Estimating materials needed
You can also use our online calculator
To calculate how much material you need for a GRP roof:
Example: Standard garage 6m x 3m
Establish area in m2 and allow around 10% wastage. 6x 3 = 18m2 = 20m2
1. How much glass (CSM)?
Obviously 20m2! But you need to calculate glass in weight.
If you are using 600gm CSM the calculation is:
600gm x 20m2 = 12kg (buy a roll 28kg)
If you are using 450gm CSM the calculation is:
450gm x 20m2 = 9kg
2. How much resin?
Take the weight of glass and multiply by 3.
12kg x 3 = 36kg of resin (buy 2 x 20kg)
3. How much topcoat?
Take the area of the roof and divide by 2
20m2 divided by 2 = 10kg topcoat (buy 2 x 5kg or 20kg)
4. How much catalyst?
This depends of course on the % of catalyst that you are using – so take the total weight of resin and topcoat, and apply % - in this case
36kg + 10kg = 46kg x 2% = 0.92kg (buy 1 x 1kg)
5. How many trims?
Remember each style of trim is 3m long!
We are happy to give advice on the basis of our experience; but we accept no liability for that advice and you should rely upon your contractor or other professional.