ROOF COVERING MATERIAL SLATE

Anousha saleem D-15-AR-06Material and construction III

SlateSlate s a stratified metamorphic rock and is obtained from open quarries. It is the finest grained foliated metamorphic  rock. Many slates will form smooth flat sheets of stone which have long been used for roofing, floor tiles, and other purposes. Slate is mainly composed of the minerals quartz and muscovite or illite, often along with biotite, chlorite, hematite, and pyrite and, less frequently apatite, graphite,kaolinite, magnetite, tourmaline, or zircon as well as feldspar.

Formation of a single tile •Slates are obtained from

quarries as blocks .

•Reduced to slabs afterdividing into sections using diamond or circular saw.

•Each slab is divided intothin laminate or slate by using splitters.

Fixing and laying of slates

Slates roofs tiles are usually fixed either with nails or with hooks. Fixing is typically with double nails onto timber battens or nailed directly onto timbersarking boards.

Nails are made up of alloy and stainless steel.

Laying methodsThere are various methods of fixing a slate .1.By nailing near the head .2.By nailing near the middle.

Head nailed slates:-Slate are fixed by means of copper nails driven through holes which are punched near the head of each slate . Two holes are punched in each slate about 25mm from its head and about 40 mm from the side .The advantage of this slate is that there is two layers of slates covering the roof so there is no risk of water getting through holes.

Center nailed slates:-One low pitched roofs, slates are commonly fixed by center nailing. Nails are not driven exactly in the center but at a distance towards the head of the slates .The advantage of this method is that the slates are firmly held in position because of this less number of slates are required.

COST 25-30/Sq.ft

Quality of a good slate•It should be free from white patches , hard, tough durable and give a sharp metallic ringing sound when struck with each other.•It should be easily holed.•It should not split and absorb water more than 2% of its weight when soaked for 24 hours.SizeCommon sizes are 600*300 mm,500*250 mm and 450*200 mm

The ProsAppearance variation in sizes and colors give aesthetic appearance.Fire Resistance Slate roofing is one of the most fire resistant roofs that exist Longevity It needs less maintenance and runs for almost 20-30

years.The ConsWeight The weight of slate roofing tile is anywhere between 800 and 1,500 pounds per square (100 square feet). So it is necessary to built a structure that can bear its over all weight

THANK YOU