I’m installing some roof drains in a concrete roof and need some advice. I just had a roofer install 6 drains for me and I need at least 10 more. The building is 40,000sq ft. with a flat roof. Some drains were present when I bought the building and some are new. The roofer that installed the 6 drains did it like this:
- spud back the rocks.
- Cut a hole.
- put put the drain on the concrete.
- flashed with some kind of tar.
- flashed with lead putting black tar under the lead.
- covered with lead with more black tar-like stuff.
- put tar over the lead.
- Put a fiberglass mesh on the tar and more tar over that.
The job looks OK, but the new drains he installed sit about 1" higher than the roof. The result is a roof drain that sits in a puddle about 1" deep and does not drain all the water.
I’m considering installing more drains myself and maybe fixing the roofers drains. Here is what I’m thinking.
- spud the rocks to the felt.
- Cut a hole the size of the drain.
- cut a recess in the concrete for the drain to countersink into. The roof deck is 3" concrete and my recess would be about 1/2" - 1".
- Set the drain in the hole (that is now below the roof surface).
- flash with lead.
- cover with tar.
- flash with tar and fiberglass mesh.
My hope is that my roof drains will sit level to, or just below the roof. I think this will help drain more water and keep the roof dry.
Any comments on countersinking the drains a bit? Is there any reason not to do it?
Also, what materials should I use to flash. I know I can get lead sheets but do i need to use fiberglass too?
This is the drain I plan to install:
bigrocksupply.com/marathon-b … i-864.html
Thanks in advance for your help with this!