Quick-setting gun grade PU foam that expands up to 50 times its can volume. Ready to cut, plaster or paint in around an hour. Fills gaps, fixes frames and adds insulation in one go.
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Buy 12 – 119
£0.30£0.36
8.4% off
£3.29£3.95
Buy 120 – 239
£0.60£0.72
16.7% off
£2.99£3.59
Buy 240+
£0.70£0.84
19.5% off
£2.89£3.47
Discount applies across all variants of this product.
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.
Pro Tip: Dampen the surfaces and the foam itself with a light water mist before and during application PU foam cures faster and expands better with moisture present.
This gun grade foam suits most general construction and fit-out work. It's commonly used for fixing and sealing door and window frames, filling gaps around pipes and cables, insulating cavities in walls and floors, and sealing joints in timber frame construction. The expansion and adhesion make it useful for securing frames in position before final fixing, and the sound-deadening properties add value in acoustic applications. Works well on timber, masonry, blockwork, concrete and most rigid plastics.
Best For
Fixing and sealing door and window frames
Filling irregular gaps around services
Insulating cavities and voids
Sound deadening on party walls
Securing frames before final fixing
Compatible Materials
Timber and softwood
Masonry and blockwork
Concrete
Most rigid plastics
Metal frames
Key Features
Expands up to 50 times can volume
Ready to cut or plaster in approx. 1 hour
Paintable once cured
Sound deadening properties
Gun application for controlled bead
Not suitable for: Not recommended for use on polyethylene, polypropylene, PTFE or silicone surfaces. Avoid using in completely sealed voids where moisture cannot reach the foam to aid curing.
Shake the can thoroughly before use a good 30 seconds of shaking makes a real difference to yield and consistency. Screw the can onto your foam gun and adjust the flow using the trigger and rear valve. Apply in beads rather than flooding the gap, allowing space for expansion. Light moisture on surfaces helps the foam cure properly.
Shake can vigorously for at least 30 seconds
Attach can to foam gun applicator
Dampen surfaces lightly with water
Apply foam in controlled beads, filling no more than 50% of the gap
Allow foam to expand and cure for approximately one hour
Trim excess with a sharp knife or saw
Plaster, paint or seal as required
Do I need a special gun for this foam?
Any standard foam gun applicator will work. If you're using foam regularly, a decent metal gun is worth the investment it lasts longer and gives better control than the cheaper plastic ones.
How much gap can one can fill?
With 50 times expansion, a single 750ml can covers a surprising amount. As a rough guide, expect to fill around 40 50 linear metres of a 10mm bead, though this varies with gap size and application technique.
Can I use this foam outdoors?
Yes, but cured foam should be protected from prolonged UV exposure. Paint it, render over it, or ensure it's covered by trim or cladding. Exposed foam will yellow and degrade over time in direct sunlight.
This is a single-component polyurethane foam that cures through moisture reaction. The closed-cell structure provides thermal insulation and resistance to water penetration once fully cured. The foam remains slightly flexible after curing, accommodating minor structural movement without loss of adhesion or seal integrity.
Foam Type
Single-component polyurethane
Application Method
Gun grade
Expansion Rate
Up to 50x can volume
Tack-Free Time
Approximately 10 15 minutes
Cut Time
Approximately 1 hour
Paintable
Yes
Can Size
750ml
Box Quantity
1, 12, 120
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