Fortified For Safer Living

Transcription

1 Fortified For Safer Living Module 1: Construction Failure and Damage from Wind and Water Introduction: The Fortified Code Plus Program The Fortified For Safer Living standards is a Code Plus program that prepares builders to construct stronger and safer homes in the face of natural disasters. This program is composed of a series of modules. This introductory module is intended to introduce participants to the process of reviewing plans and to inspect homes to assure they meet Fortified For Safer Living standards. We ll introduce the Fortified Program and review the kinds of failures and damage that occur from wind and water, and discuss how you can build to better resist the forces of the wind. We ll get into wind loads and the design considerations that go with that because we expect our plan reviewers to have a good understanding of the key factors that are involved in building better and stronger. And that means we need to go through the plan review process with a focus on keeping water out, keeping the building envelope intact, and providing a load path that keeps the home from coming apart. The plan review process we re discussing here is strictly for the Fortified For Safer Living Standards program. This is not a plan review in lieu of a building permit plan review. That process will still need to be followed on your projects. Rather, the Code Plus program focuses on things that are often missed in the normal building construction and inspection and process. And in some cases, we re adding additional features that go beyond the code. We are assuming as the basis of this program that our participating builders are building to the latest modern building codes and are still having all the usual code inspections done. Getting Started: The Fortified Building Guide and Plan Review Checklist The Fortified Process as we ve laid it out begins with someone deciding that they want to build a Fortified For Safer Living home. This means the design professionals involved in developing the home will use our 2008 IBHS or its affiliates, All Rights Reserved Module 1, Page 1

2 Fortified For Safer Living building guide that establishes the Code Plus features that are built into the process. And they ll be using this builder s guide in conjunction with a plan review checklist to make sure that all the Fortified items are included in the plans. Once the house plans are prepared, they are sent to a third-party reviewer. And that s the person we re focusing this training on that person who will be providing the review to ensure that the design includes all the necessary Fortified items and is calling out the correct materials and connections. The Fortified reviewer will develop a site-specific inspection checklist for the Fortified program inspector to use for assuring that what is called out and what is needed is actually built and included in a specific building. At various steps through the process, the reviewer will send information to IBHS, which is used for an audit function of sorts. We will capture and check that information for the purpose of issuing a certificate at the end of the process that indicates that this home has been built to the Fortified standard. Site Inspections Typically, there will be four specific inspections during the construction process, which are conducted by the trained and certified Fortified Inspector. And there may be some extra inspections as well, depending on the type of construction and the schedules and so forth. But the primary ones we always conduct include those for the foundation, roof deck, and framing stages, and then a final inspection. At the foundation inspection we ll be looking at things like these: Has the reinforcement been put in? Is everything laid out properly? Have the holddowns at the corners been installed? Have the anchor bolts been installed? At the roof deck inspection we ll be checking to make sure that the roof sheathing has been properly attached and anchored down. (One of the most critical problems we ve seen in so many storms is that the building envelope gets opened up, a piece of roof sheathing gets lost, and water pours into the house.) At the predrywall inspection, we look at the framing system to make sure that there are connections between all the different pieces of the home from the roof all the way down to the foundation. And one of the terms you re going to be hearing a lot as we go through this inspection is something called the load path. In a structurally sound building, the loads in all the different parts of the building, from the roof, walls, and so forth, 2008 IBHS or its affiliates, All Rights Reserved Module 1, Page 2

3 are all directed down to the foundation. And there are a series of inspections that go on in this stage of the construction process. A final inspection takes place at the very end of the job, after the home is completed. At this inspection, we go through and look at some of the other elements that make the home safer. At this point, once all the information on the inspection checklist has been verified and photo documentation has been reviewed, a Fortified Certificate is issued for the home. And just as a note, homes that are built in areas that don t have a history of strong code adoption and enforcement may require additional inspections. That s because the Fortified designation is focused on hazard-resistant features; we re still counting on the building code officials and the local enforcement to make sure that houses are built in the way they should be. So if your community is not well set up to provide these inspections and hasn t had a code adopted for some time, then it may be that we ll need extra inspections carried out. The Building Code Effectiveness Grading Schedule The code issue we just spoke of is covered in the BCEGS the Building Code Effectiveness Grading Schedule. This is a program administered by the ISO (the Insurance Services Office) that was originally developed in fact by IBHS. This program rates each building department on a scale of one to ten, with ten as the worst rating. So a building department with a rating of six or higher isn t doing a very good job of enforcing a model code. When the BCEGS rating is six or higher, this indicates that extra inspections, extra work, may be required in an area. And that s something that you need to check on specifically for the building department in your area. Some states that don t participate in the BCEGS program have an automatic rating of ten, and where this is the case, this program requires additional inspections or designs. Module 1: Construction Damage & Failure from Wind and Water Now let s look at some cases focusing on building system failures and damage caused by wind. One of the most common areas where we see damage from wind is in the roof covering. And what we have found in the analysis of claim files and post-disaster investigations is that of the homes that are damaged enough to have a claim filed for loss, 95% have damage to the roof covering and it really doesn t matter if it s shingles or tiles or other kind of roof covering. The roof covering is one of the weak links IBHS or its affiliates, All Rights Reserved Module 1, Page 3

4 There are some improvements in the roof coverings available today, but there are still widespread problems when it comes to wind resistance. The photograph above shows a ceiling with total collapse, and that is in a house that lost only its roof covering. It didn t lose any roof sheathing. The 2008 IBHS or its affiliates, All Rights Reserved Module 1, Page 4

5 ceiling collapse was caused by water intrusion through the joints of the plywood. This can be a really major problem when the roof covering is lost. Soffit Failures In some cases, just losing soffit material will allow damaging amounts of water to blow in. And keeping the water out in a hurricane is critically important. You could have a home that s structurally intact after a storm but it could still need to be gutted and rebuilt because the interior is so badly damaged from water intrusion. Soffit failures are something that we ve seen a lot more of in recent storms. I think the reason the topic didn t get much play after Hurricane Andrew is because in that storm the roofs were typically gone as well. So if the roof was missing, you didn t really care a whole lot about whether the soffit was still in place or not. The structural failures we saw in Andrew were so bad that it was hard to tell what failed because the answer was everything. With the improvements in the code since Andrew we ve seen the structure staying intact but now we re losing soffits. And that is probably one of the most difficult problems for us to solve. We think that proper installation of soffits is a critical thing, and it s certainly something that we re looking at in the Fortified Program. Looking at some of the damage from recent storms, it s clear that a lot of people were putting up the soffit material and thinking that as long as it stayed in place it was okay. Nobody was really looking closely at how it was being attached, how it was being installed. Some of the preliminary work we ve done indicates that if you do follow the manufacturer s recommendations for high wind zones, then there s a pretty good chance of the soffits staying up. Manufacturer s installation instructions. Those are the magic words of the day. The manufacturer s installation instructions are absolutely critical for all facets of construction. And typically, soffits have not been installed in accordance with the instructions from the manufacturer. We might even talk about my favorite term: the tribal knowledge of building code. This is the first building code that ever was. They figured out what how to build something and they passed it on verbally from generation to generation. So tribal knowledge is something we need to get rid of. We need to go into the building codes and really teach people how to build in accordance with the manufacturer s installation instructions IBHS or its affiliates, All Rights Reserved Module 1, Page 5

6 We ll come back and touch on that a little bit later on with some statistics. But it is interesting to note here that in the damage from Hurricane Charlie, 75% of the homes that had claims had soffit damage. It was that widespread. There s a classic example shown in the photograph above. You can see a little bit of a channel up against a wall where the soffit material was just stuck in there and it popped out pretty readily. We found it blown up, blown down, damaged in all kinds of different ways. This reflects poor installation as well as a lack of standards and standard test methods. The photo above also shows a case where there should be a center support for the soffit. And there should be a center support to hold the soffit material here at the edge. These are the big points of failure. Roof Sheathing Failures Another common area of damage is to roof sheathing. We did see instances with Hurricane Charlie, and a lot of cases back in the time of Hurricane Andrew. Even though codes and standards improved after that we still have seen some damage. In most cases, it was when the roof sheathing was stapled on. We ll come back and revisit the recommendations for how to fasten sheathing and how to put it on in a Code Plus way that s not going to cost you much more money at all. In fact, for the typical 2,000-square-foot home the additional cost is about $7 more than conventional practices. It s really not that much more in terms of cost. And of course, this next picture (below) shows that a number of the staples that were used didn t 2008 IBHS or its affiliates, All Rights Reserved Module 1, Page 6

7 even penetrate into the sheathing. So, even if you use staples, they still need to go into the structure to be effective. Damage at Gable Ends When you do lose the roof sheathing then you open up the structure for water pour in. Where we ve seen that damage occur most frequently is at the gable ends where the wind is whipping around the end of the building. It can lift off the roof sheathing and cause a lot of damage internally. And when you lose that roof sheathing, then the trusses may fall over. You end up with very serious destruction. We ve found that time after time the gable ends were one of the weak links. So you will see we make this a focus in the Fortified program, both in terms of strengthening the gable end and in terms of keeping the sheathing on in these areas where the highest wind loads occur. That is why one of the things we look at is the bracing of the gable ends. Frequently it s not done well or is incompletely done, and so we re going to 2008 IBHS or its affiliates, All Rights Reserved Module 1, Page 7

8 concentrate on how to brace gable ends. When our Fortified inspectors come along they re going to be well trained on how to look for that proper bracing and ensure it s correctly installed. The illustration above shows how the wind loads develop when the wind comes in from against the gable end. You get a positive pressure buildup on the bottom side of the overhang as the gable end is trying to lift that up, and at the same time the flow that s going over the top of the roof is creating a very large suction or negative pressure on the top that s trying to lift this up. The way a lot of the overhangs are built is with a little bit of a sort of a ladder detail where there are a couple of members running along with some braces between them and everything really ends up pivoting on the nails that are coming into the truss or rafter system right at the end of the gable wall. And when you see that happening, it s very easy for the ladder assembly to lift off and pop those fasteners loose. Therefore, the newer codes concentrate on putting more fastener to secure the ladder assembly, making sure that if the overhang sticks out more than 8 or 12 inches, then you would run an extension to brace the assembly, as well. Other damage that we ve seen with gable ends is a failure between the gable triangle, and the wall below it, as shown in the photo below 2008 IBHS or its affiliates, All Rights Reserved Module 1, Page 8

9 It s actually a fairly rare occurrence to see this because most often it all falls apart and you end up seeing the end of the building wide open and a tremendous amount of damage, as shown below. This type of failure probably was often caused by a combination of external pressure and internal pressure. Which leads us to one of the big issues that we focus on in this program: trying to protect the window and door openings so that they don t burst open IBHS or its affiliates, All Rights Reserved Module 1, Page 9

10 Window Failures and Internal Pressures When a door or window bursts open, the wind pressure that would have occurred at that door or window enters into the house and it s like blowing up a balloon. You get that pressure on the inside of the house that adds to the forces on the outside of the house that are trying to pull it apart as wind blows around a house. And we ll see this in some more graphic detail in a minute. There are a combination of forces on the outside and the inside that really stress the skin and the walls of a building. So protection from windborne debris is an important feature of the Fortified For Safer Living Program when it comes to hurricane protection. The windborne debris testing that s done for product approval is generally done with a 9-pound 2x4 traveling at 34 miles per hour. In a real hurricane, the fact is that there s an awful lot of debris from different sources blowing around. It can be roof tile, for instance, which can pierce through shutters and really cause some problems, or large pieces of plywood or structural members. So in a real-life event, we re trying to protect the building, both from windborne debris and from the internal pressure being created inside IBHS or its affiliates, All Rights Reserved Module 1, Page 10

11 The photograph above (previous page) is one of our poster children for the internal pressure problem. This was a house on Pine Island that went through Hurricane Charlie. The window in the front area blew in. Wind pressure got inside. It actually lifted the roof trusses off the house even though they were strapped down and opened up the whole house. Most of the houses in the community were still intact. So this house shows how a home either stays together or doesn t based on whether wind pressure gets inside or not how an entire roof can be blown off as a result of internal pressures. Another common area of damage in both the more recent storms and older storms is unreinforced masonry. In modern construction in the high-wind areas, reinforcing is going to be required in every masonry structure. We have seen a real progression from no reinforcing to a little bit of reinforcing at the corners and near each opening to what we have now: a pretty welltied-together masonry home if it s built to the new codes. The photo above shows an example of failure where it s clear that the connections weren t that good. The structure was probably, again, impacted by pressure that built up when the garage door blew, and it ended with this wall blowing off. There s very little indication of a connection between the wall and the rest of the building. You can see the nice clean break in separation at the ends of that wall where it popped out. Notice that the garage door is in the middle of the garage, sitting on top of the washer and dryer. So it s pretty evident the garage door blew in, 2008 IBHS or its affiliates, All Rights Reserved Module 1, Page 11

12 causing the internal pressurization that resulted in the loss of the entire end wall, the gables, and even the sheathing off this roof. So this is a major issue. With the building shown in this next photo (below), which is a little bit bigger structure, we had the same kind of problem. This was on North Captiva Island, a resort community with condos. As we look at the corner of this condo that was blown out, there is no sign of any connection between the wall members and the various places. And interestingly, we found the sliding glass doors lying intact but just tilted over into the room. Lots of the pieces of the wall framing just broke away and there s no sign of any connection between them IBHS or its affiliates, All Rights Reserved Module 1, Page 12

13 Pile Foundation Failures Pile foundations are another element that we ll look at here briefly and discuss in more detail in one of the modules when we look at the effect of storm surge. With piles, it s not just a question of being elevated enough. It s also a question of how deep down the piles go. As the picture below indicates, the surge came in from the storm and eroded away the sand dune that the house was sitting on. Obviously, the columns weren t deep enough and the home fell in. A good rule of thumb is that your piles go down at least below sea level. If they don t, then there s a very good chance that they ll get eroded underneath. Discontinuous Columns Another problem that we ve seen showing up is with discontinuous columns. The photograph below (next page) shows a case where they ran up piles to support the structure, but then each piece going above that was connected. There really weren t any kind of moment connections in there for holding the structure together. So while the top two stories held 2008 IBHS or its affiliates, All Rights Reserved Module 1, Page 13

14 pretty much straight and true, there was a tremendous amount of movement within that bottom story. Most likely the house had to be totally destroyed. Double-Entry Doors Another area where we ve seen frequent damage is in double-entry doors. I don t know how many people we talked to after Hurricane Charlie who actually stayed in their homes and were up leaning against the doors trying to keep them shut a very dangerous thing to do. You re near glass. You re near a door. One fellow was all bandaged up and we asked him what had happened. He had been trying to hold the door shut. The doors blew open, knocked him back into a mirror, and at about that time a piece of pile went flying near his head. His wife finally convinced him to go to a different part of the house. Another issue with in-swing double-entry doors. In-swing double entry doors are a real problem because the only thing holding the door shut are the flush bolts (shown in the two pictures below, next page), and then the latch holding the active leaf to the inactive leaf. Water pushes against these doors. It leaks in around the weatherstripping. This type of door is just not a good weathertight assembly. So we recommend the use of out IBHS or its affiliates, All Rights Reserved Module 1, Page 14

15 swing doors. That way, when the wind is blowing against the door, it pushes it tight against the weatherstripping, tight against the stops, and reduces damage and water intrusion. Garage Door Failures Garage door failures are something else that we ve seen a lot of. However, we have seen the failure rate drop dramatically with the new reinforced doors. Houses with pressure-rated and, in particular, pressure- and impactrated garage doors fared much better. But choosing a door with that pressure rating is a very important factor because it means that you re going to have stronger tracks, stronger rollers, and a stronger door that s much more likely to stay in place when the wind blows IBHS or its affiliates, All Rights Reserved Module 1, Page 15

16 One big difference between the pre-wind rated doors and the wind-rated doors is in the quality of the components: the track, the rollers, the springs, the hinges. It s another area where we need to be 100% sure that the products that are used meet the current building code requirements. We have seen cases as the one shown in the photo above where you do see one of the stronger brace doors. This was impacted. There s a little bit of a hole from the impact of the debris but it didn t open up the home. It 2008 IBHS or its affiliates, All Rights Reserved Module 1, Page 16

17 didn t let a lot of pressure in. And so from our standpoint, this door was a success. Even though it s had some damage, it really served the purpose of protecting the home. Opening Failures When a door on one side of the house fails in wind and pops open, it s common to see sliding glass doors knocked out on the other side of the house or some other subsequent damage. We ve seen some cases where doors failed on both sides of the house and the wind whipped though the home, actually blowing furniture out of the house and into the pool. In the top picture below (next page), you can see there s a couch that s been pushed out through the doors. It s holding the vertical blinds there. In the picture below that one, everything s gone. That mitered glass unit didn t hold up at all. But the good news is we can design with those windows today and install them so that they work. This building is from a premodern code era and those windows just were not designed to take that pressure IBHS or its affiliates, All Rights Reserved Module 1, Page 17

18 Siding Failures We ve also seen a lot of cases where siding is blown off and the walls have been opened up. We ve seen this more in terms of some of the vinyl siding: cases where people didn t pay attention to the details of installing vinyl siding in a high wind area IBHS or its affiliates, All Rights Reserved Module 1, Page 18

19 There are some good products out there that will stay on. In fact, after Hurricane Charlie (in which we had some very high wind speeds) we saw manufactured homes, or what we would call mobile homes, in the area that did have vinyl siding that stayed on. In terms of the siding that was installed in the factory, almost all of it was still intact. It was the cases where they had put the pieces together in the field and added in some extra pieces that you saw it had come off. When we got up into the panhandle of Florida where winds had been lighter, we saw a lot of site-built homes with vinyl siding. Vinyl siding was off all over the place. So it really does make a difference what you use and how you install it. Hurricanes and Design Wind Speeds We ve referred to Hurricane Charlie several times in our discussion. One reason for that is that it was the only design event that we had in 2004 and By design event we mean that the wind speeds blew at or close to the design wind speed for the area. In terms of a strong wind event, Charlie is the strongest to have occurred since Hurricane Andrew, and Charlie had even stronger winds than Hurricane Katrina by probably 20 or 30 miles an hour. In fact, with Charlie, particularly near the coast, the winds were probably about 10 to 15 miles an hour above the design value, so it was a little bit of a design-plus event. It didn t really eat up the safety margins that we as engineers normally build in, but it certainly did stress those homes more than anything else that we ve seen. As Charlie passed through the state of Florida it got over to Orlando still at design level wind speed. Beyond Orlando, then it was below design wind speed. But between Punta Gorda and Orlando we saw design events. What bothers us a lot is when we have a hurricane that isn t a design event and we still see a lot of failures. And we re seeing that happen, particularly with older buildings. But we re finding out that new buildings that are hit by design events do pretty well. Module 1 Summary To summarize what we ve discussed here today in terms of the building envelope, there are a number of failures related to wind and water intrusion that we are concerned about. These include loss of roof covering; loss of roof sheathing (when the sheathing is not attached well or it s on the gable ends); debris impact; broken windows; door failures (particularly 2008 IBHS or its affiliates, All Rights Reserved Module 1, Page 19

20 inward opening doors or double-entry doors); and window and door anchorage connections (in some of the past storms that we ve looked at, it s not that uncommon to find a whole window intact where it fell into the home because the screws that were anchoring it into the wall were so poorly installed, and then the glass was broken when it hit the ground). In addition, garage doors and sliding glass doors have been a weak point both in terms of water intrusion and failure. And when they do fail, there s a big opening. So there s a real opportunity for a lot of wind and water to enter the home. Water leakage hasn t necessarily gotten the billing that we think it will in the future. And one of the indications of that is that I had an opportunity to go down and look at some of the damage from Hurricane Wilma in the Cancun area. And there were a number of hotels where the sliding glass doors and windows all stayed intact but they still had 5 inches of water in the rooms. When a storm comes in and sits there for some period of time, just pouring water and blowing water at a home, the leakage around windows and doors can be devastating. There were a number of homes in the Orlando area that had all kinds of water leakage even though structurally they were still in pretty good shape. And then there are ridge vents or off-ridge vents, any of the openings in the roof are areas where water gets in and can affect things we try to focus on those as well in the Fortified Program, trying to promote the management and control of water intrusion as best we can with current technology. In fact, this area of water intrusion is the last big identified problem that we have to solve in residential construction. We have the buildings standing up in the winds. We have opening protection that works, and we have vents that let wind in (as they re supposed to do) but unfortunately allow water in (which they re not supposed to do). So we need to solve these problems. Let s summarize some of the major structural issues that we ve been looking at, as well. We re looking at gable end failure, and failure at roof to wall connections. Often, when we ve seen the roof to wall connections come apart, it s been caused by a breach of the envelope. The wind pressure has gotten inside the home and lifted off the roof because the pressures are so well distributed over the whole inside of the house that it creates a tremendous force. We ve also seen real problems with elevated foundations because of piles that were not deep enough, and because of connections that weren t done well enough. We ve seen wall connection problems, lack of bracing in the 2008 IBHS or its affiliates, All Rights Reserved Module 1, Page 20

21 wall structure, and finally, we have seen some foundation problems. This list here is in order of frequency. Gabling failures are typically the most frequent and then the foundation failures are clearly the least frequent IBHS or its affiliates, All Rights Reserved Module 1, Page 21