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External siliacate paints and limewashes

Lime rendered, dashed and limewashed building in north Cumbria undertaken by Lattimer Construction with Jack in the Green

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traditional limewashDevon farmhouse, lime washed by Jack in the Green in 2011

In order for external lime renders to breathe, they need to be painted with mineral paints. Modern plastic based masonry paints-although marketed as being ‘waterproof’-will trap moisture within walls. If water gets behind them, through cracks or due to leaking gutters or other moisture ingress, they will blister and peel off. This page is concerned with external paints, please see our main paint page for advice and details of internal wall paints.

Traditionally, limewash, often mixed with tallow or linseed oil for thier water-repelling properties, has been the only means of coating external lime renders.

Town House in Ulverston, Cumbria, lime rendered, dashed and limewashed with silicate paint lime window reveals and concrete sills Limewash has been used successfully for hundreds of years and recoated regularly forms a durable yet breathable external coating, protecting the underlying substrate from damage. Limewash is susceptible to water damage however and needs to be re-coated every 3 or 4 years. Read more about the properties and use of limewash on our breathable paint page.

Blackwell Arts and Crafts House, Bowness-on-Windermere, was re-painted in lime paint by Jack in the Green in 2011

Lime Paints

Relatively recently, thicker more durable lime paints have become available on the market. Whilst these mean that maintenance is usually needed less regularly they are much more expensive than regular limewash. Unlike limewash these can cover cement mortars but often contain plastic based additives which decrease breathability. Although lime paints are more expensive than limewash, like normal limewash these paints are susceptible to water damage especially in exposed locations so should only be used with confidence in situations where the building in question does not have problems with shedding water.

House near Carnforth lime rendered, dashed and painted with silicate paint by Jack in the Green in 2011

silicate paints

Silicate paints are growing in popularity especially as they are suitable for buildings where low levels of maintenance are a priority. Like limewash, silicate paint is a microporous (breathable) coating system, forming a durable layer of permeable stone. Silicate paints have been used widely and successfully (particularly in Germany) for over 125 years.

mixture of stone and concrete lintels/surrounds painted with silicate paint

Chemically akin to the composition of lime renders and plasters, silicate paint is based on burnt quartz (potassium silicate) and water. When the water evaporates the silicate reacts chemically with the mineral surface (best with lime) and petrifies- turning back into stone. Silicate coatings therefore create a physical bond with mineral substrates and will not peel off. Therefore, silicate paints are extremely hardwearing and durable, resistant to weather and atmospheric pollution. Used externally, silicate paints ‘weather’ extremely slowly from the surface and this ‘chalking’ effectively makes them self cleaning. They are also resistant to fungal & mould growth.

So what kind of surfaces are silicate paints appropriate for? Silicate paints are suitable for all mineral surfaces-lime renders, cement renders, concrete and bare stone. This makes them particularly suitable for buildings where a variety of substrata (for example patched render, stone/cement lintels, window surrounds or sills) need to be painted in one colour. Like limewash silicate coatings have a flat matt finish, almost velvety in texture. Silicate paints are also availble for internal surfaces, see Ty Mawr's website for more details.

Lime rendered wall dashed and painted with silicate paint in Furness, Cumbria, by Jack in the Green in 2011  limewashed render and dash with silicate painted lime window surrounds with concrete sills

Silicate coating systems are based on a three or four coat process, depending on the nature of the substrate. For new renders and clean mineral surfaces, it is necessary to apply a silicate primer, followed by two coats of silicate paint. There are a variety of primers available for different substrata, consult your supplier to find out what’s best for your building. Links to some suppliers are detailed below. Check out the technical datasheets provided by suppliers and manufacturers for more detailed information.

Silicate paints (and their associated priming systems) are much more expensive than traditional limewash. Needing maintenance only after 20-25 years however they last much longer than limewash and even than modern synthetic masonry paints! Considering the price of scaffolding and labour costs of re-coating limewash every 3 or 4 years, even after the initial outlay, silicate paint is a viable alternative to traditional limewash.

This page is meant only for general advice. We do not sell paint and we take no responsibility for the manufacturers or products listed below. Browse the links below, our general/internal paints page and/or look at our links page for further advice from specialist organisations, and for details of useful books. If you'd like further advice, or would like us to do some painting for you, please get in touch via the means outlined below.

suppliers

Mason's Mortar, Edinburgh, Limewashes and Lime paints

Wormersley's external lime and silicate paints

Earthborn silicate paints

Ty Mawr silicate paint range

Mike Wye Associates paint range

Cornish Lime's Beeck mineral paints page


home lime plastering lime and lathwork repair lime pointing paint carpentry suppliers and links
Page last updated by HE 27.11.11
Jack in the Green builders (Devon) is run by Glyn Tyler. For queries regarding painting and limewashing in Devon contact Glyn at jackinthegreenbuilders@gmail.com
or telephone 01884 829584


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