Expert: Daniel Humphrey - 2/24/2008

Question
Hi Dan,

I live in Las Vegas (Really hot in the summer) and I am enclosing a small patio area 8x12)which already has a roof.

I've studded up the wall and have installed plywood on the outside. Over this siding, I'd like to run 1"x4"x8' pine boards. My question is, is there a way I can make these boards waterproof so they won't warp? I plan to finish them in a stain or a paint with the water proofing over the that...is this the correct procedure?

Thanks for you time,

Don

Answer
Don,

Mostly, it's the sun that does the warping, as you probably know. In direct sunlight, the best thing you can do to protect the wood is paint both sides and the ends with a stain that has UV blocking properties. Stain allows the wood to breathe and expand and contract better than paint does. Full sunlight on a board will still make one side a different temperature than the other, but if it is stained a light color, this will be reduced.

When applied to a wall, it is best to attach furring strips about every two feet on center in order to create an air gap between the wood and plywood sheathing. This helps keep both sides of the wood about the same humidity.

If you are placing them vertically, you can make a board-and-batten wall, where each board is held by another. You start with the boards placed with a small gap so that the nail from the batten won't hit the board. The board is positioned so that the cupping is likely to force the edges outward. Then over this gap you place the battens so that the edes are likely to cup inward. Just one screw or nail in the middle of the board and the middle of the batten at every furring strip is enough. You generally avoid nailing each edge of the board or the batten because it will encourage splitting.

A board is most likely to cup in the direction of the end grain. Usually, a board will show some signs of cupping even right off the stack, and you just pay attention to this.

Good luck. Don't hesitate to write again if you need me to clarify anything.

Dan