How long do windows last
Timber window frames last 30 to 60 years with a repaint every 5, PVC frames 25 to 35, aluminium 30 to 50. The glass unit inside them lasts 15 to 25. Most 'my windows are done' verdicts are really a failed glass unit inside a healthy frame, and the unit swap costs a fraction of the replacement it gets mistaken for.
A window is a frame on one clock and a sealed glass unit on a faster one, and nearly every window decision goes wrong by reading the fast clock as if it were the slow one. The glass fogs at year 18, someone says “the windows are done,” and a frame with decades left gets priced for replacement.
What each part lasts
| Part | Typical lifespan | What usually ends it |
|---|---|---|
| Timber frames | 30–60 years | rot, paint failure, seal degradation |
| PVC frames | 25–35 years | seal failure, hardware wear, colour drift |
| Aluminium frames | 30–50 years | thermal-bridge failure, gasket degradation, coating failure |
| Double-glazed unit (IGU) | 15–25 years | seal failure (fogging), gas loss, spacer degradation |
| Triple-glazed unit | 20–30 years | seal failure, gas loss |
| Exterior timber door | 30–60 years | rot, warping, hardware wear |
| Composite / steel door | 25–40 years | seal failure, hardware wear, coating failure |
| Skylight / roof window | 20–30 years | flashing failure, seal degradation, hardware wear |
The ranges come from the durability handbooks and trade field data the planning model is built on. The pattern to take from the table: every frame material outlasts the glass unit inside it. A house glazed once will re-glaze its units at least once, often twice, before any frame is due, so “how long do windows last” is really two questions with two budgets.
Timber’s number has a condition attached
Timber frames reach 30 to 60 years only on a repaint cycle of about every 5 years. The paint is not cosmetic; it is the membrane that keeps water out of the joinery, and rot starts where the paint film fails, at the sill and the lower joints first. A timber window that missed two repaint cycles is aging on a steeper curve than its calendar age suggests. The same logic runs through exterior timber doors, on a refinish cycle of roughly every 4 years. PVC and aluminium trade that maintenance for a shorter, flatter life: nothing to repaint, less to extend.
The unit swap is the decision most owners never get offered
When a unit fogs, the honest repair is a new IGU in the old frame. The window seal replacement cost guide prices the two options: a replacement unit runs EUR 150–350 per window, a full window several times that. The gap is why the distinction earns its own decision. Run the annual-cost arithmetic honestly: a EUR 250 unit in a PVC frame at year 28 of 35 is buying years the frame may not have, while the same unit in a maintained timber frame at year 30 of 60 is the obvious call. You can check your own case in the free repair-or-replace calculator.
When to start planning
Sanna’s house in Turku was glazed in 2004: timber frames, repainted more or less on cycle, double-glazed units now 22 years old. Two units on the weather side have started fogging. The frames are at year 22 of a 30-to-60 range, mid-curve and sound; the units are at the end of theirs. She books a glazier for the failed units this summer and expects to rotate through the rest over the next few years as they fail, one by one, while the frames stay. New windows enter her plan somewhere in the 2030s, as a decision rather than a surprise.
What this means before you call anyone
Diagnose which clock ran out before asking for prices, because the trades sell what they are: a glazier replaces units, an installer replaces windows. A quote for full replacement when only units have failed is not dishonest, it is the answer to the question as asked. The plan in appkeep tracks frames and glass units as separate components, so the fogging year and the frame year each arrive as their own flagged decision instead of one alarming quote.
Is this a repair year or a replacement year?
You give the component, its age, and the repair quote you are holding. You see which costs less per year of service, and how much life a repair can honestly buy at this age. The method is the one property managers run: cost divided by the years it buys, not the size of the two numbers side by side.
The answer
Pick a component, its age, and the repair quote to see the year you are in.
The money is one input, not the decision. See the repair-or-replace guide for the third option (waiting, with a date) and the four times the arithmetic gets overruled: safety, energy rules, insurance, and a third failure in a year.
This runs on typical market prices and lifespans, not your own component. Signed in, appkeep runs the same method on your house's real age, cost, and history.
- Lifespans and installed replacement costs are the sourced seed behind appkeep's plan (RgdBOEI 2012 / NEN 2767, NAHB, BRE, CIBSE, trade bodies, manufacturer guidance). Prices are per unit, VAT-inclusive, in today's money. Each carries its own confidence label, shown next to the number.
- A repair does not reset the component's clock. The years a repair buys are capped by the life the component has left, and past roughly three-quarters of its life that shrinks fast, because wear accelerates. The tool reflects that in the years-a-repair-buys figure.
- The tool prices the money. It cannot see the component's condition, whether this is its first fault or its third, or a safety or insurance rule that forces the call. Those sit with you and the linked guide.
Common questions
How long do double-glazed windows last?
The sealed glass unit (IGU) lasts 15 to 25 years; a triple-glazed unit 20 to 30. The frame around it lasts far longer: 25 to 35 years for PVC, 30 to 50 for aluminium, 30 to 60 for maintained timber. When double glazing fogs between the panes, the unit's edge seal has failed and the unit is replaceable on its own, inside the existing frame. Treating a failed unit as a failed window is the single most expensive misreading in this component.
Do fogged windows mean I need new windows?
Almost never. Fog between the panes means the insulated glass unit's seal has failed and moisture has entered the cavity. The unit is swapped inside the existing frame for a fraction of a full window replacement, provided the frame itself is sound. Check the frame separately: rot on timber, cracked seals or failed hardware on PVC. A glazier replaces units; a window installer sells windows. Which one you call shapes which answer you get.
How long do uPVC windows last?
PVC window frames last 25 to 35 years. The endings are seal failure, hardware wear, and colour drift rather than structural failure, so a PVC window's last years are usually about draughts and stiff handles, not danger. The 40-year figures sometimes quoted sit at the very top of what any industry source supports; plan on 25 to 35 and treat anything more as a bonus. Handles and hinges are replaceable along the way; the seals and gaskets are what age.
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