A door that drags on new carpet or flooring is one of the most common joinery headaches after a renovation. The good news is that trimming a door is well within DIY reach for most homeowners — you just need the right tools, careful measuring, and a bit of patience to get a clean result.
Why Doors Drag After New Flooring
When new carpet, vinyl plank, or timber flooring is laid, it raises the floor level — sometimes by as much as 10–20 mm depending on the product and underlay. Interior doors that previously swung freely can suddenly bind or scrape. This is completely normal and doesn't mean anything is wrong with your door or the installation.
Tools and Materials You'll Need
- Tape measure and pencil
- Combination square or straightedge
- Circular saw or hand saw (a circular saw gives a cleaner, straighter cut)
- Masking tape (to reduce tear-out on the cut line)
- Sandpaper (80–120 grit) or a sanding block
- Timber sealer, primer, or paint to finish the cut edge
- Sawhorses or a stable work surface
- Screwdriver (to remove hinge pins or door)
Step 1 — Measure How Much to Remove
The standard clearance gap under an interior door is 10–12 mm above a hard floor, or enough to clear the carpet pile without dragging. Measure the gap you currently have, then measure how much the door is dragging. The difference tells you how much to trim.
Important: Only remove what you need. Taking off too much leaves an unsightly gap and can affect draught-stopping and privacy. Double-check your measurement before cutting — the old joinery saying "measure twice, cut once" exists for good reason.
Step 2 — Remove the Door
Tap out the hinge pins with a screwdriver and hammer (start from the bottom hinge), then lift the door free. Carry it to a flat work surface like a pair of sawhorses. Trying to cut a door in place is awkward and rarely gives a straight result.
Step 3 — Mark the Cut Line
Using your tape measure and a combination square, mark the cut line clearly across the full width of the door. Apply a strip of masking tape along the cut line — this dramatically reduces tear-out and splintering, especially on hollow-core doors or painted surfaces.
Mark your line on the tape with a pencil so it's easy to see.
Step 4 — Make the Cut
Set your circular saw to cut just a fraction outside (waste side of) your pencil line, then use a straightedge clamped to the door as a guide fence for a perfectly straight cut. Cut slowly and steadily.
Hollow-core doors: Be aware that most interior doors in NZ homes are hollow-core. They have a solid timber frame around the perimeter (typically 30–40 mm wide) and a hollow or cardboard-honeycomb centre. If you need to remove more than about 30 mm, you risk cutting into the hollow section, which leaves the bottom edge unsupported and looking rough. If you need to remove more than this, talk to a joiner — it's possible to reglue the bottom rail back in, but it's a fiddly repair.
Solid timber doors: These are more forgiving and can generally have more material removed, but they're also heavier and harder to handle alone.
Step 5 — Clean Up the Edge
Once cut, remove the masking tape carefully. Sand the cut edge smooth with 80–120 grit sandpaper, rounding the corners very slightly so they don't splinter in use.
Seal the cut edge immediately. Raw timber or MDF absorbs moisture, which can cause swelling and warping over time — particularly important in NZ's varied climate. Apply a coat of timber sealer, primer, or the same paint used on the door faces. Allow it to dry fully before rehanging.
Step 6 — Rehang and Test
Lift the door back onto the hinges, replace the hinge pins, and swing the door through its full arc. Check the clearance across the full width — floors aren't always perfectly level, so one corner may still catch. If needed, a few passes with a hand plane or another light trim can sort this out.
Tips for Different Flooring Types
| Flooring Type | Typical Height Added | Notes |
|---|---|---|
| Carpet + underlay | 10–20 mm | Varies with pile height and underlay thickness |
| Vinyl plank (LVP) | 4–8 mm | Check manufacturer specs |
| Engineered timber | 12–15 mm | Includes underlay |
| Tile | 8–15 mm | Depends on tile and adhesive bed thickness |
Always measure your actual situation rather than relying on these figures alone.
When to Call a Professional
Call a qualified joiner or carpenter if:
- You need to remove more than 30–35 mm and the door is hollow-core
- The door is a fire door (these have specific construction requirements and must not be modified without checking manufacturer guidelines — fire doors may be required under the NZ Building Code in certain locations)
- The door frame itself is racked or out of square, causing the bind
- You're dealing with an external door, where weathertightness and security are critical
- You're not confident using power tools safely
A skilled joiner can also advise whether it's more cost-effective to trim the existing door or replace it entirely. You can find qualified local joiners and carpenters on tradedirectory.co.nz.
A Note on Safety
Always wear safety glasses and hearing protection when using a circular saw. Secure the door firmly before cutting, and keep hands well clear of the blade path. Review safe tool use guidelines at WorkSafe NZ if you're unfamiliar with power tools.
