Solar Panels on GRP Flat Roof ?

I have a flat roof topped of with GRP.

Planning to get some additional panels to go with the main roof installation. No drama.

I was expecting free standing with ballast. But the surveyor has suggested bolting them down though the roof to the joists.

Panic mode engaged, I’m like no way. Rather not have panels on the flat if it could mess up the integrity of the flat roof.

Am worrying uncessarily?

Anyone here got panels on a flat roof without making holes and future problems.

Thanks.

I’ve got panels on a flat roof (3 degrees pitch, but close enough) but it’s corrugated steel, not grp. It mostly annoys me because there isn’t sufficient angle to allow the panels to be self cleaning. No leaks though. I put panels on because it was cheaper than insulating to prevent us roasting on hot days (it’s ona pergola)

I can’t see any benefit to fixing through the deck, only drawbacks. They should be checked for wind uplift but only to determine the appropriate level of ballasting.

My dad was an architect…. He never had anything that put a hole in a flat roof as he said it would always end badly.

That said, the ballast to hold the panels down is going to be pretty heavy I’d imagine so you may have an issue there as well.

I built the main structure of the roof many years ago.

The joists are oversized then, so no worry with the ballast weight.

Perhaps they think the shiny/slippy GRP surface will allow the panels to move around in the wind.

At the moment… No way to any holes in the GRP.

Thankyou for your comments above.

would it not be possible to fabricate a structure on top and secure it in other ways?

id sooner have those big panels secured, but not at the expense of drilling through the roof

my installer managed to make my main roof not waterproof anymore and currently looking for a way to resolve that

Fabricate a uni strut structure ie triangles and find alternate methods of fixing, then the solar panels can also be on an angle for self cleaning

Another vote for avoiding putting holes through the roof.  Weight of panels and supporting structures (even without ballast) can create ponding on roofs that weren’t built for the weight, then you’re into double trouble with any holes put in.

GRP’s combustible as well, and PV panels do go on fire.

How old’s the GRP?  Might be worth shelving it until you’re replacing the roof, then think about the roof and panels together.

Edit,: sorry, hadn’t seen your reply about joists and weight.