How to Calculate Lumber for an Addition
- 1). Count the total number of boards of each nominal size, like 2-by-4s, 2-by-8s and 2-by-2s, you need based on detailed plans for your addition. Keep separate calculations for each board or timber size.
- 2). Count the number of all studs, sills, stringers and every other component of your addition.
- 3). Note the lengths of all the boards you will cut. For example, if you plan to use vertical studs that are 7 feet 10 inches long, cut two studs from each 16 foot long board.
- 4). Calculate the lineal feet of for all the waste boards. For example, if your addition includes 14 foot long stringers or joists, you will waste 2 feet of lumber for every stringer or joist.
- 5). Add the lineal feet of all the wood you will use, waste and that will be unusable.
- 6). Translate your order from lineal feet into board feet if your lumber yard prefers to bid on your order in board feet. Board feet equals the actual length in inches multiplied by the nominal width in inches multiplied by the nominal height in inches and then divided by 144.
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