essarily those of UNESCO and do not commit the Organization.
The designations employed and the presentation of material throughout this
publication do not imply the expression of any opinion whatsoever on the part
of UNESCO concerning legal status of any country, territory, city or area or of its
authorities, or concerning the delimitation of its frontiers or boundaries.
M. Asghar Husain : Director of the Division for Educational Policies and Strategies
Alfeo Tonellotto : Chief of the Architecture for Education Section
Authors : Dr. E. A. Adam in collaboration with Prof. A. R. A. Agib
Text editing and graphic design : Barbara Brink
Printed by : Graphoprint for the
United Nations Educational, Scientific and Cultural Organization
7 Place de Fontenoy, 75352 Paris 07 SP, France
Paris June 2002
UNESCO
© Pr
Pr
ef
ef
ace
ace
This publication has been prepared within the framework of the UNESCO project
Improvement of Educational Facilities in the Least Developed Countries of the Arab
States
, 522/RAB/11.
Co-financed by AGFUND and AFESD, the main component of the project was to
construct the El Haj Yousif School in the Khartoum area using compressed
stabilised earth block building technology, a practical way of demonstrating the
potential of earth as a viable and desirable construction material.
In order to make the knowledge acquired during the construction process of El Haj
Yousif school widely available, this publication
Roofing Systems in Sudan
and a twin
publication
Compressed Stabilised Earth Block Manufacture in Sudan
have been
prepared.
The roof is an essential part of any building. It is both an esthetic and structural
element, the shape and materials used determine the style of the entire
construction. Its main function, however, is to enclose a given space and provide
protection of this space from the weather. A weather tight roof is essential for
preserving the structure of the entire building. If the roof is badly constructed with
inappropriate poor quality materials, heat loss or gain will result as well as water
penetration and consequently the rest of the building will suffer damage.
In general a roof should provide adequate strength and stability, weather resistance,
thermal insulation, fire resistance and sound insulation. This can be achieved in a
number of ways depending on availability of materials and expertise.
In recent years the potential for earth as a valuable and desirable construction
material is being rediscovered. Methods derived from the traditional techniques are
being developed to improve the quality of earth construction and broaden the
potential for its application. Earth is primarily used for the construction of walls but
it can also be used for the construction of roofs where its good insulation
properties are particularly advantageous, especially in hot dry climates.
PREFACE CHAPTER 1
-
Introduction
1.1 Why the Roof is so Important
1.2 Different Roof Systems used in Sudan
1.3 Choosing a Roof System
CHAPTER 2 -
Flat Roofs
2.1 Traditional Earth Roof
2.2 Improved Traditional Earth Roof
2.3 Shagig Roof
2.4 Timber Board Roof
2.5 Precast Concrete Element Roof
CHAPTER 3 -
Truss and Lean-to Roofs
3.1 Truss and Lean-to Roofs
3.2 Thatched Roof
3.3 Fibre Reinforced Roof
CHAPTER 4 -
Vaults
4.1 Vault Roofs
4.2 Jack Arch Roofs
CHAPTER 5 -
Domes
5.1 Thatched Domes
5.2 Brick Domes
CHAPTER 6 -
Comparative Costs
6.1 Cost Comparison of Various Types of Roofs Used in Sudan
CHAPTER 7 -
Some Conclusions
7.1 The Roof - weighing up the options
GLOSSARY
1
3
3
3
5
7
8
10
11
12
15
17
18
20
23
25
26
29
31
32
33
35
37
39
41
CONTENTS CHAPTER
Introduction
1 1.1
1.1
Wh
Wh
y the Roof is so Impor
y the Roof is so Impor
tant
tant
The roof is one of the most essential components of a building. Its most important
function is to protect the rest of the building from the weather. Without a roof a
building not only loses its esthetic identity but the structure of the building will
rapidly deteriorate with the inevitable exposure to the elements - wind, rain, snow
and sun.
1.2 Diff
1.2 Diff
er
er
ent Roof Systems used in Sudan
ent Roof Systems used in Sudan
Roofs commonly used in Sudan may be classified in four main categories:

Flat roofs,

Truss and lean-to roofs,

Vaults,

Domes.
Selected types of roof systems of the four main categories commonly used in
Sudan are described in this publication. Examples are given of some of the recent
developments made in roof construction, designed to improve the performance of
traditional systems, concentrating in particular on structural rather than thermal
improvements.
1.3 Choosing a Roof System
1.3 Choosing a Roof System
As a general rule the choice of which type of roof to use is governed by:

Availability of materials,

Economic feasibility,

Climatic performance,

Ease of construction.
These criteria are closely related to the main functional properties that a roof
should meet i.e.:

Structural resistance to loads and stresses,

Provision of thermal comfort,

Effective protection against weather, i.e. rain and wind,

Fire resistance,

Sound insulation.
The types of roofs most commonly used in Sudan are flat roofs or jack arch roofs,
mostly used in areas where the rainfall is low or medium. Pitched roofs are
frequently used in areas where rainfall is heavy as they are effective at shedding
rainwater without any damage to the roof structure.
CHAPTER
Introduction
1
3 CHAPTER
Flat Roofs
2 CHAPTER
Flat Roofs
2
7
2.1
2.1
T
T
r
r
aditional Ear
aditional Ear
th Roof
th Roof
Traditional earth roofs are still used in various
parts of Sudan, especially in areas of low to
medium rainfall. They are popular because of
their low cost, ease of construction, and high
resistance to heat penetration. Construction
materials required to build such roofs are also
readily available.
The traditional earth roof can be laid directly on
top of earth walls. The roof for a room of about
4 x 4 metres is constructed as follows:

A central timber joist (mirig), about 180 mm in
diameter, is laid on the walls across the
centre of the space to support the whole
roof structure,

Round wooden rafters, 100 - 120 mm in
diameter, or rectangular timber rafters (100 x
40 mm) are laid on the walls over the mirig
at 500 mm centres. They are laid at a slight
incline to facilitate water runoff,

Reeds (hassir) are laid over the rafters and
fixed firmly with thatch rope,

Dry thatch or hay (humra) is laid over the
reeds to give more insulation,

Stabilised earth is laid over the hay cushion to
an average thickness of 100 mm. The dry
thatch or hay provides protection against
earth penetration through the sofit of the
roof,

Rainwater spouts are embedded in the
stabilised earth cover,

Upstanding parapet walls are built on all
sides,

After the earth layer is completely dry the
surface is plastered with zibla, a mixture of
earth, straw, animal dung and water, cured
for about 3 - 4 days. The zibla is then
mixed thoroughly into a workable slurry and
used to plaster the roof surface in a layer
zibla
stabilised earth
thatch or hay
(humra)
reeds (hassir)
mirig
stabilised earth
thatch or hay
(humra)
reed (hassir)
mirig 100 mm
rafter
rafter
500 mm CHAPTER
Flat Roofs
2
8
about 20 mm thick. This plaster serves as a
good sealant against water penetration and
with proper treatment of the parapet wall,
under and around the rain water outlet, this
plaster can last for about two rainy seasons
without a need for maintenance. After two
years, however, a new plaster coat needs to
be applied.
Calculation of heat flow through traditional earth
roofs shows that the internal surface temperature
reaches a peak of about 34Cº - 35Cº. This
corresponds with the lower temperature limit
recommended for thermal comfort. These peak
temperatures occur very late in the afternoon, at
about 17.00 hours, when the dry bulb
temperature has dropped considerably and
people are normally outdoors.
This type of roof construction has an initial low
capital cost, affordable for low-income groups.
However, the cost of frequent maintenance i.e.
zibla plastering about once every two years and
repair to internal wall plaster affected by possible
rain water leakage, can raise the long term costs.
2.2 Impr
2.2 Impr
o
o
ved
ved
T
T
r
r
aditional Ear
aditional Ear
th
th
Roof
Roof
Attempts by local builders and engineers have
been made to improve the structural, thermal
and water resistance properties of the traditional
earth roof. These improvements are described
below:
The main roof structure is constructed of local
round wooden sections with a diameter of
approximately 120 mm, or alternatively using
wooden sections, 100 x 50 mm, laid at 500 mm
centres. These are supported on a central round
wooden section of 180 mm diameter, or a rolled
steel joist, 140 x 60 mm, and laid to a fall a little CHAPTER
Flat Roofs
2
9
steeper than the fall of the traditional earth roof,
to facilitate water runoff. In a few cases, imported
timber rafters 100 x 100 mm are used in place of
local timber.
The roof cover is laid as follows:

Bamboo poles approximately 25 - 30 mm
diameter are laid adjacent to each other,
covering the whole of the roof area in a
solid mat,

Reed (hassir) mats are laid over the
bamboo mat,

A plastic lateritic soil mixed with hay and
cured for approximat