GRP/Fibreglass info needed

[irving2008]

Thanks all, but seems my idea is a non-starter. I need 750kN pull-out resistance and the best bigHead will manage only 1/20 of that.

The requirement is to tie down Solar PV panels to a GRP 'flat' roof without compromising water resistance or membrane integrity. Normally you ballast the panels down but that needs ~300kg ballast per panel and the roof simply wont take the load. and finding a way to fix through the membrane and insulation to the underlying joists hasn't, despite my best googling, come up with a solution. Ideas?

[Neale]

Will the GRP take the load anyway, assuming you could fix to it, or will you have to get a fixing to the underlying structure?
Maybe piece of angle screwed to side of joist and against bottom of GRP panel, hole drilled through both and then bolted together with external penny washer and appropriate sealant. Leaves protruding stud to take panel fixing bracket? My boat has plenty of examples of this kind of seal, underwater, and good for life of boat. I hope...

[irving2008]

If only it were that simple :(

This is a 'warm roof' so the GRP is bonded to the insulation, 120mm Kingspan polyurethane, which is itself pinned to 6mm marine ply over the joists. On the bottom of the insulation is a vapour barrier. any fixing to the joist would need to penetrate the ply and the vapour barrier and the insulation, and should have a thermal break in it to avoid cold spots/condensation forming...

Will the GRP take the load anyway, assuming you could fix to it, or will you have to get a fixing to the underlying structure?
Maybe piece of angle screwed to side of joist and against bottom of GRP panel, hole drilled through both and then bolted together with external penny washer and appropriate sealant. Leaves protruding stud to take panel fixing bracket? My boat has plenty of examples of this kind of seal, underwater, and good for life of boat. I hope...

[mekanik]

is the structure attached to your house or freestanding ?
If you have a vertical wall(if it's South facing) you could attach a framework to the wall to take the majority of the load and just have the bottom edge of the panels resting on a load bearing strip of ally or similar with a slayer of rubber between that and you FG roof. would need to box in the open ends to stop the wind getting under the panels and ripping them off

[Clive S]

I take it you are wanting to put pv panels on a flat roof. I was surprised just how light they are but the problem would be the wind. How about installing them in a frame and holding the frame down with very thin wire guys with the anchor points on brackets off the brickwork. A bit like they way they install aerials on to a flat roof. ..Clive

[irving2008]

Panels are on a flat crown roof, no way to have guy lines there's too much else in the way. The issue is wind uplift, the panel, even at 10°, acts as an aerofoil; it's about 3kN per panel on the 1 in 100y wind. I could take a risk of course...

[charlieuk]

in that case just fill the gap between roof and pannel if the wind cant get under it wont create any lift.

[GEOFFREY]

in that case just fill the gap between roof and pannel if the wind cant get under it wont create any lift.

I don't think that is quite true. G.

[irving2008]

I don't think that is quite true. G.

Its not.... you still get suction... but it will reduce it...

[EddyCurrent]

Ask a reputable company to give you a quote, when they come round to take a look, pick their brains, it works most times for me.