Mount flashing on new shingle roof install?

[maxim]

I'm in San Diego and will be replacing an aged shingle roof as part of a solar install. The solar company will be working with a roofing company to coordinate.

The roofer described that if I prefer they can flash the mount or part of the mount under the new shingles for a lower chance of a leak. They're ok to do this at no cost and the only downside seems to the additional resulting 2" of space between the panels and roof surface.

I'm not sure if this would be with the ironridge flashfoot2 mounts he's proposing or something else but I can find out.

Do you think this technique is worth it when installing along with new shingles? Or is the typical retrofit mount approach perfectly adequate in both scenarios?

I'd appreciate any links to how-to's or videos on this technique as so far I haven't been able to find much on it.

Thanks

[J.P.M.]

If it's a standard post type mount, I'd flash both under and over the new shingles. Every penetration on my roof is double flashed.

The additional 2" between the panels and the roof deck will probably result in panel temps. that are a bit lower (that's good) and also make under panel inspections marginally easier. Some don't care for the aesthetics of a higher panel clearance however.

[Ampster]

I agree, and of course the benefit is you only have one vender to deal with if there is an leak. How much slope does the roof have. I see you are in San Diego so snow is probably not an issue. Are the shingles wood or asphalt? Your answer may inform my answer about the need for double flashing.

[Mike90250]

Double flashing seldom causes a leak !

[Ampster]

I agree that double flashing never causes a leak but on a roof with more than a 1 to 1 slope the sheet metal cost gets expensive unless one is using those rubber gasketed flashings. Then again we each probably have a different description of what double flashing looks like. Regardless of the slope and especially if the slope is less than 4 in 12 I would suggest putting a patch of Bituthene under each support before attaching the supports. It is extra insurance because it will seal around the fasteners and take very little labor to place and is probably less expensive than an extra sheet metal flashing on top of a smaller sheet metal flashing. I use the term bituthene and it was described somewhere elso on this forum as silver something. .

[Ampster]

.........
I'm not sure if this would be with the ironridge flashfoot2 mounts he's proposing or something else but I can find out.

Do you think this technique is worth it when installing along with new shingles? Or is the typical retrofit mount approach perfectly adequate in both scenarios?

.......

I missed that part of your question. You will have a much more secure stanchion if you don.t use retrofit mounts because they often have several fasteners going through a flange at the bottom instead of just one. It sounds like this is a tear off roof so either way you will have a good chance they hit the rafters with whatever fastening system they use.

[solarix]

This is contentious subject. If you check with the shingle manufacturers, they'll void the warranty if you break the shingle seal and pull nails when retrofitting flashings into a shingle roof. OK when put in during the initial shingling. Also, if you check with the National Roofing Association, they define a "penetration" as a skylight, plumbing vent, electrical conduit, etc. - not fasteners. Flashing every solar fastener is not "best practice" as some solar mounting manufacturers claim. (It violates the shingle warranty) In retrofit applications, I recommend a compression sealed post mount or oversize "L-foot".

[maxim]

Thanks for all the insight everyone. Yes it's a complete tear down for the roof install using asphalt shingles. Not sure what the exact pitch is but it's fairly modest as I can walk it with little issue.

Sounds like consensus is to do the double flashing.

Can anyone point me to a video or article visualizing this for solar mounts so that way I know what to expect during the install? Or provide some key terms to look for? I'd like to get a better sense for the gap increase.

Thanks again.

[Ampster]

This is contentious subject.

Hardly contentious, more like consensus. If you read the thread more thoroughly, you would see that this is a new roof and the OP is having the standoffs placed before the new roof is put on. None of the issues you raised are relevant.

[Ampster]

Thanks for all the insight everyone. Yes it's a complete tear down for the roof install using asphalt shingles. Not sure what the exact pitch is but it's fairly modest as I can walk it with little issue.

Sounds like consensus is to do the double flashing.

Can anyone point me to a video or article visualizing this for solar mounts so that way I know what to expect during the install? Or provide some key terms to look for? I'd like to get a better sense for the gap increase.

Thanks again.

If the pitch is less than 4 in 12 I would do a waterproof membrane like Bituthene or similar under the new roof. The roofer can decide best practice whether standoffs go over or under membrane. Then you would not need double flashing. The membrane will add additional expense not needed if slope is greater than 4 in 12.