How many times have you been asked to build a second story deck for a customer and they want to use the space underneath the deck instead of wasting it? Some customers want storage; some want living space; some want three-season rooms there.

The obvious problem is that during wet weather water runs between gaps in the deck boards. Making the deck sufficiently waterproof is easily done. Of course you can cover your deck boards with some sort of solid surface, either hot-mopped tar, rubber, or a fiberglass mesh system. But most clients want a natural, traditional-looking deck.

Between the Boards There are two main types of product that will enable you to give customers what they want under the deck. One is a rubber sheet that lays over the framing, with the deck surface secured on top of it. The other is a plastic system that installs between the floor joists. Both are readily available from manufacturers and can be shipped to the jobsite. But because homeowners generally don't want to see the plastic sheathing stretched between framing members, conceal the system with the customer's choice of ceiling, whether wainscoting or a vinyl soffit system. Looks don't have to be sacrificed to functionality.

Install at Framing Stage Waterproofing beneath the deck surface can be done in a day or less, and you won't have to spend time and money tracking down specific tools and parts because it can be installed using the simplest tools.

It's important, however, to check for leaks before you install the deck surface. Should there be a problem, it's much easier to fix when you have access to the system from the top. Test by spraying with a hose to simulate rain.

When customers call and want a deck built, be sure to tell them about the new options available that can add living or waterproof storage space under the deck. —Carl Sperry is a contractor living in South Carolina.