Brick Repointing for Period Properties

The mortar joints between bricks in period properties gradually deteriorate over decades, requiring repointing to maintain structural integrity and weather protection. For Victorian, Edwardian, and Georgian homes in North London, proper repointing is essential maintenance that preserves the building while preventing water ingress and associated damage. However, inappropriate repointing using wrong materials or techniques causes serious harm to historic brickwork. This guide explains proper repointing for period properties, covering materials, techniques, and costs.

Why Period Properties Need Repointing

Mortar in period buildings naturally degrades over time due to:

• Weather Exposure: Rain, frost, and temperature changes gradually erode mortar
• Pollution: Historic London pollution (now reduced) accelerated deterioration
• Natural Ageing: Lime mortars gradually carbonate and can become friable
• Building Movement: Slight settlement causes mortar to crack
• Water Damage: Blocked gutters or rising damp exacerbate mortar failure

After 80-120 years, many Victorian and Edwardian properties need repointing. Signs include:

• Crumbling or soft mortar that falls away when touched
• Mortar recessed significantly behind brick faces
• Gaps appearing in joints
• Water penetration through walls during heavy rain
• Bricks becoming loose
• Vegetation growing in joints

The Critical Importance of Lime Mortar

Period properties were built with lime mortar, not modern cement mortar. Using the correct material is absolutely critical:

Why Lime Mortar is Essential:

• Breathability: Lime is permeable, allowing moisture to evaporate through walls. Period buildings without cavity walls must breathe to stay dry
• Flexibility: Lime remains slightly flexible, accommodating minor building movement without cracking
• Softer Than Bricks: Lime is intentionally weaker than bricks, acting as a sacrificial material that protects bricks
• Self-Healing: Lime can re-carbonate and heal minor cracks over time
• Compatibility: Works with original materials without causing damage

Why Cement Mortar Damages Period Buildings:

• Impermeable: Traps moisture inside walls, causing damp problems and brick decay
• Too Hard: Harder than historic bricks, concentrating stress and causing bricks to crack and spall
• Inflexible: Cracks under building movement, creating water paths
• Causes Salt Damage: Forces salts into bricks where they crystallise and cause damage
• Aesthetically Wrong: Different colour and texture from original mortar

In conservation areas and listed buildings, cement repointing can breach planning regulations. Even where not legally required, lime mortar is essential for building health.

Types of Lime Mortar

Non-Hydraulic Lime (NHL 2 or Fat Lime):

• Softest, most breathable option
• Sets very slowly by absorbing CO2 from air (carbonation)
• Suitable for internal work and sheltered external locations
• Used in Georgian and early Victorian buildings
• Requires experienced craftspeople

Moderately Hydraulic Lime (NHL 3.5):

• Most commonly used for Victorian and Edwardian repointing
• Sets partly through hydraulic set (chemical reaction with water)
• Suitable for most external walls
• Good balance of workability, strength, and breathability
• Appropriate for London's clay bricks

Eminently Hydraulic Lime (NHL 5):

• Harder, less breathable
• Sets primarily through hydraulic reaction
• Suitable for very exposed locations or harder bricks
• Less commonly needed in domestic properties

Hot Mixed Lime:

• Traditional method mixing quicklime with sand
• Creates very soft, breathable mortar
• Requires specialist knowledge
• Used for conservation of important historic buildings
• More expensive and challenging to work with

For most Victorian and Edwardian homes in North London, NHL 3.5 lime mortar provides the best performance and compatibility.

Matching Original Mortar

Repointing should match the original mortar in colour, texture, and composition:

Colour Matching:

• Examine original mortar (dig out small sample from less visible area)
• Note colour—Victorian mortars range from cream to buff to light grey
• Use appropriate sand to achieve colour match
• Avoid white or strongly coloured mortars unless original was similar
• Create sample panels to confirm match before starting work

Texture:

• Sand grading affects texture
• Sharp sand creates rougher texture
• Well-graded sand closer to original appearance
• Avoid overly smooth or rough finishes unless matching original

Joint Profile:

• Finish should match original joints
• Flush or slightly recessed most common in Victorian work
• Avoid "ribbon" or "strap" pointing with raised mortar (wrong for period buildings)
• Never use weatherstruck joints (angled) on period facades unless original

The Repointing Process

1. Raking Out Old Mortar:

• Remove failed mortar to depth of 15-25mm (at least twice the joint width)
• Use hand tools or carefully controlled power tools
• Never use angle grinders or disc cutters—they damage brick edges
• Clean out joints thoroughly, removing all loose material
• Brush out dust and debris
• Slightly undercut joints to provide mechanical key

2. Preparation:

• Dampen brickwork before repointing (critical—prevents bricks sucking moisture from mortar)
• Don't oversaturate—damp not wet
• In hot weather, mist walls regularly during work

3. Mixing Mortar:

• Typical mix: 1 part NHL 3.5 lime to 2.5-3 parts well-graded sharp sand
• Mix thoroughly dry, then add water gradually
• Aim for firm but workable consistency
• Mix only what can be used in 3-4 hours
• Keep mixed mortar covered to prevent drying

4. Application:

• Press mortar firmly into joints using small pointing trowel
• Fill joints in thin layers (maximum 10mm per layer)
• Allow layers to firm before adding next
• Compact mortar well to eliminate voids
• Fill slightly proud then scrape back flush when firm
• Avoid smearing mortar on brick faces

5. Finishing:

• When mortar is "thumb-print hard," finish joints with appropriate tool
• Flush finish most common for Victorian work
• Brush gently to achieve slight texture matching original
• Avoid over-working which brings lime to surface (looks white)
• Clean brick faces with soft brush when mortar fully set

6. Curing:

• Protect new mortar from direct sun, wind, rain, and frost for at least 7 days
• Cover with hessian or similar breathable material
• Mist regularly in hot or windy conditions
• Allow at least 2-4 weeks before painting (if applicable)
• Full cure takes several months as lime carbonates

When to Repoint

Best Seasons:

• Spring and autumn ideal—moderate temperatures and moisture
• Avoid winter—frost damages uncured lime mortar
• Summer possible but requires careful moisture management
• Never repoint when frost is forecast within 7 days
• Avoid very hot weather (above 25°C) unless you can maintain moisture

Extent of Repointing

Full Repointing: All joints replaced:

• Required when mortar has failed throughout
• Ensures consistent appearance
• Opportunity to address all areas at once
• More economical per square metre than piecemeal work

Partial Repointing: Only damaged areas:

• Appropriate when only certain elevations or areas have failed
• More challenging to match existing mortar colour and texture
• Can look patchy if not carefully executed
• May need full repointing in future

For period properties, full repointing of affected elevations generally gives better results than patchy repairs.

Costs of Repointing

Lime Mortar Repointing (per square metre):

• Ground floor level (minimal scaffolding): £40-£60 per sq m
• First floor (scaffolding required): £50-£70 per sq m
• Upper floors or complex scaffolding: £60-£85 per sq m
• Conservation specification (listed buildings): £70-£100+ per sq m

Whole House Examples:

• Small Victorian terrace (front elevation only): £2,500-£4,500
• Large Victorian terrace (all elevations): £8,000-£15,000
• Semi-detached Edwardian house: £6,000-£12,000
• Georgian townhouse: £15,000-£30,000+

Costs include scaffolding, materials, labour, and waste disposal. Conservation projects with specialist contractors and supervision cost more.

Scaffolding:

• Single elevation: £800-£1,500
• Whole house: £2,000-£4,000
• Hire period typically 4-8 weeks
• Consider undertaking other external works while scaffold is up (window restoration, roof repairs) to maximise value

Common Mistakes to Avoid

• Using Cement Mortar: Causes serious, often irreversible damage to historic brickwork
• Raking Out with Angle Grinders: Damages brick arrisses (edges)
• Insufficient Depth: Mortar must be raked back at least 15mm, preferably 20-25mm
• Wrong Mix: Too strong (too much lime or wrong type) or too weak
• Not Damping Bricks: Results in weak mortar as bricks suck out moisture
• Poor Colour Match: Obvious new mortar detracts from appearance
• Repointing in Cold Weather: Frost damages uncured lime mortar
• No Protection During Curing: Wind, sun, and rain prevent proper curing
• Repointing Over Paint: Remove paint first or mortar won't adhere properly

Choosing a Repointing Contractor

Lime mortar repointing requires specialist skills. Look for:

• Proven experience with lime mortar and period properties
• Portfolio of completed repointing projects
• Understanding of appropriate materials and techniques
• References from similar period properties
• Knowledge of conservation principles
• Willingness to create sample panels before starting
• Proper insurance and guarantees
• Membership of relevant trade bodies (FMB, Guild of Master Craftsmen)

Avoid builders who suggest cement mortar or don't understand the importance of lime for period buildings.

Maintenance After Repointing

Properly executed lime repointing should last 80-100+ years. Maintain it by:

• Keep gutters and downpipes clear to prevent water running down walls
• Address any sources of damp promptly
• Inspect annually for any damage or deterioration
• Repair small areas promptly before problems spread
• Never paint lime mortar unless historically appropriate—it needs to breathe
• Avoid pressure washing which can damage mortar