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The mixer, bunker, gauge boxes and all tools shall be kept clean, and care shall be taken to ensure that fresh plaster is not contaminated with set plaster. 

## 9.1.13.5 Waterproof plaster 

Waterproof plaster shall consist of waterproofing compound, cement and sand mixed in strict accord- ance with the manufacturer’s specification. The water proofing compound shall be a mass product of a repudiated manufacturer and shall be approved by the Engineer. 

## 9.1.13.6 Workmanship 

Plaster shall be of 2 or 3 coats. If plaster is to be applied to smooth surfaces, a dash coat shall be ap- plied as a bonding surface. The dash coat shall be of mush consistency, composed of 1 part Portland cement and 1.5 parts of sand. 

The plaster coats shall be applied according to the thicknesses given below, whereby additional thick- ness, which will be required due to unevenness in the masonry surface, is not included: 

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## 9.1.13.7 Tolerances 

All surfaces shall be true to line, level, plumb and all junctions, angles and arises truly scare. On two or three coat work, the plaster surface shall not show any deviation greater than -+5mm. 

## 9.1.14 Rendering 

## 9.1.14.1 Rendering with plain finish 

Plain finished rendering shall be carried out with 1:5 cement-sand in two or three coats. Three coat work shall be carried out on metal latching and on other backgrounds which the Engineer determines by inspection to be too uneven to permit two coat work. 

Rendering applied to external walls shall contain a waterproofing agent to the approval of the Engi- neer. Undercoats shall not exceed an average thickness of 10 mm and finishing coats shall have a thickness of 8 mm to 10 mm. Three coat rendering shall have a total thickness of 35 mm. 

Where rendering is to be applied to surface of concrete or block work, such surfaces shall be treated by a means approved by the Engineer to provide a mechanical key for the rendering. 

Where dissimilar wall backgrounds meet to form a continuous surface, a 150 mm wide strip of ex- panded metal shall be fixed over the joint between the dissimilar surfaces before the first undercoat is applied. 

Surfaces shall be cleaned of all residual mould, oil, dust, loose particles and other deleterious material before rendering work begins. 

Each undercoat shall be combed or scratched to provide a key for subsequent coats as soon as under- coat has set firm. 

