Patio and Sliding Door Repairs: Common Faults and Fixes

Sliding patio doors take a different kind of punishment to a hinged door — the whole weight of the panel runs along a track on rollers every time it's opened, rather than swinging on hinges. That different mechanism means different faults, and a different set of fixes. Here's what typically goes wrong with uPVC and aluminium patio doors, and what's usually involved in putting it right.

Door is heavy or hard to slide

This is the classic patio door complaint, and it's almost always down to the rollers rather than anything else. Sliding doors run on small wheeled rollers set into the bottom of the panel, which sit in a track fixed to the sill. Over years of use these rollers wear flat, pick up grit and debris, or the track itself accumulates dirt that the rollers have to push through every time the door moves.

A door that's become progressively harder to slide, especially if it's also started to sag slightly at one end, usually needs its rollers adjusted or replaced rather than anything more drastic. Most patio door rollers are adjustable via a screw accessible either on the bottom edge of the door or through a small cover on the frame, allowing the door to be raised slightly to reduce drag.

Keeping the track clear

A surprising number of 'broken' patio doors turn out to be a track full of grit, leaves, sand or old paint that's built up over time and is physically obstructing the rollers. Regularly vacuuming and wiping out the track, and checking nothing has been dropped or trodden into it, prevents a lot of unnecessary wear and can restore smooth running on its own.

It's also worth checking the track itself for dents or damage — a track that's been knocked out of true, often by something heavy being moved through the doorway, will cause the door to bind at that spot no matter how good the rollers are.

Lock won't engage or the door doesn't sit flush

Patio doors typically lock via a hook or claw mechanism operated by the handle, engaging a keep on the frame — similar in principle to the multipoint systems used on hinged doors, and explained in more depth in our multipoint locking mechanism guide. If the door has dropped slightly on worn rollers, the same alignment problem occurs: the lock hooks no longer meet their keeps cleanly, and the handle becomes stiff or the door won't lock at all.

In this case, adjusting or replacing the rollers to bring the door back to the correct height often resolves the locking issue at the same time, without needing to touch the lock mechanism itself.

Misted or condensation-prone glass

Patio doors typically use large double or triple glazed units, and like any sealed unit, the seal around the edge can fail over time, letting moisture in and causing permanent misting between the panes. This is a glass unit fault rather than anything to do with the sliding mechanism, and is fixed the same way as any other misted double glazing — by replacing the sealed unit while keeping the existing frame and door in place.

Draughts and water ingress at the threshold

Because patio doors sit low to the ground and slide rather than compress shut like a hinged door, the seals along the bottom track and meeting rail are particularly important. Worn or perished brush seals along the bottom of the door are a common cause of draughts and, in heavy rain, water finding its way in at the threshold.

These seals are generally replaceable without needing to remove the whole door panel, and it's a relatively inexpensive fix compared with the discomfort (and potential water damage) of leaving it.

Bifold and French doors — a related but different mechanism

Bifold doors share some symptoms with sliding patio doors — heavy operation, panels dragging, locks not engaging — but the mechanism is quite different, relying on top-hung or bottom-rolling hinged panels that fold rather than slide as a single sheet. If you've got a bifold set giving trouble, it's worth a separate look, since the adjustment points and common faults differ from a straightforward sliding patio door.

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