Cavity Closers

Cavity closers seal the gap between the inner and outer leaves of a cavity wall at every window and door opening. Without them, you get cold bridging at reveals, moisture tracking into the building, and — on fire-rated openings — a breach in the façade’s fire compartmentation. The right closer handles all three jobs in one installation: thermal insulation to satisfy Approved Document L, damp-proofing to meet Approved Document C, and fire resistance to comply with Approved Document B.

Our range covers every specification from budget insulated closers to 60-minute fire-rated systems, in cavity widths from 50 mm to 300 mm. All products are BBA approved or BBA certified, NHBC accepted and supplied in packs ready for next-day delivery.

Cavity Closer Types: Insulated vs Fire Rated

Timloc FR30 — 30-Minute Fire Rated Cavity Closers

Timloc FR30 fire rated closers deliver 30 minutes of fire integrity and 15 minutes of insulation, independently tested by Warrington Fire. The rigid uPVC profile encapsulates a mineral wool core that also provides thermal insulation (0.036 W/m·K) and acts as an integrated DPC. Available in cavity widths from 50 mm to 300 mm, supplied in 2.4 m lengths, packs of five. Compliant with Approved Documents B, C and L.

Timloc FR60 — 60-Minute Fire Rated Cavity Closers

Where the fire strategy calls for higher resistance — protected routes, multi-residential cores, or specific door and wall assemblies — Timloc FR60 closers provide 60 minutes of fire integrity with the same mineral wool core and uPVC profile as the FR30. Available in the same cavity width range (50–300 mm) and supplied in 2.4 m lengths. Independently tested to meet Approved Document B requirements for higher-risk openings.

Timloc Thermo-Loc Platinum Plus — Insulated Closers

The Timloc Thermo-Loc Platinum Plus is a high-performance insulated cavity closer featuring a durable uPVC profile with expanded polystyrene (EPS) insulation. It achieves ψ-values of ≤0.8 W/m²·K at reveals, helping meet SAP calculation targets under Part L. It also acts as an effective DPC, preventing moisture tracking at reveals. Available in cavity widths from 50 mm to 150 mm, this is the go-to thermal closer where fire rating is not required at the opening.

Kingspan Thermabate — Premium Insulated Closers

Kingspan Thermabate uses a fibre-free rigid thermoset urethane (PUR) core with a thermal conductivity of 0.022 W/m·K — the best in the category. BBA certified and LABC Registered Detail, Thermabate eliminates the need for cut bricks, special reveal blocks or separate DPC installation at openings. Available in 100 mm width, supplied in 3 m lengths. Ideal where the thermal performance specification is tight and every fraction of a W/m·K counts.

ARC Eco-Closer — Combined Closer, DPC & Fire Stop

The ARC Eco-Closer and Eco-Closer Plus combine cavity closure, DPC and fire stopping in a single mineral wool product — reducing the number of separate components at the reveal. The Eco-Closer Plus achieves ψ-values of ≤0.8 W/m²·K and suits cavities up to 300 mm, making it the widest-range single-product reveal solution in our range.

Cavity Closer Sizes: Which Width Do I Need?

Match the closer to your cavity width — every size below is stocked in 2.4m lengths. Standard insulated closers handle thermal and damp requirements; switch to the fire-rated column where the opening needs 30 or 60 minutes' integrity.

Browse the full fire-rated ranges: Timloc FR30 (30 minute) and Timloc FR60 (60 minute). Working out what the opening actually requires? Our cavity closer sizing guide covers measuring up, Part L and fire requirements in detail.

How to Choose: Fire Rated or Insulated?

The fire strategy for your project determines whether you need a fire-rated closer or a standard insulated one. If the drawings or fire engineer’s report specify a fire rating at the opening — typically 30 or 60 minutes — you must use an FR30 or FR60 closer. Never substitute a standard insulated closer where fire rating is specified.

For openings where no fire rating is required, choose between Thermo-Loc Platinum Plus and Kingspan Thermabate based on the thermal performance needed. Thermabate’s PUR core (0.022 W/m·K) outperforms the EPS-based Thermo-Loc on pure thermal conductivity, but the Thermo-Loc offers a wider range of cavity widths and is typically more cost-effective.

Not sure whether your openings need FR30 or FR60? Read our FR30 vs FR60 comparison guide for a full breakdown, or call 0118 922 7941 — we’ll check against your fire strategy drawing.

Related products: cavity fire socks & barriers for fire compartmentation within the cavity itself.