A sliding door that scrapes or drags along the floor is one of the most common joinery problems in NZ homes, and in most cases it's a straightforward fix. The door has usually dropped because the roller carriages have worn out, come off the track, or simply need adjusting. With a few basic tools and a bit of patience, many homeowners can sort this out themselves in under an hour.
Why Sliding Doors Drop
Sliding doors hang from a top track via roller carriages (also called trolleys or hangers). The bottom of the door sits in a shallow guide channel — it doesn't carry the door's weight, it just keeps it aligned. When a door scrapes the floor, the most common causes are:
- Worn or broken rollers — the nylon or steel wheels degrade over time, especially in high-traffic doorways
- Rollers off the track — a knock or heavy use can dislodge a carriage from the top rail
- Adjustment screws backed off — most carriages have a height-adjustment screw that can work loose
- Bent or dirty track — debris, corrosion or physical damage can cause the door to drop or bind
- Sagging door frame — less common, but house movement (especially in older NZ homes on timber piles) can shift the frame out of level
Tools and Materials You'll Need
- Phillips head and flathead screwdrivers
- Pliers
- Step ladder
- Replacement roller carriages (if needed — match the brand and track profile)
- Silicone spray lubricant or dry PTFE lubricant
- Soft cloth and vacuum
- A helper (useful but not essential)
Replacement rollers are available at Bunnings and Mitre 10. Take your old roller or a photo of the track profile with you, as there are several different systems used in NZ.
Step 1 — Remove the Door
Before adjusting anything, it's easiest to take the door off completely.
- Slide the door to the centre of the opening.
- Lift the door firmly upward — most sliding doors simply lift off the bottom guide channel first, then angle out from the top track.
- If the door won't lift clear, look for a retaining clip or anti-jump block on the top track and remove it first (usually a small screw-fixed plastic piece).
- Lay the door flat on a padded surface to protect the glass or finish.
Internal cavity sliders are a little different — check whether your door slides into a wall cavity, as these may need the architrave removed to access the track. If you're unsure, it's worth calling a joiner.
Step 2 — Inspect and Adjust the Rollers
With the door removed, examine the roller carriages at the top of the door:
- Spin each wheel — it should roll freely and smoothly. A stiff, flat-spotted or cracked wheel needs replacing.
- Check the adjustment screw — most carriages have a screw (often accessible from the door face or bottom edge) that raises or lowers the roller. Turn it clockwise to raise the door, anti-clockwise to lower it.
- Look for damage — bent axles or cracked housings mean the whole carriage should be replaced.
If the rollers are fine, the issue may simply be that the adjustment screws have backed off over time.
Step 3 — Clean and Lubricate the Track
While the door is off, clean the top track thoroughly:
- Vacuum out dust, grit and debris
- Wipe with a damp cloth
- Apply a silicone spray or dry PTFE lubricant along the track — avoid oil-based lubricants as they attract dirt
Also check the bottom guide channel and clear any build-up.
Step 4 — Rehang and Fine-Tune
- Hook the roller carriages back onto the top track, then lower the bottom of the door into the guide channel.
- Replace any anti-jump clips.
- Slide the door back and forth — it should glide smoothly without touching the floor.
- Use the adjustment screws to fine-tune the height until there's a consistent 3–5 mm clearance above the floor and the door sits plumb.
Replacing Worn Roller Carriages
If the wheels are worn or broken, replacement carriages are inexpensive and widely available. The key is matching the track profile (typically a round tube, a C-channel, or a flat rail) and the wheel diameter. Many NZ homes use joinery from local manufacturers, so if you can't find a match at a hardware store, contact a local joinery supplier or PlaceMakers for advice.
Checking for Frame or Structural Issues
If you've adjusted the rollers and the door still scrapes, or if the top track itself is visibly twisted or the frame is out of square, the problem may be structural. NZ homes — particularly older weatherboard or pile homes — can experience foundation movement that shifts door frames out of level. This is worth investigating, as it may point to a broader issue. BRANZ has useful guidance on building performance and house movement.
If the door is part of a weathertight or exterior assembly, any repairs to the surrounding frame or cladding may need to comply with the NZ Building Code (in particular Clause E2 — External Moisture). Check with your local council whether a building consent is required before making structural changes.
When to Call a Professional
Call a qualified joiner or carpenter if:
- The door frame is visibly racked, twisted or rotted
- You suspect foundation or structural movement
- It's a cavity slider and you can't access the track without major disassembly
- The door is large, heavy (e.g. a solid timber or double-glazed unit) and awkward to handle safely alone
- You've replaced the rollers and the problem persists
A licensed joiner can also advise on whether an older door system is worth repairing or should be replaced. You can find qualified local joiners and carpenters on tradedirectory.co.nz.
Safety note: Large sliding doors — especially those with glass panels — are heavy and can be awkward to handle. Always get a helper when lifting a door on and off the track, and take care not to stress the glass.
