1. Building Construction I Sofia Sebastian 1
Roofs
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2. Building Construction I Sofia Sebastian 2
Flat RC Roof
Flat roofs – timber or reinforced concrete
Advantages of flat roofs
Easy to put up
Create extra usable space if they are accessible
Easily maintained
They lose heat
A reinforced concrete roof is built exactly like a reinforced concrete floor slab
Solid or
hollow pot construction
Disadvantages of flat roofs
They are not as weather proof as pitched roofs
The finishes do not last as long as roof tiles
Building Construction I Sofia Sebastian

3. Building Construction I Sofia Sebastian 3
Flat RC Roof
The top of the structural slab for a flat reinforced concrete roof is laid level
Fall – 1:80
The falls are provided by a cement and sand screed that has the correct slope
Finishing off a flat reinforced concrete roof
The edges of a flat reinforced concrete roof can be finished off by constructing
An overhanging roof that takes the edge of the roof over the surface of the external wall
A parapet roof that extends the edge of the external wall higher than the roof
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Finishing off a flat reinforced concrete roof
Overhanging roof
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5. Building Construction I Sofia Sebastian 5
Finishing off a flat reinforced concrete roof
Parapet roof
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6. Building Construction I Sofia Sebastian 6
Flat RC Roof
Finishing off a parapet roof
Copings – short sections of concrete fitted together, finish off the top of the exposed external wall of a parapet roof and shed rain
Coping are bedded in a dpc of bituminous felt to improve their water resistance
Copings should be wide enough o overhang the wall by at least 50mm
The tops of the copings slope in one or two directions to shed rain
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Water proof roof finishes – Laying a bituminous felt roof
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8. Building Construction I Sofia Sebastian 8
Flat RC Roof - Water proof roof finishes
1. Bituminous felt – sheet material with a fibrous base soaked in bitumen. Usually laid on timber roofs
2. Mastic asphalt as laid on roof – is a mixture of graded limestone bonded with asphaltic cement to form water proof material that is plastic when heated.
Mastic asphalt – material containing bitumen that is laid as a hot elastic covering. As it cools, it hardens to form a joint less cover that is usually put on concrete roofs.
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9. Building Construction I Sofia Sebastian 9
Insulated concrete flat roof detail
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Insulated metal roof detail
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11. Building Construction I Sofia Sebastian 11
Construction detail of an Insulated flat roof on a cavity wall
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12. Building Construction I Sofia Sebastian 12
Green roof detail
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13. Building Construction I Sofia Sebastian 13
Roof surface
Building Construction I Sofia Sebastian