Fibreglass flat roofing tips for a beginner
This article displays the steps on how to make a fibreglass GRP coating. This could be used for a new flat roof, a flat roofing terrace or walkway or even a balcony. It does not provide detail about trims, guttering, insulation or decking.
Note that the terms fibreglass, GRP (glass reinforced plastic or polyester) and glass fibre are all used interchangeably. Fibreglass is an outstanding material for flat roofing systems with durable, long-lasting performance.
A recommended method for fibreglassing a flat roof
1. Surface Preparation: keep it dry and clean
Make sure the surface area is suitable to accept GRP. This means it needs to be clean, dry and free of loose debris. Debris will weaken the bond between the laminate and the surface.
Caution: Moisture and damp interfere with the bonding; the laminate must be free of water as this will inhibit the interaction between the resin and the surface and make it weaker.
In surfaces that are damp (fresh concrete), a primer can be used. This is designed to increase bonding and is often used on new concrete. We recommend using a G4 primer for most cases. The primer can be applied using a brush and or roller which will allow for acceptance of the GRP laminate.
2. Prepare the resin
Create a mixture of unsaturated polyester resin and catalyst – ideally, you should follow manufacturer’s instructions. Using a clean paddle, mix until the solution is homogenous. A slight colour change may occur.
Note: the catalyst used for the polyester resin is usually MEPK (Methyl ethyl ketone peroxide). The ratio used on a volume of catalyst per volume of resin is between 1 and 3 %. More catalyst is added when temperatures are colder.
Apply polyester resin coating to primed areas (preferably a low drain resin) which will prevent any release of the matting on the vertical surfaces.
3. Prepare the glass fibre mat
Size up enough glass fibre mat to cover the designated area. Using a stanley knife, cut the glass fibre matting such that it overlaps joints 1 to 2 inches more than the required area.
4. Apply resin to the glass fibre mat
Apply a mixture of the polyester resin to the glass fibre mat. In this case, we recommend using a foam roller and a paddle roller afterwards – this helps consolidate the resin and drive out excess air. Allow the laminate to harden – this could take up to 24 hours and will depend on the temperature of the surrounding air.
5. Apply topcoat to the cured fibreglass laminate
5. Once the laminate has hardened, lightly sand back the new laminate and apply a layer of topcoat – this is a resin-based layer that can be coloured in both RAL and BS colours. It provided a higher level of water resistance and acts as an external shell.
Contact a specialist
Any problems? You might want to contact a specialist. If so, give us a call on 02921 900 011 or send an online enquiry. At Strandek Flat Roofing, we’ve been installing new flat roofs since 1976 across Cardiff, Bristol and beyond. Our fibreglass flat roofing systems come with 20-year guarantees and our flat roofers are highly sought after.
Health & Safety
Flat roofing is a dangerous endeavour. Be sure to take adequate precautions when installing a new flat roofing system.
Material Data Sheets
Material data sheets, also known as MSDS sheets provide information regarding the hazardous nature of the materials in use. For grp roofing, these are usually polyester resin and MEPK catalyst.
Training Courses
For individuals looking to gain experience in roofing, relevant skills can be acquired by attending local training courses in roofing.
Apprenticeships
Others can pursue roofing specialisation by choosing a relevant apprenticeship.