A fire door is built to sit in its frame with a gap of roughly 3mm all round. Inspectors usually allow 2mm to 4mm at the sides and the head. The door's own label or certificate has the final say.
Hold a steel rule up to it. If you get 6mm at the top of the lock side and almost nothing at the bottom, the door has dropped.
Hinges first
Check the hinges before anything else. Most fire doors hang on three of them, and the top one carries the most weight.
On reports we often see a hinge with two screws left out of eight. The other six have stripped their holes, so the door drops at the lock corner, rubs on the floor and gets planed.
What we do next depends on what is behind the hinge. If the timber is sound, longer screws and a packer may be enough. If the recess has torn out, we cut it back, fill it with new hardwood and fix the hinge into that.
A cheap butt hinge from a DIY shed is not what a fire door was tested with. We use hinges made for fire doors and the screws that go with them.
A small tweak or a frame job
A door that is only slightly out can often be brought back with new hinges or one packer. That takes under an hour.
The harder case is a gap that is wide at the top on one side and nothing at the bottom on the other. Hinges will not cure that, because the frame has moved. Fixing it means taking off the architrave, packing and fixing the frame again, sealing behind it with fire-rated foam and putting everything back. Two of us, most of a day. We price it as its own line so nobody is surprised.
The bottom edge
Carpet catches the bottom of a door, so people trim it. Years later the gap is too big.
Many doors are allowed a bigger gap at the threshold than at the sides, but the certificate says how much. We measure before we cut anything, and we never plane past what the door allows.
Packers and lippings
A packer pushed in the wrong place does more harm than none, because it can pull the frame or leave a hollow. Ours are sized to the gap and fixed through.
If a door has shrunk, or was cut too small when it was fitted, a hardwood lipping on the edge can bring the gap back, provided the door's certification permits it.
Questions we get asked
How much gap is too much?
Around 4mm at the sides and head is the usual upper limit. Check the door's own certificate for the exact figure.
Will new hinges be enough?
Often they are. If the frame has moved, the frame needs work too.
Send the list with the postcode. We will come back with a price for each door.
Get a price