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The lime putty, when mixed at a 1:3 ratio, fills these voids to create a compact mortar. Analysis of mortar samples from historic buildings typically indicates a higher ratio of around 1 part lime putty to 1.5 part [18] aggregate/sand was commonly used. This equates to approximately 1 part dry quicklime to 3 parts sand.
Lime render is the first coat of lime "plaster or the like" [1] applied to the external surfaces of traditionally-built stone or brick buildings. It allows the building to 'breathe' – as lime is porous, it allows for the collection and evaporation of moisture .
It is usually not recommended to replace more than 20% of the lime content with cement when rendering the facade, and it is a matter of contention whether adding any concrete is ever appropriate in order to maintain the benefits of lime over concrete. Lime plaster is permeable and allows for the diffusion and evaporation of moisture.
Mixes for renders were patented, including a "Water Cement, or Stucco" consisting of lime, sand, bone ash and lime-water (Dr Bryan Higgins, 1779). Various experiments mixing different limes with volcanic earths took place in the 18th century.
In old buildings with walls that shift over time, cracks can be found which allow rain water into the structure. The lime mortar allows this moisture to escape through evaporation and keeps the wall dry. Re−pointing or rendering an old wall with cement mortar stops the evaporation and can cause problems associated with moisture behind the cement.
Some have a polymer additive added to the traditional cement, lime and sand mix for enhanced water resistance, flexibility and adhesion. [9] [10] Acrylic premixed renders have superior water resistance and strength. [11] They can be used on a wider variety of surfaces than cement render, including concrete, cement blocks, and AAC concrete paneling.
Roughcast or pebbledash is a coarse plaster surface used on outside walls that consists of lime and sometimes cement mixed with sand, small gravel and often pebbles or shells. [1] The materials are mixed into a slurry and are then thrown at the working surface with a trowel or scoop.
R-value (insulation) - Radial arm saw - Radiant barrier - Radiator reflector - Rafter - Rainscreen - Raised floor - RAL colour standard - RAL colors - Rammed earth - Random orbital sander - Rapid construction - Ready-mix concrete - Real estate - Rebar - Rebar detailing - Rebar spacer - Reciprocal frame - Reciprocating saw - Red List building ...