Estimating Wood Needed for an Addition

Measure in linear feet the area in which you plan to put the walls of your new addition. Multiply this by 2 to give you the linear feet of lumber needed for your top and bottom braces. For example, if the total length of the walls you plan to add is 32 feet, your linear feet of lumber needed for the top and bottom braces is 64 feet.

Count one stud for every linear foot of wall you plan to add, assuming that your studs will be centered every 16 inches. Counting one stud per foot gives you extra studs for framing corners, windows and doors. In our example from Step 1 the measurement of the new walls was 32 feet, so you would have a count of 32 studs. Round up any fractions to the next whole foot.

Multiply the stud count by the height of the wall. For example, if you plan on having 8-foot-high walls, you need 32 studs, each measuring 8 feet. Multiplying 32 times 8 feet gives 256 feet, which is the total amount you will need.

Add the linear feet you calculated in Step 1 to the linear feet you calculated in Step 3. In our example, 64 feet from Step 1 and 256 feet from Step 3 totals 320 feet. This is the estimated number of linear feet of lumber you need.

Add 5 to 10 percent to your estimate. In our example, add 16 to 32 feet to your total estimate. Therefore, you would actually purchase between 336 and 352 linear feet of lumber.