Fxxxxxg polystyrene walls

Had a mare this afternoon. Wall mounted lights small things should of been simple...... the bloody walls had thin skim of plaster which crumbled at touch of it and behind was polystyrene, tried pigs tails, plugs, anchors not one of them gave a good fixing. For fittings not to weighty what do you recommend for quick drying for metal against plaster gotta be something pretty handy for jobs like this?

Toggles, design for plasterboard. 
 

https://www.google.co.uk/search?

the plasterboard has a polystyrene backing for insulation purpose, so either long screws and plugs if on to solid wall, toggles for anything else. 

Is there no substance to the wall material ?   It must be half inch  plasterboard  at least.  ?   Did you try whirlygigs  ?  

INSIDE or OUTSIDE of wall?

Inside would surely be plasterboard?

Outside it could be an ICF house (insulated Concrete Formers) in which case you want long screws to reach the concrete core, and plenty of sealant to keep water out of the hole.

Evans Electric said:

Is there no substance to the wall material ?   It must be half inch  plasterboard  at least.  ?   Did you try whirlygigs  ?  

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I did mate i tried curly wurlys it was just like a real thin skim of brittle plaster and then the polystyrene nothing just seemed to grip it very well and like you know every attempt just makes hole bigger and the positioning of where you can get bracket ends up out of proportions to others

ProDave said:

INSIDE or OUTSIDE of wall?

Inside would surely be plasterboard?

Outside it could be an ICF house (insulated Concrete Formers) in which case you want long screws to reach the concrete core, and plenty of sealant to keep water out of the hole.

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Inside. Was really thin brittle layer of plaster and anything trying to grip either this or polystyrene wasn't gripping. Sometype of decent adhesive surely would of been a better bet 

walls don't stand up with polystyrene alone, so there must be somthing solid behind it somewhere.

How deep did you probe?  Could be ICF still, in which case there will be a concrete core if you probe deep enough.

binky said:

walls don't stand up with polystyrene alone, so there must be somthing solid behind it somewhere.

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ProDave said:

How deep did you probe?  Could be ICF still, in which case there will be a concrete core if you probe deep enough.

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The gap between polystyrene and brick work behind was a good 3 inches I think. And that didn't look upto much. Nothing lesson learned I spose....get some long arse screws. Definately would of had more chance than piss balling around with curly wurlies and anchors

Interesting walls - never encountered them - they sound terrible

OP - are you sure that there wasn't about 12mm of plasterboard then the "polystyrene"?

Sounds a really odd set up. Suggestion:  Dig out a bit of the polystyrene, insert a piece of wood, and fix it in place with a bit of expanding foam or perhaps plaster.

I have just fastened wall units up in my kitchen. Consisted of 12mm plasterboard bonded onto 25mm insulation which is dot and dabbed onto thermalite, none known for their strength.

I got a 35mm hole saw and drilled into some 40mm scrap timber, this gave me some 32mm wooden cores. I then 32mm holesawed through the plasterboard and insulation, then a 8mm hole into the thermalite, pumped some resin into the thermalite hole, bit of 6mm screwed rod into hole, fit wooden core into hole, screw rod sticking proud about 12mm past the core which is now flush with plasterboard. Rock solid fixing, worked a treat.

Just rereading your problem, think I would use a 67mm and 70mm holesaws and some 3” timber and make up some wooden cores rawlplugged on the brick, 67mm holesaw into your strange wall and cores made with the 70mm holesaw.