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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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Presentation on theme: "EDT 300 - Sill and Floor Construction1 Weekend Cabin Retreat Project Sill and Floor Construction Sacramento City College EDT 300 Kenneth Fitzpatrick, P.E."— Presentation transcript:

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

2 2EDT 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.

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

4 4EDT 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.

5 5EDT 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.

6 6EDT 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").

7 7EDT 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.

8 8EDT Sill and Floor Construction

9 9

10 10EDT Sill and Floor Construction

11 11EDT Sill and Floor Construction

12 12EDT Sill and Floor Construction

13 13EDT Sill and Floor Construction

14 14EDT 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.

15 15EDT 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.

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

17 17EDT 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.

18 18EDT 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.

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

20 20EDT Sill and Floor Construction

21 21EDT Sill and Floor Construction

22 22EDT 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".

23 23EDT 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.

24 24EDT 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.

25 25EDT 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.

26 26EDT 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.

27 27EDT Sill and Floor Construction Floor Systems

28 28EDT Sill and Floor Construction Floor Systems

29 29EDT Sill and Floor Construction Floor Systems

30 30EDT 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.

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

32 32EDT Sill and Floor Construction Floor Systems

33 33EDT 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.

34 34EDT Sill and Floor Construction Floor Systems

35 35EDT Sill and Floor Construction Floor Systems

36 36EDT 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.

37 37EDT Sill and Floor Construction Floor Trusses

38 38EDT 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.

39 39EDT 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.

40 40EDT Sill and Floor Construction Floor Trusses

41 41EDT 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

42 42EDT 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.

43 43EDT 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.

44 44EDT Sill and Floor Construction Other Subfloor Materials

45 45EDT 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.

46 46EDT 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.

47 47EDT Sill and Floor Construction Subfloor Materials

48 48EDT 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.

49 49EDT 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

50 50EDT 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.

51 51EDT Sill and Floor Construction Cantilevered Joists

52 52EDT 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.

53 53EDT 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.

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

55 55EDT 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.

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

57 57EDT Sill and Floor Construction Post and Beam Construction

58 58EDT 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.

59 59EDT Sill and Floor Construction Post and Beam Construction

60 60EDT 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.

61 61EDT Sill and Floor Construction Post and Beam Construction

62 62EDT 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.

63 63EDT 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.

64 64EDT 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.

65 65EDT 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.

66 66EDT Sill and Floor Construction Post and Beam Construction

67 67EDT Sill and Floor Construction Post and Beam Construction

68 68EDT Sill and Floor Construction Post and Beam Construction

69 69EDT 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.

70 70EDT 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.

71 71EDT 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.

72 72EDT 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.

73 73EDT 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.

74 74EDT Sill and Floor Construction Post and Beam Construction

75 75EDT Sill and Floor Construction Post and Beam Construction


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