Existing roofs can be made fire-retardant by coating them with a layer of specially prepared mud, provided the rafters (of bamboo) supporting the roof can take the additional weight of mud layer.
Materials Required
Mud, chopped straw, cow dung, bitumen; kerosene and paraffin wax.
Preparation of Mud
Add 64 kg of chopped straw to 1 cubic meter of mud, taken from a pond, while the mud should have 25 to 30 percent of clay and the rest may be silt or sand. This mixture must be kept wet for 1 week and should be frequently mixed with a shovel and kneaded by foot or otherwise.
Preparation of Bitumen
Bitumen of 80/100 grade is melted in a tar drum and added to kerosene gradually in the proportion of 100 : 20, and then 1 part by weight of paraffin wax in molten form is added and mixed well.
Mixing Bitumen with Mud
To the mud already prepared, the bitumen mix (as discussed above) is added, at the rate of 25% by weight and well mixed with shovel and then kneaded. This mix is now ready for application over the thatched roof.
Application over Roof
The water-proof mud plaster prepared (described as above) is applied with trowel as a first coat of 10 to 15 mm at the top and 10 mm at the bottom of the thatched roof. When this has dried, a second coat of 10 mm is applied at the top to close the crazing of the first coat. When this has also dried up, two coats of cow dung-mud- bitumen. in the proportion of 4 : 4 : 1. with required bitumen-kerosene in the ratio of 1 : 2 is brushed on in two coats. To make the roof appear white, white-wash mixed with animal glue may be applied.
Cost
Such an application will increase the durability of the roof to 6/8 years costing only Rs. 800/- for a house of 25 m2 plinth area.
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