1. Structural Components
Chapter 26
Structural Components

2. Links for Chapter 26 Floor Construction Wall Construction
Roof Construction
Environmental Design
Related Web Sites

3. Conventional Floor Framing
Floor joists range from 2” X 6” to 2” X 14” and spaced at 12”, 16”, or 24”
Mudsill rests on the masonry foundation
Provides a base for all framing
Attached to foundation with anchor bolts
Either 3/4” or 5/8” in diameter

4. Conventional Floor Framing

5. Conventional Floor Framing
Girder (beam) is used to support the floor
A flitch beam consists of steel plates bolted between wood members
Glu-lam beams are laminated with sawn lumber and more structurally stable
Engineered wood girders consists of laminated veneer strips glued together

6. Conventional Floor Framing
Girder (beam) is used to support the floor
Steel beams are used for long spans and do not shrink or expand
A post is used to support beams and are ” X 4” or 6” X 6” depending on beam width
Steel posts do not draw moisture and remain a more true size

7. Conventional Floor Framing

8. Conventional Floor Framing
Joists support the subfloor
Joists that span past a girder are cantilevered
Joists shaped as an “I” are called trusses
Laminated veneer lumber is used for heavy loads with single or multi-spans
Engineered joists support larger loads with less material

9. Conventional Floor Framing

10. Engineered Floor System

11. Floor Bracing Joists will tend to roll as loads are applied
Blocking is used at the center of the joist span to help transfer lateral loads
Sheathing is placed over the joists to form the subfloor
Face grain should be perpendicular to the floor joists

12. Floor Bracing

13. Post-and-Beam Construction
Girders are supported on a post and concrete pier
Usually 4” X 6”
Spaced at 48” o.c.
Flooring is 2 X 6 or 2 X 8 tongue and groove boards or 1 3/32” plywood

14. Post-and-Beam Construction

15. Framed Wall Construction
Bearing walls support the weight of the roof or other floors
Extra support is required under it
Nonbearing walls have no structural purposes
Sometimes called partitions
Can be removed without causing damage

16. Framed Wall Construction

17. Framed Wall Construction
Sole plate is the bottom plate and disperses the wall load to the floor system
Studs are vertical framing members to transfer load from top of wall to floor system
Top plates are used to hold the wall together
Two are required on bearing walls and must lap by at least 48”

18. Framed Wall Construction
Sheathing is used as an insulator against weather
Double-wall construction is when sheathing is applied to an exterior wall
Single-wall construction is when a vapor barrier and no sheathing is used on an outside wall

19. Framed Wall Construction
Sheathing helps walls not to twist or rack
Shear panel resists these forces
Let-in braces stiffen stud walls

20. Framed Wall Construction
Header is an opening above a door or window
Trimmers support headers
Subsill is on the bottom of a window

21. Roof Construction Eave on the roof extends beyond the walls
Cornice is the covering on the eaves
Fascia is trim placed at the end of the rafters
Roof sheathing covers structural members
Skip sheathing is used with either tile or shakes

22. Roof Construction

23. Roof Construction Finished roofing is the weather protection system
Pitch describes the slope of the roof
Rise is the vertical distance of the slope
Run is the horizontal distance of the slope
Span is the horizontal measurement between inside edges of supporting walls

24. Roof Construction

25. Roof Construction
Conventional framing involves the use of wood members placed in a repetitive fashion
Ridge board is the horizontal member at the ridge and runs perpendicular to the rafters
Rafters are the sloping members used to support roof sheathing and finished roofing

26. Roof Construction

27. Roof Construction
Common rafter spans and supports the roof loads from ridge to top plate
Bird’s mouth is the notch cut in rafter where the rafter intersects a beam or bearing wall
Hip rafter is used on the slopes of the hip
Valley rafter is used on the slopes of the valley

28. Roof Construction

29. Roof Construction
Ceiling joists span between top plates and bearing walls
Ridge braces are used to support downward action of the ridge board
Ridge beam supports the upper end of the rafter/ceiling joists

30. Roof Construction

31. Truss Roof Construction
Truss is a component used to span large distances without intermediate supports
Top chord supports the roof sheathing
Bottom chord resists outward thrust of the top chord and supports
Webs span between top and bottom chords
Ridge blocks provide nailing surface for roof sheathing

32. Truss Roof Construction

33. Truss Roof Construction
Cantilevered truss is when the truss extends beyond the support
Hip truss is used to form hip roofs
Vaulted or scissors truss have inclined bottom chords
Metal hangers keep floor, ceiling, and roof members from separating

34. Truss Roof Construction

35. Truss Roof Construction

36. Environmental Design
It is important to be familiar with chemicals that are commonly found in the home
Formaldehyde is a colorless gas found in most resin-based construction products
It can cause irritation to nose, throat, and eyes and cause headaches, coughing, and fatigue

37. Environmental Design
Optional material can be used that does not contain harmful chemicals
Grass-based boards can be used for sheathing
Low-toxic products that repel moisture
All natural carpets reduce allergy reactions

38. Environmental Design
Gas and oil heaters are more efficient, they do produce toxic chemicals and reduce the quantity of natural resources
Electric heaters are nontoxic yet are more expensive and less efficient

39. Related Web Sites
American Lumber Standards Commission, Inc. -
Gypsum Association -
The Masonry Society -
Wood Truss Council of America-