Repointing Calculator — How Much Mortar for Repointing?

This calculator determines the volume of mortar needed to fill the horizontal (bed) and vertical (perp) joints in your brickwork, then converts that volume into quantities of sand, cement and lime based on your chosen mortar mix.

The formula

Mortar volume = Wall area x (Horizontal joint volume + Vertical joint volume) per m²

For standard bricks (215x65mm with 10mm joints):

• Courses per metre height: 1000 / 75 = 13.33
• Horizontal joint volume per m²: 13.33 courses x 1m x joint width x raking depth
• Vertical joints per course per m: 1000 / 225 = 4.44
• Vertical joint volume per m²: 4.44 x 13.33 x 65mm height x joint width x raking depth

Mortar mixes

• 1:1:6 (cement:lime:sand): General-purpose repointing mortar. Good workability and flexibility.
• 1:4 (cement:sand + plasticiser): Modern alternative. Stronger but less flexible than lime-based mixes.
• 1:3 (lime putty:sand): Heritage and conservation mortar. Softer, more breathable — essential for pre-1920 buildings. Lime putty is batched and sold by volume, so we report it in litres rather than 25kg bags.

Dry volume conversion

Wet mortar consolidates by roughly 25–33% from the loose dry mix volume, so we apply a conservative 1.33 dry-volume factor (adjustable in Advanced options) to the required wet volume before converting to material quantities. Bulk densities used: building/sharp sand 1600 kg/m³, OPC cement 1440 kg/m³ (the standard 0.0174 m³ per 25kg bag), and hydrated-lime powder 600 kg/m³. Mature lime putty (~1350 kg/m³) is measured by volume in litres for the conservation mix.

How much mortar to remove

The amount of mortar you rake out is the same amount you put back, so the bed-joint and perp-joint volumes shown in the results tell you both how much old mortar to remove and how much fresh mortar to mix. Rake out to at least twice the joint width — 20mm for a standard 10mm joint — per SPAB best practice; LABC quotes 12-19mm as the typical working range. Set the raking depth in the inputs to match how deep you are cutting, and the calculator scales the volume accordingly. Use a plugging chisel or hand rake, not an angle grinder, which SPAB and LABC both warn damages the brick arrises.

Estimating repointing cost

Enter a price per 25kg bag and the calculator returns an indicative materials cost (cement plus hydrated lime; lime putty is volume-batched and excluded from the bag count). This is materials only — labour, scaffolding and access dominate a real repointing quote. As a 2026 UK guide, repointing labour-and-materials runs roughly £30-£60 per m² for cement mortar and £60-£90 per m² for lime mortar (source: UK trade cost guides), higher in London and the South East. Treat those as a sense-check against tradesperson quotes rather than a fixed price.