Expert: Richard Taylor, AIA - 11/7/2006

Question
I read your answer to Ed Brady on 8-11-04 about adding a roof deck (very informative, thanks) . I am working on a similar project in New Hampshire, building a garage with a hip roof and want to eliminate the pitched roof on one quarter, next to the 12' long ridge and create a 12' X 12' roof deck.
First , am I impractical? Second , it would seem that your advice to Mr Brady would be applicable , but I need  additional information.. Since this deck built on sleepers would be surrounded on 3 sides by vertical walls, one side the existing house , one side the ridge line (approximately 4' tall) and the third side a sloping wall running from the ridge to the corner of the hip roof. How do I waterproof the intersections with the membrane roofing? All drainage would be to the fourth open side.  Is it as simple as continuing the membrane roofing up the walls ,under the siding (how is this done on the existing siding ? Does the membrane roofing need radius support at the 90's?  Any additional flashing?

 Any insight would be greatly appreciated!

Answer
Sal - thanks for your question(s)!

The answer to all of them is...yes!  You should lap the membrane up on the three interior sides - in your area at least 18" or so.  This will require to remove and replace some of the existing siding - no way around that!

Radius support isn't necessary, but it wouldn't hurt to put cant strips at the wall/roof intersection.  Additional flashing isn't needed if you run the rubber up and under the siding.

Details for rubber roofing applications can be found at: http://technicaldatabase.fsbp.com/TechnicalResources/DetailDrawings/RubberGardEP...

Hope this helps!

Richard Taylor, AIA
Richard Taylor Architects, LLC
www.rtastudio.com
www.rtaplans.com