Decking Over a Roof – Question from Fine Home Building Article
Emanuel Silva did an excellent job in the October/November 2014 edition of Find HomeBuilding showing how to build a deck over a roof. I have not had any problems doing this myself with the abundance of good photos and clear description. However, I cannot figure out the proper design to ensure water that goes through the decking and onto the EPDM membrane below is supposed to drain. If you look at the picture on page 79 of the article (attached) the facial broad is fully covering where water would drain out. How should I design this so that the water between the facial board and membrane drain properly? My gut tells me to leave a one inch gap between the bottom of the facial and membrane to serve as a drain, but the picture does not show it that way and there’s nothing in the narrative that addresses this. I am sure Mr. Silva is far more skill than I am and so I think I must be missing something.
Please Help.
Morris Germain
Tuscaloosa, Alabama
Replies
You've got it right..
The fascia board should be ripped so that there's a space between the bottom of the board and the top of the membrane. You have to decide how much to let any water and debris that gets through the decking to wash out at the edge of the roof. The other way would be for the fascia to hang out past the edge of the overhang an inch or so to allow water to fall over the edge behind the fascia.
Fascia detail
Mo,
A 1" gap is totally unnecessary, 3/8" to 1/2" is more than enough, simply rip the front frame board (it is not the fascia board) down
3/8-1/2" or cut in a design, such as a short arc between each joist, which-ever suits your fancy.
Geoff