A flat roof is essentially a low-pitched roof and is defined as a pitched roof of ten degrees or less to the horizontal. Generally the angle of pitch is governed by the type of finish, which is applied to the roof. A key aspect of Jamaica homes for sale.
The function of the flat roof is to:
a) Prevent the entry of rain and dust, particularly at joints and junctions
b) Resist the effect of wind (both pressure and suction), sunlight and solar intensity
c) Meet the requirements of current building regulations on structural stability, fire precautions, thermal insulation, condensation, vapor insulation, and loads, dead and imposed, according to whether roof access is permitted or not.
d) Provide a suitable wearing surface
e) Permit movement due to stress and natural causes
Flat roof construction in timber
The construction of a timber flat roof involves the use of timber joists thirty-eight millimeters to fifty millimeters and from seventy-five to two hundred millimeters deep is placed on edge from four hundred millimeters to six hundred millimeters apart with the ends of the joist built into or against block walls and partitions. The depth of the joist must be sufficient to enable it to span the rooms below without sagging, while the width will normally be fifty millimeters which will allow ample space for fixing boarding.
It should be noted that the strength of the timber joist is not in its width but in its depth, therefore, it is necessary to increase the depth to increase the strength.
The flat roof must be provided with a fall to remove the rainwater as quickly as possible. The direction of the fall will be determined by the position of the roof in relation to other buildings or by its size or shape.
To obtain the fall firring pieces are fixed to the top of the roof joists and upon which the roof boarding is nailed.
Firring pieces consist of either tapered lengths of wood nailed to the top of each joist or varying depth lengths of wood nailed across the joists. Tapered firring is used for roofs covered with chipboard and the varying depth firring for boards laid parallel to the slope of the roof so that variations in the level of the boards do not impede the flow of rainwater down the shallow slope.
Flat roof in concrete
Reinforced concrete flat roofs are constructed in the same way as reinforced concrete floors – both in-situ and precast.
Trusses are structurally designed frames based on the principles of triangulation. They consist basically of upper and lower chords, tension and compression webs and devices used to fasten the members together.
Trusses are designed to carry roof loads and transmit them to the nearing wall on which they rest. Triangulation of the truss will vary according to span. It is essential that the members of a roof truss are rigidly connected together since light sections are generally used.
Advantages of Roof Trusses
- Roof trusses save materials and on site labor costs.
Roof trusses can also eliminate interior bearing partitions because trusses are self-supporting.
Trusses can be erected quickly and therefore the structure can be enclosed in a short time.
Root trusses come in a wide variety of shapes to solve nearly any problem.
Trusses are usually designed to span from one exterior wall to the other with lengths of six to nine meters or more.
Factors influencing the choice of roof types
o Size and shape of building
o Initial cost
o Ease with which services can be accommodated in the roof space
o Weather proofing
o Maintenance cost
o Speed of erection