Term
Materials - Wood Softwoods |
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Definition
Key species: Douglas fir, West Coast Hemlock, Redwood, Pines, Cedars, Spruce Used as structural & framing lumber, sheathing, roofing, subflooring, exterior siding, flooring, trim, interior paneling
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Term
Materials - Woods Hardwoods |
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Definition
Key species: maple, oak, poplar, birch, beech, cherry, black walnut, basswood, hickory, gum, ash Lumber used for flooring, cabinets, furniture |
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Term
Materials - Wood Moisture Content |
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Definition
amount of water contained in wood (expressed as % relative to weight of oven-dried wood) unseasoned (green/fresh cut) = very high MC seasoning reduces MC significantly
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Term
Materials - Wood Moisture Content & Seasoning |
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Definition
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Term
Materials - Wood Air Drying |
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Definition
12-15% moisture content dried by exposure to air over period of several months usually used for dimension or lower grades of lumber complete air drying of larger, structural timbers usually impractical
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Term
Materials - Wood Kiln Drying |
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Definition
6 - 19% moisture content dried in kiln under controlled temp. to achieve desired MC hastens drying time and kills stain, decay fungi, insects used primarily for appearance grades or finished lumber where dimensional stability and appearance are important for hardwoods, air drying in yards often combined with kiln drying
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Term
Materials - Wood Equilibrium Moisture Content |
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Definition
Point of equilibrium between moisture in lumber and surrounding air To ensure wood will experience only minor dimensional changes during use, specification of lumber stock should be as close as possible to MC the lumber will reach in use Consider temp. & humidity of location Especially important for doors, etc. that require proper fit between wood elements
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Term
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Definition
Ability of wood to resist loading depends on strength, orientation in the structure, and cross-sectional dimension of the member |
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Term
Materials - Wood Tensile Strength |
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Definition
Ability to resist stretching or stresses imposed parallel to grain Reduced by knots, splits, checks, other defects Tensile strength of wood perpendicular to grain is very low and very high parallel to grain
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Term
Material - Wood Compressive Strength |
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Definition
ability to resist loads that are crushing to members cs parallel to grain 2-5x greater than cs perpendicular to grain important relative to vertical or horizontal load-bearing members
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Term
Materials - Wood Fiber Stress in Bending |
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Definition
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Term
Materials - Wood Modulus of Elasticity (E) |
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Definition
measure of stiffness ability of member to resist deflection ratio of the amount by which material will deflect in proportion to applied load used in load-bearing calculations to determine size of horizontal members
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Term
Materials - Wood Horizontal Shear Stress |
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Definition
ability of wood fibers at top half of bending member (in compression) to resist shearing horizontally from fibers in bottom half (in tension) horizontal shearing stresses largest at each end of a beam along the central (neutral) axis avoid installing bolts along this plane
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Term
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Definition
direction of fibers in lumber as consequence of natural growth or sawing close grain: tightly spaced annual growth rings with small pores coarse grain: widely spaced rings with large pores coarse-grained woods accept stains preservatives, paints, surface sealers better than close-grained woods cross grain: slope of grain defect from aberrant growth or improper sawing; weakens lumber straight grained lumber is strongest; fibers oriented parallel to longitudinal axis of the piece
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Term
Materials - Wood Insect & Decay Resistance |
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Definition
Termite-resistant species: redwood, bald cypress (tidewater red), Eastern red cedar, Fungi/decay-resistanc species: bald cypress (tidewater red), cedars, redwood, black locust, black walnut
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Term
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Definition
Fungi: molds, stain, dry rot, soft rot Most decay in wood occurs when moisture content >30% Fungal decay does not occur in permanently submerged water (fungi need oxygen) Pressure-treated wood should be used where a member will be embedded in moist ground
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Term
Materials - Wood Preservative Treatment |
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Definition
Three major classes: Water-borne Oil borne Creosote
American Wood Preservers Assoc (AWPA): standards and certifications |
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Term
Materials - Wood Water-Borne Preservatives |
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Definition
Used to pressure treat lumber leave wood clean, odorless, easy to paint present less environmental hazard than other preservatives
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Term
Materials - Wood Water-Borne Preservatives |
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Definition
ACA - ammoniacal copper arsenate: ok for ground or water contact CCA - chromated copper arsenate: ok for ground or water contact; limited marine application ACC - acid copper chromate: ok for ground or water contact, resistant to marine borer
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Term
Materials - Wood Oil-Borne Preservatives |
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Definition
Can be used any application except contact with salt water often prohibited for use where it will come in contact with people Penta designated toxic environ. hazard
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Term
Materials - Wood Creosote Preservative |
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Definition
used where protection against wood destroying orgs high priority, painting not req'd, and odor not a concern potential hazard for human exposure creosote-tar mixtures: marine/saltwater apps; pilings for shore dwellings creosote-petroleum mixtures: economical but not used for marine installations
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Term
Materials - Wood Lumber Classification |
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Definition
American Lumber Standards Committee (PS20-70 American Softwood Lumber Standards) establishes basic principles for grading lumber Grade: slope of grain; natural & manufacturing defects; number, tightness & location of knots Common grade: suitable for general construction Select grade: higher quality surface for painting or natural finishes
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Term
Materials - Wood Lumber Classification: Uses |
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Definition
Yard lumber: ordinary construction, general building purposes Structural lumber: 2 in. or more nominal thickness; aka stress graded lumber
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Term
Materials - Wood Lumber Classification: Size |
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Definition
Lumber sized & spec'd as nominal (size before shrinkage and planing) Dressed dims smaller - except length (shrinkage longitudinal to grain is negligible) Boards: <2 in. thick, 2 in. or more wide; sheathing, flooring, roofing, finish, trim, siding, paneling Dimension lumber: 2-4 in. thick, 2 in wide or more; used principally for structural elements Timbers: >5 in x 5 in: beams, stringers, posts, caps, sills, girders, purlins, other members Most dimension lumber & timbers are stress graded
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