Lime plaster guide

Updated November 2026

Lime plaster is the traditional wall finish of British buildings, used for centuries before gypsum and cement became common in the 20th century. If you live in a house built before around 1919, there is a good chance its walls were originally plastered in lime, and understanding how it works can save you from expensive damp problems later.

What is lime plaster?

Lime plaster is a mix of lime, sand and water, often with animal hair added to strengthen it. The lime itself comes from limestone that has been burned and then slaked with water. SPAB explains that, once it is applied, lime hardens by taking carbon dioxide back from the air and turns chemically back into the same material as the original limestone, which is why it is described as the lime cycle.

Non-hydraulic and hydraulic lime

• Non-hydraulic lime, often used as lime putty, comes from relatively pure limestone and hardens only by carbonation. SPAB notes that lime putty gives a more workable mix.
• Natural hydraulic lime, sold as NHL 2, NHL 3.5 and NHL 5, contains natural impurities that let it set partly with water, so it sets faster and harder. The higher the number, the stronger it is.

For internal plaster on old walls, the 2006 Building Conservation Directory guide by Tim Ratcliffe advises that hydraulic limes should generally be avoided, and non-hydraulic lime remains the traditional choice.

Why lime suits older homes

Older solid walls manage moisture differently from modern cavity walls. SPAB’s technical advice note on the need for old buildings to breathe explains that older walls rely on moisture that has soaked into them being able to evaporate from the surface. Historic England also describes traditional construction as predominantly semi-permeable.

Lime plaster works with this. It is porous and slightly flexible, it lets moisture pass through, and, as Historic England notes, hairline cracks in lime can partly heal themselves. Mid Suffolk District Council’s 2024 guidance on renders and plasters describes cement and gypsum, by contrast, as impermeable and rigid, and unsuitable for most pre-1919 buildings.

Lime plaster against gypsum plaster

	Lime plaster	Gypsum plaster
How it sets	Slowly, by absorbing carbon dioxide over weeks	Quickly, in minutes to hours
Breathability	Vapour permeable	Much less permeable
Flexibility	Slightly flexible, small cracks can partly heal	Hard and rigid
Best for	Pre-1919 solid walls, lath and plaster, listed homes	Modern homes and plasterboard
Drying before decorating	Usually four weeks or more	Often one to four weeks
Typical cost per m²	£50 to £100	£25 to £40

Costs from Homebuilding and Renovating (June 2025) and BestBuilders (September 2026).

Why gypsum and cement can cause damp in old walls

SPAB’s advice note explains that if dense plasters are used inside, moisture is prevented from evaporating, which it links with higher damp levels and salt damage. In practice, a solid wall that has been replastered with gypsum or rendered in cement can trap moisture, so it shows up as damp patches, peeling paint or blown plaster, often at the edges of the newer material.

That does not mean every bit of gypsum in an old house must come out, but it is worth fixing the cause of any damp first, as SPAB advises, and using lime for repairs on solid walls.

How lime plaster is applied

Traditional internal lime plaster usually goes on in three coats:

1. Scratch coat, no thicker than about 15mm, scratched to give the next coat a key. On laths, hair is added for strength.
2. Floating coat, also up to about 15mm, which straightens the wall.
3. Finishing coat, between about 2mm and 5mm, trowelled smooth.

Tim Ratcliffe’s guide says the scratch coat usually needs about two weeks to firm up before the floating coat, and sometimes up to four, with about a week or so before the finishing coat.

Curing and protecting lime

Lime must not dry out too fast. Tŷ-Mawr advises keeping it damp for at least seven days after application, protecting it from frost, wind, rain and direct sun, and avoiding lime work when temperatures are likely to fall below 5°C for long periods. Hessian that can be wetted down is often used, and Ratcliffe warns against dehumidifiers.

Painting lime plaster

Painting lime plaster is one of the most searched questions about it, and the answer is simple: use a breathable paint and give it time.

• Wait. Homebuilding and Renovating suggests at least four weeks for lime to cure fully. Tŷ-Mawr suggests four to six weeks before clay paints and four to eight weeks before silicate paints on fat lime plasters.
• Limewash is the traditional option and can go on while the plaster is still green, although Tŷ-Mawr says this is not advisable with dark pigments such as olive, strong red and blue.
• Clay paints and other breathable mineral paints are good modern options.
• Avoid standard emulsion, which Homebuilding and Renovating notes typically contains vinyl or plastic that will seal the lime plaster.

For painting new gypsum plaster, see our separate guide to painting new plaster.

How much does lime plastering cost?

Lime plastering costs more than gypsum because it takes more coats, more time and more care. Recent national guides give these figures:

Source	Lime plaster cost
Homebuilding and Renovating, June 2025	£70 to £100 per m²
BestBuilders, September 2026, including VAT	£50 to £90 per m²
MyJobQuote, August 2026	Around £50 per m²
Homebuilding and Renovating, 2023 plasterer’s quote for hacking off, new laths and three coats	£190 to £220 per m²

Our own guide price for lime plastering in Brighton and Hove is £600 to £1,200 and up per room. The final price depends on whether we are repairing or fully replastering, the condition of the wall or laths underneath and how much old gypsum or cement has to come off first.