What threshold gap is acceptable?

There is no single figure that applies to every door. The acceptable arrangement at the bottom of a door comes from the doorset's test evidence and the manufacturer's installation instructions, together with what the door is required to do — a door with a smoke control requirement is treated differently from one without. We work to the evidence for your doorset rather than quoting a universal number.

Can a drop seal be fitted to an existing fire door?

Sometimes, and it is often the tidiest remedy where the floor level varies or a threshold cannot be raised. It depends on whether a compatible device can be fitted to that leaf in the way the documentation supports, since surface and morticed devices affect the leaf differently. Morticing a leaf without evidence that it can accept the device is not something we would do.

The gap only appears at one end of the door. Why?

Usually because the leaf has dropped, the frame has moved, or the floor finish is uneven across the opening. Fitting a seal to close the widest point without correcting the cause tends to produce a door that binds at the other end. We deal with the alignment first and the seal second.

New carpet has been laid and the door now catches. What now?

This is a common one after refurbishment. Trimming the leaf is not a free action — how much can come off a fire door leaf, if anything, depends on the construction and the manufacturer's documentation. Where trimming is not supported, the answer is usually to address the floor finish at the opening or to change the threshold arrangement.

Do you produce the report that records these findings?

Formal door-by-door inspection reports are arranged through a specialist fire door inspection contractor where one is required. Parsec Fire Doors works from that report, or from an existing report or FRA action list, and carries out the resulting repairs, remedials, installation and replacement. Our pre-works site assessment confirms remedial scope and is not a formal inspection report.

Guide

Fire Door Thresholds & Drop Seals: Gaps, Smoke Control and Remedies

The bottom of the door is where floor finishes, settlement and well-meant refurbishment all collide. This page covers threshold findings, what the gap under a door is actually being judged against, and which remedies hold up.

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Why the Bottom of the Door Is Treated Separately

The gap under a door is not governed by the same considerations as the gaps around the head and stiles. Floor finishes change over the life of a building, thresholds get removed during refurbishment, and doors are frequently trimmed to clear new carpet. The result is that threshold findings often reflect building history rather than the door as supplied.

What is required at the threshold depends on the doorset and its role. Where smoke control is part of what the door has to achieve, the arrangement at the bottom matters a great deal more than where it is not. The right reference is the test evidence and installation instructions for that doorset, not a figure carried over from another building.

Findings We Are Asked to Resolve

Common

Excessive gap after new floor coverings

A previous contractor trimmed the leaf to clear carpet, or the threshold was removed and never reinstated, leaving a gap larger than the doorset arrangement supports.

Common

Missing or damaged drop seal

A device that no longer deploys, has been painted solid, or was removed during hardware work and never replaced.

Alignment first

Uneven gap across the width

A dropped leaf, moved frame or uneven floor. Correcting alignment usually resolves more than fitting a seal to the widest point.

Depends on evidence

Threshold plates and strips added on site

Ad hoc strips fixed across the opening to close a gap. Assessed against what the doorset documentation supports rather than accepted as complete.

Care needed

Doors trimmed beyond what is supported

Where the leaf has been cut down further than the construction allows, making good may not be possible and replacement is the honest answer.

Binding and failure to latch

A door catching at the threshold often shows up elsewhere as a closing or latching defect. Both are dealt with at the same visit.

Remedial Routes, Roughly in Order

Threshold work is usually a sequence rather than a single fix, and the cheapest sound remedy is often the least visible one. We work through causes before components.

Correct leaf alignment, hinge condition and frame position where these are the cause
Reinstate or adapt the threshold arrangement where one has been removed
Fit a compatible drop seal where the doorset documentation supports it
Address floor finish levels at the opening where refurbishment created the gap
Renew perimeter seals and closing hardware disturbed by the same works
Replace the leaf or doorset where the construction can no longer support a sound remedy

How Threshold Items Get Completed

Threshold entries rarely travel alone. They are usually completed alongside perimeter gap adjustments, seal renewals and closer work on the same doors, which is what makes a visit worth mobilising.

Send us the report or action list you hold and we will price the threshold entries against your door references, noting where a remedy depends on evidence for the doorset. Our close-out records set out what was completed door by door.

Threshold work sits within the wider remedial picture.

Gaps & clearances Intumescent & smoke seals Fire door closers Fire door repairs & remedials Common fire door defects Repair or replacement?

Frequently Asked Questions

Threshold Findings to Close Out?

Send us your inspection report or FRA action list and we will price the threshold and drop seal entries against your door references, together with the alignment and closing work usually recorded on the same doors.

Get a Fire Door Quote 07841 613936