Lime Plastering

Why lime plaster matters in a period Surrey home

Lime plaster is vapour-open: it lets moisture pass through the wall and evaporate away, which is how solid-walled period buildings stay dry. Gypsum plaster and cement render block that movement, trapping moisture in the wall — where it rots embedded timber, feeds damp patches and spalls the faces off soft handmade brick.

The damage is slow and expensive. We're regularly called to cottages where a 1980s re-plaster in gypsum under vinyl emulsion has left the base of every wall damp, the skirtings soft and the brickwork behind crumbling — walls without damp-proof courses always carry some moisture, and the hard coat stopped the wall shedding it. Much of our damp and replastering work in older properties is exactly this: stripping failed modern materials and returning the wall to a breathable build-up. Lime also moves with the building — old houses flex with the seasons, and lime's slight give tolerates movement where brittle gypsum cracks.

Lime putty or NHL: which lime for which job?

Lime putty is non-hydraulic: it sets slowly by carbonation — absorbing carbon dioxide from the air over weeks — and gives the softest, most breathable, most authentic finish for internal work. Natural hydraulic lime (NHL 2, 3.5 and 5) contains reactive clays, sets faster with water, and suits exposed or damp locations.

As a working rule: internal three-coat work on lath, timber frame and soft brick wants lime putty — a coarse haired mix for the scratch and float coats, a fine putty-and-sand set coat. NHL 2 is the gentlest hydraulic lime and earns its place where putty would stay soft too long: cold ceilings, plinths, late-season repairs. NHL 3.5 and 5 are harder and faster-setting, better suited to external work than the inside of a listed cottage. We match your existing plaster — aggregate, hair, coat thickness — rather than defaulting to a bag mix, and put the specification in writing for the house's record.

What does lime plastering cost in 2026?

Three-coat lime plastering in Surrey typically costs £60–£120 per square metre in 2026, depending on the mix, the condition of the backing and whether lath needs replacing. That's two to three times the cost of modern gypsum work — the materials cost more and the coats need days of curing between them.

Where a job lands is mostly about what's behind the plaster: sound masonry taking a straightforward three-coat build sits at the lower end, while re-lathing, consolidating friable backing or matching an unusually thick historic build-up pushes towards the top, and small patch repairs carry a minimum charge. Lime is an investment in the fabric, not a decorating cost — on the listed cottages around Farnham, Godalming and Shere, a correct lime repair protects the structure, satisfies the conservation officer and reads properly on a survey when you sell. A cheap gypsum patch does none of those things and usually has to come off again.

Do I need listed building consent for re-plastering?

Like-for-like repair of lime plaster in a listed building — replacing failed lime with matching lime, on the existing pattern — does not usually need listed building consent. Wholesale stripping, changes of material, or removal of historic fabric such as original lath or decorative plasterwork almost always does. When in doubt, ask the conservation officer first.

The caution protects you: unauthorised works to a listed building are a criminal matter and the liability passes with the house. Our habit is a short written specification — what's failing, what we propose, which mixes — that you or we can put in front of the conservation officer before work starts; in our experience a clear like-for-like proposal gets a quick, friendly answer. Original lath ceilings, in-situ run mouldings and period cornice are part of the listing too, so we repair them in lime rather than ripping out and replacing in modern materials.

How long does lime take to dry — and what paint can go on it?

Lime plastering is slow by design: allow several days between each of the three coats, and several weeks after the set coat for the plaster to carbonate before decorating. Then use breathable finishes only — limewash, clay paints or silicate mineral paints. Vinyl emulsion seals the surface and undoes everything the lime was chosen to do.

The timetable depends on weather, mix and thickness. A putty mix carbonates from the surface inwards and wants patience: gentle warmth and ventilation help, while blasting it with heaters causes shrinkage cracking and a weak, dusty face — we won't compress the cure to hit a decorator's booking. Limewash remains the classic finish, applied in thin coats that bond chemically with the plaster; clay and silicate paints widen the palette with similar breathability. The same logic runs outside the house — a solid-walled cottage wants breathable lime render or roughcast externally, and we handle both sides of the wall.