A patio or bi-fold door that drags, sticks or takes both hands to move almost always has worn rollers, a fouled track, or both. It is a repair, not a replacement — typically £120–£260, and the door usually ends up gliding better than it has in years.
A single 2.5 × 2.1m glazed pane weighs roughly 130kg, and every gram of it sits on four small wheels. Grit gets into the track, the wheels wear flat, the door starts to drag, and the harder it is to move the more force gets put through the mechanism.
Left long enough, the door drops far enough that the locking points miss their keeps — and now the door is both hard to move and insecure. Fix it early and it is a roller job. Leave it and it becomes a lock job too.
Doors lifted out, track cleaned and inspected for damage, rollers replaced, door rehung, height adjusted at each roller, locking points realigned to their keeps, brushes and gaskets checked. On a bi-fold, the top track carriages and the bottom guides are both checked, and the panels are re-set so they fold square.
If the track itself is damaged — and it can be, if the door has been running metal-on-metal — the track has to be replaced or, on some systems, a repair track can be fitted over it.
| Job | Typical cost |
|---|---|
| Patio door rollers replaced & realigned per door | £120 – £260 |
| Lock / locking mechanism replaced per lock | £80 – £180 |
| Gaskets & weather seals renewed per window | £60 – £140 |
Ranges include VAT and installation. Final price depends on size, spec, access and site condition — a survey gives you a fixed number.
Worn rollers, a track full of grit, or both. A large glazed pane can weigh over 100kg and it all bears on four small wheels. Cleaning the track and replacing the rollers usually restores it completely.
Typically £120–£260, including realigning the door and resetting the locking points.
Usually the panels have dropped and are no longer square, so the hinges are fighting each other. Re-setting the carriages and adjusting each panel normally fixes it. If the head has deflected because the lintel is undersized, that is a structural problem and no amount of adjustment will hold.
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