Fixing a Foggy, Sticking or Broken Sliding Door
A sliding glass door usually does not need replacing, it needs the right repair. A door that sticks or drags is a mechanical fault: worn rollers or a dirty, damaged bottom track, both of which are serviced or swapped without touching the glass. A foggy or misted double-glazed door means the sealed unit has failed, and the fix is replacing the glass unit while keeping the frame. A cracked or smashed pane is a glass replacement in the existing door. In most cases a targeted repair is far cheaper than a full door replacement.
Key takeaways
- Sticking or dragging: worn rollers or a fouled track, a mechanical fix, not a glass one.
- Foggy or misted glass: the sealed double-glazed unit has failed and the glass is replaced.
- Cracked or smashed: the pane is replaced in the existing door and frame.
- The frame and door are usually kept; only the failed part is replaced.
- A targeted repair almost always beats a full door replacement on cost.
Sticking and dragging is mechanical
When a sliding door gets hard to move, judders, or drops at one end, the glass is fine and the problem is underneath. Sliding doors ride on small rollers that run along a bottom track, and those rollers wear flat, seize, or clog with grit over years of use. Worn rollers are the single most common cause of a heavy, sticking door.
The track itself is the other culprit. Dirt, sand, and small stones pack into the channel, and the track can dent or bow, so the door grinds instead of gliding. Cleaning the track and either adjusting or replacing the rollers restores smooth movement without any glass work at all.
Because this is a mechanical service, it is one of the cheaper glazing-adjacent jobs, and catching a dragging door early avoids the rollers chewing up the track and turning a small fix into a larger one.
Foggy glass means a failed sealed unit
A double-glazed sliding door that mists up between the panes, where you cannot wipe the fog off either side, has a failed insulated glass unit. The perimeter seal that keeps the cavity dry has broken down and let moisture in, and once that happens the fogging is permanent and the unit no longer insulates as it should.
The fix is to replace the sealed glass unit, not the whole door. A new made-to-measure IGU is fitted into the existing frame and sash, so you keep the door hardware and frame and only pay for the glass unit and its refit. This is a standard job and much cheaper than replacing the entire door.
Fogging is purely a sealed-unit issue, so it does not apply to single-glazed doors. If a single-glazed door looks hazy, that is usually surface residue or scratching rather than an internal seal failure.
Cracked or broken glass
A cracked, chipped, or smashed sliding door pane is a glass replacement. The old glass is removed and a new pane, toughened because a sliding door is a safety-glass position, is cut to size and reglazed into the existing door and frame. The frame, track, and rollers are reused unless they are separately damaged.
For a broken pane, a glazier makes the opening safe first, then measures for the replacement, since toughened glass is made to order and cannot be trimmed on site. That can mean a temporary board-up until the new pane arrives, which is normal for toughened work.
Across all 3 faults, sticking, fogging, and breakage, the door and frame are almost always kept and only the failed component is renewed. We connect you with vetted local specialists so you can compare 3 free quotes and confirm a repair before anyone quotes you a full replacement.
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Frequently asked questions
Almost always worn rollers or a track fouled with grit and debris. The glass is fine; it is a mechanical fault fixed by cleaning the track and adjusting or replacing the rollers, one of the cheaper repairs.
Yes. Internal fogging means the sealed glass unit has failed, and the fix is a new made-to-measure insulated glass unit fitted into the existing frame and sash. The door and hardware are kept, so it costs far less than a full replacement.
Repair, in most cases. Rollers, tracks, sealed units, and single panes are all serviced or replaced individually while keeping the door and frame. A full replacement is only warranted when the frame itself is damaged or corroded.