Draught-Proofing Period Homes Without Causing Damp

Why Period Homes Need a Gentler Approach to Draught-Proofing

If you live in a Victorian terrace, a Georgian townhouse, or a stone-built cottage, you will know the charm of original features — and the chill of a winter draught. It is tempting to reach for the mastic gun and seal every gap you can find. But in an older property, a blanket approach to airtightness can create far worse problems than a cold neck. Trapped moisture leads to damp patches, peeling plaster, and eventually rotten timbers. The key is to balance draught-proofing with breathability and ventilation, so your home stays warm without becoming a sealed box.

How Old Buildings Manage Moisture

Period homes were constructed with materials that absorb and release moisture — lime plaster, soft brick, stone, and timber. They rely on air movement through gaps and porous surfaces to dry out. When warm, moist air from cooking, bathing, and breathing meets a cold surface, it condenses. In a breathable building, that moisture can evaporate away. If you seal all the gaps with modern impermeable materials, you trap that moisture inside. Over time, it soaks into walls and floors, causing damp and mould. So the goal is not to make your home hermetically sealed, but to control where air leaks and ensure moisture can still escape.

Where to Seal and Where to Leave Alone

Targeted draught-proofing means focusing on the gaps that cause uncomfortable draughts without blocking essential ventilation paths.

• Windows and doors: These are the biggest culprits. Use brush or wiper seals for sash windows, and draught excluders for letterboxes and keyholes. For casement windows, fit self-adhesive foam or rubber seals. Avoid silicone sealant around the frames unless you are sure the frame is not designed to breathe.
• Floorboards and skirting: Gaps between floorboards can let in cold air. Push flexible, breathable draught strips between boards, or use a rug. Seal skirting boards to the floor with a flexible acrylic sealant, not silicone, so any moisture in the wall can still evaporate.
• Chimneys: An open chimney is a huge heat loss. Fit a chimney balloon or draught excluder, but remove it when you light a fire. Never block a chimney that is in use.
• Air bricks: These are essential for ventilating sub-floor voids and preventing rot. Never cover or seal them. If you have a suspended timber floor, keep air bricks clear.

Choosing Breathable Materials for Draught-Proofing

The materials you use matter as much as where you use them. Breathable, vapour-permeable products allow moisture to pass through while blocking draughts. Look for natural fibres like sheep's wool, hemp, or flax for draught excluders. For sealants, choose acrylic or silicone-free options that remain flexible and allow walls to breathe. Avoid polyurethane expanding foams around windows and doors — they can crack masonry and trap moisture. For temporary seals, such as around sash windows, use silicone-free weatherstripping. If you are sealing gaps in a lime plaster wall, use a lime-based filler rather than cement or gypsum. Remember: if a material is airtight and waterproof, it is probably wrong for a period home.

Ventilation: The Essential Counterbalance

Even with careful draught-proofing, you need controlled ventilation to remove moisture at source. This is not about leaving windows open all day; it is about providing consistent background air changes.

• Trickle vents: If you replace windows, ensure they have trickle vents. If you have original windows, consider fitting discreet slot vents in the frame or wall.
• Extractor fans: Fit humidity-controlled extractors in bathrooms and kitchens. They should run on a timer or humidity sensor, not just when the light is on.
• Passive vents: In older properties, air bricks and chimneys provide passive ventilation. Do not block them. If you need more, consider a positive input ventilation unit in a loft, which gently pushes filtered air through the house.
• Everyday habits: Open windows briefly when cooking or showering, use lids on pans, and dry laundry outside or in a ventilated space. Small changes add up.

Common Mistakes That Lead to Damp

Even well-intentioned draught-proofing can go wrong. Here are the pitfalls to avoid.

• Sealing air bricks: This blocks sub-floor ventilation and can lead to timber rot. Leave them alone.
• Using silicone on old walls: Silicone is waterproof but not breathable. It traps moisture, which then finds another way out — often through your plaster. Use acrylic or lime-based sealants instead.
• Over-sealing one room: If you make a bedroom airtight but leave the bathroom door open, moisture migrates. Treat the whole house as a system.
• Ignoring gutters and drains: External water is the biggest cause of damp. Before you seal a single gap, check that gutters, downpipes, and drains are clear and water is directed away from the walls.
• Forgetting humidity: Aim for 40–60% relative humidity. A cheap hygrometer will tell you if you need more ventilation or less draught-proofing.

Getting the Balance Right

Draught-proofing a period home is not about making it airtight; it is about making it comfortable. Seal the gaps that cause cold draughts, but preserve the breathability that allows moisture to escape. Choose materials that work with your building, not against it. And always keep ventilation in mind — a home that can breathe is a home that stays dry. If you are unsure, start with the biggest draughts and monitor for condensation. A little patience and the right approach will keep your period property warm, dry, and full of character for years to come.