The viability of manually producing and using concrete roof tiles for low cost housing in South Africa
Date
2016-07-14
Authors
Bathke, Robert Michael
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Abstract
The roof is the element of a structure that provides the occupants
with the greater part of the shelter they have from the elements.
The roof covering is also the most exposed part of the structure
and as such it not only has to offer acceptable thermal, acoustic
and weather performance in order to provide the occupants with a
comfortable living environment but it also has to be durable if the
structure is to be considered a success.
When considering low cost houses the requirements of the roof
covering are the same as those mentioned above, except that
they have to be met in the most cost-effective way possible. At
present the most frequently usee' roof covering for both formal
and informal low cost housing in South Africa is galvanised steel
sheeting. This choice in roof covering is a compromise, it
provides a durable, easily installed and most importantly a cheap
roof while providing the occupants with exceptionally harsh living
conditions.
A survey conducted on the roof coverings available at this time
on the South African market reveals that when selecting a roof
covering for a low cost dwelling a compromise will have to be
made. This is said due to the fact that none of the roof coverings
surveyed satisfied all the requirements for an ideal low cost roof.
A South African company, Hydraform, has proposed introducing a
system that allows individuals to manually produce low cost
concrete roof tiles. This system, namely the Agri- Tile system,
utilises technology similar to that used by a number of other
commercial companies which have successfully produced large
numbers of [ow cost concrete tiles used on roofs in other
countries. Case studies of three of these companies revealed that
these low cost roof tiles provide acceptable levels of performance
while remaining relatlvety cheap.
lnltlal research into the strength and strength-gain-over-time
characteristics of the Agri- Tiles (as well as the effect on the
strength of the tiles when they were produced using five different
fine aggregates) revealed that while this system of tile production
has potential it also has a number of problems.
The potential shown by the low cost concrete tiles, the need for
such a roof covering on the South African market and the general
lack of information encountered on the topic of low cost concrete
tiles indicated that there is a need for a thorough evaluation of
this system of tile production and of the tiles themselves.
After consulting the South African Bureau of Standards and the
Agrement Board of South Africa an evaluation of the tile
production system, the tiles themselves and the material used to
produce the tiles was undertaken using the Agri-Tile as a case
study.
The evaluation revealed that only afte" significant modification
was the Agri-Tile system capable of producing tiles which, when
produced in the controlled environment of the laboratory,
consistently met the strength requirements of the South African
Bureau of Standards. In addition, the modifications made to the
tile production system eliminated the need for prefabricated
moulds, which is the most expensive item of equipment needed to
produce the tiles. The quality of the tiles was still highly
dependent on tile workmanship used to produce them and as
such no guarantee of quality will be available if the tiles are
manufactured in an uncontrolled environment.
Systematically changing the grading profile of the sand used to
produce the tiles revealed that the tiles may be produced from a
wide range of sands with different grading profiles without
compromising the strength of the tiles.
It was therefore concluded that in principal the Agri- Tile approach
using the proposed moulding system and a very wide range of
sands could make a contribution to the supply of low cost roofing
material. However, strict control over quality would be necessary
and the author doubts whether this cou' j be achieved
consistently over a wide range of bui!ding sites.
Description
Dissertation awarded with distinotion on IS May I999
A dissertation submitted to the faculty of Architecture,
University of the Witwatersrand, Johannesburg, in fulfilment
of the requirements for the degree Master of Science in
Building Management.
Johannesburg 1998