Conservation and repair of an historic lime render – Gloucestershire.

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The render probably dated from the 19th century. It had replaced an earlier render, traces of which were present here and there. Traces of coloured limewash on the quoins suggested that at one time the quoins were left unrendered as a feature element. The render now covers all the masonry except, of course, for the mullions, although during the project a small window was found beneath the render. The render was generally sound, although there were some loose sections totalling about 20 square metres, in addition there were a few long cracks associated with historic settlement. There was another 20 metres or so of cement based roughcast patches. The whole render was very grimy with a lot of lichen. The first task was power washing to remove the lichen and grime, the washer is not over powerful but enough to dislodge any defective render along the way. All the cement patches were removed and work began on repairing the exposed rubblework. The next task was to apply the first coat of lime render. Mild hydraulic lime was used mixed with a generous amounts of animal hair. The cracks were gently widened and filled with lime mortar. Numerous amounts of nail holes were filled as well as the narrow cracks on the extremities of the render. There were some areas of severe lichen encrustation that couldn’t be removed. These were keyed up to coated with a very well haired roughcast mix. The repairs were roughcast, allowed to set and then given five coats of limewash. The first two coats were unpigmented – the white contrasted well with the black nail and bee holes allowing us to do further filling. Once again a coat of white was applied. A coat of yellow ochre based limewash was applied all over for approval. The client felt that the bold colour was too much and so A fresh batch was prepared with the required modifications, this new colour was felt to be much better and so the fourth colour was applied. The difference in colours, the first colour on white and the second yellow on the first allows one to see what’s been limewashed and what hasn’t, applying the same colour again often to leads to areas being missed or inadequately coated. The render was now thoroughly coated with four layers of limewash, with the colour now approved the final coat was applied. This final coat was easy to apply because every hole had been filled and the rough texture of the roughcast had been reduced to a much more homogenous and gentle texture. The final touch was the repair of the window masonry and the subsequent limewashing of the stone in a contrasting colour. Mixes: Repair mortar for the render – 1 part lime to 2.5 parts sharp sand Reinforced with animal hair. Crack filling – 1 part lime to 1.5 parts fine sand. Limewash – undercoats Lime putty, water, Reinforced with chopped hair, fine polypropylene fibre and silver sand for the first two coats Limewash – Final coats Lime putty, water, yellow ochre and raw umber, tallow.

About byrnesurfaces

conserver and repairer of historic surfaces
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