1. PowerPoint Presentation
Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois 1

2. Sill and Floor Construction
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 Joists provide 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 beam or 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 Beams26

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 subfloor is 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 Products36
(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: Disadvantages 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

51. Oriented Strand Board
OSB is made in panel sizes similar to plywood, typically 4' x 8'.
Available in sizes up to 8' x 24'.
Allow 1/8" space along edges to prevent buckling problems.
Use the same nailing schedules that apply to plywood. 51

52. Parallel Strand Lumber
Parallel strand lumber (PSL) is made from thin strands of wood.
Fairly new category of EWP.
Used for beams, columns, and headers.
High strength and span capacity.
Low-moisture content eliminates shrinking and checking.
Large billets 12" wide by 17" deep are formed and then sawn to specific sizes. 52

53. Parallel Strand Lumber53
(Alpine Structures)

54. Parallel Strand Lumber
Advantages of PSL:
Very strong.
Allows long spans and more design flexibility.
Disadvantages of PSL:
Engineered connections are required for side-loading joists on one side.
Should not be drilled or notched.
Storage conditions should prevent swelling. 54

55. Parallel Strand Lumber
Widths available from 1-3/4" to 7".
Two plies of 2-11/16" members will match a typical 5-1/2" wall.
Lengths up to 66' available.
Eliminates the need for built-up beams. 55
(Alpine Structures)

56. Laminated Veneer Lumber
Laminated veneer lumber (LVL) is made from veneers stacked parallel to each other.
LVL is used for headers, beams, joists, columns, and flanges for wood I-beams.
Similar to plywood, but all plies are parallel to provide maximum strength.
Southern yellow pine and Douglas fir are generally the woods of choice. 56

57. Laminated Veneer Lumber
LVL is produced in a continuous billet up to 1-3/4" thick and 4' wide and two or more billets can be glued together to form thicker pieces. 57
(Trus Joist)

58. Laminated Veneer Lumber
Advantages of LVL:
High strength allows long spans.
Can be built-up on site to form larger members.
Disadvantages of LVL:
More expensive than solid lumber.
Lower moisture content than solid lumber.
Must be sized for specific load conditions. 58

59. Laminated Veneer Lumber
The 1-3/4" thick billet is most common.
Can be used individually for joists or combined to form headers or beams.
Available in depths from 5-1/2" to 14" and lengths up to 66'.
LVL generally should not be mixed with solid lumber in the same floor assembly.
LVL beams should not be drilled . 59

60. Glue-Laminated Lumber
Glue-laminated members (glulam beams) consist of 1x or 2x lumber glued into desired shapes.
Glue-laminated beams, columns, and arches were the first engineered wood products.
Virtually any length or depth can be produced. 60

61. Glue-Laminated Lumber
This construction makes extensive use of glue-laminated beams. 61

62. Glue-Laminated Lumber
Glue-laminated beams are accepted by all three US model building codes.
Three appearance grades are available.
Industrial grade: The least attractive containing visible glue stains, press marks, and knot holes.
Architectural grade: Sanded on four sides with knot holes filled with putty.
Premium grade: All checks and holes filled. 62

63. Glue-Laminated Lumber
Advantages of glulams:
High strength.
Available either straight or cambered.
Dimensionally stable and attractive.
Disadvantages of glulams:
Cost is high.
Requires special handling and storage.
Requires special equipment to handle. 63

64. Glue-Laminated Lumber
Installation
Technical support is generally required.
Producers provide span charts, installation details, technical assistance.
Special connectors are required for these large members and heavy loads.
Special handling is required to reduce checking and preserve the finish. 64

65. Wood I-Beams or Joists
Wood I-beams or joists are generally made from 2" x 4" machined-stressed lumber or LVL.
Webs are usually made from 3/8" OSB.
They are available in flange widths of 1-3/4" and 2-5/16" and depths from 9-1/2" to 20" and lengths up to 66'.
Presently, each manufacturer uses their own proprietary process. 65

66. Wood I-Beams or Joists 66
(Boise Cascade Corporation)

67. Wood I-Beams or Joists Advantages of wood I-beams:
Speed of construction.
Have knockout holes for plumbing and electrical cable.
Dimensionally stable and very straight.
Disadvantages of wood I-beams:
Require more effort to cut.
Not universally accepted.
More expensive than lumber or trusses. 67

68. Wood I-Beams or Joists
Installation of wood I-beams are similar to traditional floor joists or rafters.
Typical nails, tools, and metal connectors can be used.
Should not be mixed with solid lumber in the same assembly.
Web stiffeners or blocks are normally used at bearing points. 68

69. Wood I-Beams or Joists
Several types of engineered lumber are used in this dwelling. 69
(Boise Cascade Corporation)

70. Post and Beam Construction
Post and beam construction provides greater freedom of design.
The system uses larger structural sizes, framing connectors, and unique joining methods.
Posts carry most of the weight
The walls are usually curtain walls.
Curtain walls provide for wide expanses of glass without the need for headers. 70

71. Post and Beam Construction71

72. Post and Beam Construction72
(The Engineered Wood Association)

73. Post and Beam Construction
Curtain wall example. 73
(Pozzi Wood Windows)

74. Post and Beam Construction
Foundation for a post and beam structure may be continuous or isolated footings on which each post is located.
Posts should be at least 4" x 4" or 6" x 6" if they support the floor.
Beams should be solid, laminated, reinforced with steel, or plywood box beams. 74

75. Post and Beam Construction
A variety of beams used in post and beam construction. 75

76. Post and Beam Construction
The spacing and span of the beams will be determined by the size and type of materials and the load to be supported.
Generally, a span of 7'-0" may be used when 2" thick tongue-and-groove decking is applied.
Thicker beams should be used if the span exceeds 7'-0".
Span tables are provided in the text. 76

77. Post and Beam Construction
There are two systems of roof beam placement:
Longitudinal method: Beams are placed at right angles to the roof slope; roof decking is laid from the ridge to the eaves.
Transverse method: Beams follow the roof slope; decking runs parallel to the roof ridge. 77

78. Post and Beam Construction
The longitudinal method. 78

79. Post and Beam Construction
The transverse method. 79

80. Post and Beam Construction
Metal connectors. 80

81. Post and Beam Construction
Installation
Nailing does not provide a satisfactory connection in post and beam construction; lag bolts are used.
Metal plates or connectors are used to attach post and beam segments.
Decking planks range in thickness from 2" to 4" and are usually tongue-and-grooved along the long edges. 81

82. Post and Beam Construction
Several plank designs used in post and beam construction. 82