A man who leaves in his
building, realizing that there is leakage in the room does not fill the
comfortable in the room. Despite the fact that availability of various control
techniques and project control software many construction projects still do not
achieve their main objectives. Research in this area so far has mainly been
dedicated to identify the impact of roof leakages as the causes and to find its
remedies. There is limited research
geared at studying factors stalling the ability of practitioners effectively to
control and manage their projects. The
Optimum Shelter Design and Construction research group in the Building and Road
Research Institute (BRRI) of the CSIR (Council for Scientific and Industrial
Research) have undertaken a Roof Design Verification Survey of the affected
roofing systems in the Ashanti region and elsewhere in the country. The aim of
the research studies was to find out the main causes of the perennial roofing
problems affecting the housing industry and the national economy as a whole.
Can good roofing secure itself against leakage, corrosion and cracks?
Good roofing can withstand leakages and corrosions but not cracks in walls. Leakages can be avoided by proper design of the roof, good workmanship on roof, and use of the right sealants. Clients tend to economize by selecting wrong specifications and contractors for roofing. Selecting a knowledgeable roofing contractor and correct roofing material can definitely prevent leakage and corrosion.
Good roofing can withstand leakages and corrosions but not cracks in walls. Leakages can be avoided by proper design of the roof, good workmanship on roof, and use of the right sealants. Clients tend to economize by selecting wrong specifications and contractors for roofing. Selecting a knowledgeable roofing contractor and correct roofing material can definitely prevent leakage and corrosion.
In Ghana, especially
Kumasi, parapet roof construction became fashionable in building construction
in the 1970's. It entailed hiding the roofs of buildings from view behind
parapet walls. This concept is popularly known as “Bohyemu”, literally meaning
“construct it inside” or more appropriately “hide it in”. The paper examines
roof designs and their functional requirements in general and specifically
discusses problems associated with parapet roof construction in the country. It
outlines some examples of such
roofing and their respective problem areas which include design and poor
detailing, and offers practical suggestions that may help in solving these
problems. The paper concludes by sounding a note of caution to technocrats in
the building profession to be more diligent in the detailing, construction and
supervision of this type of roof, as well as diagnosing problems of leakages
associated with parapet roofs, since they are usually caused by a plethora of
factors which, if not well-considered and assessed, may lead to the wrong
prescriptions in trying to solve them.
This serves as a significant to the economy factor, because it is very essential to ensure that the nation buildings such as factory buildings and accommodations are used effectively as possible, and also regular maintenance should be put in place every year in other to reduce roof leaking. A flowing water test is conducted by applying a continuous flow of water across the entire membrane without plugging drains for a period of 24‐48 hours. A typical test of roof leakages determined that detailing, inadequate; methods of construction on the part of the artisan unused of proper or appropriate equipment’s as well as materials also have impact on roof leakages. Certainly roof can be classified as flat and pitched roofs. Flat roof; it is a class of roof which its pitch ranged from {0⁰ to 10⁰} zero to ten degree whilst pitch roof is starting from 10⁰ to and beyond.
This serves as a significant to the economy factor, because it is very essential to ensure that the nation buildings such as factory buildings and accommodations are used effectively as possible, and also regular maintenance should be put in place every year in other to reduce roof leaking. A flowing water test is conducted by applying a continuous flow of water across the entire membrane without plugging drains for a period of 24‐48 hours. A typical test of roof leakages determined that detailing, inadequate; methods of construction on the part of the artisan unused of proper or appropriate equipment’s as well as materials also have impact on roof leakages. Certainly roof can be classified as flat and pitched roofs. Flat roof; it is a class of roof which its pitch ranged from {0⁰ to 10⁰} zero to ten degree whilst pitch roof is starting from 10⁰ to and beyond.
Roofs are generally of
two types; flat roofs and pitched roofs. Flat roofs are defined to a pitch of 0
to 10 degrees, the prevailing climate and the materials used as roof covering
affect the choice between a flat and pitched roof. All roofs are require to
satisfy certain functional requirements, namely; to have adequate strength and
stability, be able to resist fully the weather, have adequate thermal and sound
insulation, as well as being fire resistant. This research also provides
information regarding the art of vegetative roof design and construction.
Vegetative roofs, also known as green roofs, are thin layers of living
vegetation installed on top of conventional flat or sloping roofs. We have
chosen to use the word "vegetative" rather than the word
"green" in this guide because a non-vegetative roof could be
considered to be environmentally "green" without being vegetative.
The Roles of Construction Actors in Construction
industries
There
is diverse safety in the construction industry. The major interest or actors in
the construction industry are;
The Consultant:
Cost and material considerations are among the most important and basic
considerations that Consultants must deal with. It is essential to see that
projects are contained within the client’s budget.
The Client: Is
the most important member of the construction team. He is the originator and
financier of all the projects. Omole (1986) noted that the major contribution
the client can make to the successful operations of the construction industry
lies in his skill in specifying his needs prior to the preparation of the
design.
The
Contractor: Omole (1986) additionally reveals that
the major task of Contractors is to assemble and allocate the resources of labor,
equipment and materials to the project in order to achieve completion at
maximum efficiency in terms of time, quality and cost.
WHAT
IS ROOF LEAKAGES
The roof is that structure which covers the top of
any building. Its main function is to provide comfort and adequate protection
to everything under it. Roofs in the tropics are generally designed to-insulate
buildings against heat penetration and also shade external walls. They are also
designed to shed off rainwater very quickly from the roof surface so as to
prevent leakage. The roof basically consists of two components, namely, the
roof covering material which is directly exposed to the atmosphere and the roof
structure which is an understructure supporting the roof covering material. For
the roof covering material to function effectively, it should be very durable
and be able to resist the violent solar radiation, oxidation, and the effects
of adverse weather conditions such as rainstorms, wind pressure, high daily and
seasonal temperature and moisture variations and so on. In order to get a very
reliable roof, not only should the roof covering material be of high quality
but also the roof covering material and the roof structure must function as a
coherent system and thus special care must be taken in the preparation of the
roof structure. Structurally, roofs must be sufficiently strong and rigid
enough to withstand the anticipated wind and imposed loads and should span
between structural supports without any noticeable deflection. In general,
design, construction and environmental factors do affect the roof performance
after it has been constructed and thus the roof can be kept in its functional
form through planned maintenance.
THE
ROOF DESIGN VERIFICATION
Random surveys carried out on the collapsed and roof
leaking systems in the Ashanti region and elsewhere in the country for the past
two years indicated that our perennial roofing problem is not only with old
roofs but also with newly built ones, in both rural and urban areas. There were
situations where newly uncompleted conventional houses in the Kumasi Metropolis
have had their roofs blown off in the same way as those in some rural areas. The
surveys also revealed that the perennial roofing problems are with all types of
buildings, both single and storied, including schools, offices, churches,
factories and residential buildings. Most of the roofing systems which
collapsed or where leaked were mostly pitched roofs with lightweight timber
roof structures covered with a variety of roof covering materials like
corrugated galvanized iron, aluminum, cements asbestos roofing sheets, roofing
tiles, and thatched roofs on earth or on sandcrete wall structures.
TYPE
OF ROOF
FLAT
ROOF
A roof is termed flat when the outer surface is
horizontal or is inclined at an angle not greater than 10⁰.
Flat roofs are common in hot dry areas because of lesser introduction to heavy
rainfall and also form a useful out-of floors living space or area. Flat roofs
are most commonly constructed of reinforced concrete or timber, even though
materials such as steel can be used, and are very much appropriate for very
tall buildings or those with complex plans.
PITCHED
ROOFS
A roof is termed as pitched roof when the outer
surface is sloping in one or more directions at an inclination of between 10⁰
and 70⁰,
and is usually more suitable for use in areas of prevalent heavy rainfall.
Pitched roofs come in different forms, namely the Monopitch, lean-to roof, the
symmetrical roof with a central ridge, the butterfly roof, trussed roof,
carcassing roof and asymmetrical roof with a non-central ridge.
MONOPITCHE
ROOF
A monopitch roof takes the form of a single slope,
where one wall is built higher than the other
LEAN-TO
ROOF
There is a monopitch roof of which the top of the
rafters are pitched against a wall.
ASSYMMETRICAL
ROOF
It is also a double-pitched roof, pitched to a
non-central ridge, with one slope steeper than the other.
BUTTERFLY
ROOF
This is a roof formed of two monopitch roofs falling
to a valley.
TRUSSED
ROOF
This consists of triangulated framework with top and
bottom cords with a system of web members consisting of struts and ties.
CARCASSING
ROOF
A roof
carcassing consists of framework of member to form the roof structure. The
members which make up the roofs structure are outlined below.
ROOF
COVERING MATERIAL
Since the roof of a building is fully exposed to the
rain, wind, sun and the general atmosphere, the covering to the roof structure
must be of durable quality material to meet these harsh conditions. Other
factors to be considered before roofing are the weight and cost of the covering
to be used and maintenance. The total dead-load of the covering will affect the
type of support structure required, and ultimately the total dead-load on the
foundation. Thus, careful consideration must be given to the material used for
the roof covering as outlined by. The coverings used range from the unit sheets
to smaller units in the form of tiles.
Other types of covering may be such as split bamboo
tiles, sawn wood shingles, thatch of grass and palm leaves tiles among others.
Tiles are either hand or machine manufactured and are made from clay or
concrete to a wide range of designs and colors for pitched roofs as mentioned
by, and work upon principle of either double or single lap. The vital factor
for the efficient performance of any roofing tile is the pitch. Tiles are laid
in overlapping course. In all methods of tiling, a wide range of fitting is
manufactured to enable all roof shapes to adequately protect. With all forms of
roof covering, the manufacture’s recommendation for fixing must be strictly complied
with to achieve effective performance of the roof. Roofing sheets are usually
made from lead, copper, zinc or aluminum. The size of the sheet is determined
by the type of material used in producing it and the need to allow for
expansion and construction of the sheet. The usual size of the sheet metal
roofing covering are 2438 x 1216mm, 2438 x 1080mm, 2538 x 914mm, 2438 x 803mm,
each having a range of thickness.
CAUSES
OF ROOF LEAKAGE
The random surveys showed that most of our roofing
systems have undergone continuous deterioration through leakages in the
roofing. After long time exposure to various environmental factors in the
course of their service lives, roof covering materials deteriorate and may be
damaged at some points which may cause leakages in the roof. It was realized
that lack of effective maintenance of such roofing systems especially in the
rural areas to fight the effect of time and that of the aggressive environment
as well as the repairs of accidental damages in roofs also contributed to the
final leaks of some of the roofs in some of the areas.
NAIL HOLES FROM OLD ZINC STRIP INSTALLATIONS
When
people install zinc strips, they hammer nails through the roof. When the zinc
strips stress fractures and flaps in the wind, the homeowner may remove it, but
leave behind the nails. Some of the nails come out when they pull of the strip.
This can cause very slow leaks over long periods of time. Since the holes are
near the peak of the roof, not much water flows over or through the holes.
Staining and wet spots may be seen near the peak from inside the upper floor. A
roof treatment of zinc-sulphate works better than zinc strips and does not
create holes in the roof. If you remove zinc strips, then pull all the nails
and caulk the holes (lift up shingle and squirt caulk underneath, push down on
shingle so caulk oozes up through hole) as you go. Double back to make sure you
got all the holes.
OLD ROOFING SHEET
Take a second and really think about how long you
have had your roof for. How many years has it been? How good of a job did the
last contractors do? Roofs that were built fifty years ago were made with much
different materials and were much less durable than what is used today. And
although there are new and stronger materials for roofing available that do not
mean that you should continue on with your roof past its given lifespan. Every
professional roof contractor should know exactly how many years your roof will
be expected to stick around, given that there are no accidents or horrible
storms. Shingles really last about fifteen years, twenty if you are lucky. If
you have been neglecting updating your roof because you fear that it is too
expensive – wait no more. As soon as you have the money make sure to upgrade it
because you will be spending a lot more money down the road if your old roof is
what causes a much bigger problem.
LEAVES AND TREE BRANCHES
These
materials slow water flow down the roof, hold water and cause water to flow
sideways on a roof. They need blown off the roof. Roofs are only designed for
water to flow straight down the roof. The roof is water resistant, not water
proof. This is probably the biggest cause of roof leaks. And it is also why
home insurance companies may require you to remove and treat your roof for moss
before they will begin coverage or renew a home owner's insurance policy.
IMPROPER INSTALLATION BY CONTRACTORS
I
think the biggest cause is by improper installing of a roof by contractors.
This may include flashing, not filling nail holes left by roof jacks, improper
valley flashing and also improper roof design by the builder.
WORN OR DAMAGE TO THE ROOF RIDGE CAP
Another
cause of roof leakage is a worn ridge cap. This may get worn by contractors
walking on it or dragging ropes across it (for rope and harness setups) without
protecting it with carpet until they are down with the job. Not much water
lands on the ridge, but everything that does will wet the plywood and flow
under the roofing material below. The damage is often hidden and goes undetected
for years. The ridge cap should be inspected before and after a contractor is
on the roof. Ask the contractor to take pictures of your roof ridge cap for
you.
PROBLEMS OF ROOF LEAKAGES
Weather
Roof material deteriorates with the direct exposure to
weather inclemency. Inorganic roofing materials are less susceptible than
organic materials. Exposure to pollutants or industrial atmosphere may
accelerate the decay of your roofing
material
. LACK OF MAINTENANCE
This is most common on flat or low-sloped roofs. Failure to
correct uneven roof will cause accumulation of sediments and water that will
eventually destroy your material.
DESIGN
PROBLEM
Design related problems are very expensive to
correct, and normally the corrections must be done while the replacement of the
roofing material is undergoing. Some examples are;
·
Weak structure supporting the roof that might
deflect excessively under active loads.
·
Improper roof slope, sagging, roof or inadequate
drainage system, resulting in accumulation of water.
·
Incorrectly system to allow expansion and
contraction at changes in deck material or changes in direction.
·
Incompatible roof material.
Wind:
The vacuum and the uplifting pressure created by
wind, blowing over the edge of the roof, can partially rip the roofing membrane
or system that has been applied. The roofing and insulation must be fastened
and secured to the perimeter and to the main roof structure to counteract the
forces that are being exerted on the roof.
FLASHING
MATERIAL
The function of the flashing material is to provide
a seal, a watertight seal, between roofing materials. This is an area that
should be carefully inspected prior to any other areas. Incorrect installation
procedure or attachment, and improper sealing of the flashing will allow the
water to enter between the roofing systems and the roof structure.
I
recommend that
·
there should be the uses of proper and correct tools
for correct work in other to avoid double nailing of roofing sheet.
·
Contractors should try to avoid
employing unskilled workers
·
The concrete mix for roofing should be
well mixed to achieve its required ratio and when casting should also be well
tamped to avoid leaking.
·
Curing of roofing concrete is very significant
to the ultimate strength development of the concrete and hence the need for the
contractors to cure the concrete works to avoid excessive drying out.
·
The contractors should ensure that all
the concreting materials brought to the site are protected against the adverse
weather. Fine and coarse aggregates may be stored on a cleaned surface under a
covering to avoid contamination.
·
Cement/binder may be stored under opened
shed on raised platforms.
·
Proper maintenance of roofs should be
practiced to ensure that structural members retain their life-span and to
perform their function adequately.
