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Is my roof strong enough to take solar PV?

Posted by Chris Rudge on 25 March 2013 at 9:33 am

Q: I live in an old stone cottage (c 1830) with roof rafters that I'm sure wouldn't pass current building regs for strength, even though they're not the original ones. The walls seem sound enough though. Would it be possible to put up a solar pv array that was supported on the 2 end walls (about 8m apart) and didn't put weight on the roof in between? Would it increase costs much?

A: Any Solar PV system on a roof will need regular support across its span. Though in principle the array could possibly support the weight of the array on each end wall, the array will sag considerably over that 8 mtr span. To counter this, a standard roof array needs a support bracket installed every 600mm to 1mtr or so along the whole length of each support rail length.

The only safe way for you to get a PV system installed will be for a structural engineer to specify roof strenghtening inside the loft area, with bracing to support walls. Most PV installers will have a Structural engineers service to hand, and will be able to organise a survey at reasonable cost. This way, you will be able to budget for the installation beforehand.

Unless the roof rafters are areally old and thin, which is sometimes the case on old properties, the work for support may be quite minimal.

Image: Caymax roof mounting

About the author: Chris Rudge is a qualified electrician who specialises in renewable energy.

If you have a question about anything in the above blog, please ask it in the comments section below.

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1 comments - read them below or add one

Sims Solar Ltd

Sims Solar LtdComment left on: 26 March 2013 at 10:48 pm

Agree, bring in a structural engineer that will go up into the attic, don't rely on the offerings of a 'distance assessment' that some engineers offer.

Also be aware any structural improvement will require a Building Notice and cannot be self certificated by the installer.


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