Though many homes have what’s popularly called a “bonus room” above the garage, the project we just completed in Lynnfield, Mass., is a little different. Included in the plans for this garage (which will house four cars) was a 1,100-square-foot floating roof-top deck.

The roof was framed with a slight pitch and the rail posts were incorporated into its construction, allowing us to seal the post bases into the EPDM rubber roofing system. To support the decking, we screwed 2x4 sleepers on the flat to the tapered bottoms of pressure-treated joists (2x6 upper deck, 2x8 lower), countersinking the screws so they wouldn’t damage the roof membrane. We then installed the sleeper-joist assemblies 12 inches on-center, after laying down 4-inch-wide rubber membrane strips for additional protection.

For the deck’s surface, the homeowners chose Royal Building Products’ Zuri PVC decking, which comes in 16- and 20-foot lengths. The design on the 23x24-foot upper deck made cost-effective use of the 20-foot boards; running the alternating walnut and chestnut meeting boards down the center allowed us to simply cut 20-footers in half for the walnut field decking. It wasn’t until after we started installing the decking that we decided to run the pattern in the other direction as well. To dress up the lower deck, the homeowners selected a Zuri 6x6-foot compass-rose inlay kit. We installed the inlay flush with the decking, adjusting for the thickness of the PVC backerboard by routing 1/2 inch off the top of the joists before adhering and anchoring it in place.

John Solari owns JFS Construction Co., in Scituate, Mass.