Expanding Foam – Gun Grade B3

Gun grade expanding foam is one of those products that earns its place on every van. This B3 polyurethane foam delivers serious expansion up to 50 times the original can contents making it ideal for filling irregular gaps, fixing door and window frames, and adding insulation where you need it most. The gun-grade formula means you get proper control over the bead, which matters when you’re working around frames or filling cavities without making a mess of everything within arm’s reach.

What makes gun grade foam worth using

The key difference with gun grade expanding foam is precision. Unlike hand-held cans with their awkward straws, a proper foam gun gives you a consistent bead and lets you stop and start without clogging. That means less waste, cleaner work, and fewer of those moments where foam decides to expand in directions you didn’t ask for. For anyone fitting frames, sealing around pipes, or insulating gaps in blockwork, this level of control pays for itself quickly.

This B3 foam sets quickly you can cut, saw or plaster over it in approximately one hour. Once cured, it takes paint well and can be sealed over with most common finishes. It also provides decent sound deadening, which is worth knowing if you’re working on party walls or anywhere noise transfer matters.

Practical on-site performance

The foam works well across most common substrates and copes with the kind of irregular gaps that turn up on real building sites. It bonds to timber, masonry, concrete and most plastics, expanding to fill voids without the need for packing or back-filling with other materials. The cured foam remains slightly flexible, which helps it cope with minor movement in frames and structures without cracking away from the substrate.

Designed for regular professional use, this foam pairs with standard gun applicators. If you’re getting through foam regularly, keeping a dedicated gun makes the whole process faster and cleaner. The B3 is available as single cans or in boxes of 12 and 120, so you can stock up without paying over the odds.