Free Concrete Block Quantity Estimator – Blocks, Mortar & Cost. Updated 2026 Prices.
Enter your wall dimensions, block type, and mortar joint thickness to calculate the exact number of 100mm concrete blocks required, mortar quantities, and a full 2026 cost estimate. All results include a standard 10% wastage allowance.
The 100mm concrete block is the most widely used masonry unit in UK construction, forming the inner leaf of virtually every cavity wall in new domestic and commercial buildings built since the 1960s. Calculating the number of blocks required is straightforward: the standard 100mm concrete block has a face dimension of 440mm × 215mm, and when laid in stretcher bond with a 10mm mortar joint, produces a coordinating unit of 450mm × 225mm. This gives exactly 10 blocks per m² of wall face area — the fundamental number used by every UK blockwork estimator.
The 10 blocks/m² figure makes quantity estimation extremely simple: measure the wall face area in m², multiply by 10, add a 10% wastage allowance, and round up to the nearest full pallet. In practice, the calculation also requires deducting the area of door and window openings, and accounting for the slightly different block counts produced by 8mm or 12mm mortar joints. This calculator handles all of that automatically.
In 2026, standard dense aggregate 100mm concrete blocks cost approximately £0.80–£1.40 per block (supply only), with lightweight and aerated blocks ranging from £1.20–£2.80 per block depending on grade and thermal performance. The UK blockwork market is well supplied by manufacturers including Tarmac Topblock, Aggregate Industries, Lignacite, Thomas Armstrong, and H+H Celcon (for aerated blocks). Prices vary by region — South East England is typically 10–18% more expensive than Scotland and Northern Ireland.
The standard UK concrete block is 440mm long × 215mm high × 100mm wide. With a 10mm mortar joint on all faces, the coordinating unit becomes 450mm × 225mm. The number of blocks per m² is therefore: (1000/450) × (1000/225) = 2.222 × 4.444 = 9.88 ≈ 10 blocks per m². This exact 10 blocks/m² figure is used universally across the UK construction industry and is confirmed by BS EN 771-3 (aggregate concrete masonry units).
Comparing with standard UK facing bricks (which give 60 bricks/m² for a half-brick wall), the 100mm concrete block provides exactly the same wall thickness (102.5mm for a brick vs 100mm for a block) but requires only one-sixth of the number of units — dramatically reducing laying time and labour cost. This efficiency, combined with the block's higher load-bearing capacity per unit area compared with a single brick, makes 100mm concrete blockwork the dominant inner leaf construction across the UK.
100mm block resources UK 2026: Aggregate Industries Topblock | H+H Celcon Blocks | Checkatrade – Find a Bricklayer / Blocklayer | NHBC Standards | Planning Portal
| Mortar Joint | Coordinating Length | Coordinating Height | Blocks per m² | Blocks per 10 m² | Blocks per 25 m² |
|---|---|---|---|---|---|
| 8mm joint | 448mm | 223mm | 10.0 | 100 | 250 |
| 10mm joint (standard) | 450mm | 225mm | 9.88 ≈ 10 | 99 (≈ 100) | 247 (≈ 250) |
| 12mm joint | 452mm | 227mm | 9.76 ≈ 10 | 98 (≈ 100) | 244 (≈ 245) |
| Wall Area (m²) | Net Blocks (10/m²) | + 10% wastage | Pallets (72 blocks/pallet) | Mortar Bags (1 per 14 blocks) | Typical Application |
|---|---|---|---|---|---|
| 5 m² | 50 | 55 | 1 pallet | 4 bags | Small partition / doorway infill |
| 10 m² | 100 | 110 | 2 pallets | 8 bags | Internal partition room divider |
| 20 m² | 200 | 220 | 4 pallets | 16 bags | Typical single-room extension inner leaf |
| 30 m² | 300 | 330 | 5 pallets | 24 bags | Medium extension or full room partition |
| 50 m² | 500 | 550 | 8 pallets | 40 bags | Detached garage or large extension |
| 100 m² | 1,000 | 1,100 | 16 pallets | 79 bags | New build house single skin blockwork |
| 200 m² | 2,000 | 2,200 | 31 pallets | 157 bags | Full new build development |
| Block Type | Density (kg/m³) | Compressive Strength | Price per Block | Price per Pallet (~72) | Typical Use |
|---|---|---|---|---|---|
| Standard Dense (7.3N) | ~2,000 | 7.3 N/mm² | £0.80–£1.20 | £58–£86 | Inner leaf cavity wall, partitions – most popular |
| Medium Dense (7.3N) | ~1,500 | 7.3 N/mm² | £0.90–£1.35 | £65–£97 | Inner leaf, partitions – easier to handle |
| Lightweight / AAC (Thermalite 3.6N) | ~600 | 3.6 N/mm² | £1.20–£1.90 | £86–£137 | Inner leaf where thermal performance critical |
| Lightweight / AAC (Celcon 7N) | ~700 | 7.0 N/mm² | £1.35–£2.10 | £97–£151 | Inner leaf load-bearing; better thermal than dense |
| High Strength Dense (10.4N) | ~2,100 | 10.4 N/mm² | £1.10–£1.65 | £79–£119 | Heavily loaded walls, multi-storey, engineering |
| Facing / Feature Block | ~2,000 | 7.3 N/mm² | £1.80–£3.50 | £130–£252 | Architectural feature walls, visible blockwork |
| Insulating Block (Aircrete 4N) | ~500 | 4.0 N/mm² | £1.60–£2.80 | £115–£202 | Highly insulating inner leaf; passive house / low energy |
All prices are indicative 2026 South East England supply-only estimates excluding VAT and delivery. Deduct approximately 8–15% for North England, Scotland, and Northern Ireland. Add approximately 10–18% for Greater London. Prices vary between suppliers — always obtain at least two quotes for larger orders. Pallet size varies by block type and manufacturer: confirm exact pallet count with your supplier.
| Item | Typical Cost Range (2026) | Notes |
|---|---|---|
| Blocklaying labour (per 100 blocks) | £60–£100 | Standard stretcher bond, internal partitions or inner leaf; complex work higher |
| Blocklayer day rate (2026) | £240–£380/day | Wide regional variation; London and South East at higher end |
| Mortar – pre-mixed (25kg bag) | £6–£11 per bag | Approximately 1 bag per 12–16 standard 100mm blocks |
| Wall ties (stainless steel, per 100) | £15–£35 | At 900mm horizontal, 450mm vertical for cavity walls; essential for structural performance |
| Cavity insulation (full-fill, per m²) | £5–£15/m² | Installed during construction; confirm specification with structural engineer or NHBC |
| Block cutting disc (angle grinder) | £8–£20 each | Diamond blade for cutting concrete blocks; lasts 200–400 cuts |
| Block splitter hire (per day) | £35–£65/day | Manual or hydraulic block splitter for high-volume cutting |
| Scaffold (domestic project) | £600–£2,500 | Required for walls above approximately 2m for safe working |
| Pallet delivery charge | £40–£90 per delivery | Often included for orders above certain value; confirm with supplier |
| DPC membrane (per metre run) | £1–£3/m | Required at or above ground level; 112mm width standard for 100mm blocks |
| Lintel (over opening, per lintel) | £25–£120 | Pressed steel or concrete lintel depending on span and load; structural engineer to specify |
The single most useful number in 100mm blockwork is 10 blocks per m² of wall face area, using standard 440 × 215mm blocks with a 10mm mortar joint. This gives coordinating dimensions of 450 × 225mm — exactly fitting 10 units into a square metre. Add 10% for wastage: 11 blocks per m² to order. This is the universal UK industry standard used by every blocklayer and quantity surveyor in the country.
The standard UK concrete block is 440mm long × 215mm high × 100mm wide. With a 10mm mortar joint, the coordinating unit is 450mm × 225mm. The face area (440 × 215mm = 94,600 mm²) is exactly six times the face area of a standard UK brick (215 × 65mm = 13,975 mm²), which is why 6 brick courses exactly equals 1 block course in height when both use 10mm mortar joints.
A 100mm block wall requires only 10 blocks per m² versus 60 bricks per m² for an equivalent half-brick wall, making blockwork approximately 4–6× faster to lay. An experienced blocklayer can lay 80–140 blocks per day (compared to 400–600 bricks per day for a bricklayer) — but since each block covers 6× the area of a brick, the m² output per day is broadly comparable. The material cost per m² of blockwork is significantly lower than facing brickwork.
Using standard 100mm blocks (215mm high) with a 10mm mortar joint, each course is 225mm high. Useful multiples: 2 courses = 450mm; 4 courses = 900mm; 8 courses = 1,800mm; 9 courses = 2,025mm (approximately 2m); 11 courses = 2,475mm. This 225mm module aligns perfectly with the 75mm brick course (225/75 = 3), meaning that 1 block course equals exactly 3 brick courses in height — essential for cavity wall tying.
Dense blocks have better sound insulation (higher mass) and are harder-wearing, but poorer thermal performance. Lightweight AAC blocks (Thermalite, Celcon) have much better thermal performance (λ = 0.11–0.16 W/mK vs 0.57–0.90 for dense) and are easier to handle (typically 10–14kg vs 20–25kg for dense). For inner leaves in Part L compliant cavity walls, lightweight blocks are increasingly specified to reduce thermal bridging at wall ties and junctions. For load-bearing inner leaves carrying significant loads, dense or high-strength blocks are required.
The standard rule of thumb for 100mm blockwork is approximately 1 bag (25kg) of mortar per 12–16 blocks at 10mm joints. At 14 blocks per bag (midpoint), a 100 m² wall (1,100 blocks with wastage) needs approximately 79 mortar bags. Mortar for blockwork is typically designation M4 (1:1:5.5 C:L:S), the same as for external brickwork. Never use a mortar stronger than the blocks it joints.
The thermal conductivity (λ) of the inner leaf blockwork has a significant impact on the overall cavity wall U-value and the linear thermal transmittance (Ψ-value) at wall ties and structural junctions. Dense aggregate blocks: λ = 0.57–0.90 W/mK; medium dense: λ = 0.40–0.57 W/mK; lightweight AAC: λ = 0.11–0.20 W/mK. Using lightweight blocks in lieu of dense blocks can reduce wall tie bridging and improve the overall SAP energy rating of a new dwelling, particularly at floor/wall and roof/wall thermal bridges.
100mm dense concrete blockwork (either dense aggregate or AAC) provides excellent inherent fire resistance. A 100mm dense block wall provides a minimum of REI 120 (120 minutes fire resistance for load-bearing walls) when properly detailed — exceeding the typical 60-minute requirement for internal compartment walls in domestic buildings under Approved Document B. This fire resistance is one reason 100mm concrete blockwork is specified for party walls, compartment walls, and protected escape routes.
For party walls between dwellings, mass is the key factor in airborne sound insulation. Dense aggregate blocks (density ~2,000 kg/m³) provide significantly better sound insulation than lightweight AAC blocks (density ~550–700 kg/m³). The Building Regulations Approved Document E (resistance to the passage of sound) requires party walls to achieve a minimum airborne sound insulation of 45 dB DnT,w + Ctr. Dense 100mm blockwork with isolated plasterboard linings on both faces (robust detail) is the standard UK party wall construction for this purpose.
Fixings into dense aggregate blocks can use standard masonry drill bits and wall plugs. Fixings into lightweight AAC blocks require AAC-specific fixings and plugs — standard nylon wall plugs will not grip adequately in the softer matrix of Thermalite or Celcon blocks. Specialist screw anchors, resin anchors, or AAC frame fixings from manufacturers like Fischer, Rawlplug, or Hilti are required for medium and heavy loads. Always use fixings rated and tested for the specific block type and density.
For visible facing blockwork or feature block walls, blocks from different batches can vary in colour and texture. Always order all blocks needed from the same batch, including the wastage allowance. Request block samples before ordering and keep spare blocks from the original batch for future repairs. This is the same advice as for facing bricks — consistency of appearance requires consistency of supply from a single production batch.
Thin-joint (or thin-bed) blockwork uses precision-manufactured AAC blocks (tolerances ±1mm vs ±3mm for standard blocks) with a 2–3mm adhesive mortar rather than a 10mm bed. Benefits: faster laying (experienced operatives can achieve 150–200 m²/week), improved airtightness (less mortar joint area), better thermal performance at joints, and more accurate coursing. Used increasingly in Passivhaus and zero-carbon new builds. Blocks per m² increase slightly (approximately 10.5–11) due to the thinner joint. Specialist thin-joint mortar and training are required.
For standard 100mm concrete blocks (440mm × 215mm face) with a 10mm mortar joint, you need exactly 10 blocks per m² of wall face area. This is the universal UK industry standard. With a 10% wastage allowance, order 11 blocks per m². The calculation is: 1 block covers 450mm × 225mm (with mortar) = 0.10125 m² per block; 1/0.10125 = 9.88 ≈ 10 blocks/m². Use the block calculator above to calculate the total for your specific wall dimensions, including deductions for openings.
The standard UK concrete block is 440mm long × 215mm high × 100mm wide (work size, to BS EN 771-3). With a 10mm mortar joint on all faces, the coordinating dimensions are 450mm × 225mm × 110mm. The 100mm thickness refers to the block width — this is the dimension across the wall. The 440 × 215mm face dimension is standard across virtually all UK manufacturers, making the 10 blocks/m² calculation universally applicable regardless of manufacturer. Different block types (dense, lightweight, facing) are available in this standard face size, with different widths also available (75mm, 140mm, 190mm, 215mm) for specific applications.
Dense aggregate concrete blocks (the most common type) are manufactured from Portland cement and dense crushed stone or limestone aggregate, giving a density of approximately 1,950–2,100 kg/m³. They have high compressive strength (7.3–10.4 N/mm²), good sound insulation (due to high mass), and are the standard choice for load-bearing inner leaf walls. Their disadvantage is relatively poor thermal performance (λ = 0.57–0.90 W/mK). Lightweight AAC (autoclaved aerated concrete) blocks — brands include Thermalite (Tarmac), Celcon (H+H), Toplite, and Durox — are manufactured by introducing air into a cement-lime-sand-pulverised fuel ash mix, producing a very low density material (350–700 kg/m³). They are much easier to handle, can be cut with a handsaw, have excellent thermal performance (λ = 0.11–0.20 W/mK), and are the standard choice for inner leaf blockwork in Part L compliant cavity walls where minimising thermal bridging is important. Their drawback is lower compressive strength (3.6–7.3 N/mm²) and the need for specialist fixings. For most UK domestic inner leaf applications, either type is structurally acceptable — the choice depends primarily on the thermal and acoustic performance requirements and the specific building design.
Standard 100mm dense concrete block pallets typically contain 72 blocks (some suppliers pack 60 or 80 blocks per pallet — always confirm with your supplier before ordering). A 72-block pallet covers approximately 7.2 m² of wall at 10 blocks/m² before wastage, or approximately 6.5 m² with 10% wastage. Lightweight AAC block pallets contain varying quantities depending on block weight and block height — typically 60–80 blocks per pallet for standard 100mm × 215mm × 440mm blocks. Always confirm pallet quantities with your specific supplier before calculating the number of pallets to order, as ordering a top-up delivery risks a batch mismatch for facing blockwork.
For standard external-quality blockwork (inner leaf of cavity wall, external walls, garden walls): mortar designation M4 (approximately 1:1:5.5 cement:lime:sand by volume) is the standard UK specification — the same as for general external brickwork. M4 provides adequate strength and durability while retaining sufficient flexibility to accommodate thermal movement. For internal partitions in a protected environment: M4 or M2 (weaker, 1:2:9 C:L:S) is acceptable. For engineering applications (below DPC, retaining walls): M6 mortar (stronger, 1:0.5:4.5 or equivalent). The critical rule for blockwork is the same as for brickwork: never specify mortar stronger than the block — a mortar stronger than the block it joints causes spalling of block faces rather than controlled cracking at joints when thermal or settlement movement occurs. For AAC lightweight blocks in particular, a weaker M2 or M4 mortar is essential — strong mortars will damage the softer block surface.
The total installed cost of 100mm blockwork in the UK in 2026 (supply and lay, excluding scaffolding and VAT) varies by block type and application. For standard dense aggregate inner leaf blockwork: approximately £32–£55/m² in South East England (supply and labour, standard stretcher bond). For lightweight AAC blockwork (inner leaf): approximately £40–£65/m². For facing / feature blockwork: £65–£110/m². These figures exclude wall ties, insulation, mortar delivery, and scaffolding. Labour typically accounts for approximately 50–60% of the total cost. For comparison, facing brickwork costs approximately £80–£150/m² — blockwork is significantly more economical for inner leaf and partition applications where the block face will be plastered or rendered and not visible.
Yes, but with important caveats. Dense aggregate 100mm blocks are manufactured in frost-resistant grades suitable for external use (designation F1 or F2 under BS EN 771-3). Standard blocks used as the outer leaf of a cavity wall must be F2 (highly frost resistant) if they will be exposed to the weather without render or cladding, or F1 if they will be rendered. Many external render or cladding systems are applied over standard grade blocks that do not need to be frost resistant themselves, as the render or cladding provides the weather protection. For unrendered external block walls (e.g. garden walls or external exposed blockwork), always specify F2 frost-resistant blocks to avoid rapid surface degradation. AAC lightweight blocks are not suitable for unprotected external use without render or cladding — they must be protected from prolonged water exposure.
Whether Building Regulations approval is required depends on the application. For blockwork forming part of a structural wall (inner leaf of a cavity wall in a new building, extension wall, or load-bearing partition), Building Regulations Approved Document A (Structure) applies and a Building Regulations application or Building Control oversight is required. For a new dwelling or extension, the blockwork specification will be part of the structural engineer's design and building notice / full plans submission. For a non-structural internal partition wall (not load-bearing), Building Regulations are generally not required in England — but if you are creating a new room or habitable space, other regulations (ventilation, fire, sound) may apply. Garden walls are generally permitted development up to 2m height (1m adjacent to highways) — no Building Regulations required for most garden walls. Always check with your Local Authority Building Control before commencing work if you are unsure.
A single leaf 100mm dense aggregate concrete block wall provides significant inherent fire resistance. Under BS EN 1996-1-2 (Eurocode 6 – fire design) and the UK National Annex, a 100mm dense aggregate block wall achieves a fire resistance of REI 120 (load-bearing capacity R, integrity E, and insulation I for 120 minutes) when properly detailed. For non-load-bearing partition walls, fire resistance is even better. This performance exceeds the 60-minute fire resistance required for internal compartment walls and room partitions in domestic buildings under Approved Document B. AAC lightweight blocks also provide good fire resistance, though slightly lower than dense blocks due to lower mass. The fire resistance of the overall wall assembly depends on the block type, wall thickness, mortar, and any applied finishes — always confirm with the block manufacturer's fire test data for specific assemblies.
The nominal width (thickness) of a concrete block determines the wall thickness and primarily affects the structural strength and thermal performance of the wall. The standard UK block widths and their main applications are: 75mm — thin partition walls in non-load-bearing internal applications; 100mm — by far the most common, used for inner leaf of cavity walls, partitions, and many single-leaf applications; 140mm — used where higher compressive strength or better sound insulation is required (single-leaf internal walls between floors in flats, schools, etc.); 215mm (one-brick equivalent) — solid external walls, heavily loaded structural walls, and retaining walls. All these widths use the same 440mm × 215mm face dimension, so the blocks per m² remains 10 regardless of width. The choice of 100mm vs wider blocks is driven by structural load, acoustic requirements, and the overall wall construction type.
Finding a reliable blocklayer (or bricklayer who also lays blocks — most do both) requires the same approach as for brickwork. Key steps: ask for recommendations from neighbours or friends who have had similar work completed; check reviews on Checkatrade, TrustATrader, or Google — look specifically for reviews mentioning blockwork or inner leaf work; obtain a minimum of three written quotations specifying block type, mortar specification, and all works included; confirm the operative carries public liability insurance (minimum £1–2 million); and agree a written contract with a staged payment schedule for projects above approximately £1,000. Be cautious of very low quotes — these may indicate cutting corners on block quality, mortar specification, or wall tie installation. Wall ties are particularly critical: under-specified or poorly installed wall ties in a cavity wall are a serious structural defect that can be costly to rectify retrospectively.
Additional block and blockwork resources UK 2026: Aggregate Industries Topblock | H+H Celcon Aircrete Blocks | Checkatrade – Find a Blocklayer | NHBC Standards | TrustATrader | Planning Portal