Should old chimneys be repointed in lime mortar?

In any brick wall, water has to escape somewhere. It dries out through the mortar joints and through the bricks. In an old stack built with lime mortar, the joints are the softer, more porous part, so moisture leaves through them and the bricks stay in good shape. The mortar is designed to wear before the brick does.

Repoint that stack with a hard cement mortar and the balance reverses. The joints stop passing moisture and the bricks become the only way out, so the face of each brick flakes and crumbles over time. The result is a stack that looks neat for a short while and then loses its brick faces. That is the main reason traditional repairs use lime. Our page on crumbling chimney bricks shows how that damage looks.

As a rule of thumb, houses built before the early twentieth century used lime-based or weak mortars with softer, hand-made or locally fired bricks, and some interwar houses did too. Seafront terraces, flint cottages and village houses around Bognor, Chichester and Arundel can fall into that group. A listed or conservation-area house is the clearest case.

You can often tell by looking. Soft, crumbly pale mortar and bricks that are slightly rough or uneven point towards lime. A hard grey mortar with sharp edges, standing proud of eroded bricks, shows that cement has gone in at some point. Modern stacks built with machine-made bricks and cement mortar are a different matter. The answer comes from looking at your own stack, so we photograph the brickwork before we recommend a mortar.

First the tired pointing is cut back by hand to a sensible depth, taking care not to damage the brick edges. The joints are brushed clean and wetted so they do not pull water out of the new mortar. The lime mortar is then packed in, finished flush or slightly recessed, and kept damp for a time so it cures properly instead of drying too quickly.

Lime mortar cures slowly, so timing matters. Work done in hot, dry or freezing weather needs protection, and a good repoint is not rushed. The mix is matched to the house, with sand chosen to resemble the original colour and texture, which keeps the stack looking as though it belongs. It takes more care and more time than a cement repoint, which is partly why it costs more. Our page on chimney repointing covers the work in general.

For a listed house, repair mortar and method can be a matter for the council as well as for you, and changes to a stack may need listed building consent. In a conservation area, the council's conservation officer can advise on how a stack should look and what suits the street. Arun District Council has a conservation team, and other councils have their own.

Asking first beats guessing, and the written quote names the mortar we propose and why. If the house is in the South Downs National Park, planning questions go to the Authority. See chimneys in conservation areas for the wider picture.

Checkatrade's October 2026 table gives an average of around £750 to repoint a chimney, and £55 per m² for brickwork against £80 per m² for stone. Lime work can sit towards the upper end of what many people expect, because the mortar costs more and the job takes longer. Checkatrade's scaffolding guide (table last updated October 2026) gives around £660 a week for a chimney, which is often the largest part of the bill.

That is why it makes sense to repoint at the same time as any flashing or flaunching work, while the scaffold is up. The survey comes first, with photographs of the joints, and then you receive one total in writing. If the old pointing is mostly sound and only a few joints are open, the smaller job is priced instead of a full repoint. The chimney repairs hub lists the other work worth bundling in.

A roofer who knows lime will not mind questions. Ask which mortar will be used and why it suits your bricks. Ask how deep the old pointing will be raked out, since cutting too deep or too wide can damage soft brick. Ask how the new work will be protected while it cures, and what happens if the weather turns.

Ask also what the finish will look like. Lime pointing is usually left flush or slightly recessed with a brushed surface, not smeared over the brick faces or ribboned out in a raised strip. A raised strip traps water on the ledge it makes. Finally, ask for photographs of the stack before and after, because the pointing is easy to judge from a picture and impossible to judge once the scaffold has gone.