Engineers have devised ways to measure specific types of strength. For a rough, general estimate of strength, refer to the specific gravity or density of the wood. When you need more detailed information, there are additional choices. Engineers measure the compressive strength by loading a block of wood parallel to the grain until it breaks, and the bending strength by loading a block perpendicular to the grain.
Both are measured in pounds per square inch psi. The force used is recorded in pounds lb. In each case, the higher the number, the stronger the wood.
Hickory 0. Specific gravity may be slightly higher in green wood. To reveal the information in a "Superphoto," first enlarge it and then move the cursor over it. Straight-grained boards are stronger than those with uneven grain, knots, and other defects. Parts such as shelves will support a heavier load if the weight rests on straight grain.
Compressive strength tells you how much of a load a wood species can withstand parallel to the grain. How much weight will the legs of a table support before they buckle? Bending strength also known as the modulus of rupture shows the load the wood can withstand perpendicular to the grain. How much weight can you hang on a peg? The stiffness or modulus of elasticity indicates how much the wood will deflect when a load is applied perpendicular to the grain.
How far will those shelves sag? The hardness reveals how resistant the surface of the wood is to scratches, dents, and other abuse. How long will that kitchen counter stay looking new and unmarred?
Wood Grain. Wood Movement. Nature of Wood Resources. Looking for something? Try these navigation aids:.
Something to share? Wood has several kinds of strength. Compressive Strength psi. Bending Strength psi. Stiffness Mpsi. Hardness lb. Alder, Red. Birch, Yellow. Maple, Hard. Maple, Soft. Oak, Red.
Sawing of trunks: 1 Plain sawing: this method results in the greatest yield. Standard inch measured cross sections: 1 Nominal size is the size of a piece of wood before it is planed at the mill. This is the size by which the wood is sold. Standardization of sizes: The nominal sizes of commercially available lumber are standardized both for length, and for cross section.
Grading of lumber Lumber is graded for strength, imperfections such as knots , and appearance. General grading for wood construction: 1 Utility- poorest, not generally used for constuction 2 Standard, construction- commonly used for building 3 Select structural- best quality, used for larger structural members.
Plywood: Veneers of wood are thin layers of wood obtained by rotary cutting. Plywood sheets are composed of several layers of wood veneer, glued together. Plywood: Each face ply is graded according to appearance and durability on a scale of A to D in descending quality, as follows: a. Plywood is commonly graded with two letters; one for each face ply. Some common grades of plywood and their common uses are as follows: a.
AA- used where both sides will be visible c. AB- used to cover unfinished framing d. AC- used for roof decking e. BC- used for general utility f. BB- used for formwork g. Plywood is available in Interior and Exterior Grades, which are determined by whether or not moisture-resistant adhesives are used Exterior Grade is characterized by moisture resistance.
Masonite can be waterproofed if necessary. Aspenite is a kind of particle board with rather large constituent fibres.
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