Best method to fit Panel to slate roof.

[Scooby]

Hi.

The PV array I'm considering will be fitted to our recently-built garage roof. It has real slate (Spanish, I think), 600mmx300mm (I think - I can confirm tomorrow...), each fixed with two nails.

Some of the potential installers who came out to quote have warned against using certain fixing methods (obviously trying to put me off the competition...), but my mind was focused on the leccy side at the time and I didn't take in what was said - *cough*.:frown2:

Are there fixing methods to be avoided? Which is best? I think I recall some involved drilling large holes through the slate to get a fixing on to the rafters below. Others may have mentioned removing whole slates and replacing them with flashing around the fixing? Or cutting sections out of them before replacing them?

Thanks for any advice.

 

[SRE]

Most of our jobs are slate - never drill through it. Any roofer worth his salt would refuse to do that anyway. Remove the slate, attach the hook, flash the hook in with lead, take a bit off the slate and replce it flush with the other slates. If you've got Spnish slate it's very brittle expect to have quite a few slates replaced, even with an experienced roofer.

Any installer telling you that isn't trying to put you off the competition just giving you sound advice and don't forget to make sure your installer has a structural assessment carried out.

 

[SolarCity]

I agree with SRE. I know that a lot of installers on this forum use the drilling/hanger bolt method but every roofer I have ever spoken to is utterly horrified by the suggestion. Drilling the slates is the quick method so make sure you ask the installers which method they intend to use and make your own mind up.

 

[PvNewbie]

I agree totally with you guys and have a policy not to fit roof bolts! The irony is I'm about to lose a job (despite efforts) because I don't fit roof bolts. The customer is convinced that the tile won't be secure enough and prefers them to be bolted down. (crikey!) He doesn't like the idea of cutting tiles back and lead flashing.

How do I get round that? I'm at the point of saying 'ok' I'll drill 48 holes in your roof and do it the way you want. But it goes against principal. I really want the work though because I know it'll lead to other work!!!!

Advice appreciated!

 

[dansk]

I agree totally with you guys and have a policy not to fit roof bolts! The irony is I'm about to lose a job (despite efforts) because I don't fit roof bolts. The customer is convinced that the tile won't be secure enough and prefers them to be bolted down. (crikey!) He doesn't like the idea of cutting tiles back and lead flashing.

How do I get round that? I'm at the point of saying 'ok' I'll drill 48 holes in your roof and do it the way you want. But it goes against principal. I really want the work though because I know it'll lead to other work!!!!

Advice appreciated!

Mate - dont do it, at the end of the day you have to put a warranty on this work, and as its widely reported on here that in a few years there is a risk of failure with the rubber seal, then guess what the customer is going to be on your case.

Plus depending on the size of bolt and the size of rafter its may not be a good combo - 35mm rafter? 10mm hanger bolt? ummmm.

Do yourself a favour on this one and walk away, it will be cheaper in the long run.

 

[solarsavings]

Most of our jobs are slate - never drill through it. Any roofer worth his salt would refuse to do that anyway. Remove the slate, attach the hook, flash the hook in with lead, take a bit off the slate and replce it flush with the other slates. If you've got Spnish slate it's very brittle expect to have quite a few slates replaced, even with an experienced roofer.

Any installer telling you that isn't trying to put you off the competition just giving you sound advice and don't forget to make sure your installer has a structural assessment carried out.

In your opinion or fact?

Hanger bolts into the rafters? an assumption maybe.

 

[Scooby]

Thanks, everyone.

That prompted me to remember that one installer was going to drill holes through the slates and then silicone around the fixing bolts afterwards...

And the last guy who came out - from one of these 'advertise nationally, go for the hard sell' type outfits - who I managed to get down to a decent quote then turned around and said "Oh, I forgot - there's a £500 surcharge for slate roofs as we remove each one for cutting and there's bound to be a few breakages..." £500 for a few slates? *Cough*.

Cheers.

 

[SRE]

We factor in £150 for lead and slate, it's swings and roundabouts sometimes it's slightly more sometimes slightly less. It's also more expensive for the roofers as they spend quite a bit longer installing on the slate roof to a tiled roof - usually about another £100, then vat on top.

 

[jimmymckinney]

morning all,i thought if you drilled straight through the slate that would be failure regarding MCS inspection,thats what my trainer said but have seen quite a few websites (MCS accredited)showing that fixing method.

 

[Worcester]

@jimmymckinney we won't drill slates, however

if you drilled straight through the slate that would be failure regarding MCS inspection,thats what my trainer said

Was your trainer, a roofer, a structural engineer or an electrician?

I don't go to the car mechanic for tooth ache and I don't go to the dentist to get the exhaust changed (extreme examples :mickey: )

 

[jimmymckinney]

it was a pv course for electricians so i think he was an electrician

 

[Matt_M]

A picture of the flashed in method as previously discussed:

 

[pirhead]

Thanks for this pic I am about to fit my first system and was begining to question in my mindwhat I Learned.. Pictres speak 1000 words:bow:

 

[Energetic]

Forgive me if i'm being dense but doesn't this bracket still require fixing through the slate?

 

[Scooby]

Well, this'll test me to see if I've learned anything for everyone's replies! (Thanks very much, by the way.)

Energetic, obviously 'fixing through the slate' needs to be done - in a literal sense - in every case. But, what I understand the posters above are saying is that, it shouldn't be done with the slate in situ, such as by drilling a hole through it into the rafter. For one thing, it'll be hard to weather-seal that hole afterwards in a reliable, long-term way. And also drilling a large screw fixing into a narrow 'modern' rafter doesn't leave too much material either side...

The 'flashing' method - as I understand it - essentially involves removing the slate where the fixing is to be, screwing/bolting a clamp to the rafter below and then refitting the slate cutting it as necessary around the clamp and using lead flashing to seal it and make it permanently watertight.

 

[Energetic]

I'm not convinced this is any better than hanger bolts, the bracket rests on the slates underneath, which are drilled through, which then take the weight of the array. At least with a hanger bolt the weight is trasferred to the rafter or truss.

Don't get me wrong there's issues with hanger bolts but there's issues with any slate fixing method i've found yet, and in many cases issues with slate roofs without PV systems. As i've said previously on other threads i've been on slate roofs with broken or even missing slates that don't seem to leak, or even get noticed by the householder.

We choose a fixing method on the individual roof, no method is 'best' or perfect for slate as there are different types, qualities and conditions of slate, you just have to go with what you think is going to do the best job for a given roof...

 

[Scooby]

I can't say I understand the different methods as I'm a lay-man not an installer. However, I am fairly familiar with roof construction.

Again, my understanding is that when using the 'brackets' (ie: the method shown in the photo above), by removing and then cutting the slate around the fitted bracket, the slates themselves are not 'underneath' any bracket and are therefore not under any weight or additional stress.

 

[Energetic]

The top slate is cut around the bracket, the overlap of the slates means there will be at least another one or two slates underneath the top one at any given point.

 

[LightGEN]

I'm sure I've seen a slate roof solution, which consisted of a metal 'flashing' (for the want of a better description) which replaces the slate at the point of mounting. The flashing has a raised lump in the middle with a hole, through which a hangar bolt passes. Can I find the link I had to this, now I want to buy some, can I 'eck.

 

[Worcester]

Dulas used to do something similar, though they may not now as they have rapidly moved away from hanger bolts due to concerns over durability.