Painting Fire Doors in London Buildings: Compliance, Intumescent Products and What You Cannot Change

Fire Doors and Why They Cannot Be Treated as Ordinary Joinery

A fire door is not simply a door that happens to be painted a certain colour. It is a tested and certified assembly — door leaf, frame, intumescent and smoke seals, hinges, latch and closers — that as a system has been tested to provide a defined period of fire resistance, typically FD30 (30 minutes) or FD60 (60 minutes) as classified under BS EN 1634-1.

The critical implication for painters and building managers in London is this: any modification to a certified fire door assembly that has not been assessed against the original test evidence can invalidate its fire resistance rating. That includes painting it with the wrong product, applying too many coats of paint, or filling gaps in the door leaf with an incompatible material.

Since the Grenfell Tower fire and the introduction of the Building Safety Act 2022, this is not a theoretical concern. Responsible persons in higher-risk buildings (defined as residential buildings over 18 metres or 7 storeys) have statutory duties to manage fire door maintenance and to ensure any works on fire doors are carried out competently and with documented evidence.

What Paint Does to a Fire Door

Standard paint — even a heavy-bodied enamel or hard gloss — plays no active role in fire resistance. Its effect is simply cosmetic. The fire resistance of the door comes from the core material (typically timber with mineral cores in composite doors), the certified frame rebate, and crucially the intumescent seals that expand under heat to close the gap between door and frame.

Where standard paint becomes a problem is through build-up. Multiple generations of paint applied to a fire door over decades can:

• Reduce the clearance between the door leaf and frame, causing the door to bind and preventing it from latching properly — a latched fire door holds significantly longer than an unlatched one
• Obscure or compress the intumescent strips fitted into door edges or frames, reducing their ability to expand when needed
• Add sufficient weight to affect the performance of the door closer, causing slow or incomplete closure

For these reasons, fire doors in London buildings that have received multiple layers of paint over the years must be assessed carefully before further coats are added. Where paint build-up is suspected, all existing coats should be stripped back before any new system is applied.

Intumescent Paints and Varnishes

Where an enhanced level of fire protection is specified for the surface of a fire door — particularly for timber doors that are exposed to view and where an aesthetically pleasing finish is required — intumescent topcoats are available. These are water-based products that, when exposed to heat above approximately 150–200°C, expand to form a protective char layer that insulates the substrate beneath.

Products in this category include Nullifire Water-Based Intumescent products, Envirograf, and the Sherwin-Williams Firetex range. These coatings are applied over a compatible primer system and, critically, must be used in accordance with the manufacturer's application instructions — deviating from the specified wet film thickness, number of coats or drying times invalidates the product's fire test data.

Intumescent paints are not a substitute for the intumescent seals fitted into the door frame and leaf edges — they are an additional layer of protection applied to the face of the door.

Colour and Certification

Fire door certification covers the door as supplied and tested. Repainting a fire door in a new colour is permissible provided:

1. The total paint thickness (all coats combined) remains within the limits assessed in the test evidence for that door type
2. The paint system is compatible with the door substrate — water-based systems on timber are generally appropriate; solvent-borne systems should be assessed against the original manufacturer's guidance
3. The door's fire certification label and markings are not obscured or removed — under the Fire Safety (England) Regulations 2022, fire doors in higher-risk buildings must retain their identification markings

If the door manufacturer has provided approved paint systems in their test evidence, these should be followed. Where this information is not available, a fire door specialist should be consulted before any work proceeds.

The Inspection Sequence Before Painting

Before any fire door painting work in a London building, the following checks must be completed:

• Confirm door certification status — does the door have a certification plug or label? Is there documentation on file?
• Check intumescent seals — are the seals present, intact and unobstructed? Are cold-smoke seals also fitted?
• Test door closure — does the door close and latch fully from all positions on the hinges without being held?
• Assess existing paint build-up — is there evidence of multiple paint layers restricting the door leaf clearance?
• Check ironmongery — are all hinges, the closer and the latch in good working order and correctly adjusted?

Only once these checks are complete and any defects rectified should redecoration proceed.

For fire door painting and inspection in London, contact us here to discuss compliance requirements, or request a free quote for your building.