Wood

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Wood cuts

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Plainsawn: grain is 0°-45° to wide face- distinct grain pattern- may twist, cup, and wear unevenly- tends to have raised grain- shrinks and swells more in width, less in thickness- less waste in cutting, so less expensive Quartersawn: grain 45°-90°- relatively even grain- wears evenly with less warpage- shrinks and swells more in thickness, less in width- more waste in cutting, so more expensive

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Softwood lumber sizes and classification

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Boards: At least 2in wide by less than 2in thick. Classified as select or common. Select board has good appearance rated A-D. A/B good for natural finish, C-D good for paint finish. Common boards have more blemishes and classified from 1-5.

Dimensions: At least 2in wide and 2-5 in thick. Are structural lumber and graded for strength. Classified as either joists and planks, light framing, and decking.

Timbers: 5in or more in least direction. Structural and graded for strength. Clasdified as beams, stringers, or posts.

Lumber classification based on manufacturer are rough, dressed, and worked. Rough has visable saw marks, dressed is plained smooth to uniform sizes, and worked lumber is dressed and then tongue and groove/shiplapped, or shaped to a pattern.

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Hardwood lumber grades and classification

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Hardwood grades are based on the amount of clear, usable lumber in a piece. Standard lengths vary from 4-16 ft and the standard grades are firsts, seconds, selects, sound wormy, and numbers 1,2,3A and 3B.

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Plywood

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Is a manufactured wood panel made of veneer sheets called plies. Bonded together with adhesives at high pressure, and grains are perpendicular to the grain of the adjacent plies. Center ply is the core and outer plies are called the face and back. Cross bands are between the core and outer faces and typically in odd 3,5, or 7 plies. Sheets are standard 4 x 8 feet with grain parallel to long dimensions at face and back. Thickness varies from 5/16 to 1 1/8". Due to stiffness it is effective in resisting lateral forces and used in diaphragms and shear walls.

Advantages over sawn lumber are great strength in both directions, resistance to shrinking and splitting, and less warpage.

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Plywood classification

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Classified as interior (moisture resistant adhesive) or exterior (waterproof adhesive). Graded A to D and will have two letters A-D has face grade A back grade D. Exterior must have inner plies C or higher while interior can be d. Species of wood for face/back is listed 1 through 5 for stiffness, or will have span rating (ex. 32/16 or 32" for roof and 16" for subfloors)

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Glued Laminated Lumber

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Grain is all approximately parallel longitudinally. Laminations are usually 1-1/2" but sometimes 3/4" for small radius turns. Come in 3 visual grades, Industrial (lowest), Architectural, and then Premium. Lamination joints are scarf or fingered.

Laminated decking is available in 3-5 in nominal thickness and in various standars lengths. Interior surface is intended to be exposed and can come in smooth, grooved, prefinished or stained.

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Wood preservatives

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Insects, fire, and decay are major threats to wood.

Insects: preventive measures for termites/ants are minimize moisture, proper ventilation, and impervious concrete foundations. Need to he adequately separated from ground, or be pressure treated. Metal strips and poisoning can be done. For marine organisms, heavy creosote treatment to be used.

Decay: caused by fungi that feed on cell walls. Requires mild temperatures, moisture and air. Without all 3 decay cannot occur. Needs to be kept dry, ventilated or continually under water. Where decay is possible (exterior) used decay-resistant species such as redwood or uses preservatives.

Preservatives: two types, oil based solutions such as creosote or water based such as chromated zinc chloride. Should be applied under pressure for deeper penetration. It is toxic and restricted or controlled by regulations.

Fire: heavy timber burns slow but other lumber can be made fire resistant with chemical impregnation of chemicals such as ammonium phosphate or by surfacs treatment such as intumesent paint which retards the increase of temperature.

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Wood joining

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Nails: common naiks for structural members, box nails are thinner and have less holding power, and finish nails are thin and small for finish elements. Also can use screws. Exterior joints must consider weathering, and structural joints must meet structural requirements, and interior joints consider appearance.

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Finish woodwork

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Millwork consists of shop fabricated items (doors, window frames, stairs, paneling, cabinets) made at mill and then delivered ready for install. Should always be protected by primer or sealer coat.

Wood trim, molding, and ornamental shapes are fabricated from better grades of soft/hardwood. Used to primarily cover joints, where they could pull away leaving unsightly gaps.

Wood siding and paneling: made from common dimension lumber, cut and dressed to standard sizes. Typically siding is seasoned Softwoods where paneling may br manufactured from both hard and softwoods. Only better grades are used for paneling/siding which are stained, painted, or allowed to weather naturally. Exterior siding patrerns should be selected for their ability to withstand weather, and should always be applied over lapped building paper.