Solar panels on flat roof...

frazk

Well-known Member
I've bought myself16 solar panels on the cheap off ebay... I was thinking once I get my flat roof replaced it'd be nice and easy to chuck some on there but the more I look into it the bigger the minefield it actually is.
I'm an electrician so connecting them up is easy, I've already fit 6 on top of my pergola to give me some free electric temporary.
I found some fixings that screw into the epdm roof and then a boot fits over the top to seal the roof again, but these are in the USA and I can't find a stockist in the UK. Has anyone used any kind of roof fixing before? I'm obviously very nervous of penetrating the new roof 😬
Another option is ballast but from what I can see I'll need approx 100kg per panel and I'm not over keen on adding around 2 ton on top of my roof!
I've come up with another idea of making a steel frame and fixing it into the facias/roof timber so that may be the route I go down.
I understand I'm meant to get PP and structural engineer etc but I'm pretty sure they'll never find out anyway....
Anyone got any other bright ideas they're using? Or know where I can find the roof fixings ill need?
Thanks
 

The Dreamer

Distinguished Member
I was going to mention PP for a flat roof fitment, but as you’re aware, I’ll not bother! ;)

As for fitment, I’d have thought a simple frame, rather like the framework you might build for decking would do the job - then it might just need a couple of secure attachments.

If you know where the joists are underneath the membrane, would it be possible to slit the membrane open at a couple of points and put a small block on the joists that you would anchor to? You could then place the membrane up the side and over the blocks - you would need to add some extra membrane yourself to do this and heat seal it, but this would stop any water pooling around the fixings themselves. A bit like how a roof light is built up slightly out of the roof if that makes sense.

....actually, just re-reading your post, it seems the roof hasn’t been replaced yet. So add a few blocks to the top of your joists and get the roofers to build the membrane up and over the blocks. When it comes to fixing your panels just screw into these blocks, stick some bitumen sealant around the fixing itself (I’d probably use coach screws with washers, and stick the bitumen under the washers before a final tightening down). If you plan it right, you could make sure the fixings are underneath the actual panels, so would be protected from direct rainfall too.

I‘ve used this stuff to good effect for sealing roof shingles...



Hope this makes sense. Equally, I’m not a professional, so don’t rely on what I say - they’re just my musings.
 

frazk

Well-known Member
I quite like that idea dreamer, I haven't decided on DIY frame or to buy one yet, but placing some fixing under the epdm could be a good idea. Even if it's like you say something to lift the rubber to stop the pooling could be a winner!
You might remember my thread about getting the roof done on the green home grant so I can't imagine them being the most helpful workmen but I can only ask.
I'll give that some thought, thank you!
 

aVdub

Distinguished Member
Probably have to take into account the wind, if it is an area prone to strong winds and ease of access for cleaning and maintenance.
 

frazk

Well-known Member
Probably have to take into account the wind, if it is an area prone to strong winds and ease of access for cleaning and maintenance.
Yep wind is the reason for the ballast to weigh the frame down or fixing it to stop it moving.
I know I need to leave at least 600mm around the side of the panels to the edge of the roof, I assume that's for access, cleaning etc.
Thanks
 

oneman

Well-known Member
If you are having the roof replaced then why not speak to the roofer, they will probably recommend fitting ? Plus it may affect warranty if you start putting loads of holes in the new roof.

Most of the installations I've seen don't have ballast, I assume because the installation is fitted to joists or battens running across the joists. I assume you are using something like these, Solar Panel Flat Roof Tilt Mount
 

frazk

Well-known Member
If you are having the roof replaced then why not speak to the roofer, they will probably recommend fitting ? Plus it may affect warranty if you start putting loads of holes in the new roof.

Most of the installations I've seen don't have ballast, I assume because the installation is fitted to joists or battens running across the joists. I assume you are using something like these, Solar Panel Flat Roof Tilt Mount
The problem is I'm having the roof done on the green home grant scheme, I haven't met or spoke to the guy doing the work yet, only a couple of their employees who quite obviously knew nothing about the actual work being done. I'll speak to them again in the coming weeks see if they have any suggestions.
Its these kinds of frames I'm thinking of fitting in an east/west config... Flat Surface Solar fixing Kits | Garage | Shelter | Flat roof
And I've since found these fixings... ROOFTRAK Integrated Fixing Point | Nicholson
If I build a steel frame to mount them frames on I think I'll get away with 6 fixings into the roof, the less the better!
They're about £350 for the 6 fixings so not cheap, then £450 for the frames, £800 all in isn't too bad but it's gone up a lot from the few lengths of 3x2 I was hoping to use originally!
 

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