Help Needed With My Leaky GRP Roof

[Jeremy Harris]

I can say with certainty that G4 will absorb a fair bit of moisture when it cures, plus it will form an excellent moisture barrier that will 100% prevent any slight remnants of moisture in the substrate from reaching the GRP.  The only thing to watch is to make sure that the third coat of G4 isn't allowed to fully cure before you start to apply the first coat of resin.  The G4 needs to be allowed to cure until it's just tacky on the surface, then roller the first coat of resin on.  Not only does this ensure a good bond, but it also allows the final coat of G4 to absorb any slight trace of moisture that might remain on the surface from condensation, and will draw moisture out of the styrene in the resin, ensuring that the critical first coat remains moisture-free.

[Russell griffiths]

9 hours ago, jack said:

Sorry for slight hijacking of this thread, but I was about to fiberglass my balconies. I was actually planning to post on this topic today or tomorrow, but seeing this thread I thought I'd keep it all together.

 

The OSB unfortunately got a decent soaking over the weekend when I forgot to cover it. I'm allowing it to dry during the day when it isn't raining, and am covering it up at the end of the day, to keep any dew off it and reduce the condensation.

 

I know that there are both temperature and moisture issues when laying fiberglass. Regarding temperature, I was planning to wait until we had a couple of clear days with expected temps in the mid teens, and then do the work on consecutive afternoons (base one afternoon, gel coat the next). The balconies get sun in the morning, which will help.

 

Based on the comments above, I'm now a little concerned that perhaps I shouldn't be considering doing this until spring next year when things have warmed/dried up.

 

I really don't want to wait though. Short of getting heaters involved, is there anything I can do to allow me to crack on with this in the next week or two, assuming weather permits?

 I had to re do my kitchen roof over the Christmas holidays a couple of years ago, so definitely not a good time 

what I did was to go and buy a big blowtorch, the sort roofers use to stick down the torch on membranes

it was the type of torch that has a big fluffy type of flame not a skinny brazing type flame. 

I got on the roof first thing in the morning with a leaf blower and gave it a really hard blow, and then heated the entire surface until it was steaming, I wanted every drop of moisture out, cup of tea and then warm it all up again until the osb was really nice and warm, allow it to cool while you cut your matting to size and your ready to go. 

Mine came out superb, it was a bit of a bodge job as it’s on a house I want to knock down so didn’t bother with fanciful details. 

 

 one thing I will strongly recommend if you have a drip edge into a gutter, then router this edge into your osb as it creates a lip that water sits behind, most of the instructions I have seen say water will flow over this lip as it’s only 1.5mm high. Which it does when in full flow it’s the little showers that sit behind it.