GRP Roofing in Bad weather Area

[Mark 9002]

Next spring / Summer I intend to replace the 35m2 leaking Box section steel roof on my garage with a GRP roof. I live in the Far North of Scotland where the weather can be a bit hit or miss. My question is, would it be possible to pre apply a coat of resin to the OSB 3 prior to commencing with the installation to waterproof the board before putting up? If so, would it need sanding to key it before commencing with the application of Resin CSM ?.
Any advice would be appreciated

 

[Notch7]

unfortunately all flat roofing systems have a bit of a complication: they need dry weather at time of installation.

I personally cant see the advantage of what you suggest -because rainwater will seep through every single gap between the boards, potentially causing long term internal damage.

And you will still need to do the resin coat and fibreglass matting in dry weather.

OSB3 is quite waterproof -it will tolerate a few showers without damage.

My experience is that properly covering with plastic sheeting works very well -if time is taken to get is properly fixed and taped in place and kept flat without wrinkles.
I manage to keep my 16 sq M shed completely dry for a year with DPM.

 

[foxhole]

Consider EPDM .

 

[Rufus Raintight]

You can apply a layer of resin to the boards but you could also go one step further and apply the first layer of the system including glass fibre to the OSB boards if you wanted to which would just leave fibreglassing the seams and adding the topcoat, at one point in time there were companies selling the OSB decking already pre-done with the first layer but it never took off because the cost of labour and transport made them too expensive.

With regards to your sanding question, it depends on how long these boards are going to be left but anything over 24 hours and you would need to rough up the resin to key it to the next layer. The problem with GRP is you do need a completely dry deck even if it was precoated with resin it would still need to be dried thoroughly before laminating.

 

[HERTS P&D]

See below, I think there are 4 or 5 videos in total.

Andy

 

[Mark 9002]

Thanks all for the info. A lot to consider. Like I said, I'm pre planning for next spring, so plenty of time to weigh up the options. The reason I asked in the first place was that somebody mentioned to me that they had a GRP roof fitted a good few years ago on a lean to garage roof, and they said that the roofers actually put the resin and mat on the individual osb boards at their yard, and then when the forecast was ok, then fitted and bandaged all seams and fixings before top coating. This was quite late in the year though, and a day of decent weather here in autumn is quite rare. Rufus, this sound more along the lines of the pre matted boards you mentioned

 

[Mark 9002]

Maybe I could do this in my garage prior to removing old steel sheet roof