Bags of prebagged repair mortar for spalling and patch repair — from area, average thickness and wet density. Transparent arithmetic, editable typical values, no code citation (none governs repair mortar consumption).
Measure depth at several points per patch and average — repair surfaces are never uniform.
Typical 1900–2300 — verify against your product datasheet.
Materials required
bags of repair mortar
Net wet mortar volume = repair area × average thickness. Gross volume = net × (1 + wastage). Material mass = gross volume × wet density. Bags = mass ÷ bag size, rounded up. Yield per bag = bag size ÷ wet density.
No IS code governs repair-mortar consumption — yield is a manufacturer-datasheet property that varies between products. The density, bag size and wastage here are editable typical site-practice values; always verify against the datasheet of the product you are actually using.
Given: 10 m² of spalled cover on a slab soffit, average depth 15 mm, 10% wastage, 25 kg bags at 2100 kg/m³.
Net mortar = 10 × 0.015 = 0.15 m³ = 150 L → with 10% wastage = 165 L
Mass = 0.165 × 2100 = 346.5 kg → 346.5 ÷ 25 = 13.9 → 14 bags
SBR bonding coat = 10 × 0.4 = 4 kg (if specified)
With 10% wastage and wet density 2100 kg/m³: 1 m² × 0.015 m × 1.10 = 0.0165 m³ = 34.7 kg ≈ 1.4 bags per m². A 10 m² spalling repair therefore needs about 14 bags.
Because none governs it. Prebagged repair mortars are proprietary products — yield per bag is a datasheet value that differs between manufacturers and grades (R2, R3, R4 class mortars vary in density and yield). We state the arithmetic and the assumptions instead of dressing site practice up as a code provision. Verify against your product datasheet before ordering.
Yes — enter the built-up volume as area × average thickness and adjust the density to your micro-concrete datasheet (typically 2200–2400 kg/m³). For sections thicker than about 50 mm, check whether your repair system specifies coarse-aggregate extension, which changes the yield.
A bonding coat (neat SBR or SBR:cement slurry) is specified when placing thin repair mortar on a prepared, SSD-conditioned substrate, particularly for overhead and vertical patches. Consumption is typically around 0.4 kg/m² of repair area — follow your system datasheet, as brush-out rate varies with substrate texture.
Often used together with this calculator — pick the next step in your design or QA loop.
Deep dive: read the full significance guide — the code clauses, assumptions and site meaning behind these numbers.