Floor System Sizes and Materials Lumber sizes Common
Floor System Sizes and Materials
Lumber sizes Common lengths 8’, 10’, 12’, 14’, 16’
Sill n Structurally graded according to knots (size, tightness, placement), wane, and straightness n Must be pressure-treated lumber n Used as a transition between masonry and standard lumber n Anchor bolts embedded into masonry are commonly used to tie the sill to the foundation n Nails can be shot into concrete with a low-caliber nail gun
Joists n Provide support for floor n Wood or steel
Joists n Size of wood joists depends upon n Species of lumber n Wood grade n Spacing n 12”, 16”, or 24” O. C. spacing is most common n Works with the 48” module common to plywood and OSB
Joists n n n Recommended live load (40 psf) Distance between supports (clear span) Joists manufacturer’s charts
Joists n Double joists must be provided under walls running parallel to the joist direction May be solid or built up of two joists n
Joists n Bridging n n n May be used between joists Transfers the floor loads to adjacent joists Stiffens joists Aligns joists vertically May be diagonal wood members, metal or 1 x 3 wood cross bridging May be solid blocking placed perpendicular between joists
Wood Floor Trusses n May be used in place of solid lumber joists to provide support for the floor n Able to span longer distances than solid lumber joists n Reduce or eliminate the need for girders, piers, and columns n Allow for designing open spaces n Formed with top and bottom horizontal chords and diagonal webs constructed of standard size lumbers
Wood Floor Trusses n Typically placed 24” O. C. n Open web construction Reduces sound transmission through floors n Aids in ease of plumbing, electrical, and heating systems installation n Sizes are determined from manufacturers’ charts n
Wooden I-Joists n Similar to wood floor trusses n May be used in place of solid lumber joists to provide support for the floor n I-joists are able to span longer distances than solid lumber joists n Speed construction n Very straight n May come with circular knock-outs
Wooden I-Joists n 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 n Used as rim joists with I-joist construction n Can be used with truss construction n Should be strapped to the sill in high wind areas n Double under exterior walls parallel to joist direction
Girders (Beams) n Built-up n n Formed with solid lumber nailed together Built on the job n Glue laminated lumber (glulam) n n Solid, 1 x__ lumber, glued together under pressure Graded according to appearance Very strong Able to span long distances
Girders (Beams) n Glulam (cont’d) n Disadvantages n Weight n Expense
Girders (Beams) n LVL (Laminated Veneer Lumber) n Glued veneers, similar to plywood n Advantages n High strength n Long spans n Disadvantages n Cost n Low moisture resistance causes delamination in high humidity
Girders (Beams) n PSL (Parallel Strand Lumber) n Composed of veneers cut into strands n Very strong n Allows long spans
Girders (Beams) n Girder size n Determined by n Type of material used n Loads imposed n Clear span of the girder n Where loads exceed material limits, the girder span must be reduced by using piers, piles, columns, or posts
Subflooring n Provides a base for the underlayment and/or finish flooring material n n n 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 n Materials n Tongue and Groove Plywood 4’x 8’ sheets speed the installation, glued and screwed.
Crawl Space Considerations n Access door is required n Recommended size 24” wide x 18” high n Large enough to allow for repair and/or replacement of under-house mechanical systems n Ventilation provided n Removes moisture from crawl space n 8”x 16” vents are common
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