Troubleshooting Guide - Lime Plaster/Render
Background showing through - Usually only a problem externally, most notably following rain on high suction backgrounds such as blockwork or porous red brick. The render has not been applied at sufficient depths.
Resolution: Ty-Mawr products use the highest quality British quicklime, and are produced under the strictest of conditions in accordance with ISO9001:2000. It must be remembered that the carbonation of lime is a very simple chemical reaction and there is very little to go wrong with it, problems are usually caused by the inappropriate selection or use of materials.
As well as providing training courses and producing the instructional ‘The Lime Handbook’, Ty-Mawr does provide an on-site supervision and advice service that can be requested.
The recommended build-ups for various backgrounds as recommended by the manufacturer should be followed at all times as these have been developed so that the plaster/render can perform correctly. Either the render will need to be removed and replaced with a render at sufficient depths in order to combat this problem. Or a more cost-effective solution would be to paint the render with breathable silicate paint. These are traditional paints that are a hard-wearing alternative to limewash, they are waterproof and yet they are also breathable, so they are compatible with lime renders and traditional solid wall construction.