Sloping a flat roof


I am adding slope to a flat roof. I will be cutting 32 foot wedges out of 2"x8"x16’ lumber. The wedges will be run ALONG existing 2x10 joists. There is a 1 inch-thick deck already on the roof. What is the best way of attaching the wedges to the joists (through the decking, so at the highest point, there will be some 8 .25 inches to get to the joist from the top)? Is there a code for that? Urgent. Thank you.


You would be better off getting the slope using a tapered insulation board. They come in 4x4 pieces and we’ve stacked them as high as 6 inches to get the slope we needed. You can have an1/8, 1/4, or half inch drop over the 4 feet. If you have a more complicated design one of your major suppliers should be able to offer you a design off your measurements to get you to a drain or around a corner. We use beacon sales for this. They also stock standard slopes if you need it without ordering it.

If you stick to the rafters you should be fine toenailing the joists in as long as your above the existing joist. I’d run it by the town inspector to make sure he looks at it first so he doesn’t have you take up the roof to check your framing.


We have done that before. Nailing into the rafters can be a little questionable at best. Don’t be shy with the blocking would be my advice.


We do this alot, cheaper than taper ISO and also readable and doesn’t require densdeck or anything other than base sheet if you are torching. I just toe nail the piss out of them then screw a 16" 2x4 block to the deck every few feet and shoot through the rafters to the block. Just keep the tops square as you nail your first couple corses of plywood. As far as code goes not sure… we just make sure they arnt Going anywhere then install plywood to code.


Reusable not readable sorry iPhone corrected me


Thanks. Good suggestion. Tapered insulation would have been great; however, it appeared to be rather expensive. Toe-nailing is an option as well as using construction screws.


Blocking to keep the joists apart or blocking as an extra piece of wood I may screw through into the joists below for extra grip?


Now that’s the spirit! I call this roof repair, as the original roof had incorrect drainage, the EPDM failed, and the middle of the deck was rotted out. I do not believe this calls for a permit. Yes, I will toe nail and use construction screws. Using the 16 inch blocking is a great idea! Thanks.


Absolutely roof repair. Have never had a building inspector, knock on wood, give us and crap about doing anything to improve the drainage or anything else over a flat. We don’t sell anything roofs that don’t include a full tear off. When we go into the city, Philadelphia, that’s typically 1-3" and not uncommon for 4+ so when the inspector shows up and see 3 tons of material from a 10 sq roof sitting in the truck they know you are the guy who is doing it right and move on.