Fibre cement corrugated barn roof

[solgen]

Hi folks,

It's been a while since I posted on the forum!

Can anyone advise on a good roof mounting system for a fibre cement roof please. I've looked at the K2, Schuco, Schletter... but nothing in my opinion seems to be that good for this roof type. The roof is a bit old so clamping to this roof with a rafter bolt will probably crack it!. The client doesn't want to change the roof yet but will at some point in the future.

Thanks

 

[SpitfireW'sale]

So far as I know a hangar bolt (rafter bolt) is the only way to mount on this roof type properly. There is very little weight on the roof covering using this method, only the compression needed to seal the rubber down on the pilot hole. If the roof can't take that amount of pressure you are going to have some real issues installing PV without breaking the whole thing!

We carry stock of suitable kit for either wood or metal purlins and will of course be happy to provide a quote for the mounting system if required. We have Schuco or Renusol in stock.

 

[SolarCity]

I agree with Spitfire. If it can't take that much pressure then it needs replacing anyway - which isn't a bad idea.

 

[Worcester]

Hanger bolts are the only way - schletter have a double bolt system. However if it won't take a bolt drilling through it and a gentle prssure of a washer, then it isn't going to last 20 years, so someoneis going to have to pick up a bill of remover panels, re-roof and re-install with a different mounting system....

I'ts not expensive to overclad with trapezoidal steel, sometimes, you don't have to remove all the old roof.

What's the roof on an inhabited / factory building / dairy or a draughty cowshed?

 

[Gavin A]

4th'd for hanger bolts as the only sensible option.

 

[solgen]

Hi, Thanks for your advice. The building is uninhabited and was probably a cowshed at some point. The energy will be supplied to the farmhouse a matter of yards away and is undergoing refurbishment with all the right levels of insulation so will be good for EPC certificate.

This may sound silly - but how do you overclad with the trapezoidal steel?

 

[Worcester]

So long as the underlying purlins are sound, you literally put new purlins over the top of the existing roof, anchored down to the existing ones and then put the trap stell on the new purlins, usually down steel purlins on steel purlins, not seen it done into existing wooden purlins. Like EVERY project we do we have structural calcs down first to ensure that the additional load including the overclad is OK, - it's a failrly standard roofing practice, - did it here: (the existing roof is under the nice new trap steel

 

[solgen]

Thanks Worcester - I'm not sure the customer will go for the additional expense of the trapezoidal roof solution, however, I will run it by them. This job is only for a 4kW system and I'm not sure the customer will want to go for the additional cost of the trapezoidal solution, but I will encourage the benefits. I will get the local council to first verify the roof is not asbestos and take a view from there. The purlins are concrete and I will get our structural engineer to perform his usual checks before proceeding further.

Thanks

 

[jason121]

If the roof is pre 1995, it will asbestos cement, so I would treat it as asbestos and do as the HSE guidelines recommend.
Spitfire has a solution for concrete purlings. Why dont go you advise customer for ground mount, cut out all the hassle. Good luck

 

[Worcester]

Wonderful concrete purlins! - have you worked out how to fix to them?

If it's only 4kw, then a quick re-roof of that area would be incredibly inexpensive.

 

[SpitfireW'sale]

If the roof is pre 1995, it will asbestos cement, so I would treat it as asbestos and do as the HSE guidelines recommend.
Spitfire has a solution for concrete purlings. Why dont go you advise customer for ground mount, cut out all the hassle. Good luck

As above - we have supplied a few jobs with concrete purlins and have a solution that works, as you can't drill into them to fix a hangar bolt as it has the potential to weaken, or even break the purlin. If it is only 4kWP then it shouldn't be too much hard work, but as previous posts if the roof can't take the hangar bolts it will probably break when you go up there to install anyway.