What is Selleys Pro Trade Expanding Foam, and where should you use it?
Selleys Pro Trade Expanding Foam is a triple expanding, non shrinking, multipurpose polyurethane (PU) foam supplied in a 750mL trade can. It expands to about three times its original volume, will not shrink, and forms a durable waterproof bond with excellent adhesion to most surfaces. Its purpose is filling large holes, cracks and gaps — around pipes, skirting boards, architraves, and door and window cavities — where the result should also reduce noise, dust and draughts.
Two features distinguish it as a trade product. It has a patented all-direction dispensing system, which matters when the cavity you are filling is above your head or behind a jamb. And once dry, in approximately 3 hours, it can be painted, sanded, plastered, grouted, cut or caulked — so it takes a finish rather than needing to be hidden.
The key numbers, and what they mean
- Expansion: up to about three times original volume.
- Dry time: approximately 3 hours under standard conditions, depending on temperature and depth.
- Pack size: 750mL can (trade format).
- Suitable for interior and exterior use — exterior only when painted.
The expansion figure is the one that decides whether the job goes well. Selleys' instruction is to fill the void to approximately half and let expansion do the rest, and the accompanying warning is blunt: do not overfill the void, and allow room for expansion. Triple expansion in a confined window reveal generates real force, and a cavity filled to the brim has nowhere for that force to go except into the frame.
The three-hour figure is a paint-ready time under standard conditions, and Selleys qualifies it with "depending on temperature and depth". Depth is the variable that matters most: foam cures from the outside in, so a deep fill can carry a firm skin over a soft core well past the point the surface suggests it is finished. Trim, sand and coat only once the foam has actually cured.
The exterior rating comes with a condition rather than being unconditional. The foam is suitable for exterior use when painted, and Selleys states that exterior UV and weather exposure requires top-coat painting to maintain durability. Bare foam left exposed outdoors is not the rated condition.
Where to use it
- Filling large holes, cracks and gaps around pipes
- Behind skirting boards and architraves
- Door and window cavities
- Reducing noise, dust and draughts through building cavities
It is suitable for many substrates and has excellent adhesion to most surfaces.
How to apply it
Store the can upright and read the can label before use. This is an extremely flammable aerosol.
- Clean the opening. Ensure surfaces are sound, firm, and free of loose debris, dust and oil.
- Shake the can vigorously, according to the directions on the can.
- Cut the nozzle as recommended and attach the applicator straw or nozzle.
- Hold the can upside down and apply the foam into the void. Fill to approximately half and let expansion fill the rest.
- Allow the foam to expand and cure. Typical paint-ready time is around 3 hours, depending on temperature and depth.
- Once cured, trim or saw away the excess. Sand or plane as required.
- Paint, plaster, grout or caulk over the cured foam as needed.
- Clean any uncured foam from tools or surfaces immediately, with the solvent specified by the manufacturer on the can.
The instruction to clean uncured foam off immediately is not a tidiness note. Cured polyurethane foam does not dissolve; on a finished surface, the only remaining options are mechanical.
Limitations — where it should not be used
- Not for continuous immersion in water or underwater sealing. It forms a durable waterproof bond, but that is not the same as being rated for permanent immersion.
- Do not overfill the void. Allow room for expansion.
- Exterior use requires top-coat painting to maintain durability under UV and weather exposure.
- The substrate must be firm, stable and clean. Use caution on moving or cracking elements — a foam fill does not stabilise a substrate that is still moving.
Storage
Store the can upright. It is an extremely flammable aerosol, so the usual aerosol precautions apply: read the can label before use and follow the storage directions printed on it.
Note that the technical data sheet published for this product does not extract as readable text beyond its storage and flammability warning, so the figures on this page come from the product page rather than a full technical data sheet. Where a job depends on a precise cure time or expansion figure, confirm it against the printed can label.
Hazard classification
Classified as hazardous under Safe Work Australia GHS 7, with the signal word Danger.
An isocyanate-based polyurethane foam with the most serious hazard profile in the Selleys range. Dangerous Goods Class 2.1, flammable gas.
- H222: extremely flammable aerosol. H229: pressurised container, may burst if heated.
- H334: may cause allergy or asthma symptoms or breathing difficulties if inhaled (respiratory sensitisation, Category 1).
- H351: suspected of causing cancer (carcinogenicity, Category 2).
- H372: causes damage to organs through prolonged or repeated exposure (STOT repeated exposure, Category 1).
- H362: may cause harm to breast-fed children.
- H332: harmful if inhaled. H335: may cause respiratory irritation.
- H315: causes skin irritation. H317: may cause an allergic skin reaction. H319: causes serious eye irritation.
What is in it
| Chemical entity | CAS number | Proportion (w/w) |
|---|---|---|
| Alkanes, C14-17, chloro- | 85535-85-9 | 30–60% |
| Diphenylmethane diisocyanate (MDI) isomers and homologues | 9016-87-9 | 30–60% |
| Isobutane | 75-28-5 | 1–10% |
| Dimethyl ether | 115-10-6 | 1–10% |
| Propane | 74-98-6 | 1–10% |
| Non-hazardous ingredients | — | Balance |
MDI at 30 to 60% is what makes this a sensitiser. Because this is the trade product, the exposure pattern is the dangerous one: repeated use, day after day, often in cavities and roof spaces. That is the classic route to isocyanate asthma.
H334 is the one to understand. "May cause allergy or asthma symptoms or breathing difficulties if inhaled" is respiratory sensitisation, and it works like skin sensitisation but in the airways. The immune system can learn to react to isocyanate vapour, and once that happens the reaction is generally permanent, can be triggered by concentrations far below the one that caused it, and gets worse with each subsequent exposure. Occupational asthma from isocyanates ends careers in spray-foam and paint trades. There is no safe re-exposure once sensitised.
The exposure happens while the foam is expanding and curing, not afterwards. Fully cured foam is inert. The risk window is from the moment you press the trigger until the foam has fully cured, and it is concentrated in exactly the places this product gets used — wall cavities, roof spaces, subfloors, window reveals. Small, enclosed, unventilated.
What to do about it: ventilate the space actively, wear an organic vapour respirator rather than a dust mask, wear gloves and eye protection, and keep other people — particularly children and anyone with asthma — out of the area until it has cured and the space has been aired.
Where this product is used regularly, respiratory protection and ventilation should be treated as a standing control with health monitoring, not a per-job decision. H362 — may cause harm to breast-fed children — means anyone breastfeeding should not use it at all.
Protection
- Respiratory protection — an organic vapour respirator where the product is sprayed, dispensed or mixed in quantity; a dust mask for sanding cured material.
- Gloves — nitrile rubber; essential where a sensitisation classification applies.
- Eye protection — chemical goggles or safety glasses.
- Ventilation — active ventilation, not an open door. Do not work in a confined space.
First aid
| Exposure | What to do |
|---|---|
| Inhalation | Move the person to fresh air at once and keep them at rest. If breathing difficulty, wheeze or tightness develops, seek medical attention immediately and say the product contains isocyanates or solvents as applicable — symptoms can be delayed by several hours. |
| Eyes | Rinse cautiously with water for several minutes, removing contact lenses if present and easy to do, then keep rinsing. If irritation persists, get medical advice. |
| Skin | Wash with soap and water. Remove contaminated clothing and wash before reuse. If a rash or itching develops, including hours later, get medical advice — this may indicate sensitisation. |
| Swallowed | Do not induce vomiting. Rinse the mouth and seek medical advice immediately. |
If poisoning occurs, contact a doctor or the Poisons Information Centre — 131 126 in Australia, 0800 764 766 in New Zealand — with the container to hand. Selleys emergency line: 1800 220 770 in Australia, 0800 220 770 in New Zealand.
Common questions about Pro Trade Expanding Foam
How much should I put in the gap?
About half. The foam expands to roughly three times its original volume, and overfilling is the main cause of damage to frames and linings.
How long before I can trim and paint it?
Typical paint-ready time is approximately 3 hours, depending on temperature and depth. Deeper fills take longer than the surface suggests.
Can I use it outside?
Yes, when painted. Exterior UV and weather exposure requires top-coat painting to maintain durability.
Can I plaster or grout over it?
Yes. Once dry it can be painted, sanded, plastered, grouted, cut or caulked.
Will it shrink back over time?
No — it is described as non-shrinking.
Is it waterproof?
It forms a durable waterproof bond, but it is not suitable for continuous immersion in water or for underwater sealing.
Can I use it upside down or overhead?
Yes. It has a patented all-direction dispensing system, and the standard method is to hold the can upside down while applying.
Does the surface need preparation?
Yes. The opening must be sound, firm and free of loose debris, dust and oil, and the substrate needs to be firm and stable.
Can I use it to fill a crack that is still moving?
Use caution on moving or cracking elements. Foam fills a void; it does not restrain a substrate that is still shifting.
How do I get it off my tools?
Clean uncured foam from tools and surfaces immediately using the solvent specified on the can. Once cured, removal is mechanical.
What size does it come in?
A 750mL can, in trade format.
Is it flammable?
Yes. It is an extremely flammable aerosol. Store the can upright and read the can label before use.
For a caulking-gun filler rather than a foam, see Pro Trade Gap Filler Fast Skin or Pro Trade Gap Filler Smooth Finish. The household expanding foam in the range is No More Big Gaps.
What is Pro Trade Expanding Foam?
Pro Trade Expanding Foam is a triple expanding, non-shrinking, multipurpose PU (polyurethane) foam product made by Selleys, designed for filling large holes, gaps, and cracks in most surfaces.
What size does Pro Trade Expanding Foam come in?
Pro Trade Expanding Foam is available in a 750 mL can (trade format), also described as a 750 ml aerosol can.
How much does Pro Trade Expanding Foam expand?
It expands up to approximately 3 times its original volume, according to the page, while the knowledge-base notes it expands 2-3 times its original volume to fill large holes, gaps, cracks, and cavities.
Can Pro Trade Expanding Foam be painted?
Yes, it can be painted once fully cured, which takes approximately 3 hours under standard conditions.
How do you apply Pro Trade Expanding Foam?
First clean the opening so surfaces are sound, firm, and free of loose debris, dust, or oil. Shake the can vigorously as directed, cut the nozzle as recommended and attach the applicator straw/nozzle. Hold the can upside down and apply foam into the void, filling to approximately half to allow room for expansion. Let the foam expand and cure (about 3 hours depending on temperature and depth), then trim or saw away excess and sand or plane as required. Finally, paint, plaster, grout, or caulk over the cured foam as needed, and clean any uncured foam from tools or surfaces immediately with solvent.
Can Pro Trade Expanding Foam be used outdoors?
Yes, it can be used both indoors and outdoors, but exterior use exposed to UV/weather requires top-coat painting.
What are the limitations of Pro Trade Expanding Foam?
According to the page, it is not for continuous immersion in water or underwater sealing, room must be allowed for expansion, exterior UV/weather exposure requires top-coat painting, and the substrate must be firm, stable, and clean, with caution needed on moving or cracking elements.
What surfaces does Pro Trade Expanding Foam adhere to?
Per the knowledge-base context, it adheres to most building materials including timber, brick, concrete, metals, PVC, most plastics, fibre cement, and weatherboard.
What temperature range is recommended for applying Pro Trade Expanding Foam?
According to the knowledge-base context, the product should be applied between 5°C and 30°C.
What should be done for cavities deeper than 5 cm?
Per the knowledge-base context, for cavities deeper than 5 cm, Pro Trade Expanding Foam must be applied in multiple layers, with water spraying between applications and 15-30 minute waiting periods between each layer.