Much attention has been paid to developing the small-scale production of concrete roofing
tiles as an affordable alternative to both traditional roofing materials, such as thatch, and
modern, mass-produced, often inappropriate, galvanized iron sheeting or asbestos cement.
These tiles are relatively low in cost, durable (with a life span expected to exceed 20 years in
most areas), aesthetically acceptable, able to offer adequate security and comfort, and
provide protection from both the heavy rain and the hot sun.
Concrete roofing tiles are now produced by small businesses in a number of countries in
Africa, South and Central America, Asia and South-east Asia, and in the former Soviet Union.
The key to the success of this technology was the development of equipment and techniques
to produce the tiles on a small scale. It typically costs US$5000 (excluding land and
buildings) to set up a concrete roofing tile workshop, and can be less than US$1000 in areas
where the vibration equipment and the moulds are made locally.
When the technology was first developed it was decided to make large roofing sheets similar
in size and shape to the corrugated asbestos or galvanized iron sheets used on many
buildings. These were reinforced with natural fibres such as sisal or coir. The fibre-cement
mortar mix was simply spread out by hand on a flexible plastic sheet in a large mould.
Afterwards the sides of the mould were taken away and the sheet with the mortar on top was
gently pulled over onto a corrugated mould where it took its shape.
Problems were experienced with decay of the fibres and cracking of the sheets after only a
few years, and so the production of fibre-reinforced concrete roofing sheets has been
abandoned in many countries.
The next development was production of fibre-reinforced concrete roofing (FCR) tiles. With
tiles (typically about 500 x 250 x 6 or 8mm) the performance of the fibre is less critical than
with sheets. The fibres are added largely to control damage caused by impact during
handling. Once placed on the roof, tiles are unlikely to crack if the fibres decay. In addition,
FCR tiles are vibrated during their production which gives them added strength and
durability. It has also been found possible to make fibre-reinforced semi-sheets (of size 600 x
600 x 8mm) by the same method without any adverse effects.
A more recent development has been to make concrete tiles without any fibre at all. These
are the so-called micro-concrete roofing (MCR) tiles. Greater care needs to be taken with
MCR tile production compared with FCR if the number of damaged or sub-standard tiles is to
be kept low. MCR tiles are also more brittle than FCR tiles, and can be damaged if dropped
or handled carelessly when transporting them or fixing them to the roof.
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Micro concrete roofing tiles
To produce a good MCR tile, care needs to be taken in the quality of the sand to make the
mortar. This should have a regular grain-size grading – without too much material of one size
and, particularly, without too much fine silty material. If the sand from one source contains
too much material of any one size it should be mixed with a sand of different grading from
another source. In addition, the batching of the quantities of sand, cement, and water needs
to be done accurately – to ensure that there is enough cement and that the mix is not too wet.
The tilemaker needs to mould the tile with care and skill, and it is important that the tiles
are properly cured.
With FCR tile production there is some capacity for these quality aspects to be less rigorously
exercised, but with MCR production there is no margin to be lax on quality control if large
numbers of damaged or sub-standard tiles are not to result. If the potential producer cannot
ensure good quality control at all stages of production, then it probably is not a good idea to
produce MCR tiles.
Equipment and materials
The equipment and materials needed to produce MCR tiles are the same as for FCR tiles,
except that no fibre is used and the sand used needs to be of good quality, as noted above.
The essential equipment is:
a tile vibrator
a water curing tank
a table to work on
The use of a vibrator is essential for MCR
tile production. Vibration helps to
consolidate the mortar mix and removes
air bubbles, which would otherwise cause
weak spots in the hardened tile. The
vibrator unit itself consists of a flat metal
plate which is suspended on dampers and
to which is attached a rotating eccentric
cam. It is the rotation of this cam which
translates into the up-and-down motion of
the plate. A hinged metal cover fits onto
Figure 1: Place the polythene interface sheet
the plate. This defines the sides of the
tile. The vibrator may be driven manually,
electrically with a standard 12-volt truck
battery, or on mains electricity.
Because cement mortar sets slowly and the
tiles need to be left on the moulds at least
overnight before they can be removed, the
producer will need enough moulds to cover a
whole days’ production. A single person
should comfortably be able to make at least
200 tiles per day, and probably considerably
more. (Note: the cost of 200, or more, moulds
should not be underestimated – they could
cost more in total than the vibrating unit
itself.) Because it is important that MCR tiles
cure in a damp environment, the enveloping
type of mould needs to be used. These moulds
are stacked one on top of the other and hence
Figure 2: Work the mortar mix under vibration
Micro concrete roofing tiles
cover the curing tiles and prevent them drying out too quickly. Although cheap concrete
moulds have been used for FCR tiles, which then cure open to the air, more rigorous
standards are needed to cure MCR tiles. The stack-up type of moulds are made of plastic.
Note also that out of a batch of 200 moulds, at least 10 should be ridge moulds for making
the specially shaped tiles for the ridge of the roof.
Tiles are moulded on top of a plastic sheet on the tile vibrator. After vibration, the tile is
removed carefully from the vibrator, still on its plastic sheet, and positioned on the mould
which forms its shape. The same number of plastic sheets as moulds will be needed, but
some additional sheets should be kept in stock to replace those which wear out.
Accurate batching of sand and cement is essential. For this reason, it is usual to have two
batching boxes to measure out exactly the right amount of sand and cement needed for one
tile. A measuring jug for water, to ensure that similar amounts of water are added for each
tile, would also be useful.
A water tank is needed for curing the tiles. As the tiles are cured in warm water for at least
five days, the tank should be large enough to hold 1000 or more tiles. A single tank to
accommodate this number of tiles would need to be about 8 metres long, 0.8 metres wide
and at least 0.6 metres high, although it probably would be more convenient to use a number
of smaller tanks.
The materials needed to make MCR tiles are:
cement (Ordinary Portland Cement)
The need for sand with a suitable grading has already been noted. More specifically, the
following guidelines are used for sand grading for MCR tiles.
maximum grain size
0.5 to 2mm
In addition, the clay and silt content should be less than 4% in all cases. A set of three sieves
with openings of approximately the sizes indicated above would be a very useful acquisition
for the serious MCR tile producer. These could be used for determining the sand size grading
and, possibly, for making sand heaps of
different sand sizes, which could
afterwards be mixed in appropriate
proportions. A clean sharp sand is the
best to use.
The water used should be clean and
free from significant quantities of
dissolved salts, particularly sulphates.
If water of good enough quality to drink
is available, then this should be used.
Pigments for colouring the tiles are
popular in some areas. Red is probably
the most common colour used for tiles.
Figure 3: Smooth under vibration
Micro concrete roofing tiles
Pigments tend to be imported and therefore expensive. Their use makes the cost of the tile
significantly more expensive, but in some areas a market does exist for more expensive
coloured tiles. Pigments add nothing to the strength of a tile and may even reduce it slightly.
The production sequence
The sequence of operations to make MCR tiles is as follows:
Fill the cement and sand batching boxes fully to the top and level off. It is normal
practice to use three volumes
of sand to one of cement, so
the sand batching box is
three times the size of the
Tip out the sand and cement
onto a wooden, plastic or
metal mixing board placed
on a table. Mix thoroughly
for up to a minute until all
the material is of one colour.
Add water to the mix
gradually, turning the mix
with a trowel all the time
Figure 4: Fill nib forming box and insert loop of wire
until it becomes wet enough
to be workable. Add the
water only slowly to ensure
that too much is not
added. It is best to use a
measuring jug and to add a
measured amount of water
each time. A few trial
mixes can be made to find
out how much water would
normally be needed. If a
set of scales is available a
ratio (by weight) can be
determined. First find out
how much cement is used
per tile by weighing out the
cement batching box
Figure 5: Pull polythene sheet with wet pantile over setting
empty, then full, to obtain
the weight of the cement
used. Mix the sand and
cement and add a
measured volume of water
until a mix of the required
consistency is obtained.
The volume of water in
millilitres is equal to its
weight in grammes and
from the weight the
water-to-cement ratio can
be calculated. A good
mix will have added to it
a weight of water equal to
half the weight of cement
(that is the water-toFigure 6: Making
Micro concrete roofing tiles
cement ratio is 0.5). One millilitre of water weighs one gramme, so the weight of water in
grammes is equal to its volume in millilitres. If, after adding your calculated volume of
water, the mix is too stiff, add a little more water but make a note of how much extra is
added. If a water-to-cement ratio of more than 0.65 is needed to make the mix workable
then the resulting tiles will be of low strength and quality, so stop and re-examine your
materials before proceeding.
Place the plastic sheet onto the vibrator unit and clamp down the sides.
Transfer the mortar mix onto the vibrator, spreading it out with a trowel.
Switch on the vibrator unit and
continue to spread the mix with the
trowel. A vibration time of 30
Figure 7: Making ridge tiles
seconds will usually be sufficient.
Vibration for more than a minute is
not recommended: it can cause the
mix to segregate.
Add the tile nib, to be used to fix the
tile to the roof, manually.
Remove the sides of the unit and
carefully slide the green tile, still on
its plastic sheet, onto the mould so
that it takes the corrugated or ridge
shape of the mould.
Figure 7: Cure in a water tank, in this case an
Stack the moulds and leave
old oil drum.
Next day remove the tiles from the
moulds and place them in the water curing tank, leaning the tiles against each other.
Leave the tiles in the tank for at least five days.
Remove the tiles from the tank and leave them to cure in the air for at least 20 days in a
cool, shaded place. Sprinkle with water at least twice a day.
References and further reading
Appropriate Building Materials, Roland Stulz and Kiran Mukerji. SKAT, IT and GATE copublication, 3rd Edition, 1993.
The Basics of Concrete Roofing Elements. Fundamental Information on the Micro
Concrete Roofing (MCR) and Fibre Concrete Roofing (FCR) Technology for Newcomers,
Decision-makers, Technicians, Fieldworkers, and all those who want to know more about
MCR and FCR. SKAT, St. Gallen, Switzerland, 1989.
An Introduction to FCR/MCR Production: A basin Video. GTZ, Eschborn, Germany, 1990.
Production and Operations Management: MCR Toolkit Element 21 - Production and
operations management for a profitable MCR
Product Information: Micro Concrete Roofing Equipment SKAT
Marketing and Selling Guide for FCR Ikin, D, SKAT
Quality Control Guidelines for FCR SKAT
Production Guide: MCR Toolkit: Element 22 SKAT/ILO Publications, St. Gallen and
Roof Structure Guide: FCR/MCR Toolkit: Element 24 SKAT
Standards Guidelines for FCR Technology SKAT
Glazing for Concrete Roof Tiles, RAS Technical Bulletin Issue No. 10, SKAT, St. Gallen,
Roof Truss Guide: Design and construction of standard timber and steel trusses FCR/MCR
Toolkit: Element 29 SKAT
Concrete Roofing Tiles: Building Issues 2 1992 Vol 4. Bo Johansson, Lund Centre for
Habitat Studies, Lund University, 1993.