Total Blocks Required
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including wastage allowance
Calculate besser blocks, mortar, and materials for wall construction
Accurate block quantity estimates for retaining walls, garden beds, and structural masonry. Get instant mortar requirements and 2026 cost breakdowns for Australian projects.
Professional masonry calculations for residential and commercial construction
Calculate exact numbers of concrete blocks (besser blocks) needed for walls, retaining structures, and garden beds. Accounts for block size, mortar joints, wastage, and openings to prevent material shortages or expensive over-ordering.
Get accurate mortar volume calculations for bedding and perpend joints. Includes sand and cement quantities for standard mix ratios, ensuring you have sufficient materials for complete wall construction without delays or material waste.
Receive detailed pricing breakdowns based on current 2026 Australian rates for concrete blocks, sand, cement, and reinforcement. Compare hollow versus solid blocks, standard versus interlocking types, and different finish options for informed material selection.
Select block type and enter wall dimensions below
Concrete blocks, commonly known as besser blocks in Australia, are precast hollow or solid masonry units used extensively in residential and commercial construction. Standard Australian concrete blocks measure 390mm length × 190mm height × 190mm width, though various sizes accommodate different structural and architectural requirements. The blocks are laid with mortar joints (typically 10mm thick) creating strong, durable walls suitable for load-bearing structures, retaining walls, boundary fences, and garden beds.
Hollow concrete blocks contain internal cavities reducing weight (15-18kg per block versus 30-35kg for solid blocks) while maintaining structural strength through their shell design. These cavities can be filled with concrete and reinforcing steel for retaining walls and seismic zones, transforming the wall into a reinforced concrete structure. Solid blocks provide superior sound insulation and fire resistance, making them preferred for party walls, fire-rated assemblies, and commercial applications where acoustic performance or structural mass is critical for design requirements.
Running bond pattern: Blocks laid in staggered courses with 10mm mortar joints. Each full block overlaps the joint between two blocks below, creating structural interlock and aesthetic consistency.
Accurate block calculation prevents costly material shortages mid-project or expensive over-ordering. The fundamental approach calculates the wall's surface area in square metres, then divides by the area covered by one block including its mortar surround. This accounts for the actual spacing between blocks created by mortar joints, which significantly affects the final block count.
Where:
Wall Area = (Length × Height) - Openings
Blocks per m² = 10,000 / [(Block Length + Joint) × (Block Height + Joint)]
Standard 390×190mm block with 10mm joints = 12.5 blocks/m²
Australian concrete blocks follow standardized dimensions ensuring compatibility with modular construction principles and building codes. Understanding block sizing helps optimize wall design, minimize cutting waste, and ensure efficient material usage throughout your project.
Dimensions: 390mm × 190mm × 190mm
Weight: 15-18kg (hollow)
Coverage: 12.5 blocks per m² (with 10mm joints)
Applications: General walling, retaining walls, garden beds, boundary fences
Most economical and widely used block type in Australian residential construction.
Dimensions: 390mm × 190mm × 190mm
Weight: 30-35kg (solid)
Coverage: 12.5 blocks per m² (with 10mm joints)
Applications: Load-bearing walls, fire walls, acoustic barriers, commercial construction
Superior sound insulation and thermal mass compared to hollow blocks.
Dimensions: 190mm × 190mm × 190mm
Weight: 8-10kg (hollow), 15-17kg (solid)
Usage: Wall ends, corners, opening jambs
Applications: Finishing courses, complex layouts, maintaining running bond pattern
Essential for proper wall construction without cutting full blocks.
Dimensions: 390mm × 190mm × 140mm
Weight: 12-15kg
Coverage: 12.5 blocks per m² (with 10mm joints)
Applications: Internal partition walls, space-saving applications, lightweight structures
Reduces wall thickness while maintaining standard height and length modules.
Mortar creates the bond between concrete blocks providing structural integrity, load distribution, and weather resistance. Standard mortar for block work uses a 1:4 cement to sand ratio by volume, though this may be adjusted to 1:3 for high-strength applications or 1:5 for non-load-bearing garden walls. Mortar consumption varies with block size and joint thickness, but typical usage is 0.015-0.020 m³ of mortar per square metre of block wall with 10mm joints.
Example: 18 m² wall requires 18 × 0.018 = 0.32 m³ of mortar
For 1:4 mix:
Cement = 0.32 × 0.20 = 0.064 m³ = 128kg = ~6 bags (20kg)
Sand = 0.32 × 0.80 = 0.26 m³ = 0.42 tonnes
(Assumes 20% cement, 80% sand by volume in mixed mortar)
Material costs vary by location, supplier, and order quantity, with bulk purchases typically offering 10-15% discounts on advertised retail prices. The following pricing reflects typical 2026 rates in Australian metropolitan areas for residential quantities. Regional pricing may differ by 15-25% depending on freight distances from manufacturing plants.
| Material | Unit | 2026 Price Range | Notes |
|---|---|---|---|
| Standard Hollow Block | Per block | $2.80 - $3.50 | 390×190×190mm, most economical option |
| Solid Concrete Block | Per block | $4.50 - $5.80 | 390×190×190mm, double weight of hollow |
| Half Block (Split) | Per block | $1.80 - $2.50 | 190×190×190mm, for ends and corners |
| Interlocking Block | Per block | $3.50 - $4.80 | No mortar required, retaining walls |
| Cement (GP) | 20kg bag | $8.50 - $11.00 | General purpose Portland cement |
| Building Sand | Per tonne | $55 - $75 | Washed river sand for mortar |
| Premixed Mortar | 20kg bag | $10 - $14 | Pre-blended, just add water |
| Steel Reinforcement | 12mm bar (6m) | $18 - $28 | For reinforced retaining walls |
| Wall Ties | Per 100 | $35 - $55 | Galvanized steel, cavity wall |
| Professional Installation | Per m² | $85 - $140 | Labor only, varies by complexity |
Professional block laying requires proper technique, consistent mortar thickness, and attention to level and plumb throughout construction. The first course is critical—it must be perfectly level and aligned as all subsequent courses follow this foundation. Use a string line stretched between end blocks (leads) to maintain straight wall alignment, and check every 3-4 courses with a spirit level to verify vertical plumb and horizontal level.
Insufficient mortar coverage: Full bedding across entire block width is essential. Partial mortar coverage (face shell only) acceptable for internal non-load-bearing walls but never for retaining walls or load-bearing structures.
Working too fast: Laying more than 1.2m height per day risks crushing mortar in lower courses before it cures. Limit height to 6-7 courses per session, allow overnight curing before continuing.
Neglecting reinforcement: Retaining walls exceeding 600mm height require reinforcing steel in cores filled with concrete. Consult engineer for walls over 1m or on sloping sites with surcharge loads.
Concrete block retaining walls exceeding 1 metre height or retaining more than 600mm of soil generally require engineering design and council approval in most Australian jurisdictions. Retaining walls must resist soil pressure, water pressure, surcharge loads, and potential seismic forces. Reinforced masonry design places vertical reinforcing bars through block cores at specified spacing (typically 400-800mm centers), with cores filled with 20 MPa concrete creating a composite reinforced structure.
Standard 390mm × 190mm concrete blocks with 10mm mortar joints require 12.5 blocks per square metre of wall area. This calculation accounts for the block dimensions plus mortar joint spacing: (390mm + 10mm) × (190mm + 10mm) = 400mm × 200mm = 0.08m² per block, therefore 1m² ÷ 0.08m² = 12.5 blocks. For narrow 140mm thick blocks or half blocks, the coverage per square metre remains 12.5 blocks as the length and height dimensions (which determine coverage area) remain identical. Always add 5-10% wastage for cuts, breakages, and project contingencies.
Hollow concrete blocks contain internal cavities reducing weight to 15-18kg per block versus 30-35kg for solid blocks. Hollow blocks are more economical, easier to handle, and adequate for most residential applications including retaining walls when cores are reinforced and filled with concrete. Solid blocks provide superior sound insulation (Rw 50+ versus Rw 40 for hollow), better fire resistance, and higher thermal mass making them preferred for party walls, acoustic barriers, and commercial construction. Hollow blocks can be converted to reinforced concrete walls by filling cores with concrete around steel reinforcement, creating load-bearing capacity exceeding solid blocks while maintaining weight and cost advantages.
Material costs for DIY concrete block walls range from $40-60 per m² using standard hollow blocks ($2.80-3.50 each), cement ($8.50-11/bag), and sand ($55-75/tonne). A typical 10m × 1.8m wall (18m²) requires approximately 225 blocks, 6 bags cement, 0.4 tonnes sand, costing $700-1,000 in materials. Professional installation adds $85-140 per m² labor, bringing total costs to $2,250-3,500 for the same wall. Solid blocks increase material costs by 60-80%. Reinforced retaining walls requiring engineering, council approval, drainage systems, and structural reinforcement cost $180-280 per m² fully installed depending on height and soil conditions.
Standard concrete block mortar uses a 1:4 cement to sand ratio by volume (one part cement to four parts washed building sand). This mix provides adequate strength, good workability, and economy for general block work including residential walls and moderate retaining walls under 1.5m height. Use 1:3 mix for high-strength applications including tall retaining walls, load-bearing structures, or engineer-specified high-strength mortar grades. Non-load-bearing garden walls and partitions can use 1:5 mix reducing cement content and cost. Add plasticizer or lime (10-15% of cement volume) to improve workability and water retention, particularly important in hot weather or with inexperienced bricklayers.
Most Australian councils allow concrete block walls under 1 metre height without approval as exempt development, though this varies by jurisdiction. Walls exceeding 1m height, retaining walls holding more than 600mm of soil, or walls within setback zones typically require development approval and engineering certification. Boundary walls (dividing neighboring properties) often require neighbor consent regardless of height. Pool fencing must meet strict AS 1926.1 standards requiring council certification even if under 1m height. Always check specific council regulations before construction as non-compliant walls may require expensive removal or retrospective engineering certification and approval.
Mortar achieves initial set within 2-4 hours allowing limited handling but requires 7 days to reach working strength (approximately 70% of final strength) before backfilling retaining walls or removing formwork. Full mortar curing takes 28 days to achieve 100% design strength, though walls are functional for most purposes after 7 days. Limit construction to 1.2m (6-7 courses) per day to prevent crushing uncured mortar in lower courses under the weight of blocks above. Keep mortar moist during the first 48 hours by misting with water or covering with plastic sheeting to prevent rapid drying that causes surface crazing and reduced strength. Cold weather (below 5°C) slows curing significantly requiring extended cure times or calcium chloride accelerators.
Yes, concrete blocks accept render (cement render) or paint finishes improving appearance and weather resistance. For rendering, apply bonding agent then 10-15mm base coat (1:4 cement:sand with plasticizer), scratched while wet to create key. After 7 days, apply 5-8mm finish coat using fine sand achieving smooth or textured finish as desired. Total render thickness 15-23mm typical. For painting, seal bare blocks with concrete sealer or masonry primer, then apply two coats acrylic masonry paint. Rendered or painted blocks require less maintenance than bare blocks while significantly improving aesthetic appeal. Render also provides additional weather protection and can disguise minor imperfections in block laying alignment or joint tooling.
"Besser block" is the common Australian term for concrete blocks, named after Besser Manufacturing Company which popularized hollow concrete block production in the mid-20th century. The term is often used interchangeably with "concrete block" though technically refers to hollow blocks specifically. There is no functional difference—besser blocks, concrete blocks, and masonry blocks all refer to the same product: precast concrete units (hollow or solid) used for wall construction. Different manufacturers produce blocks to identical Australian Standards (AS 2870, AS 3700) ensuring compatibility and consistent quality regardless of brand. The term "besser block" remains widely used in Australian construction despite the brand name origins similar to "Esky" for coolers or "Bundy" for time clocks.
Concrete block construction must comply with AS 3700 (Masonry Structures) and AS 2870 (Residential Slabs and Footings). These standards specify mortar strengths, reinforcement requirements, and construction detailing for structural adequacy and durability.
Retaining walls exceeding 1m height or supporting surcharge loads require engineering design by a structural engineer. Certified designs ensure adequate foundation sizing, reinforcement placement, and drainage specifications meeting building codes and council approval requirements.
For complex projects, hire licensed bricklayers or masonry contractors. Professional installation ensures proper mortar consistency, accurate alignment, structural reinforcement, and compliance with engineering specifications. Experienced contractors complete projects faster with superior quality and warranty protection.