Civil Engineering

Galvanized Corrugated Iron Roofing.


Written by VR Friday, 11 February 2011 02:26

Corrugated iron sheet galvanized with zinc,to protect it from rusting in wet condition is known as galvanized corrugated iron sheet.Even if appearance of corrugated iron sheet is not good it is widely used due to its light weight,fire proofness and its durability.Width of sheet is 60 to 85cm and length 1m to 3.5m.The thickness of sheet is 0.15 to 1.8mm.Spacing of purlin is 2 to 2.5m.G.I nails or screws are used for fixing sheets.End overlap of G>I sheet is 7.5 to 1.5 cm and side overlap one corrugation.Weight of G.I sheet covering is lighter than.A.C sheet roof and tiled roof thus lighter supporting structure is enough which reduce the cost of roof.


Asbetos Cement Sheets(AC Sheets).


Written by VR Friday, 11 February 2011 02:16

Asbestos cement is a mixture of cement and asbestos.Asbestos cement sheets are suitable for roofing and are available in two varieties(a) with corrugation and (b) with wider channel.Thickness of A.C sheet is 3mm to 6mm and spacing of purlin is 1.0 to 1.5m.Overlap,15cm on ends and 5cm on sides.Galvanized iron screws of minimum 5cm length with lead or bitumen washers can be used for fixing sheet on purlins.Length of A.C sheet varies from 1.5 to 3.05m.Straight and corrugated sheet of various sizes are available in market.They are now become popular due to following reason:light weight,low cost,tough,durable,water tight,fire resistant and available in bigger size unlike like tiles so supporting frame too is simple and light.They so not require any protective paint and no maintenance cost.

A.C sheet is impervious and is fire and vermin proof.They are breakable and heavier than G.I sheets.One of the disadvantage of A.C sheet is that it transfers heat and cold easily.

Manglore Pattern tiles.


Written by VR Friday, 11 February 2011 02:08

These tiles are of flat pattern and they are provided with suitable projections so that they interlock with each other,when placed in position.Special Manglore tiles are available for hip,ridge and valley portion of the roof.For covering one metre square 15 tiles are required.Life of this tile is about 25 years.They are available in sizes 320*210 mm;340*215 mm and 350*220 mm.As their size is larger,spacing of batten is 32cm centre to centre.The lowest batten very near to eaves should be nailed closer which is 25cm.Ridge tiles are laid dry and pointed with cement mortar.

The main disadvantage of tiled roof is that tiles are heavier than other roofing material thus required closer spacing of rafters and batten.Average weight of tiled roof is 7.5 N/mm2.Most of the tiles are porous and thus absorb moisture and may cause attack of vermin.


Filler Slab.


Written by VR Friday, 11 February 2011 02:01

Filler slab is a concrete slab in which the bottom portion of the slab is repaled by flat clay tiles pattern tiles.In case of concrete slab top portion under tension and bottom portion of the slab under compression.This tensile force acting on the bottom portion of the slab carried by reinforcement so concrete in that portion can be replaced by cheaper filler material like tiles.This mode of construction will reduce the cost of construction.

Procedure for the construction of filler slab.

  • Above the form work,steel reinforcements of designed size are tied together to form a grid.
  • Pairs of clay roofing tiles are placed in the gap be tween the reinforcement in line.
  • Pour freshly prepared concrete in between the reinforcement and tiles and compact it carefully.Level the concrete surface and cured if for 14 days.

Reinforced Cement Concrete Roof.


Written by VR Friday, 11 February 2011 01:56

R.C.C roofs are becoming very common in the construction of modern buildings.It is made up of concrete and steel.There are two types of roof slab(i) one way slab,when the ratio of length of room to width is greater than 2.0 (ii) Two way slab,when this ratio is less than 2.0.For one way slab main reinforcement to be run parallel to the shorter span.In two way slab main reinforcement runs parallel to both sides of the room,and at corner suitable mesh reinforcement to be provided to resist temperature stresses.


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