The Deck Upstairs
How to combine a deck with a roof that won't leak.
Synopsis: The author explains the construction of a deck over a flat or low-slope roof. He covers both built-up roofing materials, which are layers of felt and asphalt, and elastomer materials in sheet and liquid form. The wider availability of EPDM roofing may have changed the picture slightly, but his methods of supporting deck components work just the same.
My first rooftop terrace introduced me to the built-up roofing business the hard way. I’d designed a small addition with a nearly flat roof, and I wanted to put a deck on top of it to take advantage of the summer weather, the view and the privacy. I called up the roofing contractors to find out how low the bids would go, and started dreaming of deck furniture.
As the roofers looked over the job, it became obvious that details and prices fluctuated wildly. One wanted insulation on top of the roof sheathing, another underneath; some wanted gravel in the flood coat, and others said gravel was unnecessary. To make matters worse, none of them would guarantee the roof because I wanted to cover part of it with a deck.
I finally got the job done, lost money and learned a lot. Since then I’ve done a lot of successful and more profitable installations, but I’ve never stopped keeping a keen eye out for good roof-terrace detailing.
Years ago rooftop decks were called promenades or plazas, and were usually found atop fancy commercial buildings. They were covered with a hard and durable surface like quarry tile, laid over a built-up roofing membrane that kept out the water. This type of decking was occasionally used in high-end residential work, but it was too expensive for most ordinary construction.
For a more economical solution, designers looked once again…