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Chimney Removal Calculator
Calculate chimney breast volume, brick count, RSJ support requirements, propping needs, and waste tonnage for chimney removal projects in the UK.
Number of floors where breast is being removed
Width of the chimney breast projection
Depth of chimney breast from wall face
Floor-to-ceiling height per storey
Height of chimney stack above roof line
Width of the chimney stack
Depth of the chimney stack
Removing breast below requires steel support
Clear span between bearings
Floors needing temporary Acrow props
Your quoted disposal rate
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How We Calculate This
This calculator estimates the volume of brickwork, waste tonnage, and structural support requirements for chimney breast and stack removal. It uses an indicative brickwork density (≈1.9 t/m³ for solid clay-brick masonry including mortar) and common UK chimney dimensions. All figures are planning estimates — confirm the structural design with a structural engineer and the waste/skip arrangements with your licensed waste carrier.
Calculation method
Breast volume: Width × depth × height × number of floors. A typical Victorian chimney breast is 1.2m wide × 0.35m deep (one brick + plaster).
Stack volume: Width × depth × height above roof. Stacks are typically narrower than breasts (600mm × 450mm for a single flue).
Brick count: Total volume ÷ 0.00177 m³ per brick (≈565 bricks/m³). That per-brick figure is an indicative midpoint: a bare 215 × 102.5 × 65mm brick is 0.001433 m³ (≈698 bricks/m³), while the 225 × 112.5 × 75mm coordinating size (the same brick plus a 10mm mortar joint, BS EN 771-1) is 0.001898 m³ (≈527 bricks/m³). This is a solid-volume estimate: it treats the breast as solid masonry and ignores the flue void, throat and gather, so the true brick count is lower — especially for stacks and multi-flue chimneys. Treat it as a rough rubble estimate, not a re-build order.
RSJ sizing: Indicative steel beam sizes are based on standard domestic loading. The actual specification must come from a structural engineer per BS EN 1993.
Waste weight: Total volume × ≈1.9 t/m³ (solid brick masonry). Waste is heavy — a 4-yard builders' (heavy-waste) skip carries about 4 tonnes of masonry, which is its practical limit. Larger 8-yard and 12-yard skips are for lighter waste only and cannot be collected when filled with brick rubble.
Frequently Asked Questions
Yes, chimney breast removal is notifiable building work under the Building Regulations 2010. You need Building Control approval because the chimney breast may be supporting the structure above (stack, upper floor chimney breasts, or the roof). A structural engineer's calculations are typically required to specify the steel beam (RSJ) needed to support the remaining structure.
A ground floor chimney breast removal typically costs £1,500-£3,000 including the RSJ, propping, demolition, waste disposal, and making good. Removing on multiple floors costs £2,500-£5,000+. The RSJ and padstones are usually £300-£600 of that total. Prices vary significantly by region and access difficulty.
The RSJ size depends on the span and the load being carried. For a typical domestic chimney breast (1-1.5m wide), a 152x89 or 178x102 UB is common. For wider spans up to 3m, a 203x133 UB may be needed. The exact size must be specified by a structural engineer based on specific loads — this calculator provides indicative guidance only.
Yes, this is the most common scenario — removing the ground floor breast while leaving the first floor breast and stack. This requires a gallows bracket or RSJ system to support the remaining structure above. The upper chimney breast and stack become supported by the steel and the party/external wall.
A single-storey chimney breast (1.2m wide × 0.35m deep × 2.4m height) produces roughly 1 m³ of brick rubble weighing around 1.9 tonnes. A full chimney removal including the stack can produce 2-4 tonnes. Heavy masonry rubble must go in a small heavy-waste skip — a 4-yard (builders') skip carries about 4 tonnes and is usually sufficient for a single-floor breast removal. Do not order an 8-yard or larger skip for brick rubble: those sizes are reserved for lighter waste and operators will not collect them filled with masonry because the loaded weight exceeds the lorry's safe payload.
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Last updated: March 2026
Verified against UK standards · estimates only, confirm with your supplier.