Repair Systems — 03 — Facade & External Envelope
Repointing mortar — lime-based
Technical product reference for lime-based repointing mortars for masonry facade remediation on Australian Class 2 strata buildings. Covers NHL (natural hydraulic lime) and hot lime mortar systems for heritage and softer brick repointing where harder cement-based mortars would stress and spall the masonry substrate.
Lime-based repointing mortar types
Select the mortar type below to compare individual suppliers, technical data, and procurement sources. NHL grade must be matched to the compressive strength of the original brick — mortar must always be weaker than the brick unit.
NHL 3.5 Natural Hydraulic Lime Mortar
Standard NHL grade for repointing soft and moderately soft historic clay brick masonry where the original mortar was lime-based. Compressive strength 2–7 MPa — always weaker than the brick unit.
NHL 5.0 Natural Hydraulic Lime Mortar
Stronger NHL grade for moderately hard historic brick and exposed parapets where NHL 3.5 would erode prematurely. Still breathable and softer than Portland cement. Compressive strength 5–15 MPa.
Lime Putty Gauged Repointing Mortar
Softest available repointing mortar — slaked lime putty with custom aggregate — for very soft, friable pre-1920s masonry where any hydraulic binder would cause damage. Mix specification by heritage specialist required.
Disclaimer
This page provides general technical information only. Mortar type, mix proportion, NHL grade and compatibility with existing masonry must be confirmed by a qualified remedial practitioner and, for structural masonry, a structural engineer, against project-specific masonry conditions and AS 3700.