1. Floor System Sizes and Materials

2. Lumber sizes
Common lengths
8’, 10’, 12’, 14’, 16’

3. Sill
Structurally graded according to knots (size, tightness, placement), wane, and straightness
Must be pressure-treated lumber
Used as a transition between masonry and standard lumber
Anchor bolts embedded into masonry are commonly used to tie the sill to the foundation
Nails can be shot into concrete with a low-caliber nail gun

4. Joists
Provide support for floor
Wood or steel

5. Joists Size of wood joists depends upon Species of lumber Wood grade
Spacing
12”, 16”, or 24” O.C. spacing is most common
Works with the 48” module common to plywood and OSB

6. Joists Recommended live load (40psf)
Distance between supports (clear span)
Joists manufacturer’s charts

7. Joists
Double joists must be provided under walls running parallel to the joist direction
May be solid or built up of two joists

8. Joists Bridging May be used between joists
Transfers the floor loads to adjacent joists
Stiffens joists
Aligns joists vertically
May be diagonal wood members, metal or 1x3 wood cross bridging
May be solid blocking placed perpendicular between joists

9. Wood Floor Trusses
May be used in place of solid lumber joists to provide support for the floor
Able to span longer distances than solid lumber joists
Reduce or eliminate the need for girders, piers, and columns
Allow for designing open spaces
Formed with top and bottom horizontal chords and diagonal webs constructed of standard size lumbers

10. Wood Floor Trusses Typically placed 24” O.C. Open web construction
Reduces sound transmission through floors
Aids in ease of plumbing, electrical, and heating systems installation
Sizes are determined from manufacturers’ charts

11. Wooden I-Joists Similar to wood floor trusses
May be used in place of solid lumber joists to provide support for the floor
I-joists are able to span longer distances than solid lumber joists
Speed construction
Very straight
May come with circular knock-outs

12. Wooden I-Joists
Formed with horizontal wooden (solid lumber or micro lam) top and bottom flanges, grooved to receive a solid plywood or OSB vertical web

13. Joist Header Used as rim joists with I-joist construction
Can be used with truss construction
Should be strapped to the sill in high wind areas
Double under exterior walls parallel to joist direction

14. Girders (Beams) Built-up Glue laminated lumber (glulam)
Formed with solid lumber nailed together
Built on the job
Glue laminated lumber (glulam)
Solid, 1x__ lumber, glued together under pressure
Graded according to appearance
Very strong
Able to span long distances

15. Girders (Beams)
Glulam (cont’d)
Disadvantages
Weight
Expense

16. Girders (Beams) LVL (Laminated Veneer Lumber)
Glued veneers, similar to plywood
Advantages
High strength
Long spans
Disadvantages
Cost
Low moisture resistance causes delamination in high humidity

17. Girders (Beams) PSL (Parallel Strand Lumber)
Composed of veneers cut into strands
Very strong
Allows long spans

18. Girders (Beams) Girder size Determined by
Type of material used
Loads imposed
Clear span of the girder
Where loads exceed material limits, the girder span must be reduced by using piers, piles, columns, or posts

19. Subflooring
Provides a base for the underlayment and/or finish flooring material
Underlayment is material placed under finish floor coverings (i.e. as carpet, to provide a smooth, clean surface)
Underlayment can be combined with the subfloor into a single thickness
Single thickness underlayment/subfloor is generally constructed of ¾” tongue and groove plywood

20. Subflooring Materials
Tongue and Groove Plywood 4’x 8’ sheets speed the installation, glued and screwed.

21. Crawl Space Considerations
Access door is required
Recommended size 24” wide x 18” high
Large enough to allow for repair and/or replacement of under-house mechanical systems
Ventilation provided
Removes moisture from crawl space
8”x 16” vents are common