Calculating the weight of lumber can be a useful skill when constructing that outdoor deck or tool shed. By having the knowledge of the load weight of the wood, you can determine the type of foundation the wood structure must sit upon for proper support. All wood is specified in pounds per cubic foot. Generally, this wood weight is based upon a board that has been air-dried.
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Figure the cubic footage of the lumber in the following example. We are going to calculate a small stack of 2 x 4s that are eight feet long. This stack will contain 24 individual boards of yellow pine, which weighs 16.3 Kilogram per cubic foot.
Calculate the end surface of the 2 x 4, so we can then later convert this to a square footage measurement. Each store-bought 2 x 4 has the dimensional measure of 1-½ inches by 3-½ inches. We must first convert the fraction of ½ inch into a decimal. Divide 1 by 2 and the answer is .5 inch.
Multiply 1.5 inches times 3.5 inches to find the total surface-area measure at the end of the board. The result is 5.25 square inches.
Multiply the 5.25 square inches times 24 boards to find the total square area in inches for the stack of lumber. This is 126 square inches.
Convert the 126 square inches into square feet. One square foot is equal to 12 inches times 12 inches, which is equal to 144 square inches. To convert the 126 square inches into square feet, we must divide 126 square inches by 144 square inches. The solution is .875 square feet.
Find the final cubic footage of the entire lumber stack. We need to multiply the length of the 2 x 4s times the total square footage of the 24 boards. The result of multiplying .875 square feet (the end surface area of the stack) times eight feet (the length of the stack) is equal to seven cubic feet.
Calculate the total weight of the 24 yellow pine 2 x 4's. Yellow pine weighs 16.3 Kilogram per cubic foot. Multiply the seven cubic feet of lumber times 16.3 Kilogram per cubic foot. The stack of yellow pine will weigh 114 Kilogram.
Tips and warnings
- All weights are air-dried and in pounds (lbs) per cubic foot.
- Ash, white -- 18.6kg
- Cedar -- 10.4kg
- Douglas Fir -- 15.4kg
- Hickory -- 23.1kg
- Maple, black -- 18.1kg
- Oak, red -- 20kg
- Oak, white -- 21.3kg
- Pine, white -- 11.3kg
- Pine, yellow -- 16.3kg
- Walnut, black -- 17.2kg
- These above weights may vary by interspecies and climate growing conditions.
- The above list is for general use only.
- All lumber will absorb some moisture during the construction phase. Once protected from the elements, the lumber will return to the above described weights.
- Follow all local codes for proper foundation construction on any building projects.