Fixing to new slate roof

[solarsavings]

The only roof fixing that I've used and had trouble with just happens to be Hilti's plain tile roof anchor flexing under wind loading and causing the lap tile to break. Never had that happen with an hanger bolt and doubt I ever will. We use Schletter hanger bolts I'd be surprised it they weren't approved.
[h=1][/h]

 

[solarsavings]

From Schletter's website

Special roof hooks Slate/ Prefa
VA-quality, without plate
In case of slate roofs the optimum form of mounting is mainly
determined by the roof covering! In certain circumstances, a
mounting on hanger bolts can be advantageous.

Seems they are TUV certificated too.

 

[JD6400]

As per another post a long discussion with the Hilti rep and they do an identical anchor bolt and won't authorise them for use on slate, (Hilti have neen making pv mounting systems for ages on the continent)

As I say, show me the CE, TUV or BBA certificate for them and the detailed instructions for them and I'll change my mind, until then I won't use them on a house on slate. Wind load, Dead Load, Snow load, something has to flex.

Which distributors are promoting them / saying it's OK ?

And I'll happily discuss it with them *(without mentioning names!)

Not wanting to fan the flames but i have been told by a very good source this is because the hilti fixings were splitting the rafters due to the fact we use a lower grade timber in our roofs than Germany .
Flashing IMO would give me more peace of mind personally .
Seem to remember a post a couple of months ago where they had been pulled on a inspection for fixing through the tile ?

 

[Worcester]

@dp, yes that what he said, the wider offset of the german fixings (which are almost identical to the schletter ones) when used with 8mm coach screws and our narrower rafters caused the rafter wood to split. So the UK spec ones use 3 x 6mm instead of 2 x 8mm and are more in line.

 

[DomB]

Heya, I'm made it back from that first slate job! It went well, I've attached a couple of pics of how we mounted the anchors (which were basically just 90' angles like Schuco's are).

We removed the top slate, attached the anchor by coach screwing through the slates underneath into the rafter, flashed over the anchor and put on some patenation oil. We then cut a strip out of the top slate and replaced it. We used 'lead clips' to put the slates we'd had to rip out back in place (I think you can see the bottom of the lead clip holding the slate above).

For info, the slates were 20"x10". For 24 anchors we got through 9m of Code 3 150mm lead and less than 1/2 a litre of patenation oil.





Cheers

 

[Worcester]

Looks good, well done, and looks like the weather did its usual thing!

 

[MikeXl426]

Hi DomB

Thanks for that. Useful info and I'd much rather do that than use the anchor bolts!!!!!!
As you say you screwed through the slate underneath, I take it the bracket is resting on that slate and so the slate is taking the weight. Is that right? I'm just trying to get my head round this one as you've got the thickness of the battens so it seem the coach-bolts don't actually screw right to the rafter?

Thanks

Mike

 

[DomB]

That's right MikeXl426; the anchor sat on the underneath slates with the main weight bearing point being the batton underneath. The anchor was put in line with the rafter so the coachscrews basically just held the anchor in position.

We were trying to suss out how to get the anchor to sit on the rafter itself but that would have involved taking a long strip out of the two slates underneath (they were double lapped) and that would have left us with an unflashable area right at the bottom of the anchor. The other method we considered was padding the back of the slates but again that would have been alot of slate removals and lead-clippings. The way we chose was the lesser of several evils!

 

[MikeXl426]

No problems with the slates cracking then?....they can be sooooo brittle!

 

[DomB]

We did have a few cracks, aye. But mostly from tearing and walking, not from the anchor tightening. Must admit, much as yourself I suspect, I'd have preferred the weight to not be on the slates at all. I figured if people are bolting the anchors straight to the top (our dist'y said that was an option!) then having them bolted to the underlayers & flashing for water ingress was OK.

Meantime I'll defo keep my eyes out for ways of getting the anchors to sit direct on the rafters

 

[DomB]

p.s. they're slippy lil' feckers n'all!

ahem

 

[Worcester]

Meantime I'll defo keep my eyes out for ways of getting the anchors to sit direct on the rafters

Any help:

View attachment 6174

 

[MikeXl426]

Now they look like an excellent solution! Always wondered about how you fit the 'standard' hooks for slates but these looks the mutts nuts! A sensible solution.

 

[whlphil]

@worcester - Like the look of them but what happens at the bottom of the Leadwork under the bracket what fills the hole?

Typical sales pictures! avoids the bits they dont want you to see! ;-)

 

[DomB]

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