Sealing roof penetrations for solar panel mounts

Hi all,

I’m getting ready to install two 4’ x 10’ collectors for a solar hot water heating system. I need some advice on how to attach the collector panels to the roof.

The roof is tar & gravel, slightly sloped at approx. 12 degrees (2.5"/1’). The roof framing is TJIs spaced 2 feet OC. The collectors will be mounted parallel to the roof surface, on two rails. My plan is to put the rails on standoffs made from blocks of treated 2x4, with a lag bolt going through the rail, standoff, decking, and into the TJIs beneath.

Here’s a little section diagram that I drew up for the building department to get the permit:

I guess I should put each standoff in a pitch pocket? Is there an easier/better way to waterproof these penetrations?

The 14" space between the roof decking and the ceiling is completely filled with blown-in cellulose insulation. Any water that gets in will saturate the insulation and cause a big problem, so I really want to make sure that I get the waterproofing/sealing right.

if you have rock up there your going to have to chip
the rock off the surface so you can seal to smooth tar. do it in the mornig when cool, use hammer
other than that sounds like youll be allrite.

nice drawin.


Looks like a perfectly good detail to me.

Use Hammer ?? No, you would need a scratch bar. in other parts of the country they call it a spudder I think. Yes always scratch in the morning when coolist.
If you want to use a pitch pan it should be higher so that your pourable sealer"or mastic" should be trowled high enough to slope it up over your U-bracket and bolts,allow nowhere for rain to settle.
Its also a good idea to make your pitch pan flange out of lead so that you dont have to nail it. we often will solder copper to a lead flange then you dont need nailing block.

I’m jealous of your detail.

Can you drill 3 inches into a TJI ?

better check that out.

maybe I’m thinking of something different?!

Guys, do we think there should also be some sort of a sealant between the galv. pitch pan & the chipped out areas?

I was assuming that it is going to be set in asphalt.

that would “of course” have to be striped in on the flange like any other flashing. cover tape if EDDM or Karnak and membrane if a hot roof.