straps or connectors. Foundation Systems There are many types of foundations used in the construction of residential structures including concrete slab on grade, concrete footings and stem walls, piers and piles to name a few. Foundations should be constructed on clean compacted fill and shall comply with design standards of the locally adopted minimum building code. Foundation systems shall be connected to the floor system with approved connectors and installed in compliance with the manufacturer s specifications. An engineering review by a structural engineer registered in the State of Florida is highly recommended for repairs or modifications to foundation systems for large square footage structures or elevated structures, especially those with pile foundations

26 3. 2. Retrofit Techniques and Products Foundations Floor System to Foundation Connections The connection between the floor system and the foundation acts to anchor the house to the earth. This connection completes the load path from the roof to the earth resisting wind and hydrostatic loads that can impact the structure. A failure at this connection will compromise the integrity of the entire building. To retrofit this connection properly, it is necessary to evaluate the anchoring system used to connect the floor to the foundation. The most common anchoring system for wood floor systems is the use of metal straps or connectors. Approved connectors shall be installed in compliance with the locally adopted minimum building code and in accordance with the manufacturer s specifications Piers and Stem Walls Where spot piers are used, spacing shall not exceed 8 feet on center unless engineering analysis indicates a greater spacing is acceptable. Piers shall be properly anchored to resist overturning and sliding. Sills used in conjunction with piers and stem walls shall consist of approved wood of natural decay resistance or preservative-treated wood Piles All piles shall be braced to provide lateral stability in all directions. Methods used to brace piles shall be subject to the approval of the local building official. Pile to girder connections can be strengthened using metal strap connections, as shown in Figure 3.1. Spacing of the straps shall comply with the locally adopted minimum building code Connectors Connectors can be found from a variety of connector manufacturers and there are a multitude of types that can be Pile to girder metal strap. Figure 3.1 used in different situations. Retrofitting the connection between the floor system and the foundation system can include the use of a variety of connectors and anchor bolts. The use of stainless steel connectors is highly recommended within the Coastal Building Zone as galvanized connectors will rust over time and will need to be replaced periodically. All connectors and anchor bolts shall be installed in accordance with the manufacturer s specifications and in compliance with the locally adopted minimum building code

27 Retrofit Specifications for Floor and Foundation Systems 3. A. Install Code Compliant Anchoring System for Wall to Floor or Wall to Foundation Connection Install connectors from the wall system to the floor or to the foundation. Connectors used in anchoring the wall system must satisfy the requirements of the locally adopted building code and shall be installed as per the manufacturer s specifications. 3. B. Install Code Compliant Anchoring System for Floor to Foundation Connection Install connectors from the floor system to the foundation. Connectors used in anchoring the floor system must satisfy the requirements of the locally adopted building code and shall be installed as per the manufacturer s specifications. Sills that may have to be replaced during this retrofit must be replaced with materials of approved wood of natural decay resistance or preservative-treated wood. 3. C. Brace Piles Install braces on piles to provide lateral stability in all directions. Methods and materials used to brace piles shall comply with the locally adopted building code and shall be installed as per manufacturer s specifications. 3. D. Install Code Compliant Anchoring System for Girder Connection Install connectors from the girder to piles, piers or stem walls. Connectors used in anchoring the girder must satisfy the requirements of the locally adopted building code and shall be installed as per the manufacturer s specifications

28 CHAPTER 4 Other Disaster Resistant Considerations 4.1 Flood Floods happen more frequently than any other natural disaster. They occur everywhere from coastal areas, to along rivers, to desert arroyos and city streets. Sometimes flooding occurs in a flash and sometimes in a slow cresting that takes days or weeks. No matter when, where or how they arrive, they can always endanger lives and damage property. If a home is located in a Special Flood Hazard Area it is at risk of flooding Determine Flood Risk To determine if the home is located in a Special Flood Hazard Area, contact the local floodplain management official, a mortgage lender, or an insurer or insurance agent. They will help determine in what flood zone the property is located. If a Flood Insurance Rate Map (FIRM) indicates that the property is in flood zone A, AE, A1-A30, AH, AO, AR, V, VE, or V1-V30, then the home is in a Special Flood Hazard Area. The next step is to determine the base flood elevation (BFE) for the building. The local floodplain management official will have this information. In the case of Zone AO, use the depth of flooding shown on the FIRM as the BFE. The final step in the process is to determine the elevation of the lowest floor of the home. The lowest floor refers to the lowest enclosed area of the home, including the basement. Consult the community s records or the property s survey for the elevation. If these two sources do not indicate the elevation of the lowest floor of the building, it will be necessary to hire a licensed surveyor Actions Homes not located in a Special Flood Hazard Area are considered to have no risk of flood damage and no action is required. If the home is located in one of the A Zones of the Special Flood Hazard Areas, no action is required if: The elevation of the lowest floor is at or above the BFE; Enclosed areas located below the elevation of the lowest floor are used solely for parking of vehicles, building access, or storage; The building is elevated on piles, piers, posts, or a column foundation; and Electrical, heating, ventilation, plumbing, air conditioning equipment and other services are elevated to or above the BFE. If the home is located in a V Zone of the Special Flood Hazard Areas, no action is required if: The bottom of the lowest horizontal structural member of the lowest floor is at or above the BFE;

29 Enclosed areas located below the elevation of the lowest floor are used solely for parking of vehicles, building access, or storage; The building is elevated on piles, piers, posts, or a column foundation; and Electrical, heating, ventilation, plumbing, air conditioning equipment and other services are elevated to or above the BFE. If the home is in a Special Flood Hazard Area and the conditions listed for the A and Z Zones are not met, the home is at risk of flood damage. It is recommended that a qualified home inspector examine the home and make recommendations regarding the appropriate retrofit action or actions that should be taken to minimize the potential flood hazard Wildfire/Forest Fire More people are spreading out from the urban centers to create rural neighborhoods in what is known as the wildland/urban interface. In the process, they make themselves vulnerable to the danger of wildfires or forest fires. The trees, underbrush, and grasses in these areas provide fuel for devastating wildfires during the hot and dry seasons. Florida is no exception Preventive Measures In order to minimize the risk of loss of life and property from fires for homes located in the wildland/urban interface, the home must have the following features for minimizing fire risk: A non-combustible street number at least 4-inches high, located on a contrasting background and visible from the road. A minimum of 100 feet of defensible space around the home. This space should be free of vegetation likely to fuel a wildfire such as wooded areas and undergrowth. The defensible space can be reduced to 50 feet if the exterior of the home is covered with a material that has a fire-rating of at least one hour. For homes located on slopes of 8 to 20 percent, the defensible space on the downhill side of the building should be increased from 100 to 150 feet if the exterior of the home is a nonfire-rated material. For fire-rated exterior coverings, the defensible space should be increased from 50 to 80 feet. For homes located on slopes in excess of 20 percent, the defensible space on the downhill side should be increased from 100 to 200 feet and from 50 to 100 feet for homes with a fire-rated exterior material. Firewood should be stored at least 50 feet away from any part of the building. A non-combustible screening with a mesh size no greater than 1/4-inch should cover the fireplace chimney and the attic and sub-floor vents. The soffit and facia of the roof eaves should be made of a non-combustible material. The space below above-ground decks and balconies should be enclosed to prevent the accumulation of combustible materials and the enclosure should be made of a non-combustible material. The roof assembly with a Class A resistive fire rating. (Note that wood shakes and wood

30 shingles should not be used regardless of fire rating.) Multi-layered glazed panels in exterior windows, glass doors and skylights or solid exterior shutters. A driveway at least 12 feet wide and with at least 13.5 feet of vertical clearance below tree limbs and archways in order to provide access for emergency equipment. If the home has a gated driveway, the gate should be 2 feet wider than the driveway and it should open inward. The gate should be located at least 30 feet off the road or highway Safe Rooms/Shelters Homes are built according to local building codes. The codes were developed to consider the effects of minimum, code-approved design winds in a given area and the homes are built to withstand a design wind event. A tornado or extreme hurricane can cause winds much greater than those upon which the building code requirements are based. Therefore, having a home built to code does not mean that the house will withstand wind from any event, no matter how extreme. One possible solution to this situation is to consider retrofitting an existing home or designing into a new home a safe room or shelter that has the capability to withstand the forces associated with extreme wind events. It is important to recognize that the primary purpose of these safe rooms is to prevent loss of life, not to prevent property damage. Presented below are some of the considerations that must be addressed when designing and building a safe room. More detailed information is available from: Taking Shelter from the Storm: Building a Safe Room Inside Your Home. Published by the Federal Emergency Management Agency; Mitigation Directorate; 500 C Street, SW; Washington, DC FEMA Publication Number 320. A copy may be ordered by calling Tornado Protection: Selecting and Designing Safe Areas in Buildings. Published by the Federal Emergency Management Agency; Mitigation Directorate; 500 C Street, SW; Washington, DC FEMA Publication Number TR-83B. A copy may be ordered by calling Shelter Size The amount of floor area that the shelter must provide per person depends on the type of windstorm that the shelter will be expected to protect against. Tornadoes are not long-lasting storms. If a shelter is designed to offer protection from a tornado, the occupants will not have to stay in the shelter for a long time. As a result, comfort is not a concern and a shelter that provides 5 square feet of floor area per person is quite adequate. Shelters that are designed to provide protection from hurricanes must consider the comfort of the occupants for periods up to 12 hours. In this situation, the recommended floor space per person is increased to 10 square feet. Necessities such as water and toilet facilities should be included in the plans. FEMA Publication 320, referenced above, presents designs for in-residence shelters with a maximum floor area of 64 square feet and maximum wall length of 8 feet. A shelter with these

31 dimensions can accommodate up to six people in reasonable comfort. Shelters that exceed these basic dimensions will require consultation with a licensed professional engineer or architect New vs. Existing Home The term retrofit refers to the process of making changes to an existing home. When a new house is being built, the builder/contractor can construct walls, foundations, and other parts of the house required to accommodate the shelter. It is more difficult to make these changes to the construction of an existing house. The discussion in this document is focused on retrofit applications Foundation Types Houses with basement, crawl-space, or slab-on-grade foundation systems are suitable for the installation of a shelter. In homes with a basement, the shelter should be built in the basement. It should be an entirely separate structure with its own reinforced walls and ceiling. One or more basement walls may be used as part of the shelter in new construction if they are specially reinforced during construction. If the walls were not reinforced during original construction, independent shelter walls will be required because it is not practical to reinforce basement walls in an existing house. The shelter must be built with its own independent and reinforced ceiling. Another consideration for a retrofit basement shelter is that a portion of the basement area must be cleared and dedicated to the shelter. A concrete or concrete masonry shelter built in a slab-on-grade house requires that the concrete slab be thickened and reinforced adequately to support the weight of the shelter. In an existing slab-ongrade house, removing part of the slab and replacing it with a thickened section involves extensive effort and disruption inside the home. As a result, it is more practical to consider building a woodframe shelter because the walls are not as heavy and do not require the support of a thickened slab. A wood-frame shelter can be created from an existing room, such as a bathroom or closet, or it can be built as a new room in an open area of the house, such as the garage. It is also possible to build a shelter as an addition to the outside of a slab-on-grade house. This choice requires not only proper footings but also a watertight roof. Being built as an outside addition means that the shelter will be more susceptible to missile impact and, as such, should not be built of wood. Instead, it should be built of concrete or concrete masonry. A house built on a crawl-space usually has a floor made of wood framing supported by a perimeter foundation wall of concrete or concrete masonry. The crawl-space foundation walls are seldom reinforced and provide little resistance to the stresses of extreme winds. Building a shelter inside a crawlspace foundation house is more difficult than building a shelter inside a basement or slab-on-grade house. The main reason is that the entire shelter structure, including the floor, must be separate from the framing of the house. In order to support the shelter on its own concrete floor slab, concrete or concrete masonry foundation walls for the shelter must be erected within the crawl-space foundation area, filled with earth, and compacted. A concrete slab is then placed on the compacted earth and the shelter construction completed. An alternative approach, which may be more economical, is to build the shelter on a slab-on-grade adjacent to an outside wall of the house and provide access through a door installed in the house wall

32 In-ground Shelter Perhaps the most convenient and safest location for a shelter is below ground level. For example, an in-ground shelter can be built below the slab-on-grade of the house or the concrete garage floor. In Florida, however, a below-ground shelter is not suitable if it is below the level of the storm surge or the level of flooding from any source. In many parts of Florida, a below-ground shelter is not practical simply because of the high water table Shelter Designs FEMA Publication 320 contains a series of in-residence shelter construction drawings for five types of shelters: concrete, concrete masonry, wood-frame, lean-to, and in-ground. A builder/contractor can use these design drawings to guide the construction of a shelter specific to a given house. Before increasing the shelter size or using material types, sizes, or spacings other than those specified in the drawings, review of the modifications should be conducted by a licensed professional structural engineer. Some organizations have developed standard shelters designed for installation in existing homes. Some of these ready-made shelter systems have been thoroughly tested and approved for use as a retrofit shelter. The systems can be purchased as a package, delivered to the home, and installed by a contractor. The testing of these systems is performed by Texas Tech University s Wind Engineering Research Center in Lubbock, TX. Questions regarding the availability of approved manufactured in-home shelters may be directed to the Center at , extension

33