Fixing to new slate roof

DomB said:

Glorious! thanks Worcester. It's that dog-leg on the anchor you need to be able to get them to sit on the rafters. The way Schuco's etc are shaped I'm guessing they are designed to sit on the slates. Thanks again!

p.s. @whlphil; I'm thinking the flashing comes down further than the hole beneath it so alles klar, init

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haha yeah but I thought it looks as tho its sat off the slate slightly, which as an ex roofer I know it'll get wind driven snow in it?

It's that age old challenge, sit it on the slate and you'll transfer loads , sit it above and you'll have a bit of a gap It's down to notching the slate beneath as close to the bracket as you can, you're usually looking at no more than 5 mm under the hook, big enough not to transfer loads to the slate, and small enough to keep the 'snow' out, bearing in mind that these are under the panels as well, it'd have to be might drafty to get snow up there. Does any one know what happened last winter with the big snows we had, - did snow go up UNDER the panels? At 5 mm that's no more of a gap than you get tiled fixings, and no-one's ever commented on snow before!

If you use hanger bolts you have no load on the slates and a weather proof connection between the roof covering and grid. However, you do lose the kidolagy effect.

@solarsavings,

Sorry no-one has ever yet shown me the TUV, BBA, or BRE certifcates or suppliers installation procedures for installing hanger bolts on a slate roof, and as a Chartered Civil and Structural Engineer, until they do, I'm not risking my professional indemnity insurance on it.

Why would they? if you wanted to find them you would. MICE, I'm impressed:willy_nilly:

I've tried, I've asked, again and again, it's the distributors that promote it, and nothing forthcoming from them. Those manufacturers that I have spoken to direct won't recommed it, and the others wondered what the *** I was talking about. Seems that slate roofs in Germany are actually constructed differently from here!

Just a quick word of advice or warning for those of you not yet working on slate roofs, we just had a nightmare of a job.

Main roof was welsh slate, turned out when re-roofed they'd stretched the gauge and the width such that there was an 8 - 10mm gap between each slate widthways, and the gauge instead of being 10" was 11" so they'd saved a row of slates in the re-roof, then the new holes had been punched near the centre so some were in the gap to cap it all they'd used galavanised nails, What should have been a simple one day job, turned into two..

Second roof which initiallly had been assessed to be spanish slate turned out to be brazillian - think brazillian bikini, this stuff was about as much use as covering a roof breath on it and it broke. On top of that it was also held in place by galvanised nails. Net effect we had to saw the nail heads off, as the slate ripper just couldn't get the nails out. 40 Slates broken and replaced, nothing we could do about it.

Job looks absolutely stonking now it's finished, proper brackets with proper sized screws, all nicely Iko flashed in (yes I WILL use a lead substitute! - proven, got the badges and certificates) oh and of course aluminium nails! However a straightforward 2 day job turned into a 4 day nightmare..

They've ended up with a better, more waterproof roof than they started with, and it will last longer, so in the end, job well done.

It happens to us all!

I started this thread a few weeks ago and thought I should report back. Although my question was about slates, the roof I was doing was to be covered in Marley Duo Edgemere interlocking slates. Do not be fooled by the name, it turned out they were modern concrete tiles moulded to look like slate. That means they were shiny and slippery and only 10mm or so thick, so tricky to grind out and ..... slippery. But it all worked fine using the standard schuco anchor with the smallest rise.

I could not just have left it to the roofers to do it as they had never seen solar anchors before in their lives. I did leave them to do the very last bit though. Visited today to meet DNO with main builder and noticed that where I had left some solar cables in flexible conduit to be fed out under tiles, some dim roofer had drilled a hole in the slate/tile and fed it through! At least the boss builder was embarassed when he saw it!

On a different point had a very difficult meeting with WPD there. I was pursuading them my solar design was acceptable. 4.6kW panels but east /west with a few facing south so actually with a bit of 3d trigonometry I could show that on midsummer's day the arrays would only generate 3.6kW max. They agreed through gritted teeth, but they will not let the client install an electric boiler at 10kW because the impedance is too high and they are concerned about flickering in other customers properties when boiler kicks in. For 10kW their policy requires an impedance of around 0.2ohms - tricky 275m from transformer. Their computer says "No" even for an electric boiler at 4kW. They really do seem to be doing their upmost to protect the network and pass on all possible costs to customers.

Regards
Bruce

Are you planning to try claim FITs at the sub 4kWp rate for that installation?

Yes, because the TIC is <4kW.
Regards
Bruce

Be aware that different slates act differently when a force is applied to them. Welsh slates tend to split head to toe which still leaves them insitu due to the fixing being on either side. Spanish slates have a tendency to split side to side just under the slate fixing which results in the bottom section sliding away leaving a gap between the two visible bottom slates. Drilling through slates tends to introduce a hairline crack which over time will split and compromise the integrity of the slate. I personally would remove slates, fix bracket directly to rafter and slate around with code 3 flashing over to achieve a minimum cover of 150mm each side for severe exposure area. I have hands on roofing experience and also a Chartered Surveyor with over 17 years experience of working on slate roofs only in Gwynedd, North Wales.

Can i add some comments about this as i work for Hilti, I am struggling to find approvals from any main mounting system manufacturer for using hanger bolts in slate tiles. Many slate tile manufacturers will not cover tiles under warranty which have been drilled and fixed how can you garrantee against water ingress in a drilled tile + slight over tightening can damage the tile. Another issue is BRE regulations in GB on fixing into 35MM-38MM timber substructures, BRE states that if you have a 38mm wide timber and you drill into the centre (19mm) the distance form the centre to the edge cannot be more than 3 x the diameter therefore you cannot use anything above a 6mm screw. Hilti hanger bolts are grade A2 stainless steel like other manufacturers so the comment about ours being two hard for UK timbers is not correct, all i would say is be careful in using hanger bolts on slate without having in your hands the warranty from the manufacturer because you will not want to install it and find the warranty is invalid

Brand new roof going on but the roofer was 100% happy with install. Good old lead to flash even up the bonds (you cant see from pics) so 100% WATER TIGHT.

I am glad this has worked for you, the good news is our understanding is that the BBA & BRE are working with the MCS on system and installation approvals on mounting systems for solar PV which means the industry will have a much better understanding and some guidence on what they can and cannot do. Regards

There is no real answer for slate really I mean every company I have worked with use what they think is best.