EDPM to insulation board adhesive

[wagster]

I'm building a log cabin office (about 5mx3.5m) and I'm going to insulate the roof with 50mm insulation board. The insulation is made by Mannok but is basically the same as Kingspan, foil-backed on both sides. The plan is to get the roof deck on first (pine tongue and groove boards), frame the outside edges of the roof deck with 2x2, glue the insulation down inside the frame, then glue a single sheet of EDPM on top of the insulation and frame, then finally fix the EDPM to the underneath of the soffits.

Any idea what sort of adhesive I should be using? PVA is cheap and works really well on almost anything, a lot of EDPM sites talk about contact adhesive and of course there's a plethora of "specialised" EDPM adhesives that are as expensive as the EDPM itself and might just be PVA or contact adhesive for all I know.

Any opinions on this? Has anyone done this before?

 

[Alastairreid]

Pva will not work with epdm it will not stick for any amount of time.
Water based epdm glue adhered to a wooden deck is the proper way.
Glue directly over the insulation boards will react and fail.

 

[freddiemercurystwin]

 

[cdbe]

You can buy PIR with a thin layer of plywood on one side for bonding EPDM to but probably costs a fortune.

 

[wagster]

Pva will not work with epdm it will not stick for any amount of time.
Water based epdm glue adhered to a wooden deck is the proper way.
Glue directly over the insulation boards will react and fail.

Thanks. I've ordered some SF EDPM adhesive. I think I'll experiment with a small section and see how it performs. I've seen roofing contractors bonding Kingspan to EDPM, but there's nothing like trying it out yourself. If it doesn't hold well I will board over the insulation.

 

[freddiemercurystwin]

You can adhere EPDM to certain types of insulation because they're designed to take it but what you have isn't. Madness, all for the sake of half a dozen sheets of decking, 9mm would do. And then the cost/hassle of having to sort it out if it fails in say a year or so.

 

[wagster]

You can adhere EPDM to certain types of insulation because they're designed to take it but what you have isn't. Madness, all for the sake of half a dozen sheets of decking, 9mm would do. And then the cost/hassle of having to sort it out if it fails in say a year or so.

Aha - that's good info. I'll get some decking in so.

 

[wagster]

You can adhere EPDM to certain types of insulation because they're designed to take it but what you have isn't. Madness, all for the sake of half a dozen sheets of decking, 9mm would do. And then the cost/hassle of having to sort it out if it fails in say a year or so.

Thanks for talking me out of doing something stupid! OSB arriving tomorrow.

 

[noseall]

but probably costs a fortune.

Correct.