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Spray Foam Insulation

Spray Foam Insulation near you

Spray polyurethane foam is unlike every other insulation product in one decisive respect: it does not arrive finished. Two liquid chemical components are pumped, heated, mixed at the gun and sprayed, and they react on the surface to become the insulation. The product is therefore manufactured in your roof space, under your floor or inside your wall, by the operator, on that day, in those conditions. Everything that can go wrong with it goes wrong at that moment and cannot be corrected afterwards.

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That is why the questions worth asking are about process rather than product. What the ratio and temperature of the components were, whether the substrate was clean and dry and within the temperature range the manufacturer specifies, how thick each pass was and how long the installer waited between passes, and how long the building was left before people returned. A well-installed foam is an excellent insulator and air seal in one operation. A badly installed one shrinks, pulls away from the framing, smells, or never fully cures.

The second thing to understand is that foam is permanent and opaque. It bonds to what it touches, it is not removable in any practical sense, and it hides the surface underneath it from view. In Australian housing that matters for termite inspection, for future access to wiring and plumbing, and for anyone who later needs to see the condition of a timber member. Those trade-offs are real and are the reason foam is the right answer in some situations and the wrong answer in many others.

Open cell and closed cell foam, and where each belongs

The two families behave so differently that treating them as one product is the first mistake. Ask which is being quoted and why, and ask for the reasoning in terms of your building rather than in terms of performance figures.

  • Open cell foam is softer and lighter, expands a great deal from a small amount of liquid, and is permeable to water vapour, so moisture can pass through it rather than being trapped at the face.
  • Closed cell foam is dense and rigid, insulates more per unit of thickness, and resists the passage of water vapour, which makes it both a useful barrier and a way of trapping moisture in the wrong location.
  • Open cell is more commonly used on the underside of a roof or in a wall cavity where vapour needs to keep moving.
  • Closed cell is more commonly used where rigidity, water resistance or a very thin application is required.
  • Both are applied in passes with a controlled thickness, and both need the surface prepared, dry and within the manufacturer's temperature range.
  • Neither is a substitute for dealing with an existing leak, since foam applied over a wet or leaking surface locks the problem away where nobody can see it.

How a spray foam job should be run

  • A pre-inspection of the space, including whether it is safe to enter at all, which in a pre-1980 Australian house means the asbestos question is answered first rather than assumed.
  • Confirmation that the substrate is clean, dry and within the temperature range the foam manufacturer specifies, since a cold or damp surface changes how the foam reacts and bonds.
  • Identification and protection of everything that must not be covered, including electrical fittings, cabling that needs to shed heat, flues, exhaust ducts and anything with a clearance requirement.
  • Masking and containment, because overspray travels and sets hard on whatever it lands on.
  • Application in controlled passes at the thickness the manufacturer specifies, with the stated wait between passes rather than one thick pour.
  • Recording of the batch details, the ambient and substrate conditions and the applied thickness, which is the documentation that makes a later warranty claim possible.
  • Trimming, a visual inspection for shrinkage or voids once cured, and a written statement of the re-entry and full-cure times.

The chemistry, the respirators and the time before you go back in

Spray foam is applied by operators in full protective equipment including air-fed respiratory protection, and that is not theatre. The components are hazardous chemicals, the spraying generates aerosol and vapour, and the reaction continues after the material leaves the gun. Work with hazardous chemicals is regulated under work health and safety law in every Australian state and territory, and the installer has duties to their workers and to anyone else on the site, including you.

For the household, the practical consequences are occupancy and ventilation. The building is vacated during the work and for a period afterwards that the manufacturer specifies, the space is ventilated as instructed, and people and pets return only when the installer says the re-entry time has passed. Anyone in the household with asthma or a respiratory condition should be part of that conversation before the job is booked, not after.

Ask for the manufacturer's re-entry and full-cure times in writing before the crew arrives, and plan the household around them. An installer who cannot state those times, or who says you can be in the next room while they spray, is not running the job the way the product requires. A persistent odour after the stated cure time is a reason to stop and ask questions rather than to open a window and hope.

What goes wrong with spray foam, and why it cannot be undone

  • An off-ratio or badly mixed application, which can shrink as it cures, pull away from framing and leave the gaps the foam was installed to close.
  • A lingering odour after the stated cure time, which points at the application rather than the product and is extremely difficult to remedy once the foam is in place.
  • Foam applied too thick in a single pass, which affects how it cures through its depth.
  • Bonding to the underside of roof sheeting or tiles in a way that makes future roof repair or replacement far more difficult and expensive.
  • Covering of electrical cabling, fittings, flues or anything with a clearance requirement, which is a safety problem as well as a compliance one.
  • Concealment of the timber it covers, so a termite pathway, a leak or rot can develop out of sight in a country where termite inspection of accessible timber is routine practice.
  • Sealing of ventilation paths that the building relied on, so a roof space or subfloor that used to breathe no longer does.
  • Overspray on gutters, windows, brickwork and neighbouring surfaces, which sets hard and does not come off easily.

Foam against batts, blow-in and separate air sealing

Foam's genuine advantage is that it insulates and air seals in one operation, and it does so in awkward geometry where batts cannot be fitted neatly: an irregular cavity, the underside of a roof, a rim joist, a curved or ribbed surface. Where a building has complicated shapes and a real air leakage problem, that combination is difficult to replicate with anything else.

Its disadvantages are permanence, opacity, cost, and total dependence on the quality of the installation. Batts and blow-in materials can be removed, topped up, inspected around and worked past by a later trade. Foam cannot. In a conventional Australian roof space with reasonable access and a truss roof, bulk insulation laid or blown to the right depth, combined with separate and deliberate air sealing, achieves a comparable result with none of the irreversibility.

The sensible test is whether the geometry genuinely defeats the alternatives. If it does, foam is a legitimate answer and should be installed by someone who can document the conditions and the thickness. If it does not, the reversible option is usually the wiser one, particularly in a house you may want to alter, re-roof or inspect for termites in the future.

What to get in writing, because the evidence disappears under the foam

  • The product name, the type, and the manufacturer's data sheet for the material actually used on your job.
  • The batch details of both components and the date of application, which is the only way a manufacturer can investigate a problem later.
  • The recorded substrate and ambient conditions at the time of spraying.
  • The applied thickness, stated for each area, and photographs taken before anything was lined over.
  • The re-entry and full-cure times, given before the work rather than recited afterwards.
  • A statement of what was deliberately left uncovered and why, particularly electrical fittings, flues and clearances.
  • The installer's warranty terms alongside the manufacturer's, since they are different documents and often cover different failures.

What moves a spray foam quote, and how LokalMatch fits in

The drivers are the area and the thickness, whether it is open or closed cell, how difficult the space is to work in and to get equipment to, how much masking and protection the job needs, and whether the household has to be accommodated elsewhere during the work and the cure. Access is often the largest single variable, because the equipment is bulky and the hose run from the truck to the workface has limits.

LokalMatch is where the job starts, not where it ends. Describe the space, roughly its area, what it is built of, why foam rather than another material is being considered and your postcode, and insulation businesses covering your area contact you directly; those businesses pay LokalMatch for the requests they receive. LokalMatch does not do the work, does not set or quote prices and does not vet, rank or recommend anyone, so get the product data sheet, the re-entry time and the thickness record in writing before the crew arrives.

Spray Foam Insulation: frequently asked questions

Is spray foam insulation a good idea in an Australian house?

It is a good answer to a specific problem: an awkward geometry that batts cannot fill neatly combined with a genuine air leakage issue, where insulating and sealing in one operation is worth the trade-offs. It is a poor answer in a conventional truss roof space with good access, where bulk insulation plus deliberate air sealing achieves a similar result and remains removable, inspectable and workable past by a future trade.

Can spray foam be removed if something goes wrong?

Not in any practical sense. It bonds to the surface it is sprayed onto and has to be cut and scraped off, which usually damages what is underneath. That is the single most important thing to understand before agreeing to it: unlike every other insulation material, the decision is effectively permanent, and a poor application is a problem you live with rather than one you undo.

How long do we have to stay out of the house?

As long as the foam manufacturer specifies, which varies by product and by the conditions on the day, and which the installer should give you in writing before the job. The building is vacated during spraying and for the stated re-entry period afterwards, and it is ventilated as instructed. Anyone in the household with asthma or a respiratory condition should be part of that planning. If an installer suggests you can stay in the next room while they spray, treat that as a warning.

Does spray foam cause problems with termite inspections?

It can, because foam covers the timber it is applied to and hides it from view. Routine inspection in Australia relies on being able to see accessible timber and the surfaces termites would have to cross, and foam removes that visibility in whatever area it covers. Raise it with your pest inspector before the work, not after, and ask the installer what will remain inspectable when they are finished.

Why does my spray foam still smell?

A persistent odour beyond the manufacturer's stated cure time usually indicates a problem with how the material was mixed or applied rather than with the product itself, and it is very difficult to remedy once the foam is in place. Do not simply ventilate and wait. Go back to the installer in writing, ask for the batch details and the recorded application conditions, and raise it with the manufacturer, because those records are the only way anyone can investigate it.

Can spray foam be sprayed over electrical cables in a roof space?

Not without addressing the clearances and the effect on the cabling first, which is a matter for a licensed electrician rather than for the foam installer. Cables that are surrounded by insulation cannot shed heat the way they were designed to, and light fittings, flues and other services have clearance requirements of their own. Anything with a clearance requirement must be identified and protected before spraying starts, because afterwards is too late.

Sources

  1. NSW Government: Loose-fill asbestos insulation, working in pre-1980 built homes

Written by the LokalMatch editorial team. Last reviewed 22 September 2026. How we write and check our guides

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What affects the cost of spray foam insulation

Prices depend on the details of your project. We only publish price ranges when they’re backed by real LokalMatch quote data or reliable sources. Until then, here’s what usually changes the price:

  • Area to insulate: attic, walls, basement or crawl space
  • Type of insulation
  • Removal of old insulation
  • Air sealing work
  • Access to the space
  • Ventilation changes

How to compare spray foam contractors before you hire

  • Choose a contractor who talks about air sealing and ventilation, not only adding more insulation.
  • Ask them to check the attic or walls for moisture, mould, old wiring or insulation that may contain asbestos before starting.
  • Get a written quote that states the type of insulation, the areas covered and the target insulation level.
  • For spray foam, ask about their training, curing time and when it's safe to be back in the home.
  • Consider an energy audit before and after the work to see where heat is being lost.

Questions to ask spray foam contractors before you hire

  • What type of insulation do you recommend for this area, and why?
  • Will you seal air leaks before insulating?
  • How will you keep the attic properly ventilated?
  • What will you do if you find old insulation that may contain asbestos, mould or old wiring?
  • For spray foam, how long do we need to stay out of the house?
  • Does this work need a permit or an inspection?

When to call a pro for spray foam insulation

  • Rooms that stay cold or drafty, or ice dams forming on the roof
  • Frost or condensation in the attic in winter
  • Loose, pebble-like insulation in the attic: leave it undisturbed and have it assessed by a qualified professional.

Spray foam insulation permits and local rules

Some spray foam insulation work needs a permit or has to meet local bylaws. Rules vary by municipality, so ask your pro whether a permit is needed and who will apply for it — and check with your city or town if you’re unsure.

Permits and licensing

Seasonal maintenance

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