Topcoats

Topcoat, also known as flowcoat, is a thick, gelcoat-based finishing material rather than a structural layer. It's used mainly to finish fibreglass flat roofs and the reverse (fibre) side of GRP mouldings, boat interiors, tank linings and similar surfaces where the back face needs a smooth, sealed, durable finish rather than a visible gelcoat skin. The key difference from standard gelcoat is that topcoat cures tack free, in the open air rather than under a mould surface, so it can be brushed or rollered on like a paint and left to cure without the risk of a sticky, uncured surface.

Every topcoat in this range is a high quality isophthalic polyester, Lloyds Approved, giving it the physical strength, water resistance and UV light stability needed for exterior and marine use. It can be pigmented with polyester pigment paste at roughly 10–15%, depending on the colour, so you can tint clear or white stock to a close match if you need something outside the ready-coloured options. It isn't suitable for spray application, so plan on brush or roller for a controlled, even finish. A free catalyst is included on these products: click the product image to choose yours.

Within the range, Clear and White Topcoat are the general-purpose choices for mould backs and tanking. The Grey Topcoats and Low Cost Grey Topcoat give you a standard or budget-grade grey depending on how critical the finish needs to be, Black Topcoat and Moss Green Topcoat extend the colour options, and our Non-Slip Topcoats sub-range adds an aggregate texture for decks, balconies and walkways where grip matters as much as waterproofing. We also have a huge selection of Coloured Topcoats, pigmented to order from BS, RAL, and Fascol colour ranges (colour-matching is also available). For roofing-specific formulations, see our separate Roofing Topcoats, and for a step-by-step application guide, see our Guide to Topcoating.