If water is getting in around your windows, contain it, photograph it, and find out where it is entering before anyone seals anything. A tube of sealant on the wrong spot can trap water inside the wall and hide a bigger problem. Most leaks come from a short list of causes: failed sealant, poor flashing, blocked drainage or an installation fault. Some can be fixed in an afternoon. Others mean the window needs to come out.
This guide is for Auckland and wider New Zealand homeowners. It shows you what to do in the first hour, how to read the signs, which causes are repairable and which are not, and what the rules say about consent and insurance.
TL;DR
- Mop up, photograph the damage and note when it happens (wind direction, rain strength) before you touch the window.
- Keep the drainage holes in aluminium frames clear. Water on the inside is never normal, and blocked drainage is a common culprit.
- Do not hose, silicone over gaps or paint over stains until the cause is known. Rushed patching can hide the source and weaken an insurance claim.
- A loose seal or blocked drain is a repair job. Rot in the surrounding framing or a faulty installation usually means removing and refitting the window.
- Gradual damage is generally not covered by insurance, so act early and keep records.
Table of Contents
- What to do in the first hour
- How to tell a leak from condensation
- Why windows leak
- How to find where the water is getting in
- Repair or replace: how to decide
- Insurance and keeping records
- Preventing leaks
- Special cases
- Our perspective
- Getting your leaking windows sorted
- FAQ
- Sources
What to do in the first hour
When water is dripping in during a storm, the goal is damage control, not a permanent fix.
- Contain the water. Use heavy towels or a wet vacuum so it does not spread into the lining, carpet or flooring. Restoration advisers suggest containing the water first and avoiding permanent repairs until the source is diagnosed.
- Photograph everything. Take dated photos of the wet area, the window and any staining. You may need them for an insurance claim or a builder's report.
- Write down the conditions. Note whether the leak only appears when rain is driven sideways by wind, or in any rain. This detail helps a tradesperson narrow the cause quickly.
- Hold off on the quick fix. Sealing the outside with silicone feels productive, but if the water is entering through a flashing or a sill, you may just push it somewhere you cannot see.
If water is near power points, light fittings or a ceiling that is bulging, keep clear and call an electrician or a builder before doing anything else.
How to tell a leak from condensation
Not every wet window is a leaking window. Water on the glass and pooling on the sill on a cold morning is usually condensation. Consumer NZ notes that water damage around windows can come from either condensation or leaks, and suggests reducing condensation and checking the drain holes as first steps.
Some quick pointers:
- Condensation appears on cold mornings, often across several windows, on the glass and the lower frame, and dries as the day warms up.
- A leak shows up during or just after rain, often at one window, and often at the corners, the sill ends or below the window inside the wall.
The government's Building Performance site says that dripping or pooling water inside during rain is likely to be a leak, particularly if it comes with mould, musty smells, swollen trim or staining. If your problem is mainly misted glass and damp sills on cold mornings, our guide to avoiding condensation on windows covers it in detail.
Why windows leak
Most leaks trace back to a handful of causes. The same window can have more than one.
Failed or missing sealant
Sealant between the frame and the cladding, or around the glass, dries out, shrinks and cracks over the years. Auckland's UV, salt air near the coast and big temperature swings all speed this up. A cracked bead lets water into the gap behind the frame.
Faulty or missing flashing
Flashings are the strips of material that direct water over and out of the joint between the window and the wall. Damaged or improperly installed flashing is one of the main ways water gets in. Flashing faults are an installation problem, not a maintenance problem, and a bead of sealant will not cure them.
Blocked drainage holes
Aluminium windows are designed with small drain (weep) holes so that any water that reaches the frame channel runs back outside. The Window Association of New Zealand says these drainage holes must stay open so rainwater can drain outside, and that water should never come inside. Dirt, spiders' webs, paint and over-enthusiastic sealant can block them, and the water then has nowhere to go but inwards.
Wind-driven rain
Horizontal wind pressure can push water into gaps that ordinary rain might pass by. If a window only leaks during southerly or northerly storms and only on one elevation of the house, that is a clue. It usually points to a small gap, a worn seal or a marginal installation that only fails under pressure.
Design and cladding issues
Some leaks are not really about the window. The government defines a leaky home as one where water enters from outside because of design issues or improper installation of materials and cannot drain or ventilate. Houses with monolithic cladding or very small eaves carry more risk, and Settled.govt.nz recommends a specialist moisture inspection for properties with those features.
Note that leaking internal plumbing is not classed as a leaky home problem, so a wet wall under a window can also be a pipe. Rule that out early.
How to find where the water is getting in
Water rarely shows up where it enters. MBIE's diagnosis guide says water paths can be complex and damage can be remote from the source of the leak. Its approach is to look for risk features and evidence of leaks, evaluate the surrounding area, then pick out the areas needing a closer look.
You can do a first pass yourself, on a dry day:
- Look at the sealant around the frame and the glass. Look for gaps, cracks, or sections that have pulled away.
- Check the drain holes on the bottom of the frame. Clear them gently with a soft brush or a thin plastic strip. Do not poke anything sharp through them.
- Check the sill and corners. Soft, swollen or stained trim and lining is a sign that water has been getting in for some time.
- Look above the window. Check flashings, the head of the window and how the cladding meets the frame. Settled.govt.nz advises checking flashings, joinery seals, broken sealant and dampness or rot around windows and doors.
- Look at the weather pattern. Note which side of the house is affected and under what wind.
A warning about hosing the window
It is tempting to blast the window with a hose to reproduce the leak. The Window Association warns that ad hoc hosing or water-blasting can give erroneous results, because pressure and angle can be nothing like real weather. Controlled testing is a job for a window specialist or building inspector.
When to call a professional
Call someone in if you see any of these:
- Soft or swollen framing, mould or a musty smell
- Staining that spreads on the ceiling or wall
- A leak that returns after you have cleared the drains and resealed
- More than one leaking window on the same side of the house
A window specialist can check the joinery and installation. If the problem looks bigger, a building surveyor or a weathertightness inspector can check the wall and cladding.
Repair or replace: how to decide
This is the question that decides how much you spend. MBIE's guidance is balanced: a targeted repair may suit a specific faulty window or flashing, but only when the adjacent framing is unaffected. An incomplete diagnosis can leave leaking and decay going unnoticed.
The remediation guide adds that targeted repairs carry the risk of further hidden damage, and that repeating the original faulty installation is unlikely to succeed.
| Situation | Usual answer |
|---|---|
| Blocked drain holes, dirty tracks | Clean and clear. Repair or maintenance. |
| Worn gasket or seal, loose latch, misaligned sash | Repair: new seals, adjust or replace hardware. |
| Cracked or missing sealant, framing dry and sound | Repair: remove old sealant, reseal properly. |
| Flashing missing or wrongly fitted | Window usually has to be lifted, flashings corrected, then refitted or replaced. |
| Soft or rotten framing around the window | Remove the window, repair the framing, then install new joinery. |
| Corroded or distorted frame, failed joints, old single-glazed unit | Replacement is usually the sound choice. |
What it costs
Prices vary widely with the window size, access, the cause and whether framing needs repair, so a figure without an inspection would be a guess. A simple reseal or hardware swap sits at one end. Pulling out a window, repairing the framing and fitting new joinery sits at the other. For the replacement end of the scale, see our cost to replace windows in NZ guide. For a quote on your own windows, we price after we have seen the problem.
Do you need consent?
The rules matter if you are replacing a window. According to MBIE, consent is usually not required for window work in existing dwellings up to two storeys, unless the window being replaced failed durability requirements, or the work affects a specified system. A failed window installed in the last 15 years requires consent. Because your own situation can fall either side of that line, check with your council before work starts. We explain the Auckland side in our guide on whether you need building consent in Auckland, and cover the wider rules in our building code compliance guide.
Insurance and keeping records
Insurers cover sudden, unexpected and accidental loss. They do not usually cover damage that builds up slowly. The Insurance Council's guidance on gradual deterioration says that policies are designed for sudden, accidental events and that keeping a property in good condition with regular maintenance matters.
In practice:
- Photograph the damage and keep dated records of when you noticed it.
- Do not carry out a permanent repair before the cause has been recorded. A building-remediation firm points out that rushing a repair can destroy evidence and weaken a claim.
- Check your own policy wording, or call your insurer, before you start work.
- For body corporates and unit-title buildings, a committee that knows about a weathertightness failure may have disclosure duties, and repeated patching of a known defect can affect cover, according to the same source.
Preventing leaks
A bit of regular attention goes a long way, especially on exposed or older houses.
- Clean the drain holes and tracks at least twice a year, and after painting or cladding work.
- Inspect the sealant each year and replace cracked or shrunken sections before the winter storms.
- Look at the house's exposure. Windows on the weather side take the worst of it. Deep eaves and good flashing detail help.
- Manage condensation so that sills and linings do not stay damp. Moisture from inside can look like a leak and cause the same rot.
- Fix small things early. A sticky latch or a worn seal that stops the sash closing tightly lets pressure and water in.
When you replace or add windows, the thermal performance of the frame matters too. Thermally broken frames reduce cold surfaces, which cuts condensation. See our guides to thermally broken windows and energy efficient windows.
If the leak is at a door rather than a window, the diagnosis is similar but the common failure points differ. See leaking doors and how to fix them properly.
Special cases
Brick and older homes
Brick veneer homes and older villas and bungalows have their own quirks, from the gap behind the brick to timber joinery that has moved over decades. If you are replacing windows in a brick house, our guide to replacing windows in a brick house covers the specifics. For character homes, our historic home window replacement guide goes through the options.
Commercial properties
Shopfronts and commercial doors get constant use, and a worn seal or a loose frame can let water in for months before anyone notices. The same approach applies: find the cause first, then repair or replace.
Our perspective
Most of the leaking windows we see are not mysterious. They are windows where someone treated the symptom, usually with a bead of silicone, and the water carried on finding its way in.
We only work with aluminium joinery, and that focus shapes how we approach a leak. Our first question is whether the window is doing its job: are the drain paths clear, are the seals sound, is the frame square and is it flashed properly into the wall? If the answer is yes to all of those, we look at the surrounding wall. If the answer is no, we say so plainly.
Where a repair is sensible, such as resealing, new gaskets or hardware adjustment, we do it. Where the frame or the installation is the problem, a proper replacement or insert is the better outcome. It is worth doing once, with precise installation and tidy detailing, rather than coming back to the same wall every winter. Our installation work carries a five-year workmanship warranty.
Our advice to any homeowner is simple. Do not wait for the stain to spread. Early diagnosis is cheaper than rot repairs, and records taken at the start protect you later.
Sharim
Getting your leaking windows sorted
We supply and install premium aluminium windows and doors across Greater Auckland, and we repair existing aluminium joinery. That covers sliding and casement windows, sliding, bifold, French and entry doors, and commercial shopfronts. If you are not sure whether your leak is a repair or a replacement, start with our aluminium window and door repairs page.
If the frames or the installation are beyond repair, our full replacement and insert service fits new joinery into existing openings, with double glazing and thermally broken frames where they suit the house. You can also see our full range of aluminium windows.
FAQ
What should I do if my windows are leaking in heavy rain?
Mop up and contain the water, photograph the damage, and note the wind direction and the strength of the rain. Clear the drain holes and check the sealant on a dry day. If the leak comes back, or you can see swollen trim or mould, get a window specialist or building inspector to find the source before sealing anything.
How can I stop my windows from leaking?
The answer depends on the cause. Blocked drain holes and worn seals can be cleaned or replaced. Failed sealant can be removed and redone. Flashing faults and rotten framing mean the window has to come out. Fixing the cause matters more than adding sealant on top of it.
Is water leaking around a window an emergency?
Treat it as urgent but not panicked. Contain the water, keep away from electrics, and document it. Ongoing moisture can rot framing and cause mould, so do not leave it through another winter. If water is coming through a ceiling or near wiring, call an electrician or builder straight away.
How much does it cost to fix a leaking window?
It varies with the cause. Cleaning drains or resealing costs far less than lifting a window to repair flashings and framing. Replacement costs depend on size, glazing and frame type. We inspect first and quote for the actual job, and you can see typical replacement ranges in our price guide.
Will insurance cover a leaking window?
Insurance generally covers sudden, accidental damage, not slow deterioration. Whether your claim is accepted depends on your policy and the cause, so photograph the damage, keep records and check with your insurer before starting repairs.
Sources
- Window or Door Leak Water Damage: What to Do & Cost
- Signs of a leaky home | Building Performance
- Windows and doors | Consumer NZ
- Learning about leaky buildings | Settled.govt.nz
- Technical FAQ | Window Association of New Zealand
- Weathertightness: Guide to the Diagnosis of Leaky Buildings | MBIE
- Weathertightness: Guide to Remediation Design | MBIE
- Windows and exterior doorways in existing dwellings | Building Performance
- Gradual deterioration and resultant damage | ICNZ
- Building Remediation: Why Patch-and-Repair Is Now a Risk