Trim the bottom of a door — HomeGraft

Trim a sticking or too-long internal door with a circular saw, then seal the cut edge neatly.

DR-01Work out how much needs to come offClose the door and check where it catches, or measure the gap you need over new flooring or carpet. Aim for a 6-10mm gap at the bottom for carpet, or 3-5mm for hard flooring. Mark this amount at both ends of the door with a pencil.

1 each · Pencil

Buy:ScrewfixB&QToolstationAmazon

1 each · Tape measure

Buy:ScrewfixB&QToolstationAmazon

DR-02Take the door off its hingesGet a helper to hold the door steady, then unscrew the hinges from the door (not the frame). Lay the door flat on two trestles or a workbench, with the bottom edge overhanging slightly so you can cut without hitting anything underneath.

1 each · Screwdriver

Buy:ScrewfixB&QToolstationAmazon

2 each · Trestles or workbench

Buy:ScrewfixB&QToolstationAmazon

DR-03Check what kind of door you haveMost modern internal doors are hollow-core, with a thin honeycomb card core and a solid timber block only at the top and bottom edges. Knock on the bottom edge — a light, hollow sound means hollow-core, and you should never trim more than about 12mm off in total or you risk cutting through into the honeycomb with nothing to screw the hinge into. A solid, dead sound means solid timber or solid MDF, which can take a bigger trim safely.

DR-04Check if it's a fire door before you cutLook on the top edge of the door for a coloured plastic plug or a stamped label — this marks a fire door. Fire doors have strict limits on how much can be trimmed, usually only a few millimetres from each edge, because the timber thickness is part of what makes them fire-resistant. If you're not sure how much is allowed, don't trim it — get advice from the door manufacturer or a joiner first.

RULES

KNOW THE RULES

Building Regulations Part B covers fire doors. Trimming a fire door beyond the manufacturer's stated limit can void its fire rating, which matters for flats and shared buildings.

DR-05Mark and score the cut lineJoin your two pencil marks with a straight edge or spirit level, running the full width of the door. Score firmly along this line with a sharp knife, especially on veneered or laminated doors — this stops the saw tearing the surface as it cuts.

1 each · Spirit level or long straight edge

Buy:ScrewfixB&QToolstationAmazon

1 each · Retractable utility knife

Buy:ScrewfixB&QToolstationAmazon

DR-06Clamp the door securelyClamp the door to the trestles or bench, with a scrap piece of wood underneath the cut line to protect the surface and stop splintering as the blade exits. Make sure the door can't shift while you're cutting.

2 each · F-clamps

Buy:ScrewfixB&QToolstationAmazon

1 each · Scrap timber (sacrificial board)

Buy:ScrewfixB&QToolstationAmazon

DR-07Cut along the line with a circular sawSet the blade depth to just clear the thickness of the door plus a couple of millimetres. Wearing safety glasses, guide the saw along a straight edge clamped to the door as a fence, keeping steady pressure and letting the saw do the work. Support the offcut as it comes free so it doesn't tear away and splinter the door.

1 each · Circular saw

Buy:ScrewfixB&QToolstationAmazon

1 each · Safety glasses

Buy:ScrewfixB&QToolstationAmazon

DR-08Sand and seal the cut edgeSand the cut edge smooth, easing off any sharp corners. Seal bare timber or MDF with a coat of primer, varnish or paint that matches the rest of the door — this stops the exposed edge soaking up moisture and swelling, especially near bathrooms or kitchens.

1 sheet · Sandpaper (120 grit)

Buy:ScrewfixB&QToolstationAmazon

1 small tin · Primer or matching paint/varnish

Buy:ScrewfixB&QToolstationAmazon

DR-09Rehang the door and check the fitWith a helper, lift the door back into place and screw the hinges back in. Open and close it a few times to check it swings freely and the gap is even along the bottom.

1 each · Screwdriver

Buy:ScrewfixB&QToolstationAmazon

DR-10Tidy upVacuum up sawdust from the floor and workbench, and wipe down the door. Dispose of the offcut, and store any leftover paint or varnish with the lid tightly closed for next time.

1 each · Vacuum cleaner

Buy:ScrewfixB&QToolstationAmazon

1 each · Dust sheet

Buy:ScrewfixB&QToolstationAmazon

Some links may earn us a small commission at no extra cost to you.

Save this as a project

Back to all guides