Old Cornish cottages are full of character: thick stone or cob walls, slate roofs, deep windows and low beams. They were also built very differently from modern homes, and treating them like a modern house is one of the most common causes of damp, decay and expensive repairs. Whether you've just bought a cottage or you're planning a long-overdue update, this guide covers what to look at first and how to approach the work.
How old Cornish cottages were built
Most traditional Cornish cottages have solid walls with no cavity. Depending on the area, they're built from granite, local slate stone (often called killas), or cob, a mix of earth, clay and straw that's common in mid and north Cornwall. Walls were bedded and finished in lime, which lets moisture move in and out. Roofs are usually natural slate, sometimes with older scantle slate laid in diminishing courses.
The key idea is that these buildings were designed to breathe. Moisture gets in, then dries out through the wall faces. Problems usually start when that cycle is blocked.
Damp: the most common issue
Damp is the number one complaint in old cottages, and it's often caused by later alterations rather than the original building. Typical culprits include:
Cement render or cement pointing, which traps moisture in the wall
Plastic or masonry paints on stone or cob
Raised ground levels or paths against the walls
Blocked or leaking gutters and downpipes
Concrete floors laid without regard for moisture
Poor ventilation, especially in kitchens and bathrooms
Chemical damp-proof courses and waterproof tanking are often not the right answer for solid-walled buildings. Fixing the source, lowering external ground levels, improving drainage and replacing cement with lime usually works better. Our guide to lime rendering and pointing for Cornish stone homes goes into more detail, and our stone, rendering and lime work page explains how we approach it.
Roofs, chimneys and coastal weather
A sound roof is the first priority in any renovation. Look for slipped or broken slates, failing ridge and verge mortar, rotten timbers and leaking flashings around chimneys. Chimney stacks take the brunt of Cornish wind and rain, and an unused stack should still be capped and ventilated. In exposed coastal spots, specify fixings and flashings that can cope with salt air. Reusing sound natural slate, or matching it with new natural slate, keeps the character of the building.
Insulation and energy efficiency
You can make an old cottage warmer and cheaper to run, but the materials matter. Non-breathable insulation on solid walls can trap moisture and cause the problems you're trying to avoid. Options that tend to work better include:
Wood fibre or other vapour-open insulation systems
Lime-hemp plasters and renders
Loft insulation with good ventilation
Draught-proofing windows and doors
Insulated floors that manage moisture properly
A whole-house plan is better than piecemeal fixes. Our sustainable building and eco homes page covers energy improvements more broadly.
Windows, doors and joinery
Original timber windows can often be repaired and draught-proofed rather than replaced. If replacement is needed, timber windows that match the original pattern usually suit a cottage best, and may be required if the property is listed or in a conservation area with an Article 4 Direction.
Permissions to check before you start
Before planning work on an older property, check:
Listed status. Many Cornish cottages are listed. Listed building consent is needed for works that affect character, inside or out, and carrying out work without it is a criminal offence.
Conservation areas and the Cornwall National Landscape. These can reduce permitted development rights. See our guide to building in an AONB or conservation area.
Bats. Old roofs and outbuildings are common bat roosts. A survey may be needed before roof or loft work.
Building Regulations. Structural changes, new bathrooms, rewiring and some window and insulation works need to meet Building Regulations.
Planning the renovation
A sensible order is: get a proper survey from someone who understands traditional buildings, fix the roof and keep the water out, deal with drainage and ground levels, then tackle walls, floors, services and finishes. Leaving time between stages for walls to dry out can save trouble later. If you're thinking of adding space, our home extensions and loft conversions pages explain the options.
Cornish cottage renovation FAQs
Should I remove cement render from my cottage?
Often it helps, especially where damp is a problem, but it needs care so the stone or cob behind isn't damaged. Get advice first.
Can I insulate solid stone walls?
Yes, with the right breathable materials and details. The wrong materials can make damp worse.
How do I know if my cottage is listed?
Search the National Heritage List for England on the Historic England website, or check with Cornwall Council.
Is cob difficult to repair?
Cob can be repaired well with compatible materials, but it doesn't like cement or waterproof coatings. Use builders familiar with traditional construction.
Talk to us about your cottage
We carry out property renovations across Cornwall, with care for traditional materials. Call Cornish Building Company on 01208 816991 or get in touch to arrange a visit.
