conversion of lineal feet on a diagonal deck

[Stu]

I have a 12' x 24' deck of 288 square feet. I want to run 4" width deck boards on a diagonal of 45 degrees. How do I calculate proper amount of lineal foot boards (20', 18', 16') to avoid waste. I am donating my time and costs to a church.

[Guest]

I have a 12' x 24' deck of 288 square feet. I want to run 4" width deck boards on a diagonal of 45 degrees. How do I calculate proper amount of lineal foot boards (20', 18', 16') to avoid waste. I am donating my time and costs to a church.

4" is one-third of a foot. The deck will use 3 x 288 = 864 linear feet. BUT the 45° cuts on the ends will result in larger than normal scrap. I would allow for 10-12% scrap, so 950-970 feet.

A board across the diagonal will be about 17' plus a 4" allowance for the (second) angle cut, so 18' boards will be required if you want one piece across.

It appears 26 boards (18') would do a parallelogram in the middle of the deck, leaving two triangular pieces on the ends.

Another 26 boards should fill in the triangles on the end. If you cut the long boards first, the scrap should be able to fill in the pieces near the apex of the triangle. To play it safe, I would probably get 20 18-footers and 6 20-footers. to have some longer cut pieces for the apex of the triangles.

You might squeak by with 52 18-footers, but I would recommend 46 18-footers and 6 20-footers. That makes zero allowance for bad lumber, only for the unavoidable loss of short useless pieces of scrap including 45° cuts.