What Is Lime Render

05/08/2022

The first layer of lime plaster or similar material is put to the exterior surfaces of traditionally constructed stone or brick structures as “lime render.” Because lime is porous, it enables the absorption and evaporation of moisture, allowing the building to “breathe”. 

What is ‘lime’?

The main components of lime, an inorganic calcium-containing substance, are oxides and hydroxides, typically calcium oxide and/or calcium hydroxide. As a byproduct of coal seam fires and in altered limestone xenoliths in volcanic ejecta, calcium oxide is also known by this term. Lime is a mineral with the chemical formula CaO, according to the International Mineralogical Association. The meaning of the word “lime” derives from its early use as mortar in construction.

How is lime classified? Are there different types of lime?

Lime used in construction can be either natural or synthetic, and it can be generally categorised as “pure,” “hydraulic,” or “poor” lime. Lime can also be further classed based on its magnesium concentration, such as dolomitic or magnesium lime. Lime is actually used for a variety of purposes, including lime mortar, lime plaster, lime render, lime-ash flooring, tabby concrete, whitewash, silicate mineral paint, and several sorts of limestone blocks. How different forms of processed lime are used depends on their individual characteristics. Roman concrete was created using two different types of lime mortar, allowing the Romans to revolutionise buildings, often known as the Concrete Revolution.

How did the Romans make concrete?

Lime and volcanic ash were combined to produce concrete by the Romans using a pozzolanic process. If this were combined with volcanic tuff and submerged in seawater, the exothermic reaction of the seawater hydrating the lime cemented the mixture.

What does lime render do?

Sand, water, cement, and lime are usually the main ingredients in renders. This mixture is typically made up of 6 parts sand, 1 part cement, and 1 part lime (6:1:1). However, the sand that is utilised must be clean and have a fine texture. Plastering or rendering sand is the ideal kind of sand to utilise. Sand with a somewhat finer texture is typically utilised as the top layer, with coarser sand serving as the foundation layer. 

Lime is added to the mixture to make it more elastic and keep it from cracking after it dries. Hydrated lime is the best type of lime to utilise while rendering.

How do we apply lime render?

To make sure that everything is blended well, the render mix’s components should be combined in a cement mixer. Use a trowel to apply the mixture in thin, even layers. To achieve a pleasing finish, a finishing wash or topcoat can be softly applied with a sponge, trowel, or brush.

We never make the rendering mix stronger than the material to be rendered is a straightforward rule to follow. The render will fracture as a result of the wall’s inevitable contraction and expansion, which will cause the wall to slide. The use of too much cement also contributes to render damage by causing it to shrink back and break.

 

Lime render is often used on listed buildings, as it is a traditional building material, used for hundreds of years on British and Cornish homes. If your listed building is in need of a new coat of lime render, get in contact with us to sort that out today!