Stair Design Supplement To Space Planning Basics, Third Edition

Transcription

1 Stair Design Supplement To Space Planning Basics, Third Edition Stair Construction While the guidebook is devoted to stair design and not to stair construction, it is impossible to consider stair design without some basic knowledge of how they are built and the materials from which they are fabricated. Without addressing these issues in full detail, this section will provide the ground rules for making basic decisions about stair construction. There are three distinct physical components related to stairs construction: 1) the general construction system itself, 2) materials, and 3) handrails. There are some unavoidable overlaps between these three areas. The part on construction will deal with the materials of the overall stair construction, but not the more detailed aspects of materials for tread surfaces or handrails. The part on materials will deal with the issues of tread abrasion, but not with the supports for the treads. The part on handrails will deal with the dimensional details of the handrail and its supports, but not with how the supports are connected to the main stair structure. For those interested in more complete details of stair construction, there is some direction on how to pursue that more detailed knowledge, including when and how to consult with specialists. Construction By necessity, stairs are connected to the building structure of which they are a part. It follows naturally that the construction of the stair must be compatible with that structure. In the great majority of cases, a residential building of wood frame or ordinary (wood joist floors) construction will have a 1

2 stair fabricated with wood members. Correspondingly, a building of steel frame construction will have a stair, or stairs, fabricated with steel members; and a concrete structure will normally have stairs fabricated of concrete. There are appropriate exceptions to this convention. Typically, in small (two and three story) apartment buildings of ordinary (wood joist floor) construction, exit stairs are of steel construction to comply with building code requirements for non-combustible stairs. A highly sculptural and curvilinear stair in the lobby of a major multi-story steel frame public building may be fabricated with pouted-in-place concrete in order to achieve the very fluid appearance that is natural to the plasticity of concrete. Despite these understandable exceptions, compatibility of structure and its included stairs is a good starting point when making decisions about how a stair will be built. There are standards of stair construction for wood, steel and concrete that are used repeatedly. There are also many stairs that employ variations of the standards. Some of the variations are modest, while some vary widely from the norm, resulting in adventurous and innovative stairs. A few of the books cited in the bibliography have many photographs of creative, one-of-akind stairs for both small and large settings. For the purposes of this supplement, the detailed drawings for wood, steel and concrete stair construction represent typical and conventional fabrications, with the understanding that the designer s energy and creativity can bring about exciting and imaginative results. a) Wood Stairs Wood stairs are made both on-site and in millwork shops. Experienced carpenters, as well as millwork shops that fabricate stairs, know the conventional fabrication techniques, including the several commonplace variations, such as exposed or concealed stringers, and sloped risers or projected nosings. Illus. CW-1 shows a very typical residential wood stair with an exposed stringer and steel bar stock supports for its wood railing. There are many variations in wood construction details, in addition to those shown here. When wood stair design details vary widely from conventional construction techniques, it is extremely important for the designer to fully detail every aspect of the stair in order to insure the desired result. 2

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4 b) Steel Stairs Steel stairs are typically shop fabricated, trucked to the construction site, hoisted by crane and set in place within the building, and then permanently bolted or welded in place. When steel stairs are placed within masonry enclosures, the masonry will go up around the stair, embedding support beams or angles in the surrounding masonry. There are some variations of the standard steel stair that are normally produced by stair fabricators. Illus. CW-2 shows a very typical steel stair that would serve as a required fire stair in a multi-story nonresidential building. There are many variations in steel stair construction details, in addition to those shown here. As is the case with wood stairs, if a highly customized steel stair is designed for a particular building, it is extremely important for the designer to fully detail every aspect of the stair in order to insure the desired result. Concrete stairs are also shop fabricated, with the pre-cast runs tied to the main structure through mechanical means, such as resting on pre-cast floor members or beams. Because concrete is a truly plastic material and can be formed to provide very sculptural results, the variations in concrete stair design are infinite. Illus. CW-3 shows a very typical straight run of concrete stairs that could be poured-in-place or pre-cast, with attachments for handrails incorporated in the treads. There are many variations in concrete stair construction details, in addition to those shown here. It should be obvious that sculptural and/or unique concrete stairs require meticulous detailing on the part of the designer in order to insure the desired result. c) Concrete Stairs Concrete stairs are often site fabricated, using standardized forms, with their steel reinforcing bars incorporated into adjacent poured-in-place concrete floors. 4

5 Additional Case Studies - Phase I CASE STUDY #1A Another approach to a space efficient stair for a typical townhouse is a mid-landing U stair. In this case, the entrance to the house is on the long side, suggesting that the houses are set in a staggered pattern, or the houses are joined only in pairs, or that this house is at the end of a row, as demonstrated in the sketch of Illus. CW-4. For the sake of simplicity, the floor-to-floor heights are the same as in Case Study #1, except that the living room floor is dropped farther below the primary entrance or first floor level. For maximum space efficiency, the code maximum stair riser of 7.3 is used again (with the same 10 ¾ tread), as well as the stair width minimum of

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7 Floor plans, an overall thru-section, and a larger scale section through the stair of this townhouse, as shown in Illus. CW-4. Despite the basic simplicity of the U stair, this solution contains several specific design qualities and design decisions that should be noted: This stair design is unusually compact and efficient in its use of space and in confining circulation paths to a very small area of the house. In particular, note the compactness of the second floor hallway. In general, U stairs have these qualities of spatial efficiency and confining circulation paths to limited areas of a building. In addition, they are an obvious and useful method for avoiding unnecessarily long straight run stairs. The short run of steps from the entrance level down to the living room level maintains the same riser/tread dimensions as the major run to the second floor. In Case Study #1, the short run of steps from the dining area down to the living room level used a different and more comfortable riser/tread dimension than the main stair because they were significantly removed from the main stairs. In Case Study #1A, a change in riser/tread dimensions is not possible because stair travel from the second floor to the living room is continuous and a change in those dimensions would create an unsafe condition. Headroom at the landing leading down to the basement is tight but acceptable. A design decision was made to not add another riser to the run from entry level to living room because the separation of first floor level to living room level would feel too great, and to accept the limited headroom at the landing between living room level and the basement. 7

8 CASE STUDY #2A When required fire/exit stairs are used with some frequency for personal floor-to-floor travel, there are an infinite number of design alternatives to the utilitarian fire/exit stair described in Case Study #2. One very simple alternative, when the building s overall configuration permits, is creating a major glass or window in the otherwise conventional windowless fire/exit stair, permitting natural light and view to be part of the stair travel experience, as shown in Illus. CW-5. Once variations of this kind are made to utilitarian fire/exit stairs, there is a natural inclination to re-think the utilitarian finishes and details of the commonplace fire/exit stair with variations in the use of materials, railing design and lighting; those issues are fully addressed in the second phase case studies. 8

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10 This case study presents an obvious but significant variation to the utilitarian fire/exit stair. The setting is very similar to that of Case Study 2, but rather than being in a speculative office building with completely unrelated business tenants, the building has a single corporate or institutional owner (such as a research or university administration facility) that requires a great deal of day-to-day interaction among and between its many employees. By incorporating a central exit stair, in addition to the two stairs at or near the ends of the building; the additional stair will permit the building s length to be increased and still comply with length-of-travel code requirements. With the added stair and the elevator bank in the center of the building, a vertical travel core is created in which the building s users have the option of using either means of travel. Employees a floor or two away from one another may opt to use the stair, rather than wait for the elevator, particularly if the stair structure itself is an exciting and/or appealing space. a much enhanced travel experience compared with that of a typical fire/exit stair. Note that the floor-to-floor heights are identical to those in Case Study #2, so that the same riser/tread dimensions are applicable. A larger scale (¼ = 1-0 ) plan and section of the stair are shown in Illus. CW-5. Another means of enhancing the travel experience is changing the riser/tread dimensions to a more comfortable proportion. A typical floor plan and thru-section of this building are shown in Illus. CW-5. The glass enclosure of a major portion of the stair and the use of a semi-circular mid-floor landing make for 10

11 CASE STUDY #3A A very effective variation on the circular curved stair is the use of an elliptically configured stair. Mathematically correct ellipses can be geometrically complex, but for construction purposes, they can be constructed with reasonable accuracy with just two radii, as demonstrated in Illus. CW-6. The setting for this case study is a new development of upscale, three-story townhouses in a very dense urban neighborhood. The houses are 24-8 wide from center-line to center-line of party walls, and have a depth of 49-4, as shown in the plans and section of Illus. 3A. The floor-to-floor height has been established at 9-4. A floor space 16-0 wide by 6-0 deep has been set aside for an elliptical stair. For a curved stair in this residential setting, the building code requires: Maximum riser height of 7¾ Minimum tread depth of 6 at the narrow end of the tread Minimum stair width of 3-0 The smaller radius must be no less than twice the width of the stair For this case study s elliptical stair, using the 16-0 (major axis) by 6-0 (minor axis) space that has been set aside, and the 9-4 floor-to-floor height, a 7 riser has been selected (9-4 = 112 divided by 7 results in 16 risers - 7 x 16 = 112). The code would permit higher risers, but was rejected because of the desired personal comfort in a high-end home. The treads measure 11 at a point 1-0 from the narrow end of the treads. The same stair configuration is used from the first to the second floor, and again from the second to the third floor. The extended first tread on the first floor is not repeated as the stair ascends from the second to the third floor because the open stair well at the second floor will not accommodate an extended tread. The stair to the utility basement is a simple straight run stair, with the riser and tread dimensions determined by the floor-to-floor height from the first floor to the basement. 11

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14 CASE STUDY #4A This case study is set in a one-story light industrial building in a rapidly gentrifying urban neighborhood that is attracting high-end and sophisticated businesses to serve its new and affluent residents. The 1920 s structure will now house the local showroom of a major contemporary furniture manufacturer. The existing column-free building has approximately 2750 sq. ft., about half the amount of space the new user needs for its showroom and small local sales and office staff. By adding another high ceilinged floor level, the needed square footage can be provided. As seen in the site plan and building section of the existing condition in Illus. CW-7, the building shares party walls with adjacent buildings on both its north and south sides. The building to the north is four stories high and is significantly higher than the proposed height of the showroom building. The building to the south is two stories high and its roof level is just a few feet above the height of the existing showroom structure. By raising the south party wall and the east and west walls to the proposed showroom building height, the site will be able to serve the new owner s use. 14

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16 A portion of the existing roof structure is retained to create a new major showroom level (the studio level ) and the new clear span roof covers the entire building. At the east end of the building, a relatively low ceilinged area is created for the needed office on the first floor, and two somewhat higher ceilinged floor levels above the offices (second and third floors) create spaces for furnished room vignettes. Despite the need for an elevator for moving furniture and to serve disabled visitors and personnel, the central stairway is designed as the primary means of vertical travel. The stairs are designed to be part of a broad spatial and design experience, as well as a planned element of the furniture viewing experience. A relatively low and comfortable riser height of 6 is selected to be used throughout, with an accompanying 13½ tread. The floor finish on the old roof structure is furred upward with 16

17 sleepers to make it exactly 18-0, or 36 risers above the first floor. The two vignette levels, A and B, above the office are also set exactly 10-0 and 12-0, respectively, so that the 6 risers can be accommodated. And each run of the stair is made generously wide at 5-6 in order to make the walk through the space feel unconstrained. The building requires a second means of egress, and a new enclosed fire stair is placed in the northeast corner of the building, with direct access to the service alley at the rear of the building. Because the stair will be used primarily as an emergency exit, it is treated with a bare-bones approach from a design point of view. With the 12-0 floor-to-floor height established between the two vignette display floors, the smallest number of risers that conforms with the code s 7 maximum riser height (144 divided by 7 = 20.57) is a minimum of 21 risers at (144 divided by 21 = ). It should be noted that the maximum riser height also serves the purpose of keeping the length-of- run at a minimum, leaving adequate space for the elevator. Using the same riser height to descend from the lower vignette display floor to the ground level, one finds that 18 risers requires a floor-to-floor height greater than the 10-0 between those two floor levels (18 x = ). If 17 risers are used, the lower landing is 3.41 short of the ground level (17 x = , or ). Assuming that the exterior grade at the rear of the building is approximately the same as the grade at the main entrance to the building, the exit door at the service alley will have a short step down to grade level. The fire stair configuration also requires a short ramp in the northeast corner of the office area in order to have a door from the office into the fire stair. 17

18 CASE STUDY #4B This final case study, like the two previous ones, deals with an unusual, but far from unique situation. Connecting two adjacent, or in this case almost adjacent, buildings that have unaligned floor levels is always a complex condition. In this case study, a busy retail store occupies a three-story plus basement building on a main commercial street. The store also owns its own customer parking lot on an adjacent corner lot. The store uses all three floors for displaying merchandise, and the basement for storage and its management office. In the last few years, the company s catalog and web site sales have increased far beyond expectations, making the basement s limited office and storage space completely inadequate. With the prospect of the catalog and web site sales continuing to increase, the company bought a small and non-descript fourstory commercial building that faces the nearby side street and is also adjacent to the customer parking lot. These site plan relationships are seen in Illus. CW-8. 18

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20 The company s primary purpose in acquiring this particular building is to be able to physically connect it to the retail building and accommodate personnel travel between the retail store and the new expanded management and shipping facility. A careful survey of both buildings established accurate floor elevations, also seen in section in Illus. CW-8. As can be seen in Illus. CW-8, the dimensional differences between floor levels are so varied, no single riser height will simply connect the levels. Trial calculations at 6, 6½ and 7 made it clear that the 25-6 distance between the two buildings is great enough so that low risers and deep treads (6 and 13½ ) would not present a problem due to relatively long lengths-of-run. The trial calculations included trial section sketches, so that the results of each trial could be seen graphically, as well as arithmetically. The 10-6 floor-tofloor height between the first and second floors of the retail building made the use of a 7 riser work perfectly between those two floors (10-6 = 126 divided by 7 = 21 risers). After trying different mid-landing levels using 7 risers, it was discovered that connections between the stair runs and each of the existing floor levels could be accomplished with extremely minor, even imperceptible, ramping (from a minimum of.43% up to 1.56%). The section through the new stair demonstrates the results of this stair design solution. The resulting architectural solution, as seen in the North elevation, presents a new stair enclosure with a glass wall facing the customer parking and the main commercial street. The new stair is naturally light filled, with limited summer heat gain, and more impressive public image. The South wall of the new structure is primarily opaque, with small operable windows for natural ventilation and occasional views to the South. 20

21 Additional Case Studies Phase II CASE STUDY #5A The stairs developed for Case Study #1A in the Companion Website, is the basis for this case study. The detailed drawings of the attached illustration complete the design process. As shown here, the stringers (those attached to the wall surfaces and those on the open sides of the stairs) and the treads and sloped risers are typical of the shop fabricated stair that is shipped to the construction site and attached to the floor and landing construction at the bottom and top of each stair run. The mid-landing between the first and second floors are not typically part of the shop fabricated stairs and is in place when the stair runs arrive. The open railings are made up of ¾ steel or aluminum rod stock balusters that are double bolted to the stringers. The hand rails are custom milled from 2 x 6 solid wood stock to create the finger groove for better grasping. On the wall side, the hand rails are attached to a 2 x 2 spacer, leaving a 1½ space for the grasping hand. On the open side, the handrails are bolted to the balusters. For ease of construction, the balusters are first attached to the handrail and the assembled element is then attached to the stringer. Steel balusters must be painted; aluminum balusters may be painted or have a factory anodized finish. Finishes for the other parts of the stair would be as described for Case Study #5. Natural light is available from the skylight above the stair. The primary stair between the first and second floors is lighted by a pendant fixture over the mid-landing. The stair to the basement is lighted by two low-profile, surface mounted fixtures. 21

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24 Case Study #6A The stair developed for Case Study #2A in the Companion Website, is further developed here for this case study and shown in the attached illustration. The stair is clearly a required exit stair, but it is unlike the bare bones emergency exit of Case Study #2. This stair is expected to get regular floor-to-floor foot traffic. It has more comfortable riser/tread dimensions, and is full of natural day-time light, affording expansive views to the exterior. The exposed stringers are boxed structural steel channels. The treads are fabricated from 1/8 thick steel plate, creating triangular steel members that form an open riser stair conforming with code requirements. The treads are glue-wrapped with textured linoleum for a comfortable and safe condition; the same linoleum flooring material is applied to all stair entry and landing floor surfaces. The railing is custom fabricated from stock extruded and anodized aluminum shapes. The vertical members are fitted into the steel channel stringers and capped with an elliptical aluminum handrail. Stainless steel tension cables are run parallel to the handrail and 4 apart to conform with code requirements. The non-glazed wall surfaces are of the same brick used on the building s exterior. Lighting is provided by the use of three decorative sconces mounted on the brick entry walls at each floor level and with the use of a pendant fixture above each of the semi-circular mid-landings. 24

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27 Learning to become proficient in stair design requires repeated experience. The exercises in this section are geared to providing appropriate exercises for gaining the experience to achieve that goal. The exercises are sequential in the sense that they are increasingly complex in the order in which they are presented. They also are presented to give you experience with residential settings and larger non-residential buildings, as well as the opportunity for some complex and/or sculptural configurations. In addition to these exercises, there are other opportunities for gaining further experience by using some of the many published examples of stair design solutions that can be used as settings for developing your own design solutions. Each of the exercises presented here is developed as a two part exercise. Part A requires basic stair planning solutions. Part B requires the design of the architectural details, including the selection of materials and a schematic lighting design solution. In a classroom setting, it would be advantageous to have a pinup critique for each assigned exercise, so that a variety of solutions could be seen, discussed and analyzed from both Skill Development Exercises aesthetic and technical perspectives. EXERCISE 1 This townhouse is a variation of the townhouse in Case Study 1A (page ). A portion of the first and second floors have been redesigned and renovated, removing the central stair (except for the short flight to the lowered living room), with the plan to add a new stair to the exterior of the building, adjacent to the entry door. The basement has been eliminated. The new stair will connect the first floor to the second floor. The attached plan indicates the internal revisions to the first and second floors, and indicates the proposed location of the new stair with a dashed line. The floor-to-floor dimensions are 9-4 from the first to second floors; the thickness of floor constructions is 1-1. PART A - Plan and design the new stair, staying within the dashed line. The specific shape and size of the stair is not specified, but the overall size of the stair enclosure may not exceed 120 sq. ft., exclusive of the exterior walls that, at your discretion, may range from 6 to 10 in thickness. Include the 27

28 use of natural light in the stairwell. Draw plans and an overall section from the first floor level through the roof at ¼ or 3/8 = 1-0. PART B - Complete the design of the stair with the necessary details of riser and tread construction and railings, as well as a schematic lighting design solution and the selection of all materials. Draw a detailed section through the stair at ¾ or 1 = 1-0, including stair connections and/or relationships to adjacent floor and wall construction. Draw railing details at 1½ =

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30 second floors is 9-8, and 8-8 between the first floor and basement. The first and second floor thickness is 1-1. EXERCISE 2 The setting for this stair design problem is a very typical single-family suburban house of wood frame construction with a center hall foyer and stair. The general area for the stair is indicated with a dashed line within a two-story space encompassing the first and second floors. The stair to the utility basement need not be enclosed, but a major first floor opening is not anticipated. Stair planning must accommodate convenient circulation paths, including easy access to the entry closet, living room, dining room, and family room on the first floor, and an appropriate connection to the bedroom hall on the second floor. Floor-to floor height between the first and PART A - Plan and design the stair, staying within the dashed line area. Although natural light is available through the windows on the South wall, the addition of a skylight is possible. Draw floor plans and at least one ¼ or 3/8 = 1-0. PART B - Complete the design of this stair with the necessary details of riser and tread construction and railings, as well as a schematic lighting design solution and the selection of all materials. Draw a detailed section(s) through the ¼ or ¾ = 1-0. Draw railing 1 ½ =

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33 EXERCISE 3 The setting for this stair design problem is a five-story university science building that houses classrooms, labs, offices, and two large lecture rooms on the first floor. There are two required egress stairs at the extreme ends of the L shaped corridor. The structure is a basic steel frame with a floor assembly of steel bar joists, heavy gauge steel deck supporting 3 thick poured-in-place concrete floor slabs. The enclosing stairwell walls must have a two-hour fire rating. Both stairs must exit directly to the exterior, with the condition at Stair #1 being easier to resolve due to its location at the end of the building. Despite the central bank of elevators, it is assumed that the stairs will receive a great deal of daily use and should not be thought of as stairs for emergency use only. While the stairs could be of concrete construction, it is assumed that they will be fabricated of steel, as is typical for this type of building. Make note of the fact that there is enough space at the corridor entry point of both stairs for a generous landing. Also note that Stair #2 must provide exterior egress from the first floor corridor as well as for those coming down the stair from above. Typical floor-to-floor height is Floor height from first to second floor is 16-0 ; ceiling heights are variable depending upon plenum needs. PART A - Plan and design a stair for Conditions #1 and #2, with the understanding that they may be very similar above the first floor level. Condition #2 offers the opportunity for a great deal of natural light through the use of windows on the north and west walls. Draw floor plans of both stairs, as well as at least one section through each ¼ or 3/8 = 1-0. PART B - Complete the design of these stairs with the necessary details of riser and tread construction and railings, as well as a schematic lighting design solution and the selection of all materials. Draw a detailed section through both stairs at ¾ = 1-0. Draw the railing details at 1 ½ =

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36 EXERCISE 4 The setting for this stair design problem is a seven-story building designed to house an international research/think-tank institute. The central stair is intended to be as much a vehicle for personal interaction as it is a means of vertical travel through the building. Its central location within the building and its ability to afford long vistas and a break from the regular confines of the building. The area contained within the dashed circular line is not meant to suggest a shape for the stair s structure, but rather a generalized location for an appendage to the building. This is the opportunity for an adventurous design solution, as well as enough space to be generous with stair width, large landings, and quite low risers. The exterior walls adjacent to the stair do not necessarily have to be of the same buff brick material as the building s other exterior walls. While the stair may be enclosed with doors at any or all floor levels, it may remain open and meet IBC requirements through the use of suppression systems and/or internal draft systems. All floor to floor heights are 12-6 ; ceiling heights are variable, based on plenum needs. PART A - Plan and design a stair for this setting. Take advantage of the lack of spatial limitations. Draw floor plans and at least one ¼ or 3/8 = 1-0. PART B - Complete the design of this stair with the necessary details of riser and tread construction and railings, as well as a schematic lighting design solution and the selection of all materials. Despite all of the potential glass area of the enclosing walls, do not forget the need for night-time lighting. Draw at least one detailed section through the stair at ¾ = 1-0. Draw railing details at 1 ½ =

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39 EXERCISE 5 The setting for this stair design problem is a group of attached condominium townhouses of ordinary construction with masonry exterior walls and a floor assembly of wood joists, particle board sub floor, and gypsum board ceiling. They do not have basements. As seen in the attached illustration, the sloping ceiling of the living room rises from a low point of 7-8 at the north end of the room, to a height of 16-2 at the south end. Note that Section AA indicated skylights in the roof structure. The free standing stair connecting the first floor to the second floor bedroom corridor must be located within the area of the dashed line arc shown in the southeast corner of the living room. Provide a safe condition at the second floor corridor with a continuation of the stair rail into a guardrail along the corridor as it overlooks the living room. As a design option, the stair may connect (partially or fully) to the east wall of the living room. The floor-to-floor height from the first to the second floor is 8-6 ; the second floor thickness is 10. PART A - Plan and design the new stair. Windows in the east wall of the living room, and the skylights above the living room, may be re-positioned to provide an optimal daylighting condition for the stair. Draw a plan and an overall ¼ or 3/8 = 1 0 PART B - Complete the design of the stair with the necessary details of riser and tread construction and railings, as well as a schematic lighting design solution and the selection of all materials. Draw a detailed section through the ¾ or 1 = 1-0. Draw railing 1 ½ =

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42 EXERCISE 6 Kareoke The setting for this stair design problem is the entrance lobby of an eight story suburban hotel with a restaurant and bar on the mezzanine level. There are two central elevators to serve the mezzanine and the guest accommodations above. The enclosed egress stairs on either side of the lobby and mezzanine serve only those areas of the building; egress stairs for the guest accommodation floors above lie far beyond the lobby/mezzanine structure. The building s structure is a steel frame; the mezzanine floor assembly is of steel bar joists, a poured-in-place floor slab on a corrugated steel deck, and a fire rated acoustic tile ceiling. The overall mezzanine floor thickness is 2-0, including the enclosed plenum space. A free standing stair connecting the first floor with the mezzanine shall be located within the area prescribed by dashed line shown in the attached floor plan. The floor-to-floor height between the first floor and the mezzanine is The hotel owner has asked for a distinctive stair that will set the tone for this up-scale establishment. PART A - Plan and design a distinctive stair in the designated area. Draw a plan and one or two ¼ or 3/8 = 1-0 PART B - Complete the design of this stair with the necessary details of riser and tread construction and railing, as well as a schematic lighting design solution and the selection of all materials. Draw a detailed section of the ¾ or 1 = 1-0. Draw a detailed section of the ¾ or 1 =1-0. Draw railing 1 ½ =

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