I don't have a kettle, but built a cart for my WSM. I used beadboard for the sides and some stain grain oak for the top. If you get the sides of the grill away from the wood, you will be fine. Heat will rise so just give it some room. The real reason not to use pressure treated wood for the top is that it has a real tendency to split. Even the 4x4 post are notorious for splitting, keep us posted on the project! Sorry I took this pic with my cell.