Calculate the Amount of Material Needed to Build a Wood Joist Floor


Multiply the length of the floor by 12, divide by 16 (16 inches center to center),  round-up to the next whole number, add 1 to it,  and that will be the number of floor joists needed along its length.

Example 22 feet (length) X 12 = 264 divided by 16 = 16.5 rounded-up =  17 + 1 + 18.

The width of the floor shall be the length of the joist needed but if you will be joining the joist on a stringer(s) the length of each joist will be equal to the distance where each will join (on stringer) plus a couple of feet on each, to overlap them at each join.

Multiply the number of joists needed along its length you calculated first by the number of joists needed to make a full length joist along the width of the floor and that will be the total amount of joists needed.

On the outside edge along the floors length you will need 2″ X 10″ etc.. nailed flush to that edge and to the ends of each joist so the total amount needed for that will be equal to the length on each side of the floor.

The amount needed to build a stringer is equal to the length of the floor multiplied by 4.

To figure out how much lumber is needed to sheath the floor just simply multiply the width by the length (equals square footage), add 10% for wastage and that’s the square feet of lumber needed. If using plywood square footage divided by 30. Example 30 ft X 40 ft = 1200 SF divided by 30 = 40 sheets.

Plans how to build your own wood floor.


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