The torch down modified bitumen I used, had an additional product to use if you wanted to walk on the roof. It was about 1/4 inch thick and was torched on top of the finished torch down roof. I imagine this would work well under the sleepers for a deck.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13