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1. PowerPointPresentation PublisherThe Goodheart-Willcox Co., Inc.Tinley Park, Illinois 1

2. Chapter 13 Sill and Floor Construction 2

3. Introduction • Framing methods vary from one section of the country to another. • Personal preference and experience are also factors. • Two basic types of floor framing are: • Platform framing. • Balloon framing. 3

4. Introduction • Typical floor framing structural components include: • Plates. • Joists. • Studs. • Post and beam construction is also used for walls and floors. 4

5. Platform Framing • In platform framing, floor joists form a platform on which the walls rest. • Another platform rests on top of the walls when there is a second story. • Platform framing is used more extensively than balloon framing. • The platform automatically provides a fire-stop between floors. 5

6. Platform Framing • Construction is safe because work is performed on a solid surface. • The sill is the starting point in constructing a floor. • Rests on the foundation and supports the floor joists or the studs. • Generally 2" x 6" lumber. • Box sill construction is generally used, which consists of a 2" x 6" plate called a mudsill. 6

7. Platform Framing • Box sill construction. 7

8. Platform Framing • Detail of the first and second floor. • Using box sill construction. 8

9. Sealing the Sill • A seal is required between the foundation and sill plate. • The seal prevents outside air from entering the house. 9

10. Balloon Framing • Balloon framing has diminished in importance in recent years. • Distinguishing features include: • Wall studs rest directly on the sill plate. • Each floor “hangs” from the studs. • Two advantages of balloon framing are: • Small potential shrinkage. • Good vertical stability. 10

11. Balloon Framing • Disadvantages of balloon framing are: • Less than desirable surface on which to work during construction. • The need to add fire-stops. • Two types of sill construction are used: • Solid (standard). • T-sill. 11

12. Balloon Framing Sill Construction • Solid (standard) sill. • Studs are nailed directly to the sill and joists. • No header is used. 12

13. Balloon Framing Sill Construction • T-sill construction. • Header rests on the sill and serves as a fire-stop. • Studs rests on the sill and are nailed to the header as well as the 8" or 10" wide sill plate. 13

14. Balloon Framing for Second Floor • Joists are supported by a ribbon and nailed to the studs on the second floor level. 14

15. Joists and Beams • Joistsprovide support for the floor. • Usually made from a common softwood. • Southern yellow pine, fir, larch, hemlock, or spruce. • Engineered wood and metal joists are also available. • Floor joists range in size from 2" x 6" to 2" x 12". 15

16. Joists and Beams • Standard lumber sizes. 16 (National Forest Products Association)

17. Joists and Beams(Joists) • Size of joist required depends on the span, load, species and grade of wood, and joist spacing. • When using metal joists, the gauge of metal should be considered instead of species and grade of lumber. • Floor joists may be spaced 12", 16", or 24" on center. 17

18. Procedure for Using Span Data Chart • Select species of wood to be used. • Select appropriate live load. • Determine lumber grade to be used. • Scan the lumber grade row and note the maximum spans. • Select the joist size and spacing that will support the desired live load; 16" OC spacing is typical. 18

19. Floor Joist Span Data 19

20. Floor Joist Span Data 20

21. Floor Joist Span Data 21

22. Span Data Example • Span is 14'-0" and number one dense southern pine is to be used. • Live load is 30 pounds per square foot. • Chart shows the following choices. • 2" x 8" joists 12" OC or 16" OC. • 2" x 10" joists 12" OC, 16" OC, or 24" OC. • 2" x 12" joists 12" OC, 16" OC, or 24" OC. • Best selection is 2" x 8" joists, 16" OC. This will span up to 14'-5". 22

23. Steel Floor Joists • Steel floor joists are beginning to be accepted for residential construction. • Joist depths ranging from 6" to 12" with thicknesses from 0.034" to 0.101" are generally used. • Usual spacing is 24" OC, but other spacing is also used. 23

24. Steel Framing Detail • Typical steel framing where floor joists bear on the foundation. 24

25. Joists and Beams(Beams) • When the span is too great for unsupported joists, a beamor load-bearing wall is needed to reduce the span. • A beam may be a solid timber, built-up beam, or a metal S- or W-beam. • Load-bearing walls may be concrete block, cast concrete, or frame construction. 25

26. Methods of Supporting Floor Joists with Beams 26

27. Supporting Partition Walls • Partition walls that run parallel to the floor joists require added support. 27

28. Openings in the Floor • Openings in the floor for stairs and chimneys required double joist framing. 28

29. Cross Bridging • Cross bridging is used to stiffen the floor and spread the load over a broader area. • Bridging boards or metal bridging are used. 29

30. Metal Bridging 30

31. Floor Trusses • A truss is a rigid framework designed to support a load over a span. • Floor trusses are often used in place of floor joists in residential construction. • Floor trusses consist of a top chord, bottom chord, and web. • Chords are the horizontal flanges on the top and bottom of the truss. • The web is the truss framework. 31

32. Floor Trusses • Trusses provide clear spans with a minimum depth in a lightweight assembly. 32 (Trus Joist)

33. Engineered Floor Trusses • Engineered floor trusses are designed with the aid of computers. • Usually fabricated from 2" x 4" or 2" x 6" lumber and generally spaced 24" OC. • Each truss has a built-in camber. • Stress-graded lumber is used in their construction to reduce material. • Webs may be metal or wood. 33

34. Typical Truss Webs 34 (TrusWal Systems, Inc.)

35. Subfloor • The subflooris attached to the top of the floor joists and provides a work surface during construction. • Plywood, tongue-and-groove boards, common boards, and other panel products are used for subfloors. • Panel products reduce installation time. • 5/8" or 1/2" thick plywood is preferred. 35

36. Typical Panel Products 36 (Georgia-Pacific Corporation)

37. Installing Subfloor Panels • Joist spacing must be very accurate. • All panel edges must be supported. 37

38. Installing Subfloor Panels • Plywood grain direction of the outer plies should be at right angles to joists. • Panel products should be staggered so that end joints of adjacent panels are on different joists. • Panels may be glued as well as nailed to the joists to increase strength and reduce squeaking and nail pops. 38

39. Cantilevered Joists • Cantilevered joists are required when a section of the floor projects beyond a lower level. • When floor joists run perpendicular to the cantilevered section, longer joists form the cantilever. • When joists are parallel to the overhanging area, cantilevered joists are required. 39

40. Cantilevered Joists • Generally, joists should extend inside the structure twice the distance they overhang. 40

41. Framing Under Slate or Tile • Flooring materials such as ceramic tile, slate, or stone floors require a substantial base. • If a concrete base is provided, the floor framing must be lowered to provide for the concrete. • Dead weight may be as much as 50 pounds per square foot. 41

42. Framing Under Slate or Tile • A smaller size joist may be used and the space between joists reduced to provide adequate support. • Cement mortar mix is generally used for the base. 42

43. Engineered Wood Products • Engineered wood products (EWPs) combine wood veneers and fibers with adhesives to form beams, headers, joists, and panels. • EWPs have uniformly high quality and strength. • They increase the supply of usable wood from smaller and inferior trees. 43

44. Engineered Wood Products • The use of engineered wood products will continue to grow. • Advances in adhesive technology have made EWPs possible. • Phenol-formaldehyde and urea-formaldehyde are the most common types. • Phenolics are more expensive than urea resins. 44

45. Engineered Wood Products • Band boards are available in 9-1/4",11-1/4", 12", 14", and 16" depths. • Engineered headers are available in 1-1/4" depth and 3-1/2" width. 45 (Alpine Structures)

46. Engineered Wood Products • Advantages of EWPs: • High quality and consistency. • No knots, checks, or warps. • Uniformly dried to 8% to 12% moisture content. • Provides superior design flexibility. • Disadvantage of EWPs: • Lack of industry standards. 46

47. Engineered Wood Products • Application of EWPs. 47

48. Oriented Strand Board • Oriented strand board (OSB) is made from long strands of wood and resin. • First introduced in 1978 as a low-quality particle board panel. • Aspen is the preferred wood for making OSB. • Outer layers are oriented to the long dimension, others are perpendicular. 48

49. Oriented Strand Board 49 The Engineered Wood Association)

50. Oriented Strand Board • Advantages of OSB: • Less expensive than plywood. • Unique appearance can be appealing as a design element. • Disadvantages of OSB: • Subject to swelling. • Not designed for exposure to the elements. 50