The best insulating sprays, compared.
Top pick: Soudal Soudafoam Gap Filler – Highest score at 92: 750 ml gun grade at about £7.19, 4.6 from 411 reviews. The gun is not in the box. Best value: Gorilla Filler 500 ml – About £6.75 for 500 ml straw foam, 4.3 from 7,701 reviews, score 86. A cheaper can scores 84 and the nozzle clogs. Updated 22.10.2026.
Insulating spray in a UK DIY aisle is a one-component polyurethane expanding-foam aerosol. You buy it to fill gaps and draughts, and for a little thermal and acoustic fill around frames, pipes and skirtings. It is not spray foam on roof timbers, and it is not an electrical coating. You tell cans apart by the applicator, any stated gap and cure time, and whether a fire line is a tested joint or only a class on the can. A straw nozzle is usually one session, because foam left in the tube blocks it. Gun grade uses a threaded valve, and the foam gun is bought separately. A window or door frame still needs packers and a low-expansion foam specified for that opening. Those checks are in the [insulating spray buying guide](/hub/diy-supplies/insulating-spray/sub/insulating-spray-buying-guide). These aerosols contain isocyanates. Wear gloves and goggles, ventilate, keep flames away, and do not burn cured foam off or pierce the can. Call a professional for a fire-resisting joint or for spray foam on rafters.
Insulating spray in a UK DIY aisle is a one-component polyurethane expanding-foam aerosol. You buy it to fill gaps and draughts, and for a little thermal and acoustic fill around frames, pipes and skirtings.
26 products checked · 58 hrs invested · +21,400 readers
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Personal buying guide
Question 1 of 2
Do you already have a foam gun?
Across 411 amazon.co.uk reviews, the Soudal Soudafoam Gap Filler, model 130585, is a gun-grade 750 ml can at about £7.19 that reviewers use to stop draughts and to fill around plasterboard at a doorway. The listing states a one-day full cure, water resistance and heat resistance, and the gun is not in the box. Reviewers who already own a gun prefer the control to a disposable straw, and some say a bead sets in a few hours and does not shrink. It stays sticky until the trigger is familiar, it needs shaking often, and foam leaks if the gun is taken off and put back on. One later use barely expanded compared with the first jobs, and one reviewer said the window foam was better on frames. The maker's UK sheet quotes about 28 litres and 0.037 W/m·K for this gun gap-filler family. The amazon.co.uk listing does not repeat those figures. It is the top pick when you already have a foam gun and a cleaner.
Pros
Cons
Best for: You already own a foam gun and a cleaner, and the job is draughts and general gaps rather than a new window frame.
Less suitable: A first can if you have no gun, or a uPVC frame that needs low post-expansion foam.
Specifications
Common questions
Do I need a separate foam gun?
Yes. The title says gun grade. The gun is not in the box.
How long does the listing say it takes to cure?
The full cure time field says 1 day. Reviewers also describe it setting in a few hours.
Is it marked waterproof?
The listing says water resistant. Heat resistant is also in the special-features field.
Across 3,768 amazon.co.uk reviews, the Gorilla Weatherproof two-pack is about £10.82 for two 500 ml stone-coloured straw cans. The title and the UK texts name Gorilla even though the brand field says JKG Unknown. Reviewers use it on draught gaps and a window bay, and one said their bead set in about 3 hours and trimmed with a knife after about 24 hours. The lighter colour is a reason some prefer it to beige foam, and a few found it less sticky so they could push excess into place before it set. The nozzle is called flimsy, overhead cavities drip unless you go slowly with a board, and the area needs masking because it spreads. Water resistance is not filled in the attributes. Outdoor and weatherproof are. Gun grade is not stated. It is the twin pack to open when you have two separate one-session jobs and you accept the brand-field clash. The score is 88, the same as the dearer Ferris two-pack, with a much larger review file.
Pros
Cons
Best for: You have two separate gaps you can foam in two sessions, and you want the stone colour on a straw can.
Less suitable: One small hole, a buyer who needs the brand field to say Gorilla, or a job that needs a gun thread.
Specifications
Common questions
How many cans are in the pack?
The title and bullets say two cans of 500 ml each. The unit count is 1,000 ml.
Why does the brand field say JKG Unknown?
That is the brand field on the listing. The title and the UK reviews name Gorilla Weatherproof expanding foam.
Is a foam gun required?
Gun grade is not stated. Reviews mention a spray straw on the can.
The Ferris two-pack, part FER1512, is about £15.99 for two 500 ml cream polyurethane straw cans. The brand field is Ferris while the title says Original Gorilla Filler. Across 652 amazon.co.uk reviews the line is 4.4, and the score is 88, level with the cheaper Gorilla two-pack. UK review texts say the foam does the filling job, and one reviewer called it stronger than a Screwfix foam they had used, including on a leaking toilet surround. Drips and poor control are the repeating complaint, the nozzle tries to unscrew as the angle changes, and one nozzle arrived broken while the other blocked at once. Each tube is one use once foam cures inside it, so leftover foam in the second can is easy to waste. Bullets claim energy-bill savings with no figure, which is not a measured result. It suits you only if you specifically want this Ferris listing and you will use both cans in separate sessions.
Pros
Cons
Best for: You want this Ferris two-pack in particular and you have two sessions in which each can will be used up.
Less suitable: A single hole, a buyer comparing twin-pack price with the Gorilla two-pack, or anyone treating the energy-bill line as a saving.
Specifications
Common questions
Is the brand Gorilla or Ferris?
The brand and manufacturer fields say Ferris. The title says Original Gorilla Filler. The model line is Gorilla filler01, part FER1512.
Which materials does the listing name?
Wood, metal, brick and concrete. Surfaces named are metal, window and wood. Water resistance is water resistant.
Does the pack include a foam gun?
No. Included components say expanding foam filler. Reviews describe a nozzle or tube.
Across 7,701 amazon.co.uk reviews, the Gorilla Filler weatherproof can is about £6.75 for 500 ml of white straw foam that reviewers put around door frames, pipework and a window, and one used it to steady a bath. The listing says the cured foam can be cut, sawn, painted and sanded, and it names stone, wood, brick and metal, with waterproof as the water-resistance field. The nozzle is usable for a straw can if you work quickly, which matches the fast expansion several reviewers liked. Upward beads drip, the cure is very sticky, and the straw is one use unless it is cleared with acetone or nail-varnish remover. A cracked lid and a damaged first delivery appear in the texts, though that cracked lid did not stop the job. The part-number field prints a beauty-mask code, which does not match model GF2, so ignore that cell. It is best value when you have one ordinary gap and no foam gun.
Pros
Cons
Best for: You have one ordinary gap today, you do not own a foam gun, and you will mask and work quickly.
Less suitable: Several gaps over more than one day, or any joint that needs a stated fire class.
Specifications
Common questions
Does this can include a foam gun?
No. Reviews describe a nozzle on the can. The included-components field says filler.
Which surfaces does the listing name?
Stone, wood, brick and metal. The listing also says the cured foam can be cut, sawn, painted and sanded.
Is a fire class printed?
No fire class is on this listing. Do not treat the weatherproof line as a fire rating.
The Gorilla Heavy Duty can, model 115953, is about £9.93 for 353 ml of grey straw foam. It states gaps and cracks up to 2.5 cm, tack-free in 8 to 12 minutes, and trimming in 45 minutes. Across 490 amazon.co.uk reviews the line is 4.2, and the score is 84. UK review texts praise a hard set by about 24 hours, sanding once cured, and a smaller tin that wastes less if the whole can must go in one session, including around an extractor opening. The same texts say the tube clogs after the first use, one of two cans failed to discharge, and the supplied gloves tore within minutes. Outdoor foam must be painted or coated because sunlight may discolour it. A no-shrinkage line is a listing claim, not a test run for this page. The package dimensions of 19.7 x 65 x 65 cm do not describe a 353 ml aerosol, so ignore that cell. It suits a gap you have measured at or under 2.5 cm when you will paint the outside.
Pros
Cons
Best for: You have measured a gap at or under 2.5 cm, you will use the can in one go, and you will paint any foam that daylight can reach.
Less suitable: A large void, a second session tomorrow, or a buyer comparing millilitres with the 500 ml straw cans.
Specifications
Common questions
How wide a gap does the listing allow?
The bullets say gaps and cracks up to 2.5 cm.
Can I leave it uncovered outside?
The listing says outdoor foam must be painted or coated, because sunlight may discolour it.
When can I trim it?
The listing says tack-free in 8 to 12 minutes and trimming in 45 minutes. It also says the foam is paintable and sandable.
Across 338 amazon.co.uk reviews, the Paint Factory Bond & Fill can is a straw-style 500 ml filler at about £5.82. Reviewers use it on skirting gaps and a window surround before plaster, once the can has been shaken hard. The title says quick setting, but the attributes do not give a cure time, a colour or a water-resistance line, and several attribute lines do not describe this can. UK review texts say it fills a wall-to-floor gap and a mouse hole in a cupboard after it dries solid. The complaint that returns is weak expansion on the first pass even after a water mist, plus a nozzle that clogged within minutes so the rest of the can was thrown away. One reviewer could not seat the spout, and another wanted a spare nozzle. The listing says some products cannot be delivered outside mainland UK, and that Amazon confirms this at checkout. The score is 84, the same as Gorilla Heavy Duty, which is why the lower price is not best value. It suits a single small cavity if you accept that the tube may die during the job.
Pros
Cons
Best for: You have one small cavity, you will shake the can hard, and you can finish before the nozzle blocks.
Less suitable: A gap you need to measure, a can you want to open tomorrow, or any job that needs a stated fire class.
Specifications
Common questions
Is this gun grade?
Gun grade is not stated. Reviews describe a spout or nozzle on the can.
Does the listing say it is waterproof?
The listing asks the question. The attributes do not give a water-resistance value.
Can it be delivered outside mainland UK?
The listing says some products cannot be delivered outside mainland UK, and that Amazon confirms this at checkout.
The Bond-It Fill 'n' Fix, model BDFIXG750, is about £9.31 for 750 ml of gun-grade polyurethane with a stated full cure of 24 hours. Across 80 amazon.co.uk reviews the line is 4.1, the thinnest sample here, and the score is 82. Reviewers who fitted a gun liked trigger control, and one compared it with an ordinary straw can. The title's 40-times expansion is the claim those reviewers dispute, and one can stopped with foam still inside after a small opening. Another can would not fit the reviewer's gun, and a delivery arrived with no lid, injection tube or documents. The listing states DIN 4102 Class B3 and says that is a foam rating for products with no fire-resistant additives. A bullet about doors and windows also claims the foam can reduce the need for mechanical fixings. That fire line is not a tested UK fire stop, and the fixings claim is not a reason to leave a frame unpacked. The colour field says transparent, which is the listing cell, not a measured shade. It suits you if you already run a matching gun and you treat B3 as ordinary filler.
Pros
Cons
Best for: You already have a standard foam gun that you have checked against this valve, and you want a general gap filler.
Less suitable: A fire-resisting joint, a new window you hoped to foam instead of fixing, or a buyer who needs the 40-times claim to be true.
Specifications
Common questions
What fire class does the listing state?
DIN 4102 Class B3. The same line says this is a foam rating for products with no fire-resistant additives. It is not a tested fire stop.
Is the foam gun in the box?
No. The can is for a standard gun applicator. Included components are one BDFIXG750 can.
Where does the 40-times figure come from?
It is in the product title. It is a listing claim, not a result from a test stored for this can. UK reviews dispute it.
Shelf prices and stars are the amazon.co.uk snapshot of 19 October 2026 already stored for these seven listings. This is not a laboratory test. Stars and review depth take the largest share. Fit for the job keeps a straw can and a gun can as different tools. A stated gap, a cure or trim time, water resistance and an outdoor paint note are the spec you can use. A fire class is only what the listing prints. Price against that job picks best value, which is not the same can as the highest score. A 40-times line, a weatherproof bullet and an energy-bill claim stay pack claims. A blocked nozzle, a gun thread that did not fit, and an expansion claim reviewers dispute are deductions.
Amazon stars and review depth
35%The largest share. A 4.6 from 411 reviews sits above a 4.2 from a few hundred. A 4.3 from 7,701 reviews is a deep straw-can sample, not an automatic win over a higher-rated gun can.
Fit for the job
30%Straw and gun grade are different tools. A gun-grade can without a gun in the box does not outrank a straw can for a single hole. A straw can does not outrank a gun can when you already meter several gaps.
Spec you can use
20%A stated gap, a cure or trim time, a water-resistance field and an outdoor paint note. A fire class is scored only as what the listing prints. DIN 4102 Class B3 is not treated as a fire stop.
Price against the job
15%The lowest useful straw price with a deep review file can be best value without holding the highest score. Price per millilitre ignores the gun you still have to buy.
Buy the applicator and the job before the expansion slogan. Insulating spray on amazon.co.uk, in this aisle, is a one-component polyurethane can for a gap, a draught or a skirting, not roof spray foam and not a fire-resisting joint. A straw can is often one session. Gun grade needs a gun you buy separately. Cover cured foam that daylight can reach.
Insulating spray in UK DIY is a one-component polyurethane expanding-foam aerosol for gaps, draughts, and a little thermal and acoustic fill around frames, pipes and skirtings. It is not contractor spray foam on roof timbers, and it is not an electrical coating. You judge a can by the applicator, any stated gap width and cure time, and whether fire wording is a tested joint or only a class printed on the can.
These foams expand after they leave the can. A bead packed to the face can push out, and on a frame it can bow the section. Fill short, let it cure, then trim.
UK reviews of these straw cans say the nozzle blocks once foam cures in the tube. Clear it at once if you must pause. Do not plan a second session on the same straw.
DIN 4102 Class B3 is not a fire stop. A 40-times title line and an energy-bill bullet are listing claims. Weatherproof is not a licence to leave foam in the sun.
Straw and gun grade are different tools. A straw nozzle is often one session because the tube blocks once foam cures inside it. Gun grade needs a foam gun, which is not in the can. When each one fits is set out in the [gun-grade and straw guide](/hub/diy-supplies/insulating-spray/sub/insulating-spray-gun-grade-vs-straw). A static crack, a pipe hole or a skirting gap fits these aerosols. A window or door frame needs low post-expansion foam and mechanical fixings.
None of these cans is a tested fire stop. Bond-It prints DIN 4102 Class B3 and says that is foam with no fire-resistant additives. Hertfordshire Building Control limits polyurethane foam to the narrow joint that was tested, often with mineral-fibre backing, to BS EN 1366-3 or 1366-4. A B3 filler is not a cavity barrier. Only Gorilla Heavy Duty states a gap, up to 2.5 cm, and it tells you to paint outdoor foam.
Three typical situations, each with a recommendation from this comparison.
You have one ordinary gap today and you do not own a foam gun. The Gorilla Filler 500 ml straw can is best value at about £6.75, with 4.3 from 7,701 reviews. The listing says cured foam can be cut, painted and sanded. Upward beads drip, and the straw is one use unless you clear it. It is the wrong can for a second day.
You already own a foam gun and a cleaner, and the job is draughts and general gaps. The Soudal Soudafoam Gap Filler is the top pick at about £7.19, score 92, 750 ml gun grade, 4.6 from 411 reviews. The gun is not in the box. It leaks if you take the gun off and put it back on. A new window frame is a different foam.
You have measured a gap at or under 2.5 cm and you will use the can in one go. Gorilla Heavy Duty, 353 ml, is the only listing here that states that gap, with tack-free in 8 to 12 minutes and trim in 45 minutes. It is about £9.93, 4.2 from 490 reviews. Paint any foam that daylight can reach. The tube clogs after the first use.
The top pick is the Soudal Soudafoam Gap Filler at about £7.19. It scores 92, the highest here: 750 ml gun grade, 4.6 from 411 reviews, and a stated full cure of 1 day. The foam gun is not in the price. Best value is the Gorilla Filler 500 ml straw can at about £6.75, score 86, with 4.3 from 7,701 reviews. Paint Factory is cheaper at about £5.82 and scores 84, with weak expansion and a nozzle that clogs in the UK texts, so the lower shelf price is not best value.
Soudal Soudafoam Gap Filler
Highest score at 92: 750 ml gun grade at about £7.19, 4.6 from 411 reviews. The gun is not in the box.
Gorilla Filler 500 ml
About £6.75 for 500 ml straw foam, 4.3 from 7,701 reviews, score 86. A cheaper can scores 84 and the nozzle clogs.
Editorial
Peter F. is the editor for DIY & tools at productscompared.co.uk. Comparisons in this category are checked against amazon.co.uk listings, review evidence and public UK sources.
Guides on what to look for, how to use a product, and common mistakes.
Public UK sources and the amazon.co.uk listings compared on this page. Prices stored 19 October 2026. Updated 22 October 2026.
This page contains affiliate links. If you buy through them, we may earn a commission at no extra cost to you. Prices, stars and review counts are the amazon.co.uk figures already stored for this set. This is not a laboratory test.
