School buildings in developing countries
Practical Action
damaged by water. Note that if walls are to be left unplastered it is important to point the
mortar joints for neater appearance and to reduce weather damage. Even if it is decided not
to plaster a wall, a thin layer of limewash applied every year can help to reduce rain damage
and improves the appearance.
Roofs
Pitched and flat roofs are the two most common roofing types, though as discussed previously
other types, e.g. vaults, domes and corbelling, are also possible. Flat roofs of low cost
materials such as compacted earth or a lime based mortar are generally only used in dry
climates as in wetter areas they would be easily damaged by rain and let in water. Flat roofs
have been used in the some temperate countries where the climate is wetter, typically made
of timber decking covered by bitumen felt sheets, but this is a more expensive option, and no
guarantee that the roof would not leak. Bitumen-based sheets would also be likely to soften
and deteriorate significantly in the hot sun in tropical countries, so the use of expensive
additives in the formulation might be needed to reduce this.
Note the two most common types of roof construction of pitched roofs - the gable roof and the
hipped roof
Figure 6: Gable Roof
Figure 7: Hipped roof
There is no particular advantage of one of these roof types over the other, though despite the
more complicated wall construction detail required for the gable roof the overall construction
of a building with this type of roof would be less complicated than for one with a hipped roof,
where trusses of different sizes would be required and these would need to be positioned
quite accurately.
The simplest roof is the shed roof, but this is generally restricted to small one storey buildings
less than about 4 metres across, otherwise the economy gained in the construction of the roof
is lost in having to build one of the walls considerably higher than the other to give the roof
sufficient slope. Most schools are usually not as small as this.
13