How long does double glazing last, and when is it worth replacing?

"How long does double glazing last?" has two honest answers. A good frame can last thirty years or more. The parts in it, the glass units, gaskets, hinges and locks, wear out sooner, and most "failed" windows we see in London are really sound frames with one worn part. Knowing which part has gone saves you from replacing windows that only need repairing.

The short answer

A good uPVC or aluminium double glazed window commonly lasts 20 to 30 years or more, but its sealed glass units, gaskets and hinges usually wear out before the frame does. If the frame is sound, replacing the worn parts restores the window for a fraction of the cost of a new one. Replace the whole window when the frame itself has failed, or when most of the units and hardware have gone at once.

How long each part lasts

These are typical working lives in London homes. Exposure, quality and care all move them up or down.

Part	Typical life	Signs it is failing	Fix
uPVC frame	20 to 30+ years	Cracked corners, warping, chalky yellowed surface	Replace the window
Aluminium frame	30+ years	Corroded corners, failed thermal break, damaged finish	Repair or replace
Timber frame	Decades, if painted	Soft wood at the sill and joints	Splice repair or replace
Sealed glass unit	Often 10 to 25 years	Mist between panes, tide marks	New unit in the same frame
Rubber gaskets	Around 10 to 15 years	Shrunk corners, hard and cracked rubber	Re-gasket
Friction hinges	Around 10 to 20 years	Sash drops, scrapes or will not close	New hinges
Locks and gearboxes	Around 10 to 20 years	Stiff or floppy handle, will not lock	New gearbox or lock

What shortens the life of double glazing

• South- and west-facing walls. Strong sun heats the units every day, and the expansion stresses the edge seals.
• Water sitting on the frame. Blocked drainage slots let water stand against the bottom edge of the unit.
• Forced handles. Lifting a door handle hard every day because the door has dropped is the most common cause of a broken lock.
• Paint and solvent cleaners on gaskets and uPVC.
• Poor original fitting: units sitting without proper packers, or frames out of square.

How to make it last longer

1. Twice a year, clear the drainage slots along the bottom of the frame and wash the frames with warm soapy water.
2. Once a year, put a drop of light oil on hinges and the lock mechanism.
3. Adjust doors as soon as they drop. Our guide on how to adjust a uPVC door shows how.
4. Keep trickle vents open to reduce condensation on the frames. See trickle vents explained.
5. Replace one failed unit early rather than waiting until several have gone.

Repair or replace? A quick decision guide

• Frame sound, one or a few units misted: replace the units. Run the five failed-unit tests first.
• Frame sound, draughts or stiff handles: gaskets, hinges and locks. See how to replace window seals.
• Frame cracked, warped or rotten: new windows.
• Most units misted and hardware worn across the house: compare the cost of all the repairs with new windows. New windows also bring the current energy standard and a new guarantee.
• Old single glazing in a listed or conservation area home: consider secondary glazing before replacement.

Worth knowing: the date of manufacture is often printed on the spacer bar between the panes, along with the maker's name. It tells you how old the units really are, which is useful when deciding.

Talk it through with us

We repair and replace across Central and North London, so we have no reason to sell you new windows if a repair will do. Send photos on WhatsApp of the worst window and of the frame corners, and we will say which it is. For full replacement, our double glazing London page covers the options and our free survey is the next step. Or call 07915 903485.