School buildings in developing countries
Practical Action
would be particularly exposed to rain and at risk of being damaged over the long term.
Nevertheless these types of roofs are generally quite durable and domes have been found
to be particularly effective against small to moderate earthquakes provided that they have
been bonded well to the walls and the walls themselves have been strengthened so that
they have not been bowed and crushed by the movement of the heavy dome during the
quake.
Earth or lime plaster-based flat roof - in some very dry areas there is a tradition of
building flat roofs. The earth or plaster of the roof is supported on timber, or sometimes
in newer buildings reinforced concrete joists, which in turn support some form of reed or
wire matting on which the earth or lime-based plaster is placed. However, even in
relatively dry areas there can be heavy rain occasionally and after such spells the roofs
would be likely to need extensive repair.
Precast concrete or ferrocement panels or channels - which are made sufficiently long to
span the width of a roof section, for a small building, or to span between dividing walls or
supporting beams for larger buildings. For precast concrete sections the cost of moulds,
which need to be quite thick and heavy and accurately made, is a significant element of
the total cost of the component. Ferrocement components are fabricated on formers of
brick, concrete or hardwood, which are cheaper than fully made up concrete moulds.
However, the making of ferrocement components in this way is much more labour
intensive than the moulding of more conventional steel re-inforced panels or channels.
Note also that use of precast components implies a high level of standardisation of
components and relatively large-scale production, so would be most suitable for quite
large-scale school building programmes, for which they would also offer some cost
advantage compared with some other types of roofing options. The weak point of panel or
channel construction is the mortar joint that would need to be put in between individual
elements. This needs to be made to a good standard if it is not to crack and let in water.
This type of construction is not really suitable in very wet areas as it would only be a
matter of time before the mortar joints begin to leak, and putting a mastic or sealant
material would be more expensive and not give much improvement as unless a very
expensive option is chosen, this would deteriorate in high heat and exposure to sunlight.
An example of the use of channel sections is shown below.
Mortar fill
Channel section
Steel reinforced rods
Figure 3 Precast reinforced concrete channels
Other examples can be found in Bonner & Das (1996)
Maintenance - Undertaking a maintenance schedule is important for the school to remain a
safe, healthy and comfortable place for learning. As noted above, some types of materials
and construction details are more durable than others; however, all schools would require
maintenance and inspection regularly. With any type of school building the fabric needs to
be checked over thoroughly at least once a year, or after a serious wind or rain event. Small
defects which are noticed, e.g. small cracks in plaster, missing tiles, small holes in walls or
floors, or peeling of paint, would need to be repaired as soon as possible to avoid their
worsening. More serious defects, e.g. large cracks in walls, especially around openings, the
falling down of significant sections of plaster or ceiling, roofs which leak regularly, doors,
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