Inputs
Mix ratio: 1:4 (cement:sand) + plasticiser
Results
Enter your wall area then click Calculate.
UKUK Building Regulations
References & Sources
Standards Cited
- BS EN 13914-1 — Design, preparation and application of external rendering and internal plastering — External rendering
Defines external render systems, coat thicknesses, and application methods used in the calculator - BS EN 998-1 — Specification for mortar for masonry — Rendering and plastering mortar
Specification for rendering mortars including mix ratios, densities, and performance classifications
Formulas Used
- Render volume:
volumeM3 = wallArea x (thickness x numberOfCoats / 1000)
Source: BS EN 13914-1 - Dry product mass:
weightKg = (wallArea / coveragePerBagAt10mm) x (totalThicknessMm / 10) x 25kg x (1 + wastage/100)
Source: Representative manufacturer coverage data — This is dry product mass. Installed render volume is reported separately because wet/in-place density is not a bag-weight conversion. - Bags required:
bagsRequired = ceil((wallArea x totalThicknessMm/10 / coveragePerBag) x (1 + wastage/100))
Source: Representative manufacturer coverage data — Coverage per 25kg bag at 10mm: sand-cement 1.2 m2, lime 1.5 m2, polymer 1.3 m2, insulating 0.8 m2
Key Assumptions
- Dry product mass and bag count use the same representative 25kg-bag coverage assumptions — Representative manufacturer product data; verify the selected product datasheet
- Recommended mix ratios: sand-cement 1:4 + plasticiser, lime 1:1:6, polymer and insulating are pre-mixed — BS EN 13914-1 / BS EN 998-1
- Coverage per 25kg bag at 10mm thickness: sand-cement 1.2 m2, lime 1.5 m2, polymer 1.3 m2, insulating 0.8 m2 — Representative manufacturer product data; verify the selected product datasheet
- Typical wastage allowance of 10-15% for render — Industry standard practice