Using lime renders
The cement rich mix is significantly harder than most substrata to which it is applied and very much less breathable than the original lime based renders and bedding mortars. By sealing the structure with a cement based render, normal evaporation is constrained or sometimes prevented.
Any moisture penetration through the cement render due to driving rain, cracks and faults in the cement render will be retained by the softer underlying material. Once the underlying material reaches saturation point, be it brick or stone, the moisture will seek the path of least resistance, which is usually through the internal wall of the structure. This can lead to severe deterioration of internal renders and decoration. It can also cause serious damage to structural timbers, flooring and other elements of the building.
Due to the differing strengths and porosity between the cement render and the brick or stone substrata, a build up of moisture at the interface can also cause delamination of the render during periods of freezing. The delamination cannot always be seen from a visual inspection and is usually only picked up during a hammer testing survey. The hammer test will establish the extent of the damage.
In most situations it is wise to remove all of the cement based render, repair the underlying masonry and re-render in an appropriate lime mortar.
Lime render is a sacrificial finish which is intended to protect poor quality brick or stone which may be porous or subject to prevailing weather condition.
Lime rendering is a highly specialised element in the trade of plastering, and requires experienced tradesmen familiar with all aspects of the application process. At Magee Conservation we have the experienced tradesmen who have devoted the time, effort and training into this element of their trade.
Should you have a requirement for lime rendering contact our office for a quotation.
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