Visible gaps between fire door and frame in London

You notice it because the light gives it away. Daylight from the landing showing round the edge of a flat entrance door. A communal fire door that rattles in its frame when someone lets it slam upstairs. Maybe it's a draught you can feel standing in the hallway, or the door just doesn't sit flush the way it used to.

That's the sort of thing people live with for months before they do anything about it. It doesn't look dangerous. But a fire door only works as a system - leaf, frame, seals, gaps all doing their job together - and a gap that's too wide breaks that system before you've even lit a match.

What it might mean

A few things could be going on, and it's genuinely hard to say which without measuring it.

Timber doors and frames move over the years - shrinkage is common, especially in older stock, and it opens gaps that weren't there when the door was fitted. It's also possible the door was never the right size for the frame to begin with, which we see more often than you'd think in conversions where a standard door's been dropped into an opening that wasn't built for it. Less commonly, the building itself has moved slightly - settlement, structural movement - and that's shifted the frame out of true.

None of these are certainties from a description alone. That's exactly what a proper inspection is for.

How urgent is it?

This isn't a middle-of-the-night emergency, but it's not something to let drift either. Gaps beyond tolerance are a compliance failure, and it's exactly the kind of thing that gets flagged the moment anyone does a fire risk assessment or a Regulation 10 check on the building.

If you're a leaseholder or landlord and this door is due any kind of inspection soon, get it looked at before that happens rather than after. If it's a communal door in a block over 11 metres, the responsible person should already have eyes on it as part of their routine checks - but routine visual checks aren't the same as a technical assessment of whether the gap's within the doorset's tested tolerance. That's a different job.

What you can safely check

You can get a rough idea yourself before anyone comes out. A gap gauge against the door - head and jambs are typically around 3-4mm, though the correct figure depends on that specific doorset's test evidence and manufacturer's instructions, not a one-size-fits-all number. The bottom gap runs larger on a fire-only door, often 8-10mm, but if the door's meant to control smoke as well, that gap needs to be much tighter - usually no more than 3mm unless there's a threshold or drop-down seal fitted.

What you shouldn't do is start packing the frame yourself or swapping the intumescent strip for whatever's in stock at the local shop. Intumescent strips expand to many times their size in heat to seal a small, specific gap - they're not designed to bridge a gap that's grown well beyond what they were tested for. Fit the wrong one, or fit it to a gap that's too wide, and it does nothing when it matters.

What we check

When we come out, we're measuring every gap round the door - not just the one you noticed - and checking the condition of the intumescent strips while we're there, because a strip that's perished or missing is often part of the same story. We're also working out whether it's the door that's moved, the frame, or both, because that changes the fix completely. A warped leaf and a dropped frame don't get solved the same way.

Sometimes the door's fine and it's purely a frame issue. Sometimes the door itself has reached the point where packing and lipping won't bring it back within tolerance, and that's a different conversation.

How it's fixed

Where the gap's a strip problem, it's a straightforward swap - correctly sized intumescent strip fitted to the doorset's actual spec, not a generic one. Where the door or frame's shifted slightly, edge lipping or frame packing can often bring it back within tolerance without replacing anything.

Where the gap's too far gone - and past a certain point, no strip is going to bridge it - the door needs replacing. That's not something to guess at from the landing; it needs a proper look first. Our fire door repairs service covers all of this, from a strip swap through to a full replacement where the inspection shows that's what's needed.

We see all four categories of this stock across London - old timber FD30 doors in post-war blocks with strips long past their best, non-rated flat entrance doors in Victorian and Edwardian conversions, composite doors in newer developments let down by the wrong ironmongery, steel doors in plant rooms propped open with the wrong closer fitted. The fix is never one-size-fits-all, and neither is the door in front of you.

Call now if the gap's letting through a visible draught or light you can see clearly from the other side - that's usually beyond what a strip alone will fix, and it's worth getting ahead of it rather than waiting for an inspection to catch it first.