Repointing is the process of removing deteriorated or eroded mortar from the joints of existing brickwork or stonework to a minimum depth (usually 15-20mm) and refilling them with fresh mortar. It restores the weathertightness of the wall by closing the open joints through which wind-driven rain can penetrate, and maintains the bond between masonry units. Repointing is one of the most important maintenance tasks on a masonry building and, if done incorrectly, can cause serious damage to historic brickwork.

How do I know when repointing is needed?

Signs that repointing is needed include: mortar visibly recessed or eroded more than 5mm behind the brick face; open or cracked joints through which a knife blade can be inserted; friable or powdery mortar that crumbles when scratched; damp penetration or staining on internal walls; plant growth in joints; and areas where mortar has fallen out completely. Not all joints need to be repointed at the same time - selective repointing of the worst areas can extend the life of the wall without the cost of a full repoint.

What is the difference between repointing and rendering?

Repointing restores only the mortar joints between masonry units, leaving the brick or stone faces exposed. Rendering applies a coat of mortar or plaster to the entire external wall face, covering both the masonry units and the joints. Rendering is sometimes specified where the masonry is too damaged or porous to be satisfactorily repointed, or on buildings traditionally finished in render. For most historic brick buildings, repointing is strongly preferred over rendering, as rendering with cement can trap moisture and accelerate brick deterioration.

Can I use cement mortar to repoint an old house?

On any building pre-dating approximately 1920, cement mortar should not be used for repointing. Old bricks and stone are typically softer and more porous than modern materials, and a rigid cement mortar creates a hard impermeable barrier that traps moisture behind it, causes frost damage and spalling of brick faces, and concentrates movement stress in the masonry rather than the joint. Lime mortar (NHL3.5 or lime putty, matched to the original) is the correct material. Using cement mortar on a listed building is an unauthorised alteration.

Heritage & Conservation noun / verb

Repointing

/ riːˈpɔɪntɪŋ /

Also known as: pointing up, joint raking and repointing, tuck pointing

Definition

Repointing is the process of removing deteriorated or eroded mortar from the joints of existing brickwork or stonework - typically to a minimum depth of 15-20mm - and replacing it with fresh mortar. It restores the weathertightness of the wall, closes open joints that allow rain penetration, and maintains the bond between masonry units. Mortar selection is critical: on historic buildings built before approximately 1920, only lime-based mortar is appropriate.

In practice

Old mortar is removed with a cold chisel and club hammer, an angle grinder with a raking disc, or an oscillating tool - care must be taken not to damage the brick arrises (edges). The minimum rake depth is 15mm; 20mm is preferred to ensure adequate bond for the new mortar. The joint is then dampened (particularly with lime mortar, which requires moisture for bonding and to prevent rapid drying) and the new mortar pressed firmly into the joint in layers, finishing with the chosen profile.

Common joint profiles are: flush (levelled with the brick face, common in sheltered positions); weatherstruck (sloped to shed water, traditionally used on exposed elevations); recessed (set slightly back from the brick face, giving a strong shadow line - requires harder bricks); and bucket handle (concave profile, common in Victorian and Edwardian brickwork). On listed buildings, the original profile should always be matched. New lime mortar must be kept damp and protected from frost for several days while it sets.

Building Regulations

Mortar standardBS EN 998-2 - Specification for masonry mortar

Lime standardBS EN 459 - Building lime (NHL classifications)

Listed buildingsMay require listed building consent for repointing if altering character

Minimum rake depth15 mm (20 mm preferred)

Repointing is generally a repair and maintenance activity that does not require Building Regulations approval. However, on listed buildings, repointing with an incorrect mortar type (especially substituting cement for lime) may constitute an unauthorised alteration requiring listed building consent. Historic England's technical guidance notes on repointing provide detailed advice on mortar analysis, specification, and application techniques for historic masonry.

Full Building Regulations guidance

Related Calculators

Masonry Mortar Calculator

Repointing

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