Use of Limewash on older buildings

 If you’re looking to refresh your home’s exterior or interior with a breathable and traditional paint finish, limewash application is a great idea. Limewash, a mixture of slaked lime, natural pigments, and water, has been used for centuries to create a beautiful and durable finish on various surfaces, including brick, lime plaster, and lime render.

What applications can lime be used for?

Lime is an extremely versatile building material, that has been used on any building built before the 20th Century. Despite the advances within the paint industry and the vast array of paints available to today’s consumers, there are still many occasions where limewash is the most appropriate decoration for older buildings.

 
Older buildings, pre-1910, often have a solid wall construction, without a cavity and no damp-proof course. This type of construction will always contain varying degrees of moisture and rely on the building fabric, including paints, to allow moisture to migrate freely and escape. 

 
Materials such as cement based mortars and renders, gypsum plaster and emulsion paints, serve to hold moisture captive within this type of building. If the moisture is allowed to accumulate, this can result in deterioration failure.

Limewash preparation

As limewash absorbs into the surface, it works best when applied to more porous substrates, such as lime plaster, clay brick, soft stone etc. While it may appear to adhere to impervious surfaces It’s unlikely that it will provide as durable a coating as the lack of suction will impair its overall effectiveness. To ensure that the lime wash soaks into surfaces effectively, surfaces should be clean and free from grease and vegetable matter, such as lichens etc. All loose and/or flaking material should be removed. Any organic growth should be treated in an appropriate manner, such as using D/2 Biological solution.

Limewash application

It is important that a rule of one coat per day is followed, this allows each coat time to carbonate. Recoating too soon may result in the previous coat pulling away from the surface and can prevent sufficient carbonation.

Apply limewash using a large, long hairbrush. Application should be vigorous, working the wash into the substrate, using horizontal, vertical and diagonal strokes. Limewash must be applied as a thin coat and evenly across the surface. Always apply in a manner where a wet edge is maintained, this will help avoid lines from excess build-up of material. If limewash is applied too thick or heavy, this can result in crazing and cracking, should this occur wash the surface with hot water and a stiff bristle brush (i.e. a churn brush).