Not every window fault means a new window. A blown sealed unit, a worn seal or a broken hinge can be repaired for a fraction of a replacement. What cannot be repaired is a frame that has rotted, warped or cracked. This guide sorts the common signs into “fix it” and “replace it”, and clears up the condensation question that trips people up.
Points to take away
- Misting between the panes: reglaze the unit, keep the frame.
- Draughts and stiff opening: usually a worn seal or hinge, both cheap fixes.
- Rot, warping, cracked frames, or a frame pulling from the wall: replace.
- Condensation on the inside surface of the glass is a humidity problem, not a broken window.
- Several failing windows at once, or frames past 20 years: do the house in one order.
Reading time: about 6 minutes.
Signs a repair will fix
These are common, they look worse than they are, and a glazier fixes them without a new window.
- Misted or foggy glass. The seal on the sealed unit has failed and moisture is trapped between the panes. The frame is fine. A new unit fitted into the existing frame is £70 to £150. Our guide to misted double glazing covers it in full.
- A draught near the opening edge. The rubber gasket has gone hard and flat, or the sash has dropped so it no longer presses on the seal. New gaskets or a hinge adjustment, under £100 in most cases.
- Handle or lock not working. Espagnolette rods, gearboxes, handles and hinges are stock parts. A window that will not lock is a security issue but a quick repair.
- Water pooling on the inside sill. Often the drainage slots in the outer frame are blocked with dirt. Clearing them stops the leak.
Signs the window needs replacing
- Rot in a timber frame. Soft, spongy wood, especially at the bottom corners, means water has been getting in. Filler is a stopgap. Once the joints have gone, replace.
- Warped or bowed uPVC. Frames that have distorted in the sun no longer seal or lock properly and cannot be trued up.
- Cracked frame or a cracked weld at a corner. uPVC frames are welded at the corners. A split there lets water into the reinforcement and there is no repair.
- The frame has moved away from the wall. Gaps you can see daylight through, or that let water track down the inside, mean the fixing has failed and the window is coming out.
- Old metal frames with no thermal break. Single-glazed steel or aluminium frames from before the 1990s draught, corrode and run with condensation. Replacement is the only real fix.
- Past 20 years and several are failing together. At that point, repairing one at a time is throwing money at a job that is coming anyway.
Condensation: which kind you have matters
This is the sign people misread most often.
Between the two panes of glass. You cannot wipe it off because it is sealed inside. The unit seal has failed. This is a window fault and needs reglazing.
On the room-facing surface of the glass, on cold mornings. You can wipe it off. This is warm, humid indoor air hitting a cold pane. It points to moisture in the house and not enough ventilation: drying washing indoors, a bathroom without an extractor, trickle vents closed. New windows can make it slightly worse at first, because a well-sealed house traps more moisture. The fix is ventilation, not new glass.
On the outside of the glass in the morning. This is a sign your windows are working well. The outer pane is staying cold because heat is not leaking through it.
Score it: repair, replace one, or do the house
- One misted unit, one stiff window, sound frames: repair. A few hundred pounds.
- Two or three faults, frames under 15 years and solid: repair each. Cheaper than replacing.
- Frames past 20 years, more than a couple deteriorating, or any rot or warping: replace, and price the whole house at once for the volume discount and a single certificate. See the cost guide.
- Selling within a year: new windows if the current ones are visibly tired, because buyers notice.
Not sure whether yours are repairable? Get a free quote and we will match you with vetted local installers and repair firms who cover your area.