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EDT 300 - Sill and Floor Construction1 Weekend Cabin Retreat Project Sill and Floor Construction Sacramento City College EDT 300 Kenneth Fitzpatrick, P.E.

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2EDT 300 - Sill and Floor Construction Objectives u Recognize platform and balloon framing. u Plan the appropriate floor support using joists or trusses for a structure. u Determine proper joist sizes using a typical span data chart. u Describe the components of a floor system.

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3EDT 300 - Sill and Floor Construction Objectives u Demonstrate an understanding of the principles involved in post and beam construction.

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4EDT 300 - Sill and Floor Construction Types of Framing u Methods of floor framing vary from one section of the country to another. u Builders in a given area may use different methods, based on personal preference and experience. u The basic types of floor framing are platform and balloon framing.

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5EDT 300 - Sill and Floor Construction Platform Framing u Platform framing is popular for several reasons. u It can be used for both one- and two-story structures and is easy and fast to construct. u Shrinkage is uniform throughout the structure. A firestop is automatically provided. u Construction is safe because the work is performed on solid surfaces.

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6EDT 300 - Sill and Floor Construction Platform Framing u In platform framing, the sill is the starting point in constructing a floor. u A sill is the lowest member of the frame of a structure, u Rests on the foundation u supports the floor joists or the uprights (studs) of the wall. u The sill in most residential construction is a 2 x 6. u (actual dimensions 1 1/2" x 5 1/2").

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7EDT 300 - Sill and Floor Construction Platform Framing u Platform framing utilizes a method - of sill construction known as box sill construction. u The box sill consists of a 2 x 6 plate (also called a sill or mudsill) and a header that is the same size as the floor joists.

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8EDT 300 - Sill and Floor Construction

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10EDT 300 - Sill and Floor Construction

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11EDT 300 - Sill and Floor Construction

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12EDT 300 - Sill and Floor Construction

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14EDT 300 - Sill and Floor Construction Balloon Framing u Balloon framing was once used extensively, but in recent years has diminished in importance. u Its distinguishing feature is that the wall studs rest directly on the sill plate.

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15EDT 300 - Sill and Floor Construction Balloon Framing u Two types of sill construction are used: u The solid or standard sill. u The T-sill. u The studs are nailed directly to the sill and joists in solid sill construction. u No header is used. u Joists are supported by a ribbon and nailed to the studs on the second floor level.

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16EDT 300 - Sill and Floor Construction Balloon Framing u A firestop must be provided between the studs.

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17EDT 300 - Sill and Floor Construction Balloon Framing u In T-sill construction, a header is used, which also serves as a firestop. u The studs u Rest on the wall plate. u Are nailed to the header as well as the sill plate. u The sill may be very wide, to provide a good base for the joists to rest on. u Solid sill is used more extensively in two story homes.

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18EDT 300 - Sill and Floor Construction Balloon Framing Advantages u Small potential shrinkage. u Vertical Stability. u Can be used for two-story homes with brick veneer or stucco exterior wall finishes.

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19EDT 300 - Sill and Floor Construction Balloon Framing Disadvantages u A “less than desirable” surface to work on during construction. u Firestop blocks must be used.

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20EDT 300 - Sill and Floor Construction

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21EDT 300 - Sill and Floor Construction

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22EDT 300 - Sill and Floor Construction Joist and Beams u Joists provide support for the floor. u Usually made from a common soft wood such as u southern yellow pine u fir u larch u hemlock or spruce. u The size of floor joists ranges from a nominal size of 2 x 6 to 2 x 12. u Spacing from 12" to 24".

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23EDT 300 - Sill and Floor Construction Joist and Beams u The size joist required for a given situation will depend on the u length of space u load to be supported u specie and grade of wood u and distance the joists are spaced apart. u Spacing of floor joists may be 12, 16, or 24" o.c. (on center). u A spacing of 16" o.c. is most common.

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24EDT 300 - Sill and Floor Construction Joist and Beams u Span data for floor joists is presented in tables. u The span data presented assumes a maximum deflection of 1/360th of the span with a normal live load. u This is the amount which most codes require. u The normal live load is 40 pounds per square foot.

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25EDT 300 - Sill and Floor Construction Floor Systems u A floor system may also be constructed using girders or trusses u usually 4 x 6, 4 x 8, or 4 x 10 depending on the span) in the place of floor joists. u The purpose of this approach is to use fewer support members (joists). u The typical spacing of girders or trusses in this system is 48" o.c. with 1 1/8" thick tongue-and-groove plywood as the floor decking.

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26EDT 300 - Sill and Floor Construction Floor Systems u The distance which joists must span is usually so great that a beam or load-bearing wall is needed to reduce the span. u The beam may be u a solid timber u a built-up beam from dimension lumber u a metal S-beam. u Load-bearing walls may be concrete block, cast concrete, or frame construction.

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27EDT 300 - Sill and Floor Construction Floor Systems

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28EDT 300 - Sill and Floor Construction Floor Systems

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29EDT 300 - Sill and Floor Construction Floor Systems

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30EDT 300 - Sill and Floor Construction Floor Systems u Partition walls that are supported by the floor joists require added support. u It is good practice to double the joists under parallel partition walls. u If space between the joists is used as a cold air duct, solid blocking is used between the joists.

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31EDT 300 - Sill and Floor Construction Floor Systems u Openings in the floor for stairs and chimneys require double joist framing.

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32EDT 300 - Sill and Floor Construction Floor Systems

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33EDT 300 - Sill and Floor Construction Floor Systems u Cross bridging is commonly used to stiffen the floor and spread the load over a broader area. u Bridging boards are ordinarily 1 " x 3" in size with the ends cut at an angle so they fit snugly against the joist. u They are nailed securely in place midway between the beam and wall. u Metal bridging is also available.

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34EDT 300 - Sill and Floor Construction Floor Systems

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35EDT 300 - Sill and Floor Construction Floor Systems

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36EDT 300 - Sill and Floor Construction Floor Trusses u Engineered wood floor trusses for light-frame construction are widely used for residential structures. u minimum of depth u lightweight assembly u easy to handle. u The open web construction reduces transmission of sound through floor/ceiling assemblies. u Makes installation of plumbing, heating, and electrical systems easy.

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37EDT 300 - Sill and Floor Construction Floor Trusses

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38EDT 300 - Sill and Floor Construction Floor Trusses u Computers are used to design modern engineered floor trusses to assure load capabilities for a given design. u Each truss has a built-in camber so that the floor/ceiling will be level once a load is applied. u Stress-graded lumber is used in their construction so that a minimum amount of material is required.

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39EDT 300 - Sill and Floor Construction Floor Trusses u Some trusses are fabricated with lumber chords and patented galvanized steel webs, instead of the typical wood webs. u The webs have metal teeth which are pressed into the sides of the chords. u A reinforcing rib withstands both tension and compression forces. u Engineered wood floor trusses are usually fabricated from 2 x 4 or 2 x 6 lumber and generally spaced 24" o.c.

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40EDT 300 - Sill and Floor Construction Floor Trusses

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41EDT 300 - Sill and Floor Construction Subfloor u Plywood, tongue-and-groove boards, common boards, and other panel products are used for subfloors. u Plywood is advantageous. u large size of plywood u short time required to nail the sheets in place

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42EDT 300 - Sill and Floor Construction Other Subfloor Materials u One-half inch thick plywood u Composite board u Waferboard u Oriented strand broad u Structural particleboard, u These be used when joists are spaced 16" o.c. u Some builders prefer 5/8 in. stock.

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43EDT 300 - Sill and Floor Construction Other Subfloor Materials u When these products are used, the joist spacing must be is very accurate. u All edges of the panels must be supported.

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44EDT 300 - Sill and Floor Construction Other Subfloor Materials

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45EDT 300 - Sill and Floor Construction Subfloor Materials u Some localities combine the subfloor and underlayment (usually 5/8"particleboard) into a single thickness that is generally 1 1/8" thick. u The sheets have tongue-and-groove edges and require no blocking between the joists. u A single thickness sheet of 3/4" tongue-and-groove plywood may also be used for some applications.

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46EDT 300 - Sill and Floor Construction Subfloor Materials u Plywood should be installed with the grain direction of the outer plies at right angles to the joists. u It is stronger when positioned in this manner. u Panel products should also be staggered so that end joints in adjacent panels break at different joists. u A slight space must be allowed between sheets for expansion.

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47EDT 300 - Sill and Floor Construction Subfloor Materials

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48EDT 300 - Sill and Floor Construction Subfloor Materials u Subfloor panels may also be glued and nailed to the joists. u Structural tests have shown that stiffness is increased by 25 percent with 2 x 6 joists and 5/8" plywood. u Gluing advantage u squeak-free structure u eliminates nail-popping u reduces labor costs.

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49EDT 300 - Sill and Floor Construction Cantilevered Joists u Home designs where a section of the floor projects beyond a lower level are called cantilevered joists. u These joists are parallel to the overhanging area

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50EDT 300 - Sill and Floor Construction Cantilevered Joists u Rule of thumb for necessary length of cantilevered joists: u Extend the joists inside at least twice the distance they overhang outside. u If the inside distance is too short the floor may sag along the outside wall. u If a ledger strip is used, locate it along the top of the inside double header joist since the force will be up rather than down.

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51EDT 300 - Sill and Floor Construction Cantilevered Joists

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52EDT 300 - Sill and Floor Construction Framing Under Slate or Tile u Areas which have ceramic tile, slate, or stone floors require a substantial base. u If a concrete base is provided, the floor framing must be lowered to provide for the concrete.

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53EDT 300 - Sill and Floor Construction Framing Under Slate or Tile u Several techniques are used: u A smaller size joist may be used and the space between joists reduced to provide adequate support. u This is a common solution to the problem. u Another technique is to use one or more beams under the section to support the added weight. u The dead weight may be as much as 40 or 50 pounds per square foot in a bathroom with a tile floor and heavy fixtures.

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54EDT 300 - Sill and Floor Construction Framing Under Slate or Tile

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55EDT 300 - Sill and Floor Construction Framing Under Slate or Tile u The concrete base for the tile or stone should be u reinforced with wire mesh u cast on a plywood subfloor covered with building paper. u A special type of concrete is generally used. a mixture of 1 part portland cement and 6 parts sand, known as a cement mortar mix.

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56EDT 300 - Sill and Floor Construction Post and Beam Construction u Large framing members (posts, beams, planks) are spaced farther apart than conventional framing members

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57EDT 300 - Sill and Floor Construction Post and Beam Construction

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58EDT 300 - Sill and Floor Construction Post and Beam Construction u Post and beam construction provides a greater freedom of design than conventional framing techniques. u The system is basically simple, but presents problems related to u larger structural sizes u framing connectors u methods of joinery.

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59EDT 300 - Sill and Floor Construction Post and Beam Construction

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60EDT 300 - Sill and Floor Construction Post and Beam Construction u Most of the weight is carried by the posts. u The walls are called curtain walls. u Curtain walls provide for wide expanses of glass without the need for headers.

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61EDT 300 - Sill and Floor Construction Post and Beam Construction

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62EDT 300 - Sill and Floor Construction Post and Beam Construction u Wide overhangs are also possible by extending the large beams to the desired length. u Spacing of the posts is determined by the design of the building and the load to be supported.

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63EDT 300 - Sill and Floor Construction Post and Beam Construction u The foundation for a post and beam structure may be u a continuous wall u a series of piers where each post is to be located. u Size of footings will be determined by u the weight to be supported u soil bearing capacity u local building codes.

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64EDT 300 - Sill and Floor Construction Post and Beam Construction u The size of posts required will be at least 4" x 4". u If the floor is also to be supported by the posts, they should be at least 6" x 6". u Vertical height of the posts will be a factor in determining the size. u Again check local codes.

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65EDT 300 - Sill and Floor Construction Post and Beam Construction u Beams may be solid, laminated, reinforced with steel, or plywood box beams. u Spacing and span of the beams will be determined by the size and kind of materials and load to be supported. u In most normal situations, a span of 7'-O" may be used when 2" thick tongue-and-groove subfloor or roof decking is applied to the beams.

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66EDT 300 - Sill and Floor Construction Post and Beam Construction

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67EDT 300 - Sill and Floor Construction Post and Beam Construction

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68EDT 300 - Sill and Floor Construction Post and Beam Construction

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69EDT 300 - Sill and Floor Construction Post and Beam Construction u Thicker beams must be used if a span greater than 7'-O" is required. u Two systems of beam placement are possible with post and beam construction.

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70EDT 300 - Sill and Floor Construction Post and Beam Construction u First system: the longitudinal method. u Beams are placed at right angles to the roof slope. u Roof decking is laid, therefore from the ridge pole to the eaves line.

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71EDT 300 - Sill and Floor Construction Post and Beam Construction u Second system: the transverse method. u The beams follow the roof slope and decking runs parallel to the roof ridge. u A post and beam structure has a limited number of joints. u Fastening small members by nailing does not provide a satisfactory connection.

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72EDT 300 - Sill and Floor Construction Post and Beam Construction u Metal plates or connectors are used. u These are fastened with lag screws or bolts. u Decking planks for the roof and floor range in thickness from 2 to 4 inches. u The planks are usually tongue-and- grooved along the edges and they may be tongue-and-grooved on the ends as well.

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73EDT 300 - Sill and Floor Construction Post and Beam Construction u It is customary to leave the underside of the planked roof exposed. u If added insulation is required, it may be placed above the decking and under the roofing material. u Rigid type insulation should be used.

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74EDT 300 - Sill and Floor Construction Post and Beam Construction

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75EDT 300 - Sill and Floor Construction Post and Beam Construction

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