Glossary
Pointing and repointing London brickwork the right way
The mortar joints between bricks. Lime mortar required on most listed and conservation jobs.
The mortar joints between bricks. Lime mortar required on most listed and conservation jobs.
Pointing is the finished mortar joint in a brick or stone wall. Repointing is raking out and replacing failed joints. On a solid-wall London house the mortar must be weaker than the brick — normally lime — so that moisture evaporates through the joint rather than through the brick face.
A cement mortar is harder and less permeable than a soft handmade London stock brick. Water that enters the wall then has to leave through the brick rather than through the joint, and in a frost it spalls the brick face. The damage is irreversible: a spalled brick has lost its fired outer skin.
The rule of thumb is that the mortar should always be the sacrificial element. Joints are meant to fail and be replaced; bricks are not.
For most Victorian and Georgian London brickwork, a natural hydraulic lime at NHL 2 or NHL 3.5, mixed around 1:2.5 with a well-graded sharp sand matched to the original in colour and grading. The profile should match what is there — usually flush or slightly recessed. Weatherstruck and, worse, proud 'ribbon' pointing traps water and is a conservation officer's red flag.
On an unlisted house outside a conservation area, no. On a listed building, repointing affects character and normally needs listed building consent. In a conservation area it is usually permitted, but an Article 4 direction can catch it, and a materials condition on a recent permission may specify the mix.
A worked Southwark example of pointing and repointing: with 43 conservation areas — the Camberwell Grove Conservation Area and the Bermondsey Street Conservation Area among the best known — London Borough of Southwark (Southwark Council) sees pointing and repointing constantly, and an Article 4 direction is in force there, so permitted development cannot be assumed. Where pointing and repointing pushes a Southwark scheme out of permitted development, the route becomes a £548 application decided in 8 weeks rather than a £249 prior approval in 6 weeks.
| Historic mortar | NHL 2 or NHL 3.5 lime |
|---|---|
| Typical mix | 1:2.5 lime to sharp sand |
| Correct profile | Flush or slightly recessed |
| Avoid | Cement mortar, weatherstruck and ribbon pointing |
| Raking depth | Twice the joint width, minimum |
| Listed building | Listed building consent normally required |
On a modern cavity wall, yes. On soft historic brick it causes spalling and should be avoided.
At least twice the joint width, to give the new mortar a key.
On a listed building, normally yes. Elsewhere usually not.
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