Converting A Pool Room

DEAR TIM: I have a 12x30 swimming pool in a 20x40 room. Pool has been empty for 6 years. I am building a floor over the pool. Should I partially fill the pool with gravel or just brace the walls with 4x4 or 4x6 beams. Kelly Bennett, Calgary, Alberta, Canada

DEAR KELLY: That's a pretty interesting job you have going with that indoor pool. The closest I've ever come to that situation is when I converted an old gas station that had a service bay with a mechanic's pit in it into a veterinary hospital.

Covering a swimming pool with a regular floor. PHOTO CREDIT: Kelly Bennett

In that situation, because we were pouring concrete, I filled in the pit with pea gravel.

I would not do that if I were you. Your idea of using 4x4s or 4x6s is a good one. I'd create upside down trusses using this lumber to brace the walls of the old pool. There's not as much lateral stress against those walls as you might think when the pool is empty. Even with water in the pool, it does little to offset the lateral pressure of a side wall tilting in. The water simply moves up to compensate.

Be sure you make strong connections between the beams so they never fail. You also need to install a fantastic vapor barrier over the entire pool area once you've constructed the trusses. Read my past columns on this and use a vapor barrier that meets the ASTM-E-1475 standard.