Fire performance
Specifying liquid screed within fire-rated compartment floor build-ups
Liquid screed itself is generally non-combustible, but fire resistance is a property of the whole floor build-up, so the specification needs to reference the tested assembly rather than the screed in isolation.
Fire resistance ratings for floors, expressed as periods of resistance under standards such as BS EN 13501, apply to the complete tested build-up rather than to any single layer within it, which means a liquid screed cannot be said to provide a given fire rating on its own.
In practice, most cementitious and calcium sulfate liquid screeds are non-combustible materials, so their presence within a build-up does not typically compromise fire performance, but the specification should still reference the specific tested assembly, or a suitably justified variation from it, rather than assuming any screed will do.
This matters particularly on compartment floors in multi-occupancy buildings, where changing an element of the build-up, including insulation type beneath the screed or the screed depth itself, could take the floor outside the scope of the fire test evidence relied upon.
Fire and compartment floor requirements — the points that decide it
- Fire resistance is a property of the whole tested floor build-up, not of the screed layer in isolation, so specification should reference the assembly, not just the screed product.
- Most liquid screeds are classified as non-combustible, which supports but does not by itself establish a fire resistance period for the floor.
- Any change to insulation type, thickness or screed depth compared with a tested reference build-up should be checked against the test evidence or confirmed with a fire engineer before proceeding.
- Penetrations for pipework or cabling through a compartment floor need fire-stopping detailed separately from the screed specification.
- Reaction to fire classification (relevant to surface spread of flame) is a different property from fire resistance and both may be relevant depending on the application.
- Where a floor forms part of a means of escape or compartmentation strategy, the screed specification should be reviewed by whoever holds responsibility for the fire strategy, not decided by the screed contractor alone.
Distinguishing material properties from system performance
It is a common misunderstanding to ask whether a screed product is 'fire rated' in the way a door might be. Fire resistance periods apply to complete assemblies tested as a whole, including the structural deck, insulation, screed and any ceiling below, and the rating cannot be attributed to the screed layer alone.
What can be said about the screed material itself is its reaction to fire classification, essentially whether it burns, contributes fuel or produces smoke, and cementitious and calcium sulfate screeds are generally non-combustible in this sense, which is a favourable starting point but not the whole answer to a compartmentation question.
Working from tested build-ups
Where a project needs a specific period of fire resistance for a compartment floor, the design should be based on a tested build-up, often published by the insulation or deck manufacturer, that specifies each layer including the screed depth and type used in the test.
Substituting a different screed product, adjusting the depth, or changing the insulation beneath it without checking against the test evidence risks invalidating the assumed fire performance, even if the change seems minor from a purely structural or thermal point of view.
Coordination with the wider fire strategy
Fire strategy responsibility usually sits with the project's fire engineer or building control adviser rather than the screed contractor, so the specification should make clear that the screed build-up follows an approved reference assembly and flag any penetrations, service risers or unusual junctions for separate fire-stopping detail.
This coordination is particularly relevant in refurbishment of multi-occupancy buildings, where an existing compartment floor may be disturbed by removing an old floor covering or screed, and reinstatement needs to at least match the fire performance that was previously in place.
Why the tested product name matters, not just 'screed'
A fire test certificate refers to the specific screed product, its density and its depth as poured on the test rig, so a compartment floor specification that just says 'liquid screed' invites a substitution that may sit outside what was actually tested, even where the substitute is a perfectly reasonable product in other respects.
Naming the tested product, or the criteria a substitute must meet to remain within the scope of the fire evidence, gives the contractor a clear boundary rather than leaving reaction to fire classification to be checked informally after the order is placed.
Fire and compartment floor requirements — your questions
Screeding a compartment floor?
Tell us about the tested build-up you're working to and we can confirm the screed fits within it.
Or call our landline on 01392 237700
In short
Liquid screed itself is generally non-combustible, but fire resistance is a property of the whole floor build-up, so the specification needs to reference the tested assembly rather than the screed in isolation.
Screeding a compartment floor?
Tell us about the tested build-up you're working to and we can confirm the screed fits within it.