Anyone installed solar on a finished roof with closed trusses?

[Craiggo]

Hi. I’m a homeowner that will be looking for approved and reputable installers once (if!) I get clarity on what would be involved to install with my below circumstances.

Our house has a large extension built a few years ago with a south-facing pitched roof — approx 11m wide, 34° pitch, and totally unshaded.

The roof space is part of the upstairs living area, so the trusses are fully enclosed behind plasterboard. Octopus Energy refused to quote, saying they need to see three exposed trusses and won’t proceed even with build-phase photos, structural drawings, and building control sign-off.

Has anyone here installed PV on a finished/inhabited roof like this?
I appreciate that there are many building specific details required, but keen to know if in general this is feasible or best avoided.

I can provide photos if helpful.

Happy to pay more for the installation due to additional time/complexity — just don’t want to give up on a perfect roof unnecessarily. Appreciate any advice or first-hand experience.

 

[plugsandsparks]

Struggling to see the problem, obviously the cables will end up running outside instead, dont understand 3 trusses, is that their proposed fixing locations? i would expect many more trusses along an 11M span.
A photo of the roof would help also i assume its tiled

 

[PS Electrics]

PV Installers are not Structural Engineers so anything that is outside of the typical over engineered unmodified roofs typically on older properties or ones that have been modified for conversions so that beams and trusses are not visible will be outside their comfort zone/ expertise for dealing with.

Existing structural drawings, photos and building control sign off while helpful are not really enough. It is much better to be able to stick your head up a loft and visibly verify the roof construction and timber sizes and spans etc.

Therefore you will require the services of a structural Engineer, ideally if there was one on the original extension it might be worth approaching them.

The Structural Engineer will work with the PV installer to verify that the roof will be able to take the loadings of the Solar Array and its associated supports.

It should not be a problem other than adding additional costs.

I think Octopus were saying they needed to physically see exposed trusses to verify construction and a minimum of three to verify. If it is Plasterboard it may be worth exploring the possibility of exposing the trusses for their inspection, you would need to clarify that with them though. Not sure there would be that much between having the beams exposed and then made good compared to the cost of a structural calculation / report by a Structural Engineer though.

Also if the roof is tiled it may be easier to expose the roof that way to verify the roof construction. Though if scaffolding is required then it just might be easier and cheaper to employ the Structural Engineer.

I would talk to a Structural Engineer, ideally the one that worked on the original extension if possible and get some advice from them about how to proceed and what the cost would be for them to verify the loadings your roof can take.