Pay extra for re-roofer to flash the mounts, or let the solar installer do it?

[ltbighorn]

I'm working on getting our old flat/low-slope tar & gravel roof replaced with modified bitumen, before we get solar panels installed. We're in the SF bay area.

The leading candidate for reroofing says they can work with my solar installer to install the mounts during the reroofing, but they charge $50 per additional flashing, which would probably add about $800-900 to the cost. That's about ~$0.23/watt, or ~10 months to the payback period. (Or equiv to ~10% of the roofing job.) The benefit would be possibly lower chance of leaks & coverage under the roofer's warranty. I figure it'd also help reduce finger-pointing should any leaks come up. Maybe it'll also make it easier for the solar installer to accurately hit the rafters? The rafters are visible under the eaves though.

Is this a reasonable cost for the work? Is it worth paying the extra?

The solar installer has an good reputation, uses QuickMount PV mounts and torches down a layer of modified bitumen over the metal QuickMount PV flashing. (Is this double-flashing?) They didn't seem to feel that it was essential to install during the reroofing, as they say their foreman has 25 years roofing experience and on a newer roof, they'll warranty the sealing for as long the roofer's original guarantee is. Though I figure the roofer has better odds of being around in 10-15 years.

From reading other posts, it seems like a lot of people don't bother coordinating, and that leaks are uncommon with a competent installer. Is it penny-wise pound-foolish to just do the solar install after the roof is complete, or am I better off keeping $800-900 in my pocket to deal with whatever contingencies may or may not arise?

Thoughts appreciated, especially relating to experiences with flat roofs. Thanks.

[JFinch57]

I had 38KW of solar installed on a commercial building in 2010 over a hot tar flat roof that was done in 2001. The roof recently has developed about a dozen leaks and I have a very pissed off tenant. Although the solar installer gave me his word that the method they were using was good the written contract only says 5 years. This is escalating into a major headache. I would say pay the extra and have the roofer do it. He can easily say that the warranty is void from the other work. Also, especially if you have a metal corrugated deck, it's almost impossible to say where the leak is coming from because it can flow horizontally before entering the building. If the roof leaks you deal with one person and not get into finger pointing.

[peakbagger]

Building roof warrantees are somewhat infamous for being so full of loopholes that its rare that they ever cover a leak. That said the local roofing company hopefully has reputation to maintain to they generally will honor their own work. If you need to go with the manufacturers warranty read the fine print and see if it even still could be valid. The normal "out" is requirement that the roof be inspected and repaired by an authorized representative on yearly (or some other interval basis). Few owners do that and once that first inspection is missed, the warranty is null and void.

Most PV systems are on standard pitch roof so they mounting method is far less prone to leakage , a tar and gravel roof usually implies darn close to flat where there is a chance of ponding. That a completely different beast when it come down to roof leaks.

On a very low slope roof the only type of penetration I would trust is flashed in bracket with a pitch pocket around the fastener. At $50 a pop, that is actually cheap but much of the cost is mobilization and since you have multiples they probably break even. Generally for a roofing company to supply a warrantee the roofer has to be certified by the company to install and the campany will supply a set of standard details for installation including flashing in brackets. Whatever solution you use should be using one of these details. Torch applying bitumen over a fresh compatible bitumen roof does sound reasonable but it come back to once someone other than a certified installer torches a roof the warrantee is generally null and void

[ltbighorn]

I would say pay the extra and have the roofer do it. He can easily say that the warranty is void from the other work. Also, especially if you have a metal corrugated deck, it's almost impossible to say where the leak is coming from because it can flow horizontally before entering the building. If the roof leaks you deal with one person and not get into finger pointing.

That's part of why I wanted it redone with modified bitumen instead of tar & gravel. With tar & gravel it can be quite difficult to tell where the leak is coming from as the water can migrate quite far between the layers. The deck itself is wood slats, so I shouldn't have migration issues there.

Most PV systems are on standard pitch roof so they mounting method is far less prone to leakage , a tar and gravel roof usually implies darn close to flat where there is a chance of ponding. That a completely different beast when it come down to roof leaks.

Yes, the roof is nearly flat, though I haven't had any ponding so far.

Good point about fine print on roof warranties. In this case I'm actually thinking more of the roofing contractor's workmanship guarantee, rather the roofing materials manufacturer warranty, the latter of which I've heard can be difficult to get any value out of (especially since they usually cover only the material, but most of the cost is in the labor).

The manufacturer's warranty is 12-years on a 3-ply modified bitumen assembly (what I'll probably go with), or 20-years on a 4-ply system, though from what I understand 3-plys generally last 20+ years.

The roofing contractor themselves offer a contractor's workmanship guarantee of 10 years. They also will extend the workmanship warranty for an additional ten-years if they return to provide roof maintenance, on a time & materials basis, within the tenth year of the workmanship warranty period. They've been in business for 20+ years and have a good reputation so far. So that's more what I'd be hoping to get value from, and part of why it seems better to me to keep the extra 35% that a 4th-ply would cost, towards future work.

Appreciate the insight on the costs per mount. By flashed in bracket, do you mean something like a QuickMount PV mount, or something special? The solar installer was saying they put a sealant in the hole drilled for the fastener, which then has a metal flashing, which then gets the modified bitumen layer square torched over it.

[DanS26]

Step out of the box for a minute......is there any way a ballasted system would work in that application?

[ButchDeal]

Well if you are planning to re-roof it anyway, you could just go TPO and then install MiaSole :

http://miasole.com/wp-content/uploads/2015/08/miasole_salessheet_tpo_roofing_flex2-english.pdf

[ltbighorn]

Not sure about a ballasted system -- none of the bidders proposed it -- but it seems sub-optimal to put extra weight at the top of a 2-story wood-framed building in earthquake country.

Hah, MiaSole looks amusing/fancy, especially for avoiding wind stress, though would look a lot less pretty with tons of micro-inverters sitting out though. Ultimately I don't think any installers here are familiar with supporting MiaSole, even if I was comfortable with TPO. Most homes out here are tar&gravel or modified bitumen, and I couldn't see the advantages of TPO/PVC over modified bitumen, especially for the price premium. Seems like they just add complexity for a home roof, and narrow the number of experienced contractors available to service them.

[DanS26]

You may be surprised how little extra weight a ballasted system would add. A lot depends how load bearing walls are organized in the building. I definitely would research it before punching a bunch of holes in a flat roof.

[Mike90250]

$50 per flashing is on the very high side for 10 minutes labor and $5 part. So what you are doing is paying up front for the repairs that are going to be inevitable in a flat roof.

[foo1bar]

$50 per flashing is on the very high side for 10 minutes labor and $5 part. So what you are doing is paying up front for the repairs that are going to be inevitable in a flat roof.

I think it's likely more than $15 in parts and >15 minutes labor. I think the standoff by itself is going to be $10 and then you have the "chemcurb" that goes around the penetration, and then I think there's a bit of membrane on top of that.
IF my guesstimate is right, at $100/hr that'd be >$40 in parts and labor - so $50 each isn't an unreasonable proposal. IMO that they proposed $50/each is just the starting point for negotiating - there's nothing wrong with countering. And I'd certainly ask for details on what exactly they'd do - ie. is it a standoff with chemcurb around it or some other method.

[Raul]

Over the pond in here the solar system has to be guaranteed for 20 years by law and its associated mounting hardware . So when it comes to flat roof installs 1 to 40 pitch we float ballast the system . There is nothing up there that will last 20 years once you done a penetration . Any torch on membrane will fail if on metal due to different expansion contraction of materials . The only think will last a reasonable time is a lead or aluminium slate flashing primed well prior torching . That will get expensive for few mounts. Cheaper just to add few concrete slabs carefully calculated for the wind load for that site.

[ltbighorn]

I looked around here, and outside of major commercial installers, very few installers seem versed in ballasted setups. Maybe not such a popular thing in earthquake country? I don't know.

[ncs55]

Your roofer's cost is actually in line for a roofer who is using the large UL and roofing code type of flashings, (not the home depot puny flashings), and knows what he is doing. A bit on the high side but not for a flat roof, they require a little more work to seal up properly and last. And a TPO or PPO would be a better roofing type. However you might consider a more robust mounting and racking system like ProSolar. http://www.prosolar.com/ In 15 years of performing installation and maintenance, IMHO it is the strongest mounting / racking system out there. Also with whatever racking you use, it is recommended to have your modules at least 6-7 inches off of the roof. This is for cooling, production and to slow the module degradation. Also make sure your installer leaves a gap between your rows to let the heat escape, jamming them together creates more heat and voids the module warranty. You should consider all of these issues as they affect the installation of the roof mounts.

[ltbighorn]

Thanks ncs55. I appreciate the insights. Yeah, I'm going to bite the bullet and have the roofer do it and cover it under their workmanship guarantee. My roofer will be sealing them the same way they flash all roof penetrations -- a flashing sandwiched between two of the three plys. With the roofer covering the roof penetrations, the solar installer will also up their labor warranty from 5 years to 15 years (though it's anyone guess if the solar installer will be around that long).

I feel pretty confident these roofers will do a good job as far as roofers go, as they were the preferred roofer for one of the 5-star/premium solar installers I worked with, whose market niche was basically doing "the best" everything. They also do a lot of major commercial installs on flat roofs. That solar installer seemed to trust the roofer, who even if only through that partnership has a lot of experience sealing solar mounts, to the point that the solar installer was willing to GC and sub-contracting the roofer directly, and provide their own umbrella guarantee, etc.

I'm going with a different solar installer (much more price competitive), but to me this seems about the best roofing contractor I can get for this market, at least without spending double or triple for the work. The roofer has a good reputation independently, and has been in business in this area for 35 years now, with multi-generational customers etc. This gives me more confidence in their 10-year guarantee on the roof, extended to 20-years if they perform at least one inspection/maintenance within those 10 years. Their pricing, while not the cheapest, is also quite competitive.

Thanks for the tips on mounting heights & separation. I'll make sure to bring these up with the solar installer as they work on the design. Since all the panels will need to be on tilt-up racks, I think they'll probably have gaps naturally as going edge-to-edge would require more expensive, higher-height racking. My roof is not visible from any street, so there's no aesthetic concerns re: jamming them in or keeping them low-profile.

re: TPO/PVC are options, but I guess I'm a bit conservative on that front -- seems like there's very few installs of that type out here for residential roofs, much more limited selection of vendors, frequently changing formulations, and mixed reviews on the longevity/serviceability/environmental impact. The cost here is also significantly higher, to the point that even if it lasted 10 years longer, it'd only come out slightly ahead (or break even for IB Systems PVC). If I had been working with these materials everyday for the last 30 years, as an expert I might feel differently. With my limited experience, I feel comfortable going with the "known" option and pocketing the savings to deal with any potential issues down the road.

Kind of the same approach as the solar equipment -- money in my pocket is worth more than extended warranties in most cases, especially when my ability to predict how well those guarantees will actually cover my risks is limited. Self-insuring and all that.

Again, thanks very much for the advice! Now that I'm starting the action part of the process, it's all doubly relevant.

edit: fix typos

[ncs55]

We always work with the same roofer for our flat roof installs. And for the same reasons as you are. Tilts are the way to go, glad to see others are even considering tilts. They are a hard sell here in So Cal. regardless of performance increase. I only mentioned the module spacing because we see that on 99% of the systems that fail prematurely. You are on it, You are Welcome. Good luck with your installation.