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Question:

It's my first time repairing a fibreglass roof and I have some questions:

1. What do you do with the Topcoat?
2. If doing a roof for the first time would it be advisable to apply two layers of matting?
3. When fitting the OSB, is it fitted tight or should I leave a gap or tongue & grooved?

Answer:

If you are doing a new roof, we would always recommend you use 18mm T&G OSB3 boards, they need to be fitted as per manufacturer instruction so should have expansion against any walls of 10-20mm.

For general weatherproofing, 1 layer of 450g matting is sufficient but if there will be any moderate foot traffic in the future, then use 1 x 600g layer of matting. In the event of a roof balcony, roof garden or additional loading then 2 x 450g layers of matting would be required.

Resin consumption for fibreglass onto OSB is:

• 1.5kg for 450g
• 2kg for 600g
• followed by 1kg or 1.5kg for second layers where appropriate

With regard to Topcoat, coverage is 500-600g per sqm. When redoing an existing roof, you should scuff/sand the existing surface to key, brush down and clean with acetone prior to mixing and then apply the Topcoat. For best results on Topcoat, you should apply it with a Mohair roller.