Chimneys are a feature of most older Cornish homes, from granite cottages to Victorian terraces. Many are no longer used for open fires, and homeowners often want to remove a chimney breast to gain space, take down a stack that is leaking, or repair one so it lasts another few decades. Each of these jobs involves structure, weatherproofing and sometimes neighbours, so it pays to understand the options before work starts.
This guide covers the main chimney jobs we are asked about, what permissions may be involved and how Cornwall's weather affects chimneys. It is general guidance only, so always get advice for your own property.
Why chimneys cause problems in Cornish homes
Chimney stacks are the most exposed part of a house. In Cornwall they face wind-driven rain, salt air on the coast and frequent wetting and drying. Common problems include:
Failed pointing and flaunching: mortar joints and the sloping mortar cap around the pots crack and wash out, letting water into the stack.
Worn flashings: the lead or other flashing where the stack meets the roof can lift, split or come loose, causing leaks into the loft or bedrooms below.
Damp chimney breasts: stains on walls next to the chimney can come from rain getting in at the top, from condensation in an unvented flue, or from salts left by years of burning fuel.
Leaning or unstable stacks: older stacks can lean through weathering, sulphate attack in the mortar or poor past repairs. A leaning stack should be checked promptly.
Our guide to damp in Cornish homes explains how to work out where moisture is coming from before choosing a fix.
Chimney repairs: repointing, flashings and capping
If a chimney is structurally sound, repair is often the simplest option. Typical work includes repointing, renewing the flaunching, replacing flashings, resetting or replacing pots, and fitting cowls or caps to keep rain and birds out.
On older stone and brick stacks, the choice of mortar matters. Many traditional chimneys were built with lime mortar, and using a hard cement mortar for repairs can trap moisture and damage the surrounding masonry. Our guide to lime rendering and pointing explains why lime is often the better choice.
If a flue is no longer used, it can be capped at the top. It should still be ventilated, usually with a vented cap at the top and an air vent at the bottom in the room, so that moisture does not build up inside it.
Removing a chimney breast
Taking out a chimney breast inside the house can free up useful space in a kitchen, living room or bedroom. It is structural work, though, and needs to be done properly:
Support for what is above: if the breast is removed on a lower floor but the breast above or the stack is kept, the remaining masonry must be properly supported, usually on a steel beam or other support designed by a structural engineer.
Building Regulations: removing a chimney breast is normally treated as structural alteration, so Building Regulations approval is usually needed. Building Control will want to see how the remaining structure is supported. Our Building Regulations guide explains the process.
Shared chimneys: in terraced and semi-detached homes, chimney breasts are often on or within the party wall, and the stack may be shared with next door. Work that affects a party wall is likely to be covered by the Party Wall Act; see our Party Wall Act guide.
Future sale: keep the engineer's calculations and Building Control completion certificate, as buyers' surveyors and solicitors often ask for them.
If you are also taking out walls to create an open-plan space, our guide to removing a load-bearing wall covers similar issues.
Taking down a chimney stack
Some owners choose to remove a stack above the roof, especially if it is leaking and no longer used. The roof then needs to be made good with matching slates or tiles. Points to consider include:
Planning: removing a stack on an ordinary house may not need planning permission, but in a conservation area or on a listed building, permission or listed building consent may be required. Chimneys are often seen as an important part of a building's character. Our guide to building in an AONB or conservation area explains more, and our listed building guide covers consent.
Neighbours: a shared stack cannot simply be taken down on one side without considering the neighbour's flues and the Party Wall Act.
Wildlife: bats and nesting birds sometimes use chimneys and roof spaces. See our guide to bat surveys and building work.
Wood burners and reusing a chimney
If you want to use a chimney again for a wood burner or multi-fuel stove, the flue will usually need checking and often lining. Installing a stove is controlled under Building Regulations, and it is normally done by an installer registered with a competent person scheme such as HETAS, who can self-certify the work. Builders can prepare the opening, hearth and chimney repairs ahead of the installation.
Access, scaffolding and timing
Almost all external chimney work needs scaffolding or a safe access platform. On terraced streets and narrow lanes, scaffold on the pavement or road will normally need a permit from Cornwall Council. Because stacks are so exposed, work is best planned for drier spells, and lime mortar in particular needs protection from frost and heavy rain while it cures. Our guide to building work in winter covers this.
What does chimney work cost?
Costs vary widely depending on access, the height and condition of the stack, the amount of scaffolding needed and whether structural steel is involved. As very general guidance, small repairs such as repointing or new flashings tend to cost far less than removing a chimney breast, which involves structural design, Building Control fees and making good inside. Scaffolding can be a significant part of the cost of any stack work. The only way to know the cost for your home is a site visit and a written quote. Our guide on how to read a builder's quote explains what a quote should include.
Frequently asked questions
Do I need Building Regulations approval to remove a chimney breast?
Usually, yes. Removing a chimney breast is normally treated as structural work, and Building Control will want to see how any masonry above is supported.
Can I remove the chimney breast and leave the stack?
Often yes, but the stack and any breast above must be properly supported, usually with steelwork designed by a structural engineer.
Why is my chimney breast damp?
Common causes are rain getting in at the top of the stack, failed flashings, condensation in a capped flue that is not ventilated, or salts in the brickwork. Find the cause before choosing a repair.
Need help with a chimney in Cornwall? Talk to us
Cornish Building Company carries out structural alterations, repairs and renovation work across Cornwall. See our property renovation and stone, rendering and lime work services, our builders in Cornwall page and our areas we cover. Call us on 01208 816991 or contact us to talk through your project.
