Expert: Ted Barnhill (Principal, Design45 LLC) - 5/5/2011

Question
I have a house that was built with a post on pad foundation, with a large deck.  The house was later raised and a basement build under the house and deck.  A BUR roof was placed over the deck.  the BUR is about 20 years old and has done fairly well, but I am thinking of putting a EPDM roof on top.  I do not believe there is any rot under the BUR (I have lived in the house the entire time.) I understand that 1/2 inch felt board will need to be placed over the BUR and the EDPM placed on that.  For wear, we are considering placing all weather wood decking on sleeps, over the EPDM.  The problem is that once the felt board and EPDM are placed on the deck, the top of the deck will be very near the elevation of a door threshold that opens onto the deck (There is no slope to the deck/roof).  Once we place the wood decking on the EDPM the wood deck surface will be about 3 inches above the door threshold.  It is a back door and there is a roof over the door that protects the portion of the deck around the door.  We have three questions. (1) Should we place a 3 inch high wall around the door - maybe 4 feet out from the door, but under the area protected by the roof above, run the EDPM on the outside of the wall and construct the wood deck on the outside of the wall.  This would result in a low area adjacent to the door, and require a short step up to the deck after exiting the door, but it would allow the EPDM to effectively protect the deck/roof and keep water away from the door? (2) Would this be a potential problem when we go to sell the house?  (3) If this is a bad idea, what would you suggest?

Answer
Jim,

I would suggest that you try to achieve some slope to your roof - at least 1/8" per foot - to greatly extend the life of your roofing and prevent leaks.  A straightforward way to do this is with tapered rigid insulation over your existing roof, with EPDM over that.  Of course, this would exacerbate your threshold problem.

At the door location, with or without a slightly-sloped roof, I would not create a little "well" as you have described.  How does wind-blown rain and debris get out of the little 3" well?  I would rework the door so that it is at least 2" above the roof level.  This may mean cutting down your current door, or reframing it with a higher header.

I'm afraid without seeing your situation I can't make any more specific recommendations.  I hope this is helpful.

Ted Barnhill
Design 45 LLC