Gun foam vs straw foam
Updated: 23 October 2026
Two cans on the same amazon.co.uk shelf can look like the same foam until a straw will not fit the second valve. Gun foam vs straw foam is a difference in the valve, not in how premium the polyurethane is. Prices are the 19 October 2026 captures on the [insulating spray comparison](/hub/diy-supplies/insulating-spray). Peter F. used the UK reviews and Soudal's gun instructions. Foam guns are not priced on this page. A purchase through our links can earn a commission at no extra cost to you.
Two cans on the same amazon.co.uk shelf can look like the same foam until a straw will not fit the second valve. Gun foam vs straw foam is a difference in the valve, not in how premium the polyurethane is.
Two cans on the same amazon.co.uk shelf can look like the same foam until a straw will not fit the second valve. Gun foam vs straw foam is a difference in the valve, not in how premium the polyurethane is. Prices are the 19 October 2026 captures on the insulating spray comparison. Peter F. used the UK reviews and Soudal's gun instructions. Foam guns are not priced on this page. A purchase through our links can earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Applicator | Volume | Cure or trim | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Soudal Soudal Soudafoam Gap Filler | Gun grade | 750 ml | Full cure 1 day | 9.2 | about £7.19 | View offer |
| Best value |  Gorilla Filler Gorilla Filler 500 ml | Straw | 500 ml | Cut, paint, sand | 8.6 | about £6.75 | View offer |
| Alternative |  Bond-It Bond-It Fill 'n' Fix | Gun grade | 750 ml | Full cure 24 hours | 8.2 | about £9.31 | View offer |
On this page
What the valve changes
A straw can carries a plastic tube, and the foam comes out in a coarse bead. In practice that straw is a one-session tool. A gun-grade can has a threaded valve. The trigger meters the flow. Soudal's UK page for the gun gap filler assumes the gun is already there. It is not in the carton.
You can lay a thinner bead and stop without the whole can dumping into the gap. The money trap is price per millilitre. Soudal is about £7.19 for 750 ml of gun grade. Gorilla Filler is about £6.75 for 500 ml of straw foam. The gun and a cleaner sit outside the Soudal price. If you will never buy the gun, the extra 250 ml is foam you cannot dispense.
The cans in this comparison
Only two listings are gun grade. Soudal Soudafoam Gap Filler, model 130585, is about £7.19, 4.6 from 411 reviews, full cure listed as one day, gun not included. Bond-It Fill 'n' Fix, model BDFIXG750, is about £9.31, 4.1 from 80 reviews. It states DIN 4102 Class B3 and no fire-resistant additives. One reviewer could not fit it to the gun they had.
The other five are straw cans, from Paint Factory at about £5.82 to Ferris at about £15.99. None of them prints gun grade. The best expanding foam page names the skips. The buying guide is why B3 is not a fire stop.
What still goes wrong
Straw users in this set report a blocked tube, often the next day and sometimes within minutes. Paint Factory reviews include a nozzle that clogged so the can was thrown away. Gorilla Heavy Duty reviews include a tube full of dry foam while the can still held product. Gorilla Filler is usable if you work quickly, then a one-use straw unless you clear it.
Gun failures are at the joint. Soudal reviewers describe leaks after the gun is removed and refitted, and a later use that barely expanded. Leave the can on the gun. A Bond-It can that will not seat is a full tin you cannot use. Moisture, fill fraction, and clearing a gun sit on the how to use expanding foam page.
What a gun does not change
A trigger does not change the chemistry. Both grades here are one-component polyurethane aerosols, and both are sensitisers. Gloves, goggles, ventilation, no flame, and do not burn cured foam off.
Fire class does not follow the gun. Bond-It is gun grade and states B3. Soudal is gun grade and states no fire class on this listing. Hertfordshire Building Control's limit remains the tested joint, often with mineral fibre behind it. Around a window, a controlled bead can still bow a frame that is not fixed and packed.
Common questions
Can I use a gun-grade can without a gun?
No. Soudal and Bond-It in this comparison are gun grade, and neither listing includes a gun. A straw from a Gorilla or Paint Factory can will not run those valves. If you do not want to buy a gun, choose a straw can. Gorilla Filler at about £6.75 is the one with 7,701 reviews. The about £7.19 Soudal price is the can only.
Is a straw can always single use?
Not as a law of physics, and often as a fact in these reviews. Gorilla, Ferris, and Paint Factory texts describe nozzles that block after one session, sometimes within minutes. Reviewers sometimes clear a tube with acetone or nail-varnish remover. Do not plan a second day's work around that hope. If you need several sessions, a gun-grade can left on the gun is the set-up these listings support.
Does a gun stop the foam expanding too much?
It lets you put less foam in, which is how you avoid a joint that bursts past the face. The foam that has left the nozzle still expands. Soudal's own method says fill about half on the DIY page and about two thirds on the gun gap-filler sheet. Follow your can. A neat trigger does not make a general gap filler into low-expansion window foam.
Why did foam leak when I took the gun off?
Soudal's UK reviews describe leaks at the joint after the gun is removed and refitted. The can wants to stay on the gun between jobs. If you must take it off, expect a mess and check the valve before you store it. Run cleaner through the gun while the foam is wet. Cleaner will not fix a leak once the foam has cured in the thread.
Do I need foam cleaner as well?
You need it if you use a gun and you want the gun to work next time. Soudal's instructions use cleaner on fresh foam, and E-Timber treats cleaner as a separate product from the can. You do not need a gun cleaner for a straw can you will throw away after one hole. You may still want acetone for a fresh spill, tested on a hidden spot, because it can mark paint and plastic. Cured foam is cut, not dissolved.
Related pages
Sources
Public UK sources and the amazon.co.uk listings compared on this page. Prices stored 19 October 2026. Updated 22 October 2026.
- HSE: Isocyanates (retrieved October 2026)
- HSE: Isocyanate spraying (retrieved October 2026)
- RICS: Spray foam insulation consumer guide (retrieved October 2026)
- Commons Library CBP-10658 (retrieved October 2026)
- Hertfordshire Building Control: PU foam (retrieved October 2026)
- Soudal UK: Soudafoam Gun Gap Filler TDS (retrieved October 2026)
- Polycell: Expanding foam (retrieved October 2026)
- Soudal UK: Filling gaps and holes (retrieved October 2026)