Crib 5 Interliners: Schedule 3, Fire Barriers and Contract Upholstery

A fire-retardant interliner is a barrier fabric fitted between the cover fabric and the filling of upholstered furniture. It is often called a Crib 5 interliner, because the interliner test uses the same Ignition Source 5 wooden crib as the BS 5852 Crib 5 test. Interliners are widely misunderstood: in domestic furniture they are a legal route to using certain natural-fibre covers, while in contract furniture they are part of a tested composite, not a substitute for a compliant cover. This guide explains both. For the upholstery fire standard itself, see our BS 5852 Crib 5 guide.

What an Interliner Is

An interliner is usually a needled felt or woven barrier cloth made from fire-retardant fibres, fitted under the cover and over the foam or filling. When the cover is exposed to flame, the interliner chars and holds back the heat, slowing the point at which the filling beneath ignites. It is hidden in the finished piece, so it does not change the look of the cover, though it adds a layer the upholsterer must allow for.

An upholstery interliner is not the same as a curtain interlining. A standard curtain interlining or general-purpose backing cloth does not meet the upholstery interliner requirement.

Domestic Furniture: The Schedule 3 Interliner

The Furniture and Furnishings (Fire) (Safety) Regulations 1988 govern upholstered furniture supplied for domestic use. Permanent covers must normally pass the match test. There is one exception: a cover made of at least 75% by weight of cotton, flax (linen), silk, viscose, modal or wool, alone or in combination, and not coated with polyurethane, may be used even if it fails the match test, provided the furniture contains a fire-resistant interliner that complies with Schedule 3 of the Regulations.

Three points are often missed. The cover must still pass the cigarette test. The interliner does not excuse a non-compliant foam or filling, which must pass its own ignitability test. And the Schedule 3 interliner is itself tested, using Ignition Source 5 over standard non-fire-retardant foam after a water soak, so it must be a certified product, not any fabric used as a lining.

Mohair is not on the list of exempt fibres. A 100% mohair cover does not qualify for the Schedule 3 route and must pass the match test by its own performance or by treatment. For the fibre-by-fibre detail, see our FR treatment and fibre compatibility guide.

Contract Furniture: Interliners and Crib 5

The Schedule 3 exemption applies to domestic furniture only. Contract seating in hotels, restaurants, bars and offices is specified to BS 5852 Crib 5 or BS 7176, and those tests assess the full composite: cover, interliner if used, and filling together. An interliner can form part of a composite that passes Crib 5, but the certificate covers only that exact combination of cover, interliner and foam.

An interliner does not make up for a cover fabric that falls short of the standard required for the environment. For hospitality and public seating, KOTHEA’s advice is to specify a cover fabric that is itself certified to Crib 5, either inherently or by treatment, and to treat an interliner as additional protection rather than a substitute. Where a composite route is proposed, ask for the composite certificate before the fabric is upholstered.

Interliners and Inherently Fire-Resistant Covers

A cover that carries an inherent Crib 5 pass removes the cover-fabric problem at source. KOTHEA’s mohair velvet ranges carry an inherent BS 5852 Crib 5 pass as a property of the mohair fibre, with no topical treatment, so the rating is unaffected by cleaning. As with any Crib 5 certificate, confirm the foam used in the test matches the foam in your project. See our mohair velvet upholstery page for the ranges.

What to Ask Before Specifying

Domestic or contract? The Schedule 3 route is for domestic furniture only.

What is the cover’s fibre content? The exemption needs at least 75% of the listed fibres by weight and no polyurethane coating.

Is the interliner certified? Ask for confirmation that it meets Schedule 3, or for contract work, the composite certificate naming the cover, interliner and foam.

Who issued the certificate? For contract work, require a certificate from a UKAS-accredited laboratory, including the water-soak stage.

For how treatment works, see our how FR treatment works guide. For the full library, see our fabric buying guide by purpose.

Quick answers

What is a Crib 5 interliner?
A Crib 5 interliner is a fire-retardant barrier fabric fitted between an upholstery cover and its filling. The name comes from the interliner test, which uses the same Ignition Source 5 wooden crib as BS 5852 Crib 5. In domestic furniture, a certified Schedule 3 interliner allows certain natural-fibre covers that fail the match test to be used legally. In contract furniture, an interliner can form part of a composite tested to Crib 5.

Does an FR interliner make any fabric Crib 5 compliant?
No. For contract seating, Crib 5 certifies a specific composite of cover, interliner and filling, and the certificate covers only that combination. An interliner does not make up for a cover fabric that falls short of the required standard. For hospitality seating, specify a cover that is itself Crib 5 certified, inherently or by treatment, and treat the interliner as additional protection.

Which fabrics can use a Schedule 3 interliner?
Covers made of at least 75% by weight of cotton, flax (linen), silk, viscose, modal or wool, alone or combined, and not coated with polyurethane, can use a Schedule 3 interliner in place of passing the match test. The cover must still pass the cigarette test. The route applies to domestic furniture only, and mohair is not on the list of exempt fibres.

To request cuttings for an upholstery project, visit KOTHEA.com/cuttings.