How To Apply Rendering

Rendering is a waterproof barrier to protect the underlying brickwork from the damage caused by damp. If the render coat is damaged, it should be repaired as soon as possible. Repair to a smooth-rendered surface is made with a mortar mix consisting of 1 : 6:1. It may be necessary to apply two layers of mortar if the rendering is more than about lin. (1 .2 cm) deep. To provide good adhesion for the render coat, apply a bonding agent, such as PVA adhesive, to smooth-faced bricks. Rough-faced bricks can be brushed with water.

Shingle finishes/pebble dash. Patching a textured wall finish is carried out in the same way as that for a smooth-rendered surface. A surface deeper than I in. (1 .2 cm) needs two layers. Once the final layer is level with the surrounding rendering, toss the matching pebbles against the fresh mortar. Use a wooden float to press the pebbles or shingle into the mortar.

Roughcasting is a textured finish made up of a mixture of part cement to one part lime, the latter to provide suction, and two parts of pea gravel or shingle. Apply, from a bucket, the mixture to a keyed floating coat. Shingledash differs from roughcast in that the shingle (small stones) is flicked on to a final “butter” coat. First apply a rendering coat, scratched diagonally to give a key for the floating coat. The floating coat consists of one part cement to three of sand, plus a small quantity of PVA bonding agent, applied and combed with a scratcher in horizontal lines. The final “butter” coat consists of part cement, three parts sand and one part lime. “Iron” this on to a depth of about 1. in. (or 6 mm) with a steel trowel. Use the back of a laying-on trowel to flick the shingle evenly on to the surface. Pat the stones gently into the “butter” coat with a clean, dry wooden float.

Tyrolean finish is applied with a handheld machine containing a mix of Portland cement and aggregate which you can obtain bagged. One bag mixed with half a bucket of water gives the correct consistency. Pour the mixture into the machine a little at a time. Then point the machine at the surface and crank the handle. Keep the machine moving to avoid a build-up of the spray in one area. Three coats are normally needed. Work the first coat diagonally downwards at an angle of 45 deg from right to left. Apply the second similarly but from left to right. Apply the final coat working vertically from the bottom of the area upwards.

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