How to specify fire retardant paints

How do you specify fire retardant paints?

To specify fire retardant paint, state the Euroclass the lining has to achieve under BS EN 13501-1, taken from the fire strategy, and require a classification report for the coating system on the same substrate, thickness and existing finish as the project. Fix the coat build-up and maximum spreading rate the classification depends on, the fire retardant durability class for the location, and how application will be recorded. It improves reaction to fire only; it does not give fire resistance.

Fire retardant paints are used to bring timber, plywood, MDF or old painted surfaces up to the lining class a fire strategy asks for, typically on escape routes or in assembly spaces where exposed wood is part of the design. The paint only achieves the class in the combination it was tested in: that substrate, that thickness, that number of coats at that spreading rate, often with a named topcoat. Change any of those and the evidence may no longer apply.

This guide covers Uniclass Pr_35_31_68_29 Flame-retardant coatings. Intumescent coatings that protect structural steel are a different product with a different test basis, Pr_35_31_68_43, covered in the intumescent paint guide. Fire-retardant impregnation treatments for timber sit under Pr_35_31_67.

What does a fire retardant paint clause need to cover?

Some properties are specific to fire retardant paints. Others belong in every product clause. A clause that leaves either out gives the contractor room to substitute.

Fields marked Never guess (reaction to fire classification, fire retardant durability class and fire resistance) depend on the project and should never be filled from a default or a previous job. If the information is not available yet, the clause should say so with a TBC and a reason.

Which decisions does the clause depend on?

Most properties follow from the product you choose. These depend on the project, so they need a decision from the designer before the clause is written.

Which standards should the clause cite?

Cite the product standard the declaration of performance refers to, the code of practice for installation, and the test method behind each value you set. A value without its test method cannot be checked against a submittal.

BS EN 13501-1

Fire classification of construction products and building elements. Classification using data from reaction to fire tests

The Euroclass system (A1 to F, with smoke and droplet ratings) used to classify a coated lining. The classification report names the substrate and the field of application.

In the clause "Reaction to fire: Class B-s1,d0 to BS EN 13501-1 on the specified substrate."

BS EN 13823

Reaction to fire tests for building products. Building products excluding floorings exposed to the thermal attack by a single burning item

The single burning item (SBI) test behind classes A2 to D for wall and ceiling products, including coated timber.

In the clause Not usually cited directly; ask for the classification report that draws on it.

BS EN 13238

Reaction to fire tests for building products. Conditioning procedures and general rules for selection of substrates

How test substrates are chosen and when a result on one substrate can represent another. This is why the substrate in the report matters.

In the clause Use it to frame the evidence check: "substrate within the field of application of the classification".

BS EN 16755

Durability of reaction to fire performance. Classes of fire-retardant treated wood products in interior and exterior end use applications

Durability classes INT1 (interior dry), INT2 (interior humid) and EXT (exterior) showing whether the fire performance lasts in use.

In the clause "Fire retardant durability: DRF class INT1 to BS EN 16755."

BS EN 13381-8

Test methods for determining the contribution to the fire resistance of structural members: applied reactive protection to steel members

The assessment method for intumescent protection of steel. Cited here to make clear it is a different product and test basis.

In the clause Do not cite it for a flame retardant paint. Reference it only in a separate intumescent clause.

BS 6150

Painting of buildings. Code of practice

The UK code of practice for preparation, application and maintenance of paint systems, including on timber.

In the clause "Workmanship: to BS 6150 and the coating manufacturer's instructions for the classified system."

Confirm the current edition of each standard at every issue. Avoice's State of UK Specifications 2026 found a withdrawn standard cited in 40% of specifications at contract issue.

For the regulations behind these choices, see Approved Document B explained, Fire strategy reports explained, or search the Avoice Regulations library.

How do you write it in CAWS?

In CAWS, fire retardant coatings for linings are written in M60 alongside the other paint systems, not in M61, which is for intumescent coatings to steelwork. Manufacturers' M60 masters group their flame retardant systems together in the 170s, with separate clauses for new surfaces, overcoating and upgrading existing paint, and each gives the surfaces, preparation, coats and spreading rates.

The type clause leans on a general clause for flame retardant coatings, which in real masters requires fire test evidence from the manufacturer, confirmation that the testing suits the surface, and attention to existing coating layers when redecorating. Keep that clause, and make sure the compatibility clause covers any fire-retardant pretreatment already in the timber.

Clauses the type clause relies on

M60/210A

Flame retardant coatings Fire test evidence from the manufacturer, testing appropriate to the surface, and existing coating layers on redecoration.

M60/220

Compatibility Materials compatible with each other and not inhibiting fire-retardant pretreatments.

M60/440A

Previously coated surfaces generally Assessment and preparation of existing paint before overcoating.

M60/481

Uncoated wood Preparation of new timber and boards before the first coat.

M60/711A

Coating generally Conditions during application and no thinning unless the manufacturer recommends it.

Clause numbers vary between NBS versions and practice masters. The numbers here follow a manufacturer's NBS-format M60 master; what matters is that the type clause refers to clauses that exist in your M60.

How do you write it in Uniclass?

In Uniclass the coating system sits under Ss_40_90_60_85 Special coating systems. The system clause describes the substrate, the preparation, the full coat sequence and the finished performance: the Euroclass of the coated lining and its durability class.

The coating is a product clause under Pr_35_31_68_29 Flame-retardant coatings, holding the named basecoat and topcoat, binder and evidence. Because the class depends on the pairing, keep basecoat and topcoat in the same product clause, or give the topcoat its own clause that states it must be the one named in the classification.

In NBS Chorus the Uniclass product clause for flame-retardant coatings carries the NBS reference 45-35-84/406. Use whichever your practice's masters use, but do not mix CAWS and Uniclass references in one specification.

What goes in the spec, and what goes in the schedule?

The specification defines each type once. The schedule and drawings say where each type goes.

What are the common mistakes?

Most problems are a missing property, a property filled with the wrong kind of value, or a decision left silently open.

• !
  "Class 0 fire retardant paint". Approved Document B in England no longer gives the national class route for reaction to fire. Specify the Euroclass.
• !
  Evidence on the wrong substrate. A report on non-combustible board does not cover timber. Check the field of application.
• !
  Any topcoat over the basecoat. The class depends on the tested topcoat. Name it, and tell the client what may be used to redecorate.
• !
  Paint as a fire door upgrade. Coatings do not give fire resistance. Use tested door assemblies or certified upgrade systems.
• !
  Spreading rate left to the decorator. Thin coats miss the class. Set the maximum rate and require wet film checks.
• !
  Interior class in a pool hall. Humidity can degrade the performance. Specify INT2, or EXT outside.

How Avoice helps

Avoice's spec writer drafts flame retardant coating clauses from your fire strategy and finishes information, and shows what it could not settle.

1. 1
   Drafts from your drawings and schedules

   It reads the lining classes from the fire strategy drawings and the coating types (FR01 to new plywood, FR02 overcoat to existing panelling) from the decorations schedule, then picks the M60 clause or the Uniclass system and product headings.

2. 2
   Leaves a TBC with a reason

   If the existing coatings on retained panelling have not been surveyed, or the client has not chosen a colour within the classified range, the line says TBC and why. Every TBC joins one project register to close before tender.

3. 3
   Writes in your format and style

   Choose CAWS or Uniclass. Avoice adapts your practice's own M60 masters rather than replacing them with generic text.

4. 4
   Checks the clause against everything else

   QA/QC flags a lining class in the clause that differs from the fire strategy, a coating clause quoting Class 0, or a door schedule relying on paint for fire resistance.

5. 5
   Keeps product data in one place

   Classification reports, fields of application and certificates of application sit in the Product Room, linked to the clause, alongside the Approved Document B guidance in Avoice Regulations.

Related guides: How to specify intumescent paint, How to specify plywood, How to specify emulsion paint.

Software can draft and check. The designer still chooses the product and is responsible for the specification.