Chapter one
Brick chimneys and the Colhook Common works
A village that made its own brick for nearly two centuries has plenty of stacks, and plenty of pointing to keep dry.
The brickworks on Colhook Common was set up by 1779, used red and yellow clay and sand dug from the common itself, and ran until the 1960s. Nearly two centuries of local brick-making explains why a Northchapel chimney is so often a stout brick stack, and why those stacks have such different ages and conditions. A chimney is the part of the roof that gets the most weather: it stands clear of the ridge, rain hits it from every side, and frost gets into any joint that has lost its mortar. We start at the top, with the flaunching, the sloped mortar cap holding the pots in place. A hairline crack there lets rain pour down beside the flue, and the first sign is a damp tide-mark on the breast upstairs, long before anything shows outside.
At a glance
- The brickworks ran from 1779 to the 1960s
- Pointing and flaunching fail before the brick
- Lead at a stack's base is the next weak spot
1.1 Pointing, bricks and lead
The next layer down is the pointing. Old stacks were laid in lime mortar, which is softer than the brick and wears first, as it is meant to, so the joints can be raked out and refilled with a similar mix rather than hard cement. A cement repair traps water in the brick behind it, and the face of the brick then flakes away in a frost, which is the spalling you sometimes see on repaired stacks. At the base of the stack, lead flashings and a back gutter shed water round the brickwork, and these are checked for lift and splits. Where a stack leans or its bricks have crumbled, repointing will not do, and our chimney repairs page describes the rebuild options.
1.2 Working at height
Stacks are tall, usually on a ridge, and often need scaffold. Where the stack sits on a party wall with a neighbour, any work that removes it brings in a party wall notice, and taking out a chimney breast always requires Building Regulations approval. Repairs that leave the stack where it is do not. Whatever the job, we look at the chimney pots and the cowls too. Cracked pots or a missing cowl let rain run straight down the flue, and the cure is a small job, so it is worth catching before the damp reaches the plaster.
What a brick chimney tells us when it leaks
| Sign | Likely cause | Usual repair |
|---|---|---|
| Stain on the chimney breast | Cracked flaunching or open pot joints | New flaunching, re-bed pots |
| Powdery mortar at the joints | Lime pointing worn by weather | Rake out and repoint |
| Brick faces flaking | Frost in saturated brick | Replace bricks, check pointing mix |
| Damp where roof meets stack | Split or lifted lead flashing | Renew flashing and back gutter |
