How Thin Can I Lay Fiberglass?

Thin Resin Issue

• You do not want to lay your fiberglass layers too thin. There always needs to be enough resin to fully saturate the matting and provide a strong layer for the fiberglass. Otherwise, the surface will be more susceptible to cracks and damage from harsh conditions. For the thinnest layers possible, use the thinnest fiberglass cloths and mats when you buy materials for your project. These mats are often distinguished based on weight.

Weight

• For proper resin application you will need between one and a half to two times the weight in resin compared to the weight of the fiberglass mats you are laying. Plan on using about 3 to 4 fluid oz. per square foot of matting. If you buy resin by the gallon, each gallon will have around 150 oz. of resin. Even for the largest projects, only a couple gallons of resin will be needed.

Variance

• There is some variance in necessary resin based on the size of the cloth and matting. This is where you can adjust application to create the thinnest layers possible. Chopped strand matting rated at 2 oz. will require more resin to properly coat, so choose 1.5 oz. matting or lower for the thinnest possible work. Cloth and roving can go up to 24 oz., so the 1.5 oz. option will probably be your best option.

Additional Materials

• A good fiberglass coating requires a gelcoat on top of the fiberglass resin. Keep this in mind as you form the resin layer. The gelcoat will always thicken the surface slightly. Gelcoats can work even if they are very thin, but do not try to create a thin layer just by skimping on the gel coating. Obey manufacture instructions carefully. A gelcoat that is too thin will cause scaling along the surface of the resin.