Floor reaction to fire: Euroclass Bfl-s1, Cfl-s1 and Dfl-s1

At a glance

Higher critical flux is better; the smoke grade s1 (750 %·min or less) or s2 follows the class. Deemed classes are conditions in Decisions 96/603/EC and 2006/213/EC and Regulation 1292/2014, not claims about any product.

The Euroclass key for floors

A floor has its own series of fire classes. They run from A1fl, the best, to Ffl, with an fl to mark them as floorings, and a smoke grade after the letter: s1 or s2. The key below is taken from Table 2 of the Annex to Commission Delegated Regulation (EU) 2016/364, as published on legislation.gov.uk, which sets the classes the standard BS EN 13501-1 applies. Higher critical flux is better.

• The radiant panel test (EN ISO 9239-1) lays the floor under a radiant panel for up to 30 minutes. The critical flux is the radiant flux at which the flame goes out, or the flux reached after 30 minutes, whichever is lower. Bfl needs 8.0 kW/m² or more, Cfl 4.5 or more and Dfl 3.0 or more.
• The small flame test (EN ISO 11925-2) holds a small flame on the floor for 15 seconds. For Bfl to Efl the flame must not spread more than 150 mm within 20 seconds. An Ffl floor fails it.
• Smoke. s1 means smoke of 750 %·min or less; s2 is anything above that.
• A1fl and A2fl are the non-combustible and limited-combustibility classes, tested by EN ISO 1182 and EN ISO 1716. A2fl also needs 8.0 kW/m² or more.

The test standards have moved. BSI lists BS EN ISO 9239-1:2025 as current and the 2010 edition as withdrawn on 4 July 2025; BS EN ISO 11925-2:2026 as current and the 2020 edition as withdrawn on 30 January 2026; and BS EN 13238:2026, the conditioning and substrate standard, as current with its 2010 edition withdrawn on 3 August 2026. BS EN 13501-1:2018 is listed as current. A report may cite an older edition: ask which, and let the fire engineer say whether it still serves. We read none of these standards.

A class belongs to a floor as laid. Approved Document B Appendix B says a classification is only valid when the product is used within the field of application tested, that is, fixed to a substrate of that class in its end use (para B8). The substrate, adhesive, thickness and finish are part of the answer.

Does a floor need a class? What the documents say

The question designers are asked most is whether a floor must be Bfl-s1 or Cfl-s1. Some flooring sites say a class is required in escape routes or hotels. For England, the Approved Documents we read do not say so. The table sets out what we read, with the paragraph.

So a statement that Cfl-s1 is ‘required’ for a hotel corridor floor in England is not supported by Approved Document B, volume 1 or 2. That does not mean no class is ever needed: a fire strategy, an insurer, an operator's brand standard or another nation's rules may ask for one, and the fire engineer says which. The Approved Document names a floor class in one place, for the top layer of a balcony on a tall residential building, which is outside the interior floor.

Wood floors: what the EU lists let them claim

For some wood floors the European Commission listed conditions under which a floor is deemed to reach a class without being tested. Approved Document B points to this process, saying the materials covered can be found through the European Commission's website (Appendix B, para B6). The two tables give the conditions as the instruments state them. A floor is deemed to reach the class only when every condition in its row is met.

Coated floors. Commission Decision 2006/213/EC, Annex, Table 1.

Conditions common to the table: the surface coating is acrylic, polyurethane or soap at 50 to 100 g/m², or oil at 20 to 60 g/m²; the wood is conditioned to EN 13238 (50 % relative humidity, 23 °C); the floor is tested in the way EN ISO 9239-1 describes, on a substrate of at least D-s2, d0 with a density of at least 400 kg/m³, or with an air gap underneath; an interlayer of at least class E and no more than 3 mm may be used with parquet of 14 mm or more and with veneered coverings. The classes apply also to the steps of stairs.

Uncoated floors. Commission Delegated Regulation (EU) No 1292/2014, Annex.

Conditions common to the table: no surface coating; conditioned to EN 13238; mounted as above, with an air gap at least 30 mm high where one is used; an interlayer of at least class Efl, no more than 3 mm and at least 280 kg/m³ may be included. Also applies to the steps of stairs.

These are the texts of EU instruments as published on legislation.gov.uk, which records no outstanding UK changes to them. We did not check whether the European Union has amended them since 2020, or how a building control body treats them. A row in a table is not a product: a maker's declaration of performance, or a test report, is the evidence for a floor, and no product on this site is claimed to reach any class.

Stone, terrazzo and other floors

Commission Decision 96/603/EC, as amended, lists materials that are treated as class A1 and A1fl without any test. It names natural stone and slate products (worked or not), terrazzo (including precast concrete tiles and in-situ flooring), ceramics, concrete, mortars for floor screeds, and copper and copper alloys not in finely divided form, among others. Its general notes set the limits:

• a product is to be made only from listed materials;
• products made by gluing listed materials count if the glue is no more than 0.1 % by weight or volume;
• coated products must contain no more than 1.0 % homogeneously distributed organic material;
• panel products with organic layers, or with organic material that is not evenly spread (glue apart), are excluded.

On a reading of those notes, a cement-bound terrazzo or a plain stone slab fits the list, and a resin-bound terrazzo, a stone with a resin face or backing, or a coated surface may not. That is our reading of the notes, not a ruling: ask the maker what its declaration says for the product and finish supplied. For carpet, resilient floors and resin floors we read no list, and each carries the class its own tests give. Our natural stone flooring specification and terrazzo specification sheets cover the rest of those floors.

Writing a floor class into a specification

If a class is asked for, write it so that the evidence can be checked.

• Who sets it. Name the fire strategy or the fire engineer's report that sets the class. If none is required, say so, and ask the maker to declare the class as supplied.
• The class and the smoke grade, for example Cfl-s1, to BS EN 13501-1, with the edition.
• The end use. The substrate and its class, adhesive, any underlay or air gap, thickness, finish, and for a wood floor the coating type and quantity. A class for the board alone, or on a different substrate, does not carry over.
• The evidence. A declaration of performance stating the class, or a classification report from a laboratory with the right expertise (Approved Document B Appendix B, para B5, names notified bodies and UKAS-accredited laboratories), or a statement naming the row of the without-testing list relied on, with each condition checked and recorded.
• The edition of the test standards the report cites.
• Change control. A change of substrate, adhesive, thickness or finish after approval goes back to the fire engineer before ordering.

For the rest of the checks on a busy timber floor see specifying timber floors for high-traffic interiors. For the evidence file see the fire documentation matrix, and for a wall rather than a floor fire performance of wall panelling. The standards behind the declaration are on the wood flooring standards map.

Floor finish in [areas] to achieve reaction to fire class [Cfl-s1] to BS EN 13501-1 [edition], as laid, as required by [fire strategy reference, section, date]. [Where no class is required: no floor class is required by [document]; the supplier is to declare the class of the floor as supplied.]

The class is to apply to the build-up as specified: substrate [type, class [ ]], adhesive [ ], underlay or air gap [ ], thickness [ ] mm, finish [coating type and quantity, g/m²]. A class for the board alone, or on a different substrate, is not accepted.

[A declaration of performance stating the class / a classification report from [a notified body / a UKAS accredited laboratory] to BS EN 13501-1 [edition], with the test methods and their editions / a statement naming the row of the classification-without-testing list relied on, with density, thickness, end use and coating quantity checked and recorded], submitted before ordering. Any change of substrate, adhesive, thickness or finish is to be referred to [the fire engineer] before ordering.

[Natural stone / cement-bound terrazzo / ceramic] floor to be class A1fl without testing where the product is on the list in Decision 96/603/EC as amended and meets its general notes. The supplier is to confirm in writing, including any sealer, resin, coating or backing, or to give a declared class.

Standards and sources

• Approved Document B volume 2 (2019 edition incorporating 2020, 2022, 2025 and 2026 amendments, with the 2029 changes): B2 Intention (p.54), 5.17, Table 6.1, Regulation 7, 12.11, Appendix B (B5 to B8). Read 5 Nov 2026.
• Approved Document B volume 1 (same edition and amendments): B2 Intention (p.43), 3.43, Appendix B B6. Read 5 Nov 2026.
• Scotland: building standards technical handbook 2022, non-domestic, section 2.5: published 1 Jun 2022; read 5 Nov 2026. Domestic handbook and any 2026 change not read.
• Commission Delegated Regulation (EU) 2016/364, Decision 2006/213/EC, Regulation (EU) No 1292/2014, Decision 96/603/EC: as published on legislation.gov.uk; read 5 Nov 2026.
• BS EN 13501-1:2018, BS EN ISO 9239-1:2025, BS EN ISO 11925-2:2026, BS EN 13238:2026: BSI Knowledge listings: all Current; earlier editions withdrawn as stated. Standards not read.

Questions we are asked

Does a timber floor in a hotel need a fire rating in England?

Approved Document B, volumes 1 and 2, says Requirement B2 does not include guidance on the upper surfaces of floors and stairs, so it sets no class for an interior floor finish. A class can still come from the fire strategy, the insurer, the operator or another nation's rules. Ask the fire engineer, and ask the maker for the declared class.

What does Cfl-s1 mean?

C is the class and fl marks it as a flooring. In the radiant panel test the floor needs a critical flux of 4.5 kW/m² or more, and in the small flame test the flame must not spread more than 150 mm within 20 seconds. s1 means smoke of 750 %·min or less. It sits below A1fl, A2fl and Bfl, and above Dfl.

Is Bfl better than Cfl?

Yes. The classes run A1fl, A2fl, Bfl, Cfl, Dfl, Efl, Ffl, best first. Bfl needs a critical flux of 8.0 kW/m² or more, Cfl 4.5 and Dfl 3.0.

Does oak flooring achieve Cfl-s1?

We claim no product does. The EU list deems a coated solid oak floor of at least 8 mm and 650 kg/m³, glued to a substrate of at least A2-s1, d0, to be Cfl-s1, if every other condition in its row is met. The evidence for a floor is the maker's declaration or a test report.

Do stone floors need a fire test?

Natural stone and slate products and terrazzo are on the list of materials treated as A1fl without testing, subject to the general notes on glue and organic content. A stone with a resin face, backing or coating may not fit. Ask the maker what its declaration says.

What about Scotland?

Scotland's non-domestic handbook, Standard 2.5, concerns the surfaces of walls and ceilings, and its Table 2.4 classes are for wall and ceiling surfaces. We found no floor class in it. The domestic handbook and any 2026 changes were not read.

Is reaction to fire the same as fire resistance?

No. Reaction to fire is how much a product adds to a fire. Fire resistance, such as FD30 for a door, is how long a built element holds. A floor class says nothing about the second.

Who decides what class a floor needs?

The fire strategy for the building, by the fire engineer, agreed with building control, and sometimes the insurer or operator. This sheet cannot decide it for a project.