Treated Lumber or Plywood

You can use plywood or untreated lumber on the interior of the house as long as you are at least 5 feet from the exterior of the house. For this situation plywood is a good choice because of the ease of cutting a curve. This is hard to do with a treated piece of 2x lumber.

TIP Use a good construction adhesive under the plywood as a vapor barrier between the wood and the concrete. As you can see in the picture above the adhesive is oozing out of the sides.

Glue Between Plywood and Concrete

A special note please remember to check with your local building department for their interpretation of the building code. The stair building codes on this page are what we consider standard in home construction. We will in no way be liable for your interpretation of these building codes. Remember the stair building codes on this page are to give you a basic idea of what will be required in some cities.