Repair Systems
Lime & repointing mortars
Natural hydraulic lime (NHL) repointing mortar — technical reference for settlement cracks in Australian remedial building practice. Covers system selection, product comparisons, and brand equivalents.
What is lime & repointing mortars?
Lime repointing mortars are blends of natural hydraulic lime (NHL) and sand used to reinstate deteriorated mortar joints in historic, heritage, or older masonry construction. Portland cement repointing of pre-1960s brickwork is one of the most common causes of accelerated masonry deterioration — the hard, impermeable cement mortar traps moisture within the wall, which migrates through the softer masonry units and causes spalling and salt crystallisation damage. Lime mortar is softer and more permeable than the surrounding brickwork, allowing moisture to evaporate preferentially through the joint and protecting the masonry from within. Specified by heritage consultants and building inspectors for repointing works on pre-war and inter-war brick buildings; the correct NHL classification and aggregate grading must match the original mortar properties to avoid stress concentrations. Slow-curing and requires protection from rain, frost, and direct sun during the curing period.
Product Reference
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System Description
For heritage and soft brick only; must be weaker than substrate. Never use OPC as it traps moisture.
Technical Properties
- Breathable — allows moisture vapour to escape, protecting masonry from dampness
- Correct compressive strength match protects masonry units from stress concentration
Limitations
- Slow curing — requires protection from rain and frost for minimum 72 hours
- Must be sourced from specialist lime mortar suppliers to ensure correct NHL classification
PROCUREMENT SOURCES
System Description
For heritage and soft brick only; must be weaker than substrate. Never use OPC as it traps moisture.
Technical Properties
- Breathable — allows moisture vapour to escape, protecting masonry from dampness
- Correct compressive strength match protects masonry units from stress concentration
Limitations
- Slow curing — requires protection from rain and frost for minimum 72 hours
- Must be sourced from specialist lime mortar suppliers to ensure correct NHL classification
PROCUREMENT SOURCES
System Description
For heritage and soft brick only; must be weaker than substrate. Never use OPC as it traps moisture.
Technical Properties
- Breathable — allows moisture vapour to escape, protecting masonry from dampness
- Correct compressive strength match protects masonry units from stress concentration
Limitations
- Slow curing — requires protection from rain and frost for minimum 72 hours
- Must be sourced from specialist lime mortar suppliers to ensure correct NHL classification
PROCUREMENT SOURCES
System Description
For heritage and soft brick only; must be weaker than substrate. Never use OPC as it traps moisture.
Technical Properties
- Breathable — allows moisture vapour to escape, protecting masonry from dampness
- Correct compressive strength match protects masonry units from stress concentration
Limitations
- Slow curing — requires protection from rain and frost for minimum 72 hours
- Must be sourced from specialist lime mortar suppliers to ensure correct NHL classification
PROCUREMENT SOURCES
System Description
For heritage and soft brick only; must be weaker than substrate. Never use OPC as it traps moisture.
Technical Properties
- Breathable — allows moisture vapour to escape, protecting masonry from dampness
- Correct compressive strength match protects masonry units from stress concentration
Limitations
- Slow curing — requires protection from rain and frost for minimum 72 hours
- Must be sourced from specialist lime mortar suppliers to ensure correct NHL classification
PROCUREMENT SOURCES
Brand Equivalents
Side-by-side view of equivalent products across all major brands.
| Material | Ardex | Sika | Fosroc | Tremco / Other | Parchem / Mapei |
|---|---|---|---|---|---|
| Lime mortar (repointing) | Ardex | Sika | Fosroc | Surebuild 450 NHL | Unitex UniPoint |
Disclaimer
Information is general only. Product selection must be confirmed against project requirements, substrate condition, exposure class, manufacturer technical data sheets, NCC requirements, Australian Standards (including AS 3600), and consultant or structural engineer specifications. Do not rely on this reference as a substitute for professional engineering advice.
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