How Long Do Replacement Windows Last?
The frame usually outlives everything attached to it. Sealed units and hardware are the parts that fail first — and both can be replaced on their own, without a new window.
- uPVC frames typically last 20 to 35 years, aluminium 40 or more
- Sealed units are the usual first failure, commonly at 15 to 25 years
- A misted pane can often be replaced on its own — it does not mean a new window
- Hardware wears out soonest and is the cheapest thing to renew
- Exposure, orientation and installation quality matter more than the brand on the frame
Three components, three lifespans
A window is not one thing with one life expectancy. It is a frame, a sealed glass unit and a set of moving hardware, and these wear out on completely different timescales.
Understanding that saves money, because the most common reason people replace windows — misting between the panes — is a failure of the cheapest and most replaceable component, not of the window as a whole.
Frames
- uPVC: typically 20 to 35 years. Modern formulations resist yellowing far better than the material that earned uPVC its reputation in the 1980s. Dark foiled finishes on a hot south or west elevation work harder than white and may show their age sooner.
- Aluminium: 40 years and often well beyond. It does not warp, rot or discolour, and a polyester powder-coated finish holds colour for decades because it is bonded to the metal rather than laminated onto it. Frames of this age are common and the material is fully recyclable when it finally comes out.
- Timber: anywhere from 30 to 60 years or more, entirely dependent on maintenance. Kept painted and dry, good timber outlasts everything. Neglected, it is the first to fail.
These are service lives, not warranty periods, and they assume competent installation. A frame fitted out of square, inadequately packed or poorly sealed will fail early regardless of what it is made of.
Sealed units — the usual culprit
A double glazed unit is two panes bonded around a spacer bar with a perimeter seal, the cavity filled with argon and a desiccant in the spacer absorbing residual moisture. It is a sealed system, and like all sealed systems it eventually is not one.
When the edge seal degrades, moisture-laden air enters, the desiccant saturates, and condensation appears between the panes. This is the misting that people call a blown window. Expect 15 to 25 years in typical use, sooner on units taking a lot of thermal cycling — large south-facing panes, or units partly shaded so one area heats while another stays cool.
Two things are worth knowing. First, a misted unit is a cosmetic and thermal problem rather than a structural one: the window is still secure and still weathertight. Second, and more usefully, the unit can very often be replaced on its own while the frame stays exactly where it is. That is a fraction of the cost of a new window and is frequently the right answer on a frame with years left in it.
Hardware
Hinges, handles, locking mechanisms, gaskets and weather seals are the moving and flexing parts, and they wear out first — commonly somewhere between 10 and 20 years.
The good news is that almost all of it is replaceable. A window that has become stiff, that no longer pulls tight onto its seals, or whose handle has gone loose is very often a hardware job rather than a replacement job. Friction hinges and multipoint mechanisms are standard components.
Gaskets harden and shrink over time, which is the usual reason a window that was once draught-free starts letting weather in. Re-gasketing is straightforward.
What shortens a window's life
- Exposure and orientation. South and west elevations take the most ultraviolet and the biggest temperature swings. Prevailing weather on an exposed elevation — which describes plenty of properties on the Wiltshire downs and the Cotswold escarpment — is hard on seals and finishes.
- Blocked drainage. Frames have weep holes and internal drainage channels. When these silt up, water sits in the frame instead of leaving it, which attacks seals and hardware from below. This is the single most neglected piece of window maintenance.
- Poor installation. Insufficient packing, inadequate fixing, frames forced out of square or perimeters left unsealed will shorten the life of any window, however good the product.
- Abrasive cleaning. Scouring pads and solvent cleaners damage uPVC surfaces and powder-coated finishes permanently.
- Trapped moisture internally. Persistent condensation on the inside face of the glass is a ventilation and humidity issue in the room, not a window fault, but sustained wetness does the frames and seals no favours.
Maintenance that genuinely adds years
None of this is onerous. An hour or two a year covers a whole house.
- Clear the drainage channels and weep holes at the bottom of each frame twice a year. A soft brush and a rinse is enough.
- Lubricate hinges, friction stays and locking mechanisms annually with a light machine oil, avoiding the gaskets.
- Wash frames with warm soapy water, never a scouring pad or a solvent.
- Check the gaskets each autumn for hardening, shrinkage or gaps, and the external perimeter seal for cracking.
- Never paint uPVC. Never allow render, mortar or masonry paint to be splashed onto frames and left.
- On timber, keep the paint or stain intact — the moment the finish breaks, water gets in.
When it really is time to replace
Replacement rather than repair is the right call when several of these apply at once:
- Draughts you can feel with the window closed and the hardware correctly adjusted.
- Frames that have warped, distorted or, in timber, gone soft.
- Multiple sealed units failed across the house rather than one or two.
- Windows that are difficult to open, or no longer lock properly, where the hardware is obsolete and parts are unavailable.
- Single glazing, or early double glazing with no low-emissivity coating, where the thermal case for replacement stands on its own.
- Obsolete locking, particularly older cylinders with no anti-snap protection on an accessible ground-floor window.
Paperwork, and why it matters later
Keep the Building Regulations Compliance Certificate somewhere you will find it. Any replacement glazing installed in England since April 2002 is controlled work, and a buyer's conveyancing solicitor will ask for the certificate. Not having it can delay a sale or push you into buying indemnity insurance.
Keep the guarantee documentation with it. Our installations carry a 20-year guarantee, and the paperwork is what makes that straightforward to act on years later.
If something is not right
Tell us. A window that has drifted out of adjustment in its first years is usually a short visit rather than a problem, and dealing with it early stops it becoming a seal or hardware failure later. Our number is 01865 416496.
- Choosing ProductsAre Aluminium Windows Worth It?
Aluminium costs more and delivers slimmer frames, a longer life and a better finish. Whether that is worth it depends almost entirely on the size of your windows and the character of your house.
- ComparisonsuPVC vs Aluminium Windows
Both materials make excellent modern windows. The real differences are frame slimness, price and how each one suits a particular house — not a simple question of which is better.
Still not sure where you stand?
Book a free home survey and we will check listed status, conservation area designation and the regulations that apply to your property before you commit to anything.