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Breathable Exterior Paint

Introduction
 
How to choose a suitable paint which will allow lime render to breathe.
 
People often ask us the following questions with regards to choosing breathable extermal paints.
 
  • I would like to use a limewash but doesn’t it have to be reapplied every year?
  • What is the best paint for a new lime render?
  • Is there a breathable paint that will adhere to new lime render and existing areas of painted cement render?

One way to imagine it, is that a render is like your skin and the paint is what you wear on a rainy summers day: Silicate paint and limewash are like not wearing anything – you get wet but you soon dry. Standard masonry paint is like an old kagool – keeps you dryish but is also a bit sweaty. Silan paint is like a gore-tex jacket – keeps the rain out and keeps you comfortable.

 

Limewash

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Traditionally LIMEWASH was the most common of decorating products for internal as well as external applications.

Limewash in its most basic form is a dilute solution of lime putty. 

Limewash made from hydrated lime is a poor substitute as the finely ground and dried particles have had time to carbonate before being applied to the wall. It therefore creates a limewash that dusts and is easily brushed off.

Natural pigments were often added to colour a limewash on residential buildings but rarely on boundary walls or farm buildings. To increase the durability of the limewash many additives have been used in the past including beeswax, alum, tallow amongst others. Clarified linseed oil has proved to be an excellent additive to improve the water shedding properties, however, the porosity of the limewash is reduced and therefore it is only recommend for external applications.

Limewash is available in 15ltr tubs made from a PURE WHITE LIME PUTTY or an off white CHALK LIME PUTTY which is ideal for the chalk cob walls of the Wessex region. For bare render a minimum of 4 coats is required. Durability: Variable – requires maintenance every 2-3 years.

Silicate Paint

Silicate paint is not a new product - it was invented by a German, Mr Keim around 1900. The paint is however unique in the way it works. Silicate paints do not create a film over the surface of the substrate but chemically bond to it in a process called silification. This ensures that a very high moisture vapour permeability is achieved. Silicate paint can be applied to any mineral surface such as brick, lime or cement renders and has excellent durability lasting 15 years or more. Because of the unique way it works it is important that any existing paint is removed in order for the chemical process to work correctly. We stock EARTHBORN SILICATE PAINT in white and the full range of Earthborn and Keim colours to order. A primer and two coats of paint are usually required.   Coverage rates: 6m2/litre for primer and paint (the paint requires 2 coats) 

Silan Paint

Many old properties have inevitably been extended or repaired with inappropriate materials. The removal of cement based renders or standard masonry paints can sometimes not be possible as to do so may cause more damage to the structure or may be prohibitive for purely economic reasons. All too often a patch repair has had to be over painted with a standard masonry paint in order for a uniformed façade to be maintained. Lime stuff have recently introduced SILAN PAINT FROM MAPEI that is highly breathable but will also cover existing masonry paint. Predominantly known in the UK for their sealants, the Italian firm’s heritage lies in the production of traditional lime based products which still forms a major part of their business in Italy. Silan paint is unlike silicate paint and limewash which chemically bond to any mineral substrate it does create a film like a standard masonry paint. However, the unique benefit of silan paint is that its structure has microscopic holes which allow water vapour to pass through it at a similar permeability rate to that of a silicate paint. Coverage rates: 6m2/litre for primer and paint