450x450x32 concrete slabs on new felt roof - What to use to lay slabls on bitumen fel

[Mettauk]

Need to lay (stick) concrete slabs to a new felt 5m x 3.5m roof

Deck is screw fixed plywood on substantial joists, felt is two layer fully bonded with fine grit chippings imbeded in the top layer. Roof has no upstands to allow paving to go over edege by 15mm with small drip cut in underside to form a drip.

Thought of using leveling compound but can't find one that's OK outside and happy on bitumen, same issue with tile adhesive, thought of using Mapei fast set??

Anyone know a solution?

[seanandruby]

Don't think i like the idea of sticking slabs to felt, if it starts to leak....?
if you do go ahead maybe sbr might do the job.

[Mettauk]

Don't think i like the idea of sticking slabs to felt, if it starts to leak....?
if you do go ahead maybe sbr might do the job.

I get the point about leeks but that's a bit like if a damp proof membrain fails....

Its all fully bonded and "better" than a 3 coat bitumen dpm. But is on an insulated plywood deck.

I wonder what the technical issues of using cement based adhesive are? Will it react with any bitumen it comes into contact with etc?

[rxbren]

Not sure of the name or if you have to use specific slabs but you can get a frame system that would be suspended and the slabs are located on top of it I've seen it in site but we weren't laying it

[rolysatch]

i just reroofed my conservatory flat roof with epdm rubber and used promenade tiles which are for flat roofs. with those i used rubber support pads on each corner of the tiles and stuck the tiles to the pads with sikaflex. but the pads themselves aren't stuck to the roof. so it's like a big mat that isn't going anywhere. however promenade tiles although cement based are reinforced with fibreglass and only 300x300 so would be stronger than normal slabs and can handle being supported just on the corners. i dought you could do that with concrete slabs.

but you could check if sikaflex will damage the bitumen and just stick them like that possibly straight to the felt or use another pu adhesive. check the data sheet first. the otherway promenade tiles are laid is with hot bitumen. this isn't advice btw i have know idea if it will work with concrete slabs in your case.