Key Takeaways
- Period homes are breathing structures: solid walls, lime mortar, no cavity, often no working damp proof course. That is the design, not a defect.
- Around 85% of pre-1919 homes have solid walls, and 65% of homes in Kensington and Chelsea predate 1919, the highest share of any London borough (BRE; VOA Council Tax stock of properties, 2025).
- Cement pointing, cement render, gypsum plaster and vinyl emulsion cause most of the damp we find in period homes. All four were added later.
- Secondary glazing runs £312 to £520 per window and internal wall insulation £40 to £100 per m² (MyJobQuote, Checkatrade and GreenMatch, 2026).
- A full rewire of a three-bed London house is £7,000 to £9,000, against £5,000 to £8,000 nationally (MyBuilder and MyJobQuote, 2026).
- Confirm listed and conservation status first. Working on a listed building without consent is a criminal offence, not a planning breach.
From Georgian townhouses to Edwardian villas, London's period homes are some of the most desirable in the country. Renovating one rewards a careful, knowledgeable approach that respects how these buildings were made. Here is how to do it well.
Why period homes are different
They were built to manage water by absorbing it and letting it evaporate, not by keeping it out. A pre-1919 house has solid walls, usually two leaves of brick bonded together at around 215mm with no cavity, bedded in lime mortar deliberately softer than the brick. Rain soaks into the outer face and dries back out through the joints. There is no membrane, no insulation layer and frequently no working damp proof course, and none of that is a fault.
Modern construction does the opposite: a cavity, a physical barrier, sealed junctions. Apply modern thinking to a breathing wall and you get damp, and that one misunderstanding sits behind most of the failed renovations we are called in to put right. Around 85% of pre-1919 homes were built with solid walls, and London carries a heavier concentration of that stock than anywhere else: 65% of homes in Kensington and Chelsea predate 1919, the highest share of any London borough.
Sources: BRE domestic energy stock analysis; Valuation Office Agency, Council Tax: stock of properties by build period, 2025.Which period is your house, and why does it matter?
Because the era tells you what is behind the plaster before you open it up, and what has most likely failed.
| Period | What you typically find | What usually needs attention |
|---|---|---|
| Georgian, 1714 to 1837 | Solid brick, lime mortar, sash boxes behind the reveal, run plasterwork, often four storeys over vaults | Historic movement, decayed sash boxes, cement repairs, lower ground floor damp |
| Early to mid Victorian, 1837 to 1875 | Nine-inch solid walls, suspended timber floor, lath and plaster, slate on softwood with no felt | Rot at joist ends, blocked airbricks, cement pointing, services long past their life |
| Late Victorian and Edwardian, 1875 to 1918 | Same fabric, larger rooms, bay windows, a rear closet wing and side return | Bay settlement, leaking closet wing junctions, slipped slates, single glazing |
Which materials are right, and which cause damage?
Anything vapour open is right; anything that seals the surface is wrong. Get this table right and most period damp problems never start.
| Element | Right for a solid wall | What goes wrong |
|---|---|---|
| Pointing | Lime mortar, hand raked to twice the joint width, matched for colour and aggregate | Cement is harder than the brick, so moisture leaves through the brick face and it spalls in the first hard frost |
| External finish | Bare brick, or lime render where render is original | Cement render cracks, water gets behind it and cannot dry out |
| Internal plaster | Lime plaster, or a breathable insulating plaster on cold walls | Gypsum on a wall still carrying moisture blows off and brings salts with it |
| Paint | Limewash, clay or mineral silicate paints | Vinyl emulsion and most masonry paints seal the last escape route |
| Ground floors | Suspended timber with clear airbricks, or a breathable limecrete build-up | A sealed slab poured wall to wall pushes ground moisture sideways into the walls |
| Insulation | Wood fibre, cork or other vapour open systems, detailed by a specialist | Foam boards and spray foam trap moisture against cold structure and hide the decay |
Suspended timber floors and airbricks
The ground floor is timber over an open void, and it stays sound only while air keeps moving through it. Airbricks let that air in, and later work blocks them constantly: a raised patio buries them, render is run over them, insulation is packed against them from inside. External ground level should also sit at least 150mm below the internal floor, because moisture then bridges into the wall and gets treated as rising damp. Our guide to damp causes and fixes works through the diagnosis.
Upgrading the services without wrecking the fabric
Most period homes need everything renewed: a full rewire, new plumbing, an efficient heating system and better insulation. A three-bed rewire is £5,000 to £8,000 nationally and typically £7,000 to £9,000 in London, and it is notifiable work under Part P of the Building Regulations, certified by the registered electrician who does it.
The skill is in the routing, not the wiring. You cannot chase a nine-inch solid wall like a modern partition without losing plaster you then have to replace in lime. On period jobs we run circuits under lifted floorboards and in skirting voids, drop feeds from above rather than cutting up from below, and keep chases out of walls carrying original plasterwork entirely. Do it in the right sequence and it disappears; do it after plastering and you pay twice. Our list of the signs you need to rewire covers what to look for.
Sources: MyBuilder and MyJobQuote house rewiring cost guides, 2026; Approved Document P, Building Regulations, gov.uk.Can a period home be made energy efficient?
Yes, and the order matters more than the products. Draughts and uninsulated lofts lose far more heat than single glazing does, at a fraction of the cost to fix.
- Draught-proofing and loft insulation first. Cheapest per degree gained, and no moisture risk.
- Floor insulation while the boards are up. Worth doing only during a renovation, and never at the cost of blocking the airbricks.
- Secondary glazing or a sash overhaul. Secondary glazing runs £312 to £520 per window, about £3,120 for a three-bed, and changes nothing externally, which is why it is accepted in conservation areas and listed buildings. See our sash window guide before replacing anything.
- Wall insulation last, and only with advice. Internal wall insulation costs £40 to £100 per m², roughly £8,000 to £15,000 for a semi. It works, but it moves the dew point inwards, so a solid wall needs a vapour open build-up and careful detailing at joist ends and reveals.
Respect the features
Keep whatever is expensive or impossible to reproduce, which is most of it: fireplaces, cornicing, ceiling roses, sash windows and their shutters, panelled doors, balustrades and encaustic tiled hallways. Cornice buried under twenty coats of paint can be softened and cleaned back rather than ripped out and replaced with a machine-run copy that never quite matches. A blocked-up fireplace should be reopened and vented even if you never light it, because a sealed flue with no airflow reliably produces condensation and staining. What is not worth keeping is the later damage: artex over lath and plaster, hardboard over floorboards, 1980s aluminium windows in Victorian openings. In a listed building, removing original features without consent is an offence.
Check the status first
Before you design anything, confirm whether the home is listed, in a conservation area, or covered by an Article 4 direction removing permitted development rights. Those three decide what is possible, and finding out afterwards is how projects stall. Listed building consent covers anything affecting the character of the building, inside as well as out, and is administered separately from planning permission. Removing an internal wall is a Building Regulations matter rather than planning, unless the house is listed, in which case it also needs listed building consent. Either way the structural engineer we appoint designs the beam, building control inspects and signs it off, and where the steel bears into a shared wall you serve a party wall notice as building owner. Our load-bearing wall removal service covers how that runs on a period house, and the staircase renovation guide covers the other original feature most owners want to keep.
Then use trades who have actually worked on traditional construction, because the wrong materials do damage that takes years to show and costs more to reverse than the original work cost to do. GS Renovation specialises in period property, structural alterations and home renovation across London. For a free assessment, contact us or call 07472 424 226. See also renovating a Victorian terrace and the full house renovation cost guide.