Roof strengthening for Solar Panels

Topaz63

There doesn't seem to be much on this in the forum. I'm having my roof replaced and my builder commented that people appear to have Solar panels installed without any checking of strength of roof. Is this so? I sent the spec for my panels to the roof truss manufacturer but I'm not clear they did anything different as a result. The battens are currently going up: should they be strengthened?

EricMears

Topaz63 wrote: »

There doesn't seem to be much on this in the forum. I'm having my roof replaced and my builder commented that people appear to have Solar panels installed without any checking of strength of roof. Is this so? I sent the spec for my panels to the roof truss manufacturer but I'm not clear they did anything different as a result. The battens are currently going up: should they be strengthened?

Part of the installation process ought to be to check that roof will take loading and to get somebody (seldom alas the building inspector from local council) to certify that's been done.

thenudeone

An increase in weight up to a certain proportion of the original roof weight shouldn't be a problem, but obviously there's a lot more to it than that, because the space underneath the solar panel means that there is a much bigger risk of wind blowing a solar panel off than a section of roof.

When I submitted my application for building control (being ultra cautious) I sent a spreadsheet I'd done showing an estimate of the existing plus extra weight of teh panels (BTW I am not qualified or experienced in building), which seemed to satisfy the council. Average weights per square metre of different roof coverings can be found off reliable internet sites.

I've never heard of any problem being caused by panels being too heavy.

As a consumer, you can't be expected to evaluate the structural loading and wind forces, etc. Ultimately, if the supplier installs something which isn't suitable, they're liable.

If you use an MCS / REAL supplier (which you have to, to get FIT), they should be more likely to do a decent job.

I wouldn't worry about it as long as you have a fairly standard roof structure.

rogerblack

thenudeone wrote: »

I've never heard of any problem being caused by panels being too heavy.

I question if this is really possible with a normal roof structure.

For non horizontal roofs, a wind at 80MPH (say) against the roof surface is going to cause _enormously_ more downforce than the weight of the panel.

For horizontal roofs, they need to be designed for quite hefty snow-loads anyway.

If your roof is going to fall down because you put solar panels on it, it's going to fall down anyway at 6" more of snow, or 5MPH more wind.

[Deleted User]

thenudeone wrote: »

If you use an MCS / REAL supplier (which you have to, to get FIT), they should be more likely to do a decent job.

.

our installer was high profile in the eco and pv/solar panel world and also mcs registered. They did a carp job but the faults were only apparent after 2 years. The roofing system had to be re-installed by a different and fully competent company. It cost a lot but we got every penny back by going through the small claims court. The re installation involved a structural engineer as the original system was installed with no regard to wind effects. They admitted liability and eventually had a ccj against them

Topaz63

After more enquiry I've been told by the surveyor that the spec for roofing battens was increased a few years ago to a British Standard for the battens of 25x50mm, and that this size is quite strong enough for panels added to slates or tiles. As the roof is new, it does conform to this.
Both the builder and the solar supplier mentioned the effects of wind under solar panelling if not properly fitted, so I'm expecting due care! The panel fitters include a roofer and an electrician. Thanks for your replies, people. Most helpful.
My son, whose house is old, was told his battens would need strengthening. This would've added to his fitting costs, so he didn't proceed.

Cash_Cow_2

I worried about this too at the time (and all answers were wooly) but I think I worked it out that it was ultimately about 20 stone spread over the roof - not much. D