The basics of concrete roofing elements

Fundamental Information of the Micro Concrete Roofing (MCR) and the Fibre Concrete Roofing
(FCR) Technology for Newcomers, Decisionmakers, Technicians, Field Workers and all those
who want to know more about MCR and FCR

Introduction

Who may be interested in this booklet?

• MCR or FCR newcomers: All those who want to start producing MCR or FCR Elements.

• Decisionmakers: All those who have to take the decision, whether to work with MCR/FCR
Elements or not.

• Practitioners: All those who are already producing or using MCR or FCR.

• All those who are interested in MCR or FCR and want to know more about it.

What you can find in this booklet:

• Basic information about MCR and FCR.

• Some advantages and disadvantages of MCR and FCR.

• Guidelines that you should consider and first steps towards MCR/FCR.

• Hints and particular details to avoid mistakes.

• Addresses and literature for more detailed information.

What you can NOT find in this booklet:

There is

• No detailed technical information.

• No detailed instruction on how to produce MCR or FCR Elements.

• No specifications of costs and profit in your specific case.

• No information about particular problems in particular countries.

1989, 1993

SKAT

Vadianstrasse 42

9000 St. Gallen, Switzerland

What is MCR and FCR?

Low cost, good quality

MCR and FCR are building materials which have been developed for the covering of roofs, in
advanced and low cost building construction.

Concrete and fibre

MCR/FCR Elements are made of concrete which is a mixture of sand, cement, water and
eventually with natural or artificial fibres.

Small scale production

These Elements can be produced either as tiles, sheets or semi-sheets, in small decentralized
plants.

Job creation

Since the roofing elements are produced manually, many jobs for men and women - can be
created in rural and urban areas.

Foreign exchange savings

Both MCR and FCR require little initial investment and little energy input in production.
Generally the raw materials are available locally; this means foreign exchange savings instead of
importing asbestos, cement tiles and corrugated iron sheets.

Failures and improvements

Between 1977 and 1984 FCR sheet technology failed in many cases, mainly because of
insufficient training of the producers and bad roof substructures. The solution to these problems
has been the development of tile and recently semi-sheet production as well as improved know-
how transfer. While the tile production and application has grown and spread all over the world,
sheet production continued successfully only at selected places and further dissemination
remained limited.

Further development

Though the technology has reached a satisfactory state already, further research and development
is still needed. The members of the Roofing Advisory Service of SKAT, the main suppliers of
equipment and many MCR and FCR practitioners in the field are continuously improving the
equipment and the production methods. The main efforts of the Roofing Advisory Service are
heading towards research in raw materials, the role of the fibre and optimizing the size and the
shape of the elements, as well as the development of tools for better management, of quality
control and marketing. Last but not least the development of new elements which require less
timber for the supporting structure will be a need for the future.

Using MCR and FCR elements

Where a need exists

MCR and FCR are suitable in all places where a need for a low-cost locally-produced roofing
material exists. In this case concrete roofing may be a viable alternative to the traditional roofing
materials. MCR and FCR Elements may be used by anybody who knows how to handle and
apply similar roofing materials like clay tiles or asbestos cement sheets.

Lack of traditional materials

During the last few years, traditional roofing materials have increasingly lost their importance.
Grass and thatch roofs have a short lifespan and the raw material is getting scarce. Burnt clay
tiles require much energy input in production and a heavy timber substructure on the house; in
many countries wood is becoming scarce.

Disadvantages of new materials

The existing industrial alternatives as for example Asbestos Cement or Galvanized Iron are the
most widespread of nontraditional roofing products. They have some disadvantages, since their
production requires a high initial investment and there is no known way of scaling down
manufacture to decentralized small-scale production.
 Roofing Materials/ Industrial Roofing Fibre Concrete Roofing

Characteristics

Production Unit Big Industry Small Industry

Production Process High Tech Intermediate Technology

Capital Input High Low

Labor Input Low High

Know-how Difficult to obtain Easily available

Raw materials Not always available Usually available locally

locally

Production Centralized Decentralized

Location of production Usually abroad Local

Characteristics of Industrial Roofing Materials and MCR/FCR

For a typical Third World Country with dept problems and high unemployment rates, MCR/FCR
offers mainly two advantages: it creates jobs and uses, to a great extent, locally available raw
materials.

The market

Experience has shown that the MCR or FCR tile is usually competitive with all industrial roofing
materials except in some cases with Galvanized Iron Sheets.

For the rich and the poor

MCR and FCR Elements are designed to meet high quality standards in strength, shape and
color. Therefore they are used on upper middle class villas as well as on low-cost houses. Tiles
meet the need for efficient protection of a building, but they can also be rather decorative.

Limits of application

Experience in many countries has shown that the main limitations to the production and
application of this product are:

• Insufficient standard of craftsmanship in manufacture and installation.

• Improper curing or lack of curing.

• Deficient roof structures.

• Lack of good production and business management.

• Extreme weather conditions like hailstorms and hurricanes.

• Vandalism, certain ball games and fruit trees dropping heavy fruits.

• Deficient raw materials.

• Deficient tools and equipment.

• Uncertain social prestige.

• Public does not trust the new material.

It has to be noted however that the same limits apply to other materials to a varying degree,
particulary in the case of hurricanes.

Producing MCR and FCR elements

In a small workshop

The production of MCR and of FCR Elements is labour intensive. It can take place close to the
point of use and in a small workshop. A minimum of infrastructure, equipment and at least 2-3
workers are needed to work with one vibrating table.

By men and women

Both production and mounting of the MCR or FCR Elements can be made on the spot and by
local (male and female) workers. So the cost of transportation of the finished product can almost
be eliminated.

Training is a must

The simplicity of the technology makes it easy though inevitable to acquire the requisite
technical skills in a relatively short period of training time. Professional training is offered by
regional MCR/ FCR centres and by suppliers of equipment.

Preparing the mortar

The first step of production is similar to the process of mortar preparation in basic masonry
practice. For FCR the fibre is chopped up to a length of about 15-25 mm and mixed with the
basic ingredients (sand, cement, water and fibre) into a concrete mortar.

Forming the tile

One of the most demanding and skill-intensive aspect of MCR and FCR production is the
transformation of the fresh mortar into tiles or sheets. This involves spreading the fibre concrete
mix on a vibrating table, compacting it by vibration and then lifting the wet concrete screed and
casting it on a mould.

Curing and drying

On the mould it is dried for 24 hours. The "green" tiles are then placed into a tank filled with
water for a curing period of two weeks. After the curing the hard tiles are dried for another two
to three weeks before they can be used for installation on the roof.

Special transport

Since fibre concrete is a brittle material it has to be handled and laid with care. Whenever
possible the tiles should be transported directly from the workshop to the building site. The
transport vehicle must be specially prepared, e.g. with a bed of sand on the platform, so as to
guarantee a smooth Journey.

It is a sound technique...

The production of MCR and FCR is a sound technique and much practical experience is
available. Failures can be identified and are usually due to production errors. Ongoing research
and development as well as the evaluation of experiences will lead to the necessary improvement
of know-how.

... if professional training is provided

Tile making can be started in most places with a fair chance of success, if professional training is
provided and if the appropriate method is chosen. Beginning production should take into account
the history and the state-of the-art and not simply be in the spirit of "appropriate technology
enthusiasm", trying to reinvent the wheel by making the same mistakes many others already
have.

MCR and FCR for organizations

What is the target

In principle everybody can produce and work with MCR or FCR. The question is whether
producer and user are the same persons or not. Depending on the individual case, different
problems and expectations will occur. One can distinguish between private entrepreneurs who
have to make a profit from the production and Non Governmental or Governmental
Organizations where financial profit is not a main target.

The producer is the user

The situation of Non Governmental and Governmental Organizations is rather easy because if
the producer and user are the same organization, the problems are more production orientated.
Acceptance of the product is easier in such cases, because the users are involved in the
production process. On the other hand it has to be considered that a small industrial project like a
MCR or FCR workshop should be able to become self-supporting. Therefore MCR/FCR
producers for Non Governmental or Governmental Organizations should be able to meet the
same demands as the private entrepreneurs.

Many profits

For an Non Governmental or a Governmental Organization economics are not purely valued in
profit but in socio-economic benefits such as

• job creation

• Import savings

• use of local materials

• improvement of the roofing technology.

MCR and FCR offers above benefits and therefore it is a very interesting option for these
organizations.

MCR and FCR for private entrepreneurs

Marketing of the new product

In cases where the producer and user are separate, as it is mostly for private MCR and FCR
entrepreneurs, marketing becomes one of the main problems. Quality standards and costs will be
judged by the market.

Quality control and guarantees

The buyer will ask for guarantees from the producer. But the quality of the roof depends as well
on perfect production and quality control as on the appropriateness of the substructure and on
how the roofing elements are mounted on the roof. In cases where the producer sells directly to
the user he might be in a position to provide assistance and advice on the roof design and on the
mounting of the tiles.

Good installation

The producer should be able to give guarantees for the product; but in many cases he has no
influence on how the roofing elements are installed on the roof substructure. MCR and FCR
products therefore should only be sold to customers who accept the installation of the tiles or
assistance by the MCR/FCR producer.

How to start MCR and FCR

If you are considering starting working with concrete roofing elements or starting running an
MCR or FCR workshop, please reflect carefully on the following points:

• professional training

• infrastructure and equipment

• marketing and management.

Please start your reflections by answering the following ten questions.

Ten key questions

yes no

Is there a genuine demand for a roofing alternative?

Are all the following materials available in your locality:

• cement

• sand

• water

• eventually organic fibres

• good timber or metal supporting roof structures?

Do you have a secure, dry site with good access?

Can you use or sell a concrete roofing product that costs 2 to 4 US$ per sq.m in production?

Are you equipped for careful manufacturing with close supervision, maintenance of equipment
and quality control?

Are you aware that there is expenditure involved before you can even try out this technology?

Are you prepared to pay high attention to the initial know how transfer and professional training
as well as to continued education and service?

Are you aware that MCR and FCR manufacturing may present some initial problems like any
other production method? These problems can be mastered by good workers and good
management.

Are you interested in creating jobs and saving foreign exchange?

Do you realize that all building materials have a limit to their service life?
If you answer every question with yes, you have the potential to go into MCR or FCR
technology. If not, you are advised to contact one of the specialist organizations for assistance in
decisionmaking.

Ten steps to start a successful workshop

1 A feasibility and market study should be made in any case. For a single workshop it may be
carried out with the help of a simplified method by a potential workshop owner himself. An
MCR/FCR regional centre or a development project will require amore detailed study by a
specialized person.

2 The definition of the products to be sold and the required productivity output for competitive
marketing will be a result of the feasibility study. In many cases it is wise-to produce several
concrete products to spread the risk.

3 The securing of the financing of the workshop investment and the running capital is the next
step which has to be made based on the results of the market study.

4 The terms of reference for the equipment must be clear for every single case.

5 The purchase and the installation of the equipment can be made simultaneously with the
preparation of the site and the building.

6 The initial professional training course before or a short time after the beginning of production
has to be attended at a competent institution.

7 The initial production will be a three to six month period of trial and error for the workshop
team.

8 Improving the production method, quality control, productivity and application will be the next
step which may be facilitated with the assistance of the Roofing Advisory Service or other
competent partners.

9 Careful monitoring of the production process and quality control will be a continuos task for
the successful producer.

10 Good marketing, assistance to the installing persons and a certain service for main tenance of
concrete roofs are additional tasks of a successful producer.

The Roofing Advisory Service at SKAT offers the tools

The Roofing Advisory Service has established several tools for the planning and running of an
MCR or FCR workshop. SKAT will be pleased to send information about to you on request.
Marketing

A new product hasn't a ready sale

The building material market is conservative. It takes time and effort to introduce a new product.
It is the dynamic (acceptance) of the market, which decides whether a product is appropriate for
a given situation. That means, the producer has to improve his marketing efforts and, if
necessary, the quality or the appearance of the product.

Proved quality standard

MCR and FCR Elements should last ten or more years. Therefore the careful producer will be
interested in offering a certain guarantee to the customer. And he wants his products differed
from others of lower quality. This can be made with a quality seal which is provided by an
approved MCR or FCR institution.

Not in a shop

It is risky to sell MCR and FCR Elements in small building material shops "around the corner".
Most probably the tiles would not be handled with the necessary care by salesmen and
customers. Preferably the tiles and sheets should remain in the hands of persons, if possible
professionals, who feel responsible for a careful handling of building materials.

Management

Problems are guaranteed...

Improper "wild" production will most probably lead to bad prestige and to problems in the
quality of the product.

... if management is neglected

Like any industrial or semi-industrial process, MCR and FCR production requires good
management. This includes the acquisition of raw materials, hiring and guiding qualified
workers, daily control of productivity, maintenance of equipment and workshop etc.

Quality control

The most important part of successful MCR and FCR production is continuos quality control of
raw materials as well as control of the finished product and its application on the roof. This
includes testing cement, sand, fibre and water quality and also load bearing, impact strength and
the water tightness of the elements. Guidelines for quality control are available at the Roofing
Advisory Service at SKAT.

Professional training

Training is a must

MCR and FCR production need professional training both in technique and business
management. Therefore you must consider that most failures in MCR/FCR production and
application so far were due to no or bad knowhow transfer and insufficient professional training.

Process of development

Since the technical rationale of MCR and FCR is still in a process of development, and
marketing as well as management methods also have to be improved, the decision-makers should
be kept conversant with the most up-to-date data and facts and the practitioners should be well
trained before they start their production.

Hardware and knowhow

A good MCR/FCR hardware kit must be accompanied by a well adapted knowhow transfer
package and professional training, if the production has to be successful in the long run. There
are different forms of MCR and FCR knowhow transfer like training courses? management
guidelines, technical manuals etc. One has to choose the appropriate form for each specific case.
The dissemination of knowhow adapted to the local demands can be done through regional or
national MCR/FCR centres, as they exist in some countries already. For any question about
MCR or FCR knowhow transfer and training facilities you are welcome to ask the Roofing
Advisory Service at SKAT.

Raw materials

Basic materials

The basic raw materials required for the production of MCR and FCR are cement, sand,
eventually fibre and water. Optionally, colorants in the form of standard natural or chemical
pigments, such as those already in use by the concrete industry, can be added.
Good cement

Ordinary Portland cement is the type used for MCR and FCR. In order to achieve the desired
results in strength and durability, it is essential that the quality of cement measures up to the
standards required for normal concrete and masonry practice. In some cases the use of
pozzolanic binders may be taken into consideration.

Natural fibres

The chopped fibre plays its main role in giving a better cohesion to the fresh mix and it enables
the moulding of corrugated products. It is possible to use many types of natural fibres in concrete
roofing elements as long as they are clean. Coconut husk, stem fibre as for example jute or leaf
fibre such as sisal are the most common examples of vegetable fibres which have been used with
success.

No fibres?

Recent research has shown that tiles can be produced without fibres. This technology, named
Micro Concrete Roofing (MCR), requires more care in the selection of raw materials (e.g.
grading of sand). However the quality of MCR is compatible to that of FCR.

Ordinary sand

Normally any type of clean sand which is suitable for cement mortars can be used for MCR and
FCR. Sand with particle sizes between 0.125 mm and 2 mm is suitable. Aggregates up to 4 mm
may be added in MCR elements.

Clean water

The production of good quality MCR and FCR requires good quality water, preferably standard
potable water.

Workshop and site

Selection of a site

The MCR and FCR workshop needs a minimum of infrastructure: site and buildings. The
accessibility anti availability of water and to some extent sand have to be taken into account
when selecting a site. Electricity from the main or from batteries has to be available when using
an electric vibrator.

Enough water
Water is in constant demand; not only for mixing but also for general cleaning and refreshing of
the curing tanks. Therefore the site must otter a reliable water supply.

Store and office

There must be a room for storage and safekeeping of cement and tools and some provision for
administration would be useful. This room should be closed by a door.

Working space

The production of MCR and FCR has to take place under cover. The space in the workshop is
needed for storage of sand and fibres, mixing, screeding and compaction of the mortar on the
table, storage of fresh roofing elements and storage of moulds. For a one-table-operation a
covered floor area of about 25 to 35 sq.m is

Curing tanks

The curing tanks are situated close to the workshop. They can be dug out or built up by using
bricks or concrete.

Storing and maneuvering

Additional space is needed for the finished roofing elements. Sufficient manoeuvring space for
vehicles bringing raw materials or collecting finished products must be available. The
recommended minimum area is about 200 sq.m, more space may be useful for future expansion.

Equipment

Special equipment

The production of Fibre Concrete Elements requires special equipment which can be obtained
from specialized suppliers. Though some pioneer FCR producers have developed their own
equipment with some success, experience has shown that this cannot be recommended in
general.

Selfmade equipment

Do not try to develop your own MCR and FCR equipment. So far no self-built vibrating table
meets the quality which is necessary for reliable broad dissemination at a competitive price.

Vibrating screeding table

The vibrating table is the main piece of equipment for tile and semi-sheet production. The
vibrating device can either be hand- or toot-powered or driven by a car battery or connected to
the mains. The metal table is covered with a special plastic sheet before the fresh concrete mix is
screeded on it.

Wooden or metal bench

The vibrating table is fixed on a working bench, on which other accessories may be placed also.

Accessory tools

A set of masonry equipment, i.e. spades, measuring pans, sieves and a trowel, sand and cement
batching boxes, a fibre cutter, fibre weighing balance and a shovel are the basic tools.

Moulds

Moulds are obtainable for several shapes and sizes of tiles. To start MCR or FCR production a
set of at least 100 moulds for regular tiles and some additional moulds for ridge tiles are
required. The moulds are usually made of either PVC or fibre glass when sold by a supplier or of
concrete when produced locally.

Curing area

The curing tank is usually made of clay bricks, concrete blocks or stone. Whenever possible the
air curing area should be protected from the sun by a shed.

Sheetmaking equipment

The equipment described above is for MCR and FCR tile or semi-sheet production. MCR/FCR
sheet production requires a quite different table. Since compaction is done by hand a solid
wooden table with a frame is required to prepare the matrix while corrugated asbestos sheets
serve as molds.

Buying an equipment set

If you buy a set of equipment, we strongly recommend to ask for a good service network
providing spareparts and technical assistance in the case of production problems arising

We strongly recommend not to "reinvent the wheel". Equipment design and production is a very
demanding and expensive task. It should be reserved for large development programmes.
Therefore you normally buy a kit.

Roof design
A most important part

The importance of the supporting structure of a roof is often underestimated. Most damages to
concrete roofing elements on roofs can be tracked down to faults in the roof structure and in the
way the elements were placed and fixed.

Be aware of wind suction

In many cases the wind suction is higher than the wind pressure on the roof. If the roof structure
is not designed to these strong uplift forces, heavy winds may destroy the whole root. This fact
has to be considered in any kind of roof. be it covered with corrugated iron sheets, clay tiles or
concrete elements.

Roof design

The design of the roof for tiles and sheets should be simple The minimum pitch should be 22° in
moderate climatic areas, whereas 30° are recommended for areas where torrential driving rains
occur. The span of the rafters should not exceed 3,5 metres for lean-to roofs and 6 metres for
gable roofs. For wider buildings, triangular trusses provide an economical solution up to a Limit
of around 10 metres width.

Rigid timber structures

Good quality timber is desirable for the roof substructure though wood is getting scarce and
expensive. Tiles and in particular pantiles are more adaptive to uneven substructures than semi-
sheets and sheets. Pantiles may even be used on carefully selected poles. The timber
consumption of a correctly dimensioned substructure is about equal for concrete tiles, semi-
sheets or sheets as well as for a corrugated iron sheet roof. A clay tile roof normally requires
more timber.

Careful craftsmanship

The installation of the substructure and the laying of the sheets should be done by a team of
specialized carpenters and tilemakers. The tiles are fixed to the laths with special wire loops or
fixing bolts.

Tiles, sheets and semi-sheets

MCR and FCR Elements exist in three sizes: tiles, sheets and semi-sheets, which may be
coloured according to your taste.

Tiles
The dimension of the tiles can be adapted to the local needs. So far the FCR tiles produced all
over the world are mostly formed as pantiles or roman tiles of 25 cm by 50 cm and 6 mm
thickness (up to 10 mm for high risk areas). The handling of the tiles is easy since their weight is
only 2 kg. Because they are brittle like any clay or concrete product, they must be handled with
the same care as a clay tile.

Semi-sheets

The semi-sheets are designed to improve the efficiency of production output and to ease the
installation on the roof. So far semi-sheets have a size of 60 cm by 60 cm. Other shapes and sizes
may occur in the near future.

Sheets

The dimension of the sheets vary between 50 to X0 cm width by I ()() cm length and 10 mm
thickness. In some cases the sheets may be a useful alternative to the tiles provided they are
produced, transported and installed with great care.

Tiles or sheets

In most cases however the Fibre Concrete tiles or semi-sheets will be the more appropriate
product and cause less problems than the Fibre Concrete sheets.

Product size Thickness Effective Weight Cement Cement

(Dimensions) cover per m² content per m²

Tiles

500x250 mm 6 mm 0.08sq.m 20 kg 0.4 kg 5 kg

Semi-Sheets

600x600 mm 8 mm 0.25sq.m 29 kg 1.8 kg 7.2 kg

Sheets

1000x780 mm 10 mm 0.62sq.m 32 kg 9.0 kg 15 kg

The workshop

The typical cost structure of an MCR or FCR workshop in a Third World Country looks as
follows:

The cost structure includes amortization and interest for: equipment, building and land, know-
how transfer and working capital.

The capital investment for an electrical vibrating table with 200 moulds is around US$ 4.000.
Adding working capital, costs for site and building, the investment is between US$7.000 and
US$ 12.000.

Tiles made per week 1.000 2.000 5.000 10.000

Value of annual turnover (US$) 12.000 24.000 60.000 120.000

Number of production lines 1 2 5 10

Workforce (Direct Labour) 3 5 12 24

Minimum covered space required

for workshop area (sq.m) 25 50 200 400

Minimum external yard area

needed ( sq.m) 40 80 200 350

 Ex-works value of equipment

to be supplied (US$) 4.000 8.000 19.000 38.000

Synoptic view of cost factors in a MCR and FCR project

A square metre of tiles

Once a workshop is installed, Fibre Concrete sheets or tiles can be produced in most countries at
a cost between 2 and 4 US$ per sq.m. This includes costs for raw materials, labour, depreciation,
profit and interest for initial investment.

A competitive material

Analysis of field-experience allows the following statement: Compared with other roofing
methods, a fibre concrete roof including roof structure can be built at 2/3 to 3/4 of the cost of a
similar roof covered with Asbestos-Cement. There is no apparent difference in the costs of the
roof structure whether concrete roofing tiles or sheets are used.

The most serious competitor

Galvanized Iron Sheets are the most serious competitor to MCR and FCR. However, this is only
apparent: Galvanized Iron Sheets have usually a lower life expectancy and the roof substructure
needed is the same as for MCR/ FCR if made properly. However, these quality arguments often
do not count for buyers with low income, and the correct roof substructure is in most cases
neglected.

The conclusion is that in comparison to Asbestos Sheets MCR and FCR are "as good but
cheaper" and that in comparison to Galvanized Iron Sheets MCR and FCR "are better in quality
and in the medium run as cheap".