Brickwork and repointing in Hythe, Folkestone and Kent

Not every wall with some tired mortar needs repointing all over. Walls are often repointed too soon, and raking out the old mortar can itself damage the edges of the bricks. The time to act is when the mortar has actually failed.

Most houses built before about 1920 have solid walls of softer brick laid in lime mortar. Lime is weaker than the brick and lets moisture evaporate out of the wall through the joints. Repoint that wall in hard cement mortar and the moisture can no longer get out through the joints, so it leaves through the bricks instead, and frost pops the faces off them. That damage is called spalling, it is common on older houses, and much of it was caused by well meant repointing.

The rule is that the mortar should always be weaker than the brick. On a Victorian house in Folkestone or Hythe that nearly always means lime mortar. On a modern house built with hard bricks and a cavity, a cement based mortar is correct. We match the mortar to the wall, not the other way round.

The old mortar is raked out to an even depth, roughly twice the width of the joint, without widening the joints or chipping the brick edges. The joints are brushed out and dampened, and the new mortar is packed in, in layers where the joints are deep, then finished to match the profile of the rest of the wall, whether flush, struck or rounded.

Lime mortar needs looking after while it sets. It has to be kept damp and protected from sun, wind, frost and heavy rain for days rather than hours, so the weather is part of the job, and in the depths of winter it is often better to wait.

Where bricks have spalled, cracked or crumbled, they are cut out and replaced one at a time with new or reclaimed bricks matched for size, colour and texture. Matching older brickwork usually means reclaimed bricks, because brick sizes have changed over the years and a modern brick sits proud or short in an old wall.

On a coastal wall, salt crystallising in the face of a soft brick causes the same kind of crumbling, and the seaward side of a house near the front can need attention long before the others. It is worth finding out why a brick failed before replacing it, or the new one goes the same way.

Chimney stacks take more weather than any other brickwork on a house and often need repointing well before the walls below. Garden and boundary walls have no roof over them at all, so the coping along the top does the job a roof does, and a wall with a failed coping, or no damp proof course, deteriorates from the top down.

Freestanding walls also move. A long wall with no expansion joints, a wall with a tree root under it, or one leaning towards the road may need rebuilding rather than repointing, and a wall holding back soil is a structural job that needs an engineer's view first.