ARC TCB Square

The quick, robust way to fire-stop services in timber-frame walls

Whenever a soil pipe, flue or MVHR duct punches through a timber-frame external wall, the cavity you’ve just opened becomes a fast lane for fire and smoke. ARC TCB Square barriers close that gap in one push-fit step.

  • Euroclass A1 mineral-wool core wrapped in a weather-safe polythene sleeve.

  • Up to 60 minutes fire integrity / 15 minutes insulation to EN 1366-4 – third-party approved (IFCC 1727). 

  • λ 0.037 W/m·K – kills the cold bridge round the penetration and helps you keep Ψ-values low in SAP. 

  • Faster and more reliable than boxing-in linear barriers or wrapping off-cuts. 

Order by 12:00 and spend £200 ex-VAT for free next-day delivery. Tech help? Call 0118 922 7941.

Size guide – pick, click, install

Max cavity widthOuter size (mm)Hole Ø (mm)Product link*Pack qty
50 mm65 × 380 × 380150TCBSQ150/5012
55 mm70 × 380 × 380150TCBSQ150/5512
60 mm75 × 380 × 380150TCBSQ150/6012
65 mm80 × 380 × 380150TCBSQ150/6512
70-90 mm85-95 × 380 × 380150see drop-down12
95-150 mm110-165 × 500 × 500150TCBSQ150/110 etc.6-10

*Links jump straight to the bagged size on Spechunter.

Need a linear barrier instead? See ARC TCB Timber Cavity Barriers or an external-edge stop with ARC T-Barrier Masonry.

Three-step installation

  1. Fix the flanges (optional) to timber studs above and below the planned penetration to direct any water outwards.

  2. Drill the service hole through sheathing and outer leaf.

  3. Slide the square barrier over the pipe or duct and push it into the cavity until the sleeve sits flush with the sheathing; maintain the 15 mm compression that creates the seal.

No extra ties, foams or sealants required – the mineral wool’s compression and “burn-path” do the work. 

Compliance snapshot

RequirementARC TCB Square performance
Approved Doc B / Scottish Tech Handbook 260 min integrity, 15 min insulation
Part L thermal bridgeλ 0.037 W/m·K, maintains insulation line
Part E flanking soundMineral wool core damps noise at service risers
EnvironmentalA+ Green Guide rating, CFC/HCFC-free manufacture

Note: TCB Square acts as a cavity barrier, not a penetration seal; intumescent wraps are still required on combustible pipes where specified.

Frequently asked questions

Does TCB Square replace pipe collars?

No – it stops fire spread within the cavity. Use an intumescent collar or wrap to seal the pipe itself.

What’s the biggest pipe I can run through it?

Up to 150 mm OD – see table for each SKU.

Can I use it in masonry builds?

It’s designed for timber-frame walls. For masonry use ARC Fire Stop Slabs or standard Cavity Stop Socks.

Is next-day delivery guaranteed?

Yes – order before noon, spend £200 ex-VAT and check our delivery information for postcode exceptions.

Build your complete fire-stop package

Spechunter.co.uk – Chasing down specialist construction specifications since 1988.

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