Roof coverings for sloping roofs

ROOF COVERINGS FOR SLOPING ROOFS

1. SELECTION CRITERIA

Sloping or Pitched Roof Coverings are placed over the roof frame work. The selection of roof covering material depends upon the following factors:

1. Type and Nature of building

2. Type of Roof Structure, Self-weight of the

3. Slope of the Roof

4. Appearance or Roof Coverings

5. Climate of the Locality such as sun, wind, rain, snow, etc.

6. Durability of Covering Material

7. Fabrication Facilities of Covering Structure, etc. Material

8. Heat Insulation

9. Resistance to Fire

10. Cost of Roof Coverings

2. ROOF COVERING MATERIALS

For domestic buildings, Tiles and Slates are widely used as a roof covering material. For industrial buildings, the roof covering materials used are Asbestos Sheets, Galvanized Iron Sheets, etc.

1. Tiles (Clay / Concrete / Plain Tiles)

Clay Tiles are made similar to bricks. The sizes and shapes have improved from time to time. Concrete Tiles are used to a limited extent. Plain Tiles are used along with special tiles such as Mangalore Tiles and Pan Tiles.

Mangalore Tiles is a very popular type of patented tile. These tiles are machine pressed clay. tiles. They have better interlocking, resulting in better protection against heavy rain or wind.

Pan Tiles are made out of clay. The roof is covered by the use of Bent Tiles. This is comparatively of less weight. There is no leakage at the joints of the tiles.

2. Slate Roofing

Slate is a sedimentary rock. It could be split into thin sheets. Slates are available in different natural colours. Most common colours are various shades of Grey, Black and Red. A good quality slate should have (i) Hardness, (ii) Even colour, (iii) Even texture.

Also, in should be (i) Impervious and (ii) Durable.

It should also give a ringing sound when struck. It should not have white patches.

3.  Asbestos Cement Sheets (A.C. Sheets)

A.C. Sheet consists of Asbestos and Cement. Asbestos is a silky fibrous material found in veins in metamorphic rocks. It is found in several varieties. But, asbestos which is a compound of silica and magnesia is used. A.C. Sheets are good insulators.

They are available in three shapes, namely,

(i) Corrugated A.C. Sheets (Fig. 18),

(ii) Semi-corrugated (or Trafford) A.C. Sheets (Fig. 19) and

(iii) Plain or Flat A.C. Sheets.

Advantages of A.C. Sheets

1. Properties: A.C. sheets are cheap, durable, tough and water-tight.

2. Light Weight: They are of light weight and hence can be erected easily.

3. Less Maintenance: Maintenance is less.

4. Fire-Resistant: They are fire-resistant and termite resistant.

5. Workability: A.C. Sheets can be nailed, punched or sawn.

6. No Painting: Sheets need not be painted at all.

Uses

1. Corrugated and Semi-corrugated A.C. Sheet are used for roof covering. The sheets are fixed to the wooden battens from the top of the corrugations through 3 mm diameter holes using J-Bolts.

These sheets may be spanned safely up to a span to 1.68 meters.

2. Plain or Flat Sheets are used for partitioning work. They are also used in industrial buildings either independently or in combination with other type of sheets for paneling, false ceilings, wall claddings, etc.,

4.  Galvanized Iron Sheets (G.I. Sheets)

Like A.C. sheets, G.I. sheets have high durability, light in weight and fire resistant. G.I. sheet consists of thin iron metal sheet. It is galvanized with Zinc (hence called Zinc Sheet) to protect it from rusting action of water. It is given the bent-shape or corrugation for additional strength.

These sheets are widely used, though the appearance is not that good. Due to the high cost of G.I. Sheets, they are now replaced by A.C. sheets.