Lime plaster is a traditional internal wall finish used for thousands of years and still valued today for its natural benefits, especially in older and period homes. Modern gypsum and cement plasters are now more common, but lime plaster remains a popular choice thanks to its breathability and durability.
However, plastering walls using lime plaster isn't the same as more modern methods. It is more specialist and can't be finished in the same way as other plasters. Here, we aim to answer all your questions about lime plaster.
Matt Clare is the owner of Gower Plastering Services. He is a hands-on plastering contractor with over 15 years' experience across all aspects of internal and external plastering in South Wales - including work with lime plaster on period and heritage properties.
What is lime plaster?
Lime plaster is a traditional mortar used to cover the surfaces of internal walls and ceilings before painting. Matt Clare, owner of Gower Plastering, goes into more detail: “Lime plaster is a traditional building material made from lime (calcium hydroxide), an aggregate such as sand, and water.”
He adds, “It's been used for thousands of years and remains the preferred choice for heritage, period, and natural-build projects due to its flexibility and breathability.”
There are various types of lime plaster, with the most common types listed below.
Hot lime/non-hydraulic lime plaster
Made from lime putty, this is the most traditional form of lime plaster. Clare explains further, “Made from lime putty, this is the most traditional form. It's highly flexible and breathable, ideal for older or historic buildings.”
He continues, “It cures slowly through carbonation - absorbing CO₂ from the air - and must be applied in thin coats with sufficient drying time between each.”
Natural Hydraulic Lime (NHL)
Clare says, “This sets via a chemical reaction with water, making it more suitable for damp or exposed environments.” He adds, “It comes in different strengths - NHL 2, NHL 3.5 and NHL 5 - with higher numbers indicating a harder, faster-setting mix. NHL 3.5 is the most commonly used for general plastering work.”
Lime render
As the name suggests, this is typically used externally. Clare explains why, “Lime render allows walls to breathe and move without cracking - particularly important on older stone or brick buildings.”
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How to identify lime plaster
If you live in a house that was built before 1919 it is likely to have been plastered using lime — although just because your house may have been built later than this it doesn't mean lime won't have been used.
Lime plaster is usually an off-white colour (as opposed to pinkish as with gypsum-based mixes.)
When trying to identify your plaster type, check for the presence of sand and hair — both tend to be good indicators of lime plaster, as is the finish being soft to the touch and obviously old.
If you have lath and plaster, cob or solid masonry walls it will be likely that lime plaster has been used.
Reasons to use lime plaster
There are many advantages of lime plaster, and although it has largely been superseded by modern gypsum-based plasters, more and more renovators and owners of period properties are realising its importance, although even those building new homes are cottoning on to its benefits. Here, Matt Clare lists the benefits.
- Breathable
Lime is vapour-permeable, allowing moisture to pass through the wall rather than becoming trapped. This is critical in older, solid-walled buildings: sealing them with modern, impermeable materials leads to damp, rot, and structural damage. - Flexible
Lime has a natural flex, meaning it can accommodate a building's settlement movement without cracking, unlike harder modern plasters. - Natural and sustainable
Lime reabsorbs CO₂ as it cures, has a lower carbon footprint than cement or gypsum, and is a wholly natural material. - Durable and long-lasting
When applied correctly, lime plaster is extraordinarily long-lasting. Lime-plastered buildings hundreds of years old often still carry their original internal coats. - Prevents mould growth
Lime's naturally high pH inhibits mould and bacterial growth - a genuine benefit in older or damp-prone properties.
Is lime plaster expensive?
It is generally more expensive to plaster your house using lime plaster than with cement or gypsum plaster.
There are a couple of reasons for this. First, applying the lime plaster takes longer and is more involved, which means higher labour costs, although most plasterers will still charge a standard day rate.
The second reason is that lime products tend to be more expensive to buy than cement. Your final costs will also depend on the type of lime plaster you use.
Lime plaster vs Gypsum plaster
Clare says, “Neither is universally superior; it depends on the building.” He expands on the differences, “Gypsum is the modern standard: it sets quickly, skims to a smooth finish easily, and is cost-effective. It's perfectly suited to modern, cavity-walled, or drylined homes.”
However, Lime plaster is a better choice for older homes, continues Clare, “Lime is the correct choice for pre-1919 solid-walled buildings, stone structures, and heritage properties.”
However, Clare explains why Gypsum isn’t always the best choice in older homes. “Applying gypsum to an old solid wall is one of the most common - and costly - mistakes I see. It traps moisture with nowhere to go, resulting in damp patches, blown plaster, and long-term structural issues.”
He adds, “The core difference is breathability. Gypsum is relatively impermeable; lime lets the wall breathe. For any period home, listed building, or solid-walled property, lime is the right material.”
Lime plaster vs cement plaster
Cement plaster is a mixture of sand, cement and water. Although it is used as an internal finish, it is not as easy to get a smooth surface with cement plaster as with gypsum so sometimes a gypsum plaster will be applied on top.
Compared to cement plaster, lime plaster is again more breathable, flexible and eco friendly. It is also a better thermal insulator and provides an excellent bind with the wall.
On the other hand, cement plaster will set quicker and tends to be a cheaper option, both in terms of purchasing the materials and the labour required.
Modern versions of lime plaster
Several companies out there now produce modern lime plasters that aim to cut down on the curing time. These can often be applied in a single coat, skipping the need for a scratch coat — Solo Onecoat from Lime Green is one such product.
You may also have heard of the current trend for using tadelakt. This is a lime-based plaster commonly used in the Marrakech region of Morocco and is both decorative and waterproof, with a smooth surface that looks a lot like natural stone.
It comes in a range of colours and is ideal in bathrooms where it offers a beautiful yet practical finish on both walls and ceilings. Applying tadelakt plaster is a specialist skill.
Lime plastering isn't easy. DIY or pro?
Like all plastering jobs, it will be far easier and quicker for a professional to apply lime plaster to your walls than to do it yourself. However, a competent DIYer can tackle it, but Clare warns caution, "Technically, a DIYer can plaster, yes, but I'd urge caution."
He adds, "Lime has a longer open time, requires careful mix ratios, and is sensitive to drying conditions - direct sun, frost, or strong wind can all cause failure."
If you do decide to DIY lime plastering, Clare says stick to small jobs, "For small repairs, a competent DIYer can have a go, but always start on a small, inconspicuous area.
However, beyond small jobs, Clare says call in a professional, "For a heritage property, listed building, or any significant area of work, use a specialist lime plasterer. It's a skilled trade and the consequences of getting it wrong are expensive to put right."
It can be difficult to find plasterers skilled in lime plastering, but they are out there — so be sure to get trusted recommendations before hiring.
How lime plaster is applied
Lime plaster is usually applied using a three-coat system that involves building up thin layers over time, allowing each to set before the next is applied.
Clare explains how it is applied, “The first cost is a scratch coat.” He continues, “ It is applied directly to the substrate (stone, brick, or lath) and scratched while wet to create a mechanical key. This is a coarser, stronger mix.”
The second coat is known as a Float coat, shares, Clare, “A finer second coat is applied once the scratch coat has cured sufficiently. This builds out the wall and levels the surface.” The final coat is the finish coat. Clare shares what this is: “The finish coat is a fine lime putty mix worked to a smooth or textured finish.”
One important point to note is drying times shares Clare, “Crucially, each coat needs adequate drying time - you cannot rush lime the way you can with gypsum. Depending on conditions, you may have to wait days between coats.”
Depending on conditions, the scratch and float coats can take over a week to dry. The finish coat is typically quicker.
Previously the DIY content editor for Homebuilding & Renovating Steve is a keen DIYer with over 30 years of experience in transforming and renovating the many homes he has lived in. He specialises in painting and decorating, but has a wide range of building skills.
Paint to use on lime plaster
It is pointless to plaster your walls with beautiful, natural, and breathable lime plaster only to cover them with a non-breathable paint. That's why it's important to choose a paint or finish that works well on lime plaster when painting over lime plaster. Using standard emulsions or oil-based paints traps moisture, leading to plaster problems. https://www.homebuilding.co.uk/advice/painting-over-lime-plaster
DIY expert Steve Jenkins says, “You need to use a breathable, vapour-permeable paint to paint lime plaster. And make sure that the plaster is completely dry/cured before painting. This can take weeks or even months, depending on conditions.”
Lime wash is a very traditional way to finish lime plaster. It adds colour while also protecting the wall beneath. It has microporous, alkaline properties that can deter algae growth, and many conservation specialists recommend it.
However, points out Jenkins, “Lime wash can be maintenance heavy. You need to add multiple layers, as it often needs reapplication after a few years. Personally, I suggest you use a breathable paint, as it's easier to apply and offers a wider range of colours to choose from.”
Matt Clare recommends Keim Optil Interior Mineral Paint (available from Rawlins), "This is part of the Keim silicate range, widely regarded as the gold standard for lime and masonry surfaces. It chemically bonds to the substrate, is completely vapour-open, and won't peel or flake. A premium product, but worth it for heritage interiors."
FAQs
How do I prepare walls for lime plaster?
If you are using a professional plasterer to apply your lime, they may well carry out wall preparation for you. However, it can save you money to do this job yourself.
If the wall is solid stone or brick, remove any old or loose lime plaster, along with all dust and loose material. If some old plaster is still in good condition it can often be left in place.
If your walls are made from timber laths, remove broken laths and replace them and get rid of old, loose plaster.
If you want your new lime plaster to match any old plaster that you are retaining you should ask your specialist to match it as closely as possible.
Once walls are clean and ready they are usually sprayed with a fine mist of clean water.
How long does lime plaster take to set?
Lime plaster is usually applied using a three coat system and each coat must be left to dry out before the next can be applied — although the initial 'scratch coat' should only take around 10 days to set, it can take up to three or four weeks in some conditions.
The next coat usually takes another 10 days to set and the final coat around four days.
If lime plaster adorns your walls, you can leave it natural or consider limewashing for a complementary finish. Also, check out our bedroom ideas and feng shui bedroom layout suggestions for a dreamy sleep spot.
