Home Industry News Deck Math Revisited: Part Two of a Three-Part Series

Deck Math Revisited: Part Two of a Three-Part Series



Last month, I offered a broad overview of what I’m calling Deck Math Revisited, a recap of a popular series I wrote a couple years ago. Last month’s column including some tricks I’ve picked up over the years to standardize my estimating on decks. In this issue, I’ll share some techniques that can help a deck builder save money by using lumber in the most efficient way.

Our practice of teaching our contractor customers how to be more efficient when building decks is our single most effective technique for gaining long-term loyalty and increased sales.

As I mentioned last month, if a contractor consistently builds decks using 12′ and 16′ boards, his costs are going to be higher than those of a contractor who builds using 10′ and 14′ boards. That’s because any time you build in numbers that aren’t divisible by 16″, it tends to lower your costs because those size pieces of lumber cost less.

I recently sold a deck to a contractor who had previously gone to a large competitor to buy his lumber. The contractor believed he needed 48 16′ pieces of lumber for a particular deck, which happened to be an expensive exotic hardwood. That other supplier couldn’t fill the order so the contractor came to me with the same request.

I showed him how he could apply his decking material diagonally, and how to calculate the lengths differently. We were able to sell him a high volume of shorter, less expensive lengths of 10′ and 14′ pieces. We got the sale even though our price per foot on the material was a little higher, because we saved him a great deal of money by teaching him how to use his materials better.

Lumber comes in standard sizes, 8′, 10′, 12′, and so on, of course. The longer the board is, the more likely it is that it came from an older tree, so it’s more expensive.

Let’s say you were building a 24’x10′ deck, and you placed your joists every 16″. If a contractor put the boards on horizontally, he’d have to cover 24 feet. Since you can’t get a 24′ board, he could buy three 8′ boards, which equals 24; two 12′ boards, or a 16′ and 8′ boards, also equaling 24. What he can’t do is use a 10′ and a 14′ board, because, although they equal 24, they’re not divisible by 16, and he’d miss his joists.

With diagonal decking put on a rectangular deck, however, a contractor can use those shorter, less expensive boards. With each board, the pieces get 11″ shorter, or double the width of the board, which is 5-1⁄2″. Effectively, that means each board applied is a foot longer (or shorter) than the one before it. At a certain point, all the boards stay the same length, and then that process reverses.

To calculate the length of a piece of decking used diagonally one could use the long math formula the Pythagorean Theorem (A2 + B2 = C2) or my Personal Favorite Short Cut. The length of a piece of decking applied at a 45 degree angle is equal to the shortest side of the deck divided by its sine of the magic number .707 (be sure to add the width of the board on to the equation). Therefore the largest deck that can be built without seams using 20′ material is 13′, 8″, x (any width) that could be built without seams if the decking is applied diagonally. Example: Using the example drawing the 10′ side is used to calculate the longest piece needed 10′ = 120″, add the 5.5 to this for the decking width getting 125.5″, then divide this answer by .707. The answer is 177.51″, or 14″, 8′ long, so the lumberyard would need to supply 16′ as the longest board, the rest would be 14’s, 12’s, and 10’s.

Teach your contractors how to use this strategy, and you’ll gain both sales and loyalty.