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•  Softwood plywood •  Structural •  Similar to OSB •  Sheathing, subflooring,

concrete forms, etc.

•  Hardwood plywood •  Typically decorative •  Furniture, flooring,

cabinetry, etc.

Lecture 16 Plywood

Uses: Bowyer, Ch. 14

Veneer – A thin layer or sheet of wood.

Plywood is pretty strong stuff: http://www.maniacworld.com/Motivational-Speaker-Fail.html

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•  Douglas-fir and SYP dominate U.S market •  Plywood is classified by veneer grade and/or

application. E.g.: •  sheathing •  siding •  concrete form •  marine use

•  Grades are based on quality of face and back veneers, adhesive used, thickness, etc.

•  Low density hardwoods (aspen, cottonwood, gums, and poplar) may be used as core material.

Structural Plywood

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Hoop Pine Plywood Manufacture

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Typical Manufacturing Steps •  Cut blocks to length and debarked •  Hydration and heating - particularly important in the

winter •  Softens the wood •  Typically soaking, may also be done by steaming or

spraying with hot water

•  Peeling - rotary cut or sliced •  Clipping of veneer

•  “ribbon” of rotary veneer cut to 54 inch lengths •  sliced veneer - edges are squared

•  Veneer drying - impingement (jet) dryers •  Adhesive coating and lay up •  Pressing - heat cures the glue (low pressure process) •  Trim to 4x8, sanded, packaged, and shipped

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Veneer Cutting Slicing (decorative applications)

Peeling (structural and decorative)

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Sliced Veneer

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Veneer Handling and Drying

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Adhesive Coating and Lay-Up

•  Veneer layers are symmetrical to center plane •  Often oriented at 90° angles

to each other •  Lower quality veneers in

core •  Faces may be different

species for decorative plywood

•  “Balanced Construction” •  Adhesive is either

automatically or manually applied to alternate veneers.

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Pressing

•  High temperature, multi-opening press

•  Loose assembly becomes a panel

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Veneer Grades

“Natural Finish” is the highest grade of veneer. Essentially no defects or patches.

12 Examples of Veneer Patches. Also called “plugs”.

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32/16 – 32 inch span for roof sheathing / 16 inch for subflooring

Exposure 1 – Manufactured with waterproof adhesive

Exposure 2 - (Interior) adhesive is only water resistant

Exposure 3 – (Interior) non-water resistant adhesive

This grade is also called CDX – C and D face veneers with exposure 1 adhesive.