Why period homes behave differently

A Victorian or Edwardian house is not simply an older version of a modern one. It was built with solid brick or stone walls, no cavity, lime mortar and plaster, and a deliberate reliance on ventilation and the movement of moisture. The building works as a system: walls absorb rain and release it again, floors and roofs breathe, chimneys draw air through rooms. When you introduce modern materials that seal surfaces and trap water, you interrupt that system.

This is the single most useful idea to grasp before you pick up a hammer. Almost every well-meant "improvement" that causes trouble in an old house, whether cement render, gypsum plaster, plastic paint or an injected damp-proof course, causes trouble because it stops the fabric drying out.

Get to know the building first

Live in the house for a full year if you can before committing to major works. Notice where damp appears after driving rain, which rooms are cold, where floors bounce, how the light moves through the day. Keep a notebook and photograph everything as you uncover it. Commission a survey from someone experienced with historic buildings; a general surveyor may flag solid walls as defective simply because they are not cavity walls. Ask for the reasoning behind every recommendation, not just the verdict.

• Map the original plan and later alterations: extensions, removed chimneys, blocked fireplaces, replaced windows.
• Record original details before they vanish, including mouldings, door furniture, tile patterns and ironmongery.
• Find the source of any damp rather than treating the symptom.
• Check for asbestos in Artex, floor tiles and pipe lagging in anything altered after the 1950s.

Use breathable materials

Choose materials that allow moisture vapour to pass through the fabric. In practice this means lime mortar and lime putty rather than cement, lime or clay plasters rather than gypsum, and mineral or clay paints rather than vinyl emulsion. Modern cement mortar is harder and less flexible than the brick or stone around it, so it traps water, forces it into the surrounding masonry and cracks as the building moves. Lime mortar is softer, slightly flexible, and lets the wall dry.

• Mortar and render: lime-based, matched in strength, colour and texture to the original.
• Plaster: lime or clay, finished with a breathable paint.
• Insulation: wood fibre, sheep's wool, hemp or cork rather than foil-backed boards in older wall build-ups.
• Sealants and repairs: traditional linseed oil putty, limewash and microporous masonry paints.

Repair original features where you can

Sash windows, cornices, panelled doors, skirtings, fireplaces and floorboards are usually worth saving. A well-repaired sash window performs perfectly well, can be draught-proofed with discreet brush seals, and if you need better thermal performance, fitted with slim secondary glazing that leaves the original frames untouched. Replacing them with uPVC is rarely cheaper once you account for the loss of character and the planning complications in a conservation area.

Where timber has rotted, splice in new sections rather than replacing whole items of joinery. Lift and relay floorboards instead of covering them, and insulate beneath suspended timber floors with a breathable material while keeping the sub-floor void ventilated through the existing airbricks.

Damp, insulation and heating

Damp in a period house is almost always a symptom of water getting in or air not getting out. Check gutters, downpipes, high ground levels, cracked render, blocked airbricks and internal plumbing before accepting a diagnosis of rising damp. Injected damp courses are often unnecessary and sometimes harmful. Improving ventilation, whether through discreet trickle vents, extract fans or simply not blocking chimneys and airbricks, solves a surprising number of problems.

Insulate in order of benefit: roof first, then floors, then walls. Internal wall insulation on a solid wall is the riskiest of the three, because it can push the dew point into the masonry and cause interstitial condensation. A moisture-aware build-up, using wood fibre with a lime or clay finish and detailed by someone who understands older walls, is the safer approach. As for heating, size radiators generously and accept that an old house warms up slowly; it was designed around open fires and draughts, not sealed boxes.

Permissions, professionals and budget

If the building is listed, listed building consent is required for internal and external alterations, and unauthorised work can be a criminal offence. In a conservation area you will normally need permission to demolish, and permitted development rights are more restricted than elsewhere. Party wall agreements, building regulations approval for structural, electrical and thermal work, and current building safety requirements all apply to older homes too.

Assemble a team with genuine experience of historic buildings: a conservation-accredited architect or surveyor, a joiner who can splice rather than replace, and a plasterer comfortable working with lime. Budget a contingency of at least 15 to 20 per cent, because old houses hide surprises behind every lath and plaster ceiling. Sequence the work so structural repairs and weatherproofing come before decoration, and accept that doing less, more carefully, will usually serve the building better than a fast full refurbishment.