Factors for selecting roof covering

The following factors should be considered while selecting a roof covering:

1. Climate and rainfall: heavy rain needs a steep slope and an impervious covering; areas with strong wind need a firmly fixed covering.
2. Slope of roof: thatch needs a steep slope, while sheets can be laid flatter.
3. Weight and supporting structure: a light covering (CGI) needs light, cheaper trusses; tiles and slates need strong trusses.
4. Cost and availability: local materials (slate, stone, clay tiles) lower the transport cost.
5. Durability and maintenance: the life of the covering and the need for repair.
6. Fire resistance: slates, tiles and metal are better than thatch and wood.
7. Thermal and sound insulation: thatch and tiles insulate better than metal sheets.
8. Appearance: colour and texture to suit the building.
9. Ease of fixing and repair, and resistance to earthquake damage (light coverings are preferred in seismic zones like Nepal).

For Nepal, light, fire-resistant and earthquake-safe coverings (CGI sheets, light tiles) are generally preferred; heavy stone slabs or clay tiles need a strong supporting structure.