Summary

Re-pointing is one of the most common and most frequently botched masonry jobs in the UK. Bad repointing — wrong mortar, insufficient raking depth, flash pointing over old mortar — is a leading cause of brickwork deterioration. Done right, repointing can add 30–50 years to a façade; done wrong, it can cause more damage in 5 years than the original mortar degradation would have in 20.

The most important decision is mortar selection. Victorian and Edwardian brickwork was built with lime mortars that are softer and more permeable than the brick. Modern cement mortars are harder and less permeable — trap moisture in the brick, causing spalling in cold weather. This is why pre-1920 brickwork must be re-pointed with hydraulic lime mortar, not OPC mix.

For post-1920 brickwork, OPC-based M4 or M6 mortars are appropriate. The joint profile — weatherstruck, flush, bucket handle, recessed — affects both appearance and weather performance.

Key Facts

  • Minimum raking depth — 15mm (BDA guidance); 20mm preferred for structural repointing
  • Raking method — angle grinder with diamond blade is fastest but high risk of damage; cold chisel and club hammer preferred around windows; SDS drill with flat chisel efficient on large areas
  • Dust removal — clean with stiff brush; dampen (not saturate) before pointing
  • Layer thickness — max 10mm per application; build up in layers for deep joints
  • Curing — keep damp for 3–5 days in hot weather to prevent shrinkage cracking; protect from frost for 48 hours minimum
  • Joint profiles — weatherstruck (sloped outward, sheds water), flush (maintenance pointing), bucket handle (concave, traditional), recessed (raked back, modern aesthetic — not suitable for exposed locations)
  • Pre-1920 rule — always use lime mortar; cement mortar causes brick spalling within 5–10 years
  • Post-1920 standard — M4 (1:1:5–6 OPC:lime:sand) for most UK domestic facades
  • Exposed parapets — M6 minimum; consider NHL 5 lime for heritage properties
  • Chimneys — sulphate-resistant Portland cement (SRPC) required; see mortar mixes
  • Colour matching — sand colour is the dominant factor; mix test samples and cure for 72 hours before comparing
  • Frost rule — never point in temperatures below 3°C or if temperature expected to drop below 2°C within 24 hours of laying

Quick Reference Table

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Building Age Recommended Mortar Approximate Designation
Pre-1900 NHL 2 or NHL 3.5 + sharp sand M0.5–M2
1900–1920 NHL 3.5 or NHL 5 + sharp sand M2–M3.5
1920–1960 1:1:5–6 OPC:lime:sand M4
1960–2000 1:1:5–6 or 1:0.5:4.5 OPC:lime:sand M4–M6
Post-2000 Match specification; typically M4–M6 M4–M6
Below DPC SRPC 1:0.5:4.5 M6
Chimneys SRPC 1:0.5:4.5 M6

Detailed Guidance

Assessing Whether Repointing Is Needed

Not all weathered joints need repointing. Superficial weathering — slight surface recession, minor colour change — does not require intervention. Signs that repointing is genuinely needed:

  • Joint depth recession exceeding 5–10mm (probe with a key or screwdriver)
  • Friable or crumbling mortar that can be picked out with a knife
  • Visible voids or hollow sections (tap with knuckle — hollow sound)
  • Active water ingress traceable to the joints
  • Previous cement pointing that is cracking, lifting, or causing brick face damage

Over-repointing in good condition is not recommended — raking out always risks chipping brick faces, especially on soft handmade bricks.

Safe Raking-Out Methods

Cold chisel and club hammer: Slowest but safest method. Angle the chisel into the joint at approximately 30° to avoid dragging along the brick face. Work in both directions from the centre of the joint outward.

SDS drill with flat chisel: Good for large areas of hard cement mortar. Use the lowest speed setting. Very high risk of brick face damage near corners and openings — switch to cold chisel within 75mm of any corner.

Angle grinder with diamond disc: Only use by experienced operatives. Never run the disc parallel to the bed joint — always use a joint raking disc (narrower than a standard cutting disc) and only remove the centre of the joint, then follow with a cold chisel for the edges. One slip ruins a brick face.

Mortar raking tool (oscillating multi-tool): Best for heritage work and fine joints. Slow but very controlled. Ideal for gauged and rubbed brickwork where brick faces are soft.

Joint Profiles and When to Use Them

Profile Description Best For Avoid
Weatherstruck Top face raked back, sloped outward to shed water All exposed external work Not suitable for arrises (corners)
Flush Mortar pressed flush with brick face, rubbed off Internal work, rendered walls Exposed facades
Bucket handle (tooled) Concave, formed with a rounded jointing iron Traditional aesthetic, good weather resistance Not for very exposed locations
Recessed Mortar set 5mm back from face Modern aesthetic All exposed locations — pools water
Tuck pointing Grey mortar flush, thin white lime ribbon pressed in Restoration of Georgian gauged work New construction

Pointing Procedure Step-by-Step

  1. Rake out to minimum 15mm depth
  2. Brush out all dust with a stiff wire brush
  3. Dampen the joint with a fine spray or brush — not saturate
  4. Mix mortar to the correct specification (see mortar mixes)
  5. Load a pointing trowel and press mortar into the perpend (vertical) joints first — these are harder to reach
  6. Follow with the bed (horizontal) joints
  7. Work in manageable sections — about 1m² at a time before beginning to profile
  8. When mortar has stiffened to 'leather hard' (typically 20–45 minutes depending on conditions), profile with the appropriate jointing iron
  9. Brush off crumbs with a soft brush when mortar has set further (1–2 hours)
  10. Dampen the finished surface in hot/dry weather for 2–3 days

Common Repointing Failures

Flash pointing (skim pointing): Applying a thin skin of mortar over old mortar without raking out. Fails within 1–2 years. Often done to avoid the labour of proper raking.

Wrong mortar on old buildings: OPC mix on pre-1920 brickwork. The rigid cement mortar cannot accommodate the movement of soft bricks; joints crack open, water enters behind the hard skin, and in winter the trapped water spalls the brick face. Can take 3–5 years to become apparent.

Incorrect joint profile in exposed location: Recessed joints on exposed parapets or gable ends pool water and accelerate frost damage.

Over-wetting or under-wetting: Over-wet mortar shrinks excessively on curing; under-wet joints fail to cure properly and are dusty.

Frequently Asked Questions

How much does repointing cost per m²?

Trade rates vary by region and difficulty, but a guide:

  • Standard repointing on accessible walls: £30–£60/m²
  • Heritage lime repointing (slower, more skill): £60–£100/m²
  • Chimney stack (access included): £400–£1,000+ depending on height and condition

For quoting, a skilled bricklayer can typically repoint 6–10m² per day on accessible flat walling; less for intricate work, awkward scaffolding, or lime mortar which requires more careful building up.

Can I use a ready-mixed pointing mortar from a bag?

For small repairs, yes. Check the bag designation: M4 is acceptable for most domestic external work. Avoid any bag that doesn't state the designation or that uses the word 'general purpose' — these are typically M2 and only suitable for internal sheltered use. For lime repointing on pre-1920 buildings, buy NHL lime and washed sharp sand separately and mix on site.

How long do I need to leave it before painting or sealing?

Allow minimum 4 weeks before applying any breathable masonry paint or sealant. New OPC mortar continues to cure for 28 days; applying paint before this traps carbon dioxide from the carbonation process.

Should I seal the joints after repointing?

Generally no, unless the wall faces sustained driving rain and the brick type is prone to saturation. Breathable masonry treatments (silane/siloxane impregnators) are occasionally appropriate for very exposed locations; avoid film-forming sealants which prevent moisture from escaping. For damp issues originating from joints, correct the pointing first before considering sealants — a sealant over defective pointing just hides the problem.

Regulations & Standards

  • BS EN 998-2:2016 — Specification for masonry mortars (designations M1–M12)

  • BS EN 459-1 — Building lime (NHL grades)

  • BS EN 1996-2 — Eurocode 6: Design of masonry structures — design considerations and execution

  • Historic England — Traditional Buildings: Mortars, Renders and Plasters — guidance for pre-1920 masonry

  • BDA (Brick Development Association) — Brickwork: Pointing — free technical guidance sheet

  • Brick Development Association Technical Guidance — free repointing guides and mortar designation tables

  • Historic England — Repointing Brickwork and Stonework — specific guidance for historic buildings

  • St Astier NHL Technical Data Sheets — hydraulic lime product specifications

  • mortar mixes — mortar designation selection and mixing ratios

  • efflorescence — dealing with salt deposits after repointing

  • brick types — matching mortar strength to brick grade

  • rising damp — distinguishing joint failure from damp-related decay