Catalyst guide

Details on how much catalyst you should use and mix into the Fibrelast resins and topcoats.

Measuring catalyst

Catalyst is an integral part of the whole GRP roofing process and adding the right amount to the Fibrelast system is crucial. Too much catalyst and the product will start curing before you’ve had chance to apply it to the roof, not enough and it won’t activate the resin system, which means you’ll have to scrape it all back and start again.

4% Catalyst


From 6°C to 12°C

3% Catalyst


From 13°C to 20°C

2% Catalyst


From 21°C to 28°C

1% Catalyst


From 29°C to 35°C

Curing times

The weather and temperature play a large part in how long it takes for the resin system to cure. When calculating cure times make sure you take into account the temperature of the deck and resin system along with the ambient air temperature.

How the materials have been stored and how long they’ve been kept will also affect curing times. The standard shelf life for these resin products are between 2-6 months so don’t buy stock you know you’re not going to need and use the resins and catalysts as soon as possible to ensure optimum performance.

Note that the information we provide is for reference and the data we have provided is based on the roof being well constructed, any roof covering that is applied to a poorly constructed roof will fail.

Adding the catalyst

Both Fibrelast base resin and finishing topcoat require catalyst and once added will start to cure in the bucket. Make sure everything’s ready to go and always mix in small batches of around 5 litres or 1 to 2 litres for detailed areas or bandaging.

Open a can of the Fibrelast resin or topcoat and give it a good stir before you start to use, some of the additives in the base could have settled in transit or storage so you will need to make sure everything is thoroughly mixed in. After stirring pour the product into a 5 litre bucket.

Measure out the desired amount of Fibrelast catalyst and pour into the bucket with the resin and mix it in really well with a square-ended flat stirring stick or paddle. 5kgs of base or finish will need to be mixed for at least 1 minute to ensure there are no un-catalysed parts in the bucket.