EXPANDA FOAM^®

Bostik Expanda Foam^® is a one-component, moisture-curing polyurethane foam built to seal, fill, bond, and insulate in one step. It expands to fill gaps and cavities of almost any size, then cures to an airtight, moisture-resistant seal that won't shrink or crack away from the surrounding surface over time. A straw applicator comes with every can, so it's easy to direct the foam into awkward spots and apply it at any angle.
It's suited to jobs like sealing openings around roof construction, filling wall and floor cavities, and adding a sound-absorbing or acoustic baffle layer, so it works equally well for insulation and for quieting a noisy space. Builders, carpenters, and facilities maintenance teams reach for it because it holds its shape and seal reliably, whether the job is indoors or outside.

Why choose Bostik Expanda Foam^®?
It's formulated to be ozone safe and suitable for interior or exterior use. Once cured, it barely shrinks or expands further, so gaps stay filled the way you left them, and the closed-cell structure means it stands up well as a heat and cold insulator, holding steady from ‑40°C to +90°C.
It bonds firmly to concrete, brick, stone, plaster, wood, metal, and many plastics including EPS, XPS, rigid PU foam, and uPVC, giving it broad flexibility on site. A single 750ml can goes a long way too, yielding around 50 litres of foam.

Where to use it
Use it on concrete, brick, stone, plaster, wood, metal, EPS, XPS, rigid PU foam, and uPVC, for filling cavities, sealing gaps around frames, and layering in insulation. Surfaces should be clean, dry, and free of dust and grease, and lightly misting them with water first helps the foam expand and adhere properly.
It isn't designed for PE, PP, PC, PMMA, PTFE, soft plastics, neoprene, or bituminous substrates, for permanent water contact, or for filling cavities that don't have enough moisture to support the cure.

TIP: For small cracks and joints around skirting boards, architraves, or window and door frames that need a neat, paint-ready finish rather than expanding foam, pair it with Gap Seal. Use Fill It Expanda Foam for larger cavities and insulation, and Gap Seal for fine, low-movement gaps ready for paint.