Repair Systems — 03 — Facade & External Envelope
NHL 3.5 natural hydraulic lime repointing mortar
Supplier reference for NHL 3.5 (feebly hydraulic) natural lime repointing mortar — the standard specification for repointing soft, historic and heritage clay brick masonry on Class 2 strata building facades where the original mortar was lime-based. Compares Baumit, Parex, and specialist heritage lime suppliers by product range, distribution, and technical performance.
What is NHL 3.5 natural hydraulic lime repointing mortar?
Natural hydraulic lime (NHL) 3.5 repointing mortar is a feebly hydraulic lime mortar used for repointing soft, historic and heritage clay brick masonry on Class 2 strata building facades where the original mortar was lime-based. NHL 3.5 produces a soft, flexible, breathable mortar with a compressive strength of 2–7 MPa — always weaker than the brick unit, ensuring that thermal and structural movement causes the mortar to fail before spalling the brick arris.
Product Reference
3 products — 3 suppliers — NHL 3.5 natural hydraulic lime repointing mortars — scroll to view all
Baumit KalkMörtel / NHL 3.5 Natural Hydraulic Lime Mortar
NHL 3.5 natural hydraulic lime repointing mortar — heritage masonry — Baumit
System Description
Baumit natural hydraulic lime mortar using NHL 3.5 binder for repointing soft, historic and heritage clay brick masonry on Class 2 strata building facades. Baumit supplies a range of pre-blended lime mortars through their Australian distributor network — confirm current product name and availability in your state before specifying. NHL 3.5 produces a soft, flexible, breathable mortar that must be weaker in compressive strength than the brick unit so that thermal movement causes the mortar to crack before spalling the brick arris. Rake out joints to minimum 15mm depth, remove dust with compressed air, and dampen the joint before application. Apply in layers not exceeding 10mm per pass, compact each layer firmly with a pointing iron, and finish flush with or slightly recessed from the brick face. Moist-cure for 3–7 days and protect from rain and frost during the cure period.
Technical Properties
- NHL 3.5 binder — feebly hydraulic — compressive strength 2–7 MPa — softer than standard modern brick
- High vapour permeability — breathable — allows moisture trapped in masonry to escape without causing joint face failure
- Flexible mortar — accommodates minor thermal and structural movement without transmitting stress to adjacent brick arrises
Limitations
- Lower compressive strength than cement mortars — not suitable for high-load structural joints or hard, modern engineering brick
- Longer cure time than cement mortar — requires protection from rain and frost for 3–7 days after application
- Confirm current Baumit product range available in your state — distributor network varies by region
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Parex NHL 3.5 Natural Hydraulic Lime Mortar
NHL 3.5 natural hydraulic lime repointing mortar — heritage masonry — Parex
System Description
Parex natural hydraulic lime mortar — NHL 3.5 grade — for repointing soft, historic and heritage clay brick masonry on Class 2 strata buildings. Parex supplies pre-blended lime mortar products through their Australian distribution network — confirm current product code and state availability before specifying. NHL 3.5 (feebly hydraulic) produces a relatively soft, flexible, breathable mortar that must be weaker in compressive strength than the brick unit. The pre-blended formulation minimises site mixing error compared to gauged site-mixed lime mortars. Rake joints to minimum 15mm depth, clean with compressed air, dampen before application, and apply in layers not exceeding 10mm per pass. Moist-cure for 3–7 days and protect from rain, frost and direct sunlight during the cure period.
Technical Properties
- NHL 3.5 binder — feebly hydraulic — compressive strength 2–7 MPa — confirmed softer than standard modern brick units
- High vapour permeability — breathable mortar — critical for management of interstitial moisture in lime-mortar masonry
- Pre-blended formulation — consistent NHL grade and aggregate content — reduces risk of incorrect site-batching
Limitations
- Lower compressive strength than cement mortars — not suitable for structural load joints or hard, modern engineering brick
- Longer cure time than cement-based products — protect from weather for 3–7 days after application
- Confirm current Parex product range and availability in your state before specifying
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Heritage Lime Specialist — NHL 3.5 Custom Blended Mortar
NHL 3.5 natural hydraulic lime repointing mortar — heritage specialist — custom blended
System Description
Specialist heritage lime suppliers offer custom-blended NHL 3.5 repointing mortars where aggregate type, colour, and grading are specifically matched to the original mortar on the building. This approach is required for significant heritage buildings where standard pre-blended products will not achieve the necessary colour and texture match, or where the heritage authority requires provenance of the lime source and aggregate selection. The heritage specialist will typically analyse a sample of the original mortar, specify the NHL grade and aggregate blend, supply a test batch for on-site trial panel assessment, and provide a mixing and application specification for the works. Confirm state availability — specialist heritage lime suppliers operate in all major states but supply and lead times vary. limemortar.com.au is one Australian specialist; confirm current product range and availability before specifying.
Technical Properties
- NHL 3.5 binder — feebly hydraulic — compressive strength 2–7 MPa — grade confirmed by specialist to match original mortar strength
- Custom aggregate blend — aggregate type, colour and grading specifically matched to the original mortar on the building
- Very high vapour permeability — maximum breathability for management of moisture in lime-mortar masonry
Limitations
- Longer lead time than standard pre-blended products — custom blending and mortar analysis adds time to procurement
- Higher cost than standard pre-blended NHL mortars — specialist supply and custom aggregate blending increases cost
- Requires experienced lime work contractor — poor mixing proportions or application will compromise durability
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Comparison
Side-by-side comparison of NHL 3.5 lime repointing mortar suppliers. Confirm all product selections against the current manufacturer TDS before specifying.
| Supplier | Product | Distribution | NHL grade | Strength | Key feature | Primary use |
|---|---|---|---|---|---|---|
| Baumit Australia | Baumit KalkMörtel / NHL 3.5 | National (distributor) | NHL 3.5 | 2–7 MPa | Pre-blended, consistent grade | Heritage repointing — soft brick |
| Parex Australia | Parex NHL 3.5 | National (distributor) | NHL 3.5 | 2–7 MPa | Pre-blended, standard colour range | Heritage repointing — soft brick |
| Heritage lime specialist | Custom blended NHL 3.5 | State-based (specialist) | NHL 3.5 | 2–7 MPa | Aggregate colour-matched to original | Significant heritage buildings |
Do not confuse NHL 3.5 lime mortar with:
- NHL 5.0 natural hydraulic lime mortar — stronger NHL grade (5–15 MPa) — suited to harder historic brick and exposed parapets where NHL 3.5 would erode — listed on the NHL 5.0 mortar page
- Lime putty gauged mortar — non-hydraulic, softest available option (0.5–2.5 MPa) — reserved for very soft, friable historic masonry — requires heritage specialist specification — listed on the lime putty gauged mortar page
- GP cement + hydrated lime mortar — a cement-based mortar with lime added for workability — contains Portland cement and is significantly harder than NHL mortar — not suitable for soft historic brick
- Pre-mixed masonry cement mortar — factory-blended Portland cement mortar — contains no natural hydraulic lime — not a heritage-compatible product
- Polymer-modified cement repointing mortar — high-bond cement mortar with polymer admixtures — not suitable for heritage soft brick masonry
Disclaimer
This page provides general technical information only. NHL grade, aggregate selection and compatibility with existing masonry must be confirmed by a qualified remedial practitioner with heritage masonry experience, and a heritage specialist where required by a heritage authority, against project-specific conditions and AS 3700. Supplier availability and product ranges change — confirm with supplier before specifying.