Window Caulking
Window Caulking near you
Caulking a window is two jobs wearing one name. Outside, the sealant joint between the window frame and the wall is a weatherproofing element: it is what stops wind-driven rain tracking into the wall cavity, and it works alongside the flashings rather than instead of them. Inside, the seals and gap filling around the frame are an energy element, and the National Construction Code treats them as such.
Tell us about your window caulking project and we’ll help you find local caulking contractors who serve your area.
Free for homeowners · No obligation to hire
On this page
The ABCB Housing Provisions deal with this under building sealing. An external door, an internal door between a Class 1 building and an unconditioned Class 10a building, an openable window and other such openings must be sealed when serving a conditioned space, and the requirement extends to habitable rooms in climate zones 4, 5, 6, 7 and 8. Doors are dealt with by a draft protection device at the bottom edge and a foam or rubber compressible strip, fibrous seal or the like on the other edges. Windows may use compressible strips or similar, and windows complying with the air infiltration requirements of AS 2047 are exempt from that part.
Two consequences follow. A good modern window is often already sealed as a product, so the money belongs in the junction between the frame and the wall rather than in strips around the sash. And whether sealing is a code obligation at all depends on your climate zone, which is why a job that is mandatory in Canberra may not be in Cairns.
How a failed window seal announces itself
- A stain or a soft patch in the lining below a window corner, which is water that has come through the head or jamb joint rather than the glass.
- Sealant that has split, pulled away from one face of the joint, or gone chalky and crumbles under a fingernail.
- A draught you can feel with the back of your hand at the frame edge on a windy day, distinct from a draught through the sash itself.
- Paint blistering or flaking in a band around the outside of the frame, which usually means moisture is moving behind it.
- Dust lines on the sill or the reveal, which show where air has been passing for a long time.
- Insects or spider webbing consistently appearing at one corner of a frame, which is a reliable indicator of a gap.
- Noise that comes in unevenly around a window, louder at one edge, which points at a break in the seal rather than at the glazing.
Where building sealing is actually required
The Housing Provisions apply building sealing to conditioned spaces in all climate zones, and to habitable rooms in climate zones 4, 5, 6, 7 and 8. What must be sealed is listed: external doors, internal doors between a Class 1 building and an unconditioned Class 10a building such as an attached garage, openable windows and other such openings, and roof lights. Exhaust fans must be fitted with a sealing device such as a self-closing damper, filter or the like, and evaporative coolers serving heated spaces or habitable rooms in zones 4 to 8 must have self-closing dampers.
There are exemptions worth knowing. Buildings using only evaporative cooling in climate zones 2 and 5 are treated differently, and permanent ventilation openings required for gas appliances are not to be sealed. That last one matters: an open flued gas appliance depends on that air, and sealing it is dangerous rather than merely non-compliant.
The National Construction Code is a model document that becomes law when a state or territory adopts it, so confirm the version and the climate zone that apply to your address before treating any of this as a local obligation.
Sealants and seals, and where each belongs
- Neutral-cure silicone for external frame perimeters, which stays flexible in Australian ultraviolet and moves with the joint rather than tearing.
- Polyurethane sealants where the joint takes some abrasion or is wider, which are tougher but need to be specified for exposure.
- Acrylic gap filler for internal architrave and reveal joints only, because it is paintable but will not survive weather.
- Backing rod in any joint deep enough to need it, so the sealant bonds to two faces and can stretch, rather than three faces and tearing.
- Foam or rubber compressible strips and fibrous seals for the sash and door edges the Housing Provisions describe.
- Draft protection devices at the bottom edge of external doors, which is the specific component the Provisions call for there.
- Nothing that blocks a weep hole, since the drainage path out of a window frame is part of how the window is meant to work.
How a window is resealed properly
- Identify where the water or air is actually getting in, which is often above the point where the damage shows.
- Remove the old sealant completely rather than caulking over it, because new sealant bonded to old failed sealant fails at the same joint.
- Clean and dry the substrate on both faces, and prime where the sealant manufacturer requires it for that material.
- Fit backing rod in deep joints to control the depth and stop three-sided adhesion.
- Apply in a continuous bead and tool it into both faces, which is what creates the bond rather than just filling the gap.
- Leave every weep hole and drainage slot clear, and check them once the work is finished.
- Deal with the internal seals separately, using compressible strips or the appropriate device rather than sealant, so the sash can still move.
- Check the flashings if water has been getting in, because sealant alone will not fix a flashing that was never installed correctly.
Why resealing sometimes does not stop the leak
Sealant is the last line of defence, not the first. If a window was installed without a head flashing or with the sill flashing turned the wrong way, water will keep entering above the sealant line and appear at the same place no matter how many times the joint is redone. A leak that returns after a competent reseal is a flashing or an installation problem and needs the surround opened up.
The second recurring failure is blocked drainage. Australian windows are designed to let a certain amount of water in and drain it back out through weep holes at the sill. Sealing those holes, whether deliberately or by running a bead across them, traps water inside the frame where it will find another way out, usually inside the wall.
The third is the wrong product. Acrylic gap filler used externally lasts one summer. Sealant applied over a dusty or damp surface never bonds. A joint filled solid with no backing rod tears the first time the building moves. None of these are visible on the day the work is done.
What not to seal, and when to stop
- Never seal a permanent ventilation opening provided for a gas appliance, which the Housing Provisions expressly exclude from the sealing requirements.
- Never block a window's weep holes or drainage slots, which are part of the window's design rather than a defect.
- Treat paint on a pre-1970s window with caution and have it assessed rather than sanding it, because of the lead risk in older coatings.
- Leave any window above single-storey height to someone working from proper access equipment rather than a domestic ladder.
- Stop if removing old sealant exposes damaged or damp framing, since that is a repair rather than a sealing job.
- Ventilate while working indoors with solvent-based sealants and primers, and follow the product's own safety instructions.
- Do not seal an external joint as a way of managing rising or lateral damp, which is a different problem with a different fix.
Window Caulking: frequently asked questions
Is sealing around windows required by the building code in Australia?
In some climate zones, yes. The ABCB Housing Provisions require building sealing for conditioned spaces in all climate zones, and for habitable rooms in climate zones 4, 5, 6, 7 and 8. External doors, openable windows, internal doors between a Class 1 building and an unconditioned Class 10a building, and roof lights are on the list of what must be sealed. The Code is a model document, though, so what binds you is the edition your state or territory has adopted, applied to your climate zone.
Do modern windows still need seals fitted around the sash?
Often not. The Housing Provisions exempt windows complying with the air infiltration requirements of AS 2047 from the sealing provisions that would otherwise apply to them, on the basis that the product has already been tested to perform. That is one of the practical differences between a certified window and a cheap one. It does not exempt the joint between the window frame and the wall, which is a weatherproofing junction and is where most of the leakage and most of the water problems actually occur.
How long should window sealant last?
Longer than it usually does, and the difference is almost entirely preparation. A neutral-cure silicone applied to a clean, dry, correctly primed joint with backing rod behind it and tooled into both faces has a long service life even in full Australian sun. The same product applied over old sealant, onto a dusty surface or into a joint filled solid will fail within a few years. Treat a joint that has failed early as a preparation problem rather than a product problem, and expect the repair to involve removing everything back to substrate.
Can I caulk over the old sealant?
No, and it is the most common reason a reseal fails. New sealant bonds to the old sealant rather than to the building, so the joint still fails at exactly the point it failed before, only now it is hidden. Cut and scrape the old material out completely, clean both faces, prime where the manufacturer requires it, fit backing rod in a deep joint, and apply a continuous tooled bead. It is slower and it is the whole of the job.
Why is there water in my window frame even though it is sealed?
Because Australian windows are designed to admit some water and drain it back out through weep holes at the sill. Finding water inside the frame is normal; finding it unable to leave is not. Check that the weep holes are clear and have not been painted, sealed or blocked with debris. If they are clear and water is still appearing inside the room, the problem is more likely a flashing or an installation fault above the sealant line, which no amount of resealing will fix.
Sources
Written by the LokalMatch editorial team. Last reviewed 22 September 2026. How we write and check our guides
Find caulking contractors by city
Australian Capital Territory
Show 1 citiesHide cities
New South Wales
Show 8 citiesHide cities
Northern Territory
Show 1 citiesHide cities
Queensland
Show 10 citiesHide cities
South Australia
Show 1 citiesHide cities
Tasmania
Show 2 citiesHide cities
Victoria
Show 5 citiesHide cities
Western Australia
Show 2 citiesHide cities
What affects the cost of window caulking
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:
- Number, size and style of windows or doors
- Frame material and glass options
- Full-frame replacement or insert
- Repairs to rotted framing or sills
- Interior and exterior trim and capping
- Access, including upper floors
How to compare caulking contractors before you hire
- Look for an installer who measures on site and explains how the new window or door will be sealed and flashed.
- Ask whether the quote is for a full-frame replacement or an insert, and why they recommend it.
- Compare quotes on the same product type, glass options, installation method and interior and exterior trim.
- Ask who handles warranty issues: the installer, the manufacturer or both.
- For garage doors, choose a technician trained on springs and openers, since that work can be dangerous.
Questions to ask caulking contractors before you hire
- Will you replace the full frame or install an insert, and what's the difference for my home?
- How will you insulate and seal around the new units?
- Is interior and exterior trim included in the price?
- What does the manufacturer's warranty cover, and what does your installation warranty cover?
- How long will it take for the products to arrive once I order?
- Will your own crew do the installation?
When to call a pro for window caulking
- Drafts, condensation or fog between the panes
- Windows or doors that stick, won't lock or let water in
- A garage door that's off track or has a broken spring: don't try to force it, and call a garage door technician.
Window caulking permits and local rules
Some window caulking 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 licensingSeasonal maintenance
This job is part of our home maintenance checklists for:
Guides about window caulking
- ✦
Window & Door Contractors guide
Windows do more work in an Australian house than almost any other element. They are the main path for summer heat coming in and winter warmth going out, they are the part of the wall most likely to leak in driving rain,…
Read guide - ✦
Window Installers guide
Putting a window into an Australian house is regulated at three separate points, and a good installer can tell you which rule applies to which part of the job.
Read guide - ✦
Window Replacement guide
Most Australian homes reach a point where patching the windows stops being worth it: aluminium frames pitted by salt air, timber sashes gone at the bottom rail, hardware nobody makes any more, or glass that would not be…
Read guide
Ready to get window caulking quotes?
Tell us about your window caulking project.
Do you offer window caulking services?
Join LokalMatch to get matched with homeowners in the areas you serve.