A Self-Learning Manual - Institution of Engineers Mauritius

A Self-Learning Manual
Mastering Different Fields of Civil Engineering Works (VC-Q&A Method) Vincent T. H. CHU
11. What is the function of cladding in concrete buildings?
Cladding refers to the external layer of the building which provides the
aesthetic effect. Apart from the external appearance of the building, the
main use of cladding is to protect the building structure from weather in one
of the following ways:
(i) Cladding is made of impermeable materials so that rain water could
only access the building through joints. However, properly designed
joints with sealant could completely keep out the rain infiltration.
(ii) Cladding is made up of porous material (bricks) which absorbs rain
during rainfall and subsequently dries out. Water could hardly
penetrate into the building given that the cladding is of sufficient
thickness with low permeability.
12. What is the purpose of applying spatterdash before rendering and
plastering?
Spatterdash is a mixture of one part of cement to one and a half parts of
coarse sand with enough water. The mixture is thrown forcibly onto the wall
so that the impact removes the water film at the interface between
spatterdash and the substrate leading to the improvement in adhesion. The
spatterdash should cover the substrate surface completely and form a
rough texture. Spatterdash serves as an effective mechanical key to
prevent rendering and plastering material from sliding or sagging. The
roughness of spatterdash improves adhesion by providing a positive “key”
for plaster to grip. The improper application of spatterdash affects the
subsequent bonding of rendering with substrate.
13. What is the purpose of adding polyethylene film in interior slabs
sitting on grade for building structures?
Membrane materials, such as polyethylene film, are commonly used to
reduce vapour transmission from soils to concrete slab. They are often
termed “vapour retarder” and are placed on the underside of concrete
slabs sitting directly on soils for building structures. Protection from
moisture is essential because floors inside buildings are normally covered
with carpet and tiles and penetration of water vapour through concrete
slabs could result in the failure of adhesives in tiling, discoloration of
flooring products and fungal growth.
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