The warning signs your Berwick windows are done.
Windows almost never fail suddenly. They decline for about five years while everyone gets used to it, and then one July somebody notices the mould. Here is how to read the symptoms, which ones are a cheap fix, and which ones mean the opening is finished.
Condensation, fog, and the difference that matters.
Water on windows is the number one call we get from Berwick between June and August, and the first question is always the same: which side of the glass? The answer changes everything.
Water on the inside face. A single-glazed aluminium window has a U-value around 6, meaning it barely resists heat flow at all. On a 5 degree Berwick morning that pane is sitting close to 5 degrees. Warm, humid indoor air touches it, hits dew point, and runs down onto the sill. Nothing is broken. The window is doing exactly what a sheet of glass in a metal frame does. What it tells you is that you have no thermal performance at that opening, and that the water has to go somewhere, which is the sill and then the architrave.
Fog between the panes. Entirely different, and terminal. A double-glazed unit is two sheets bonded around a spacer with a desiccant and a sealed cavity, made to AS/NZS 4666. When that edge seal fails, moist air gets into the cavity, the desiccant saturates, and you get permanent haze you cannot reach or dry. The unit is finished. On the up side, this is a warranty question first: IGU seal warranties from the tier-1 manufacturers typically run 10 to 20 years, so before you pay for anything, find out when the windows went in.
Black mould in the architrave corners. This is the one we take most seriously, because it means the condensation has been running for years. The water pools in the sill, soaks into the reveal and the architrave, and the timber never fully dries out, especially on south-facing bedrooms that get no winter sun. Wiping the stain treats the symptom. Repainting buys you a season. The glazing is the cause, and it is also a health issue in a child's bedroom, which is usually what finally gets the job booked.
Chalking, sticking, and the moving house underneath.
The aluminium extrusion will outlive all of us. What wears out is everything bolted to it, and on the 1990s and 2000s Casey estate stock those consumables all reach the end of their life within a few years of each other, which is why so many Berwick houses seem to fall apart at once around the 20 to 25 year mark.
- Chalky powder coat. Run a finger down the frame. If it comes away white, the coating has oxidised. Cosmetic, not structural, but it is the visible clock on the house and it does not come back. Most owners take the chance to move from the original white to Monument or Surfmist, which changes the look of the street frontage more than anything else you can do for the money.
- Gaskets you can slide a card past. Rubber hardens at around 15 to 20 years and stops sealing. That is your draughts, your dust and a chunk of your heating bill.
- Screeching or jammed rollers. Cheap to fix, and worth fixing if the rest of the window is sound. This is maintenance, and it is on our Berwick window maintenance page.
- Blocked weep holes. The drainage slots in the bottom of the frame silt up with Casey clay dust and grass clippings. Water that should drain out backs up instead. Free to fix with a skewer, and a genuine cause of leaks blamed on the window.
- Rotted timber sash bottom rails. On the old Berwick cottages this is where the rot always starts, because the bottom rail is where water sits. Once it is soft through the section, the sash is done. Splicing is possible on genuinely significant joinery, but it usually costs more than a period-matched replacement.
The Casey clay problem nobody mentions.
This is the local one, and it gets misdiagnosed constantly. Casey sits on reactive clay. Sites across Clyde North, Cranbourne East and much of the newer estate land classify H1 or H2 under AS 2870, meaning highly reactive ground that swells as it wets up over winter and shrinks back through summer. The house moves with it. Not much, a millimetre or two, but a window frame is a precision assembly and a millimetre of rack is enough to make a sliding door bind, a sash catch on one corner, or a large fixed pane crack for no apparent reason.
The diagnostic is seasonal. If your sliding door sticks in February and runs sweetly in August, or the other way around, the door is fine and the ground is moving. Replacing it without allowing for that movement just gives you a new door that sticks, which is why we never pack a frame hard against brickwork. Tell us which season it sticks in, because that one word changes the answer.
Repair, part-house, or the whole lot.
Not everything on this page means replacement. Rollers, weep holes, flyscreens, hardware and even gaskets on some profiles are all serviceable. What is not serviceable is a failed IGU out of warranty, a rotted sash, a chalked frame, or a house full of single glazing in a Climate Zone 6 winter. Once you are past roughly half the openings, the arithmetic changes and doing the lot gets cheaper per window, because mobilising a crew, a skip and a delivery costs the same for four openings or fourteen. The per-window rate on a whole-house job runs about 15 to 25 per cent under a one-off.
Worked example, 2026. Owner in Cranbourne East, 2004 brick veneer, 12 openings, all original single-glaze aluminium. July audit finds: seven openings streaming with condensation and mould starting on three architraves, chalked powder coat throughout, two sliding windows with screeching rollers, one bathroom awning with a seized friction stay, and the 2.4m living-room slider binding only in winter. Option A, repair only: rollers and stay at about $650 all up, weep holes cleared, door adjusted. Fixes the noise, fixes nothing else, and every winter is identical to the last. Option B, the seven bad openings in double-glazed aluminium at roughly $1,900 each: $13,300, plus $380 each make-good, so about $15,960, and the five untouched windows now look twenty years older than their neighbours because the new powder coat does not match. Option C, whole house, 12 openings double-glazed at the volume rate: about $18,400 including make-good. Option C is $2,400 more than Option B for five extra windows and a house that matches. That is the conversation we have at nearly every Casey measure, and it is why we quote both ways.
The other thing worth knowing before you decide: on some 1990s and 2000s frames you may not need a new window at all. Retrofit double glazing swaps the glass while keeping the frame, at 40 to 60 per cent of the cost of full replacement. It does not suit every frame, and the honest assessment is on our retrofit vs replacement page. If you have decided the frames are going, our aluminium windows page covers the brands and styles, and the July diagnosis timing is explained on the seasonal timing page.
Warning sign questions we get asked.
Is condensation on my windows a sign they need replacing?
It depends entirely on which side of the glass it is. Water on the inside face of a single-glazed pane on a cold Berwick morning is physics, not a fault: the glass is sitting near the outside temperature, warm indoor air hits it, and it condenses. That tells you the window has no thermal performance, which is worth fixing, but nothing is broken. Fog trapped between two panes of a double-glazed unit is different. That is a failed edge seal on the IGU and the unit is finished. You cannot dry it out, and it will never clear.
Why has my sliding door started sticking in Berwick?
Three usual causes, and only one of them is the door. Worn rollers are the most common and the cheapest, and a roller swap on a 20-year-old aluminium slider is a fraction of a replacement. Debris packed into the bottom track is second, and it is free to fix. Third is the house itself. Casey sits on reactive clay, typically H1 or H2 under AS 2870, and the ground swells in winter and shrinks over summer. That movement racks the frame a millimetre or two. If your door binds in one season and runs sweetly in the other, the door is fine and the house is moving.
How long do aluminium windows last in Melbourne's south east?
The aluminium itself outlasts everybody. What wears out is everything attached to it. Rubber gaskets harden and stop sealing at around 15 to 20 years, rollers and friction stays wear out on a similar clock, and the powder coat on the mid-range builder-spec frames that went into the 1990s and 2000s Casey estates typically starts chalking around the 20 to 25 year mark. So a 2001 Berwick house is right in the window now, not because the frames failed, but because every consumable in them has reached the end of its life at once.
Should I replace all my windows at once or just the bad ones?
Do the whole house if more than about half the openings are failing, and do the bad ones if it is a handful. The reason is mobilisation, not sales. Getting a crew, a skip and a delivery to your place costs the same whether we do four openings or fourteen, so the per-window rate on a whole-house job runs roughly 15 to 25 per cent below a one-off. The other factor is appearance. New powder coat next to twenty years of Casey sun does not match, so a single window in a matched run of eight will always look like a repair.
What is the black mould on my window architraves?
It is the downstream symptom of condensation, and it is the sign we take most seriously. Water runs off a cold single-glazed pane, sits in the sill and soaks into the reveal and architrave, and by the third or fourth Berwick winter the timber is permanently damp and mould has colonised it. Wiping it off treats the stain, not the cause. If you are seeing black mould in the architrave corners of bedrooms, particularly on the south side of the house where nothing dries out, the glazing is the problem and repainting will buy you about one season.
Free window assessments across Casey.
Not sure if it is worn out or just dirty?
Free measure and an honest answer. If four openings will do, we will tell you four.