Floor System Sizes and Materials

Lumber sizes

Common lengths8’, 10’, 12’, 14’, 16’

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

Joists

Provide support for floor Wood or steel

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

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

Joists

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

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

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

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

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

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

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

Girders (Beams)

Built-up 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

Girders (Beams)

Glulam (cont’d) Disadvantages

Weight Expense

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

Girders (Beams)

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

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

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

Subflooring

Materials Tongue and Groove Plywood 4’x 8’

sheets speed the installation, glued and screwed.

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