The Central Building Research Institute of India has worked out a speedy, cheap and effective method of water-proofing existing mud walls. It consists of spraying a suitable material which gets absorbed in the wall and making it water proof. The absorbed material shows its water repellence, and it is durable against weathering.
Preparation of the Material
Fifty litres of kerosene oil are taken in an empty tar drum (cut into half) of 100 litre capacity, and molten asphalt of 801100 grade is taken out in a small container and 25 kg of it is added to the kerosene oil in doses of small quantities. Each addition is followed by constant stirring till the asphalt is completely dissolved in oil. Thereafter, the solution is allowed to cool off and then, transferred to a 200 litre-capacity stopped barrel through a fie sieve to exclude undissolved foreign matter which would otherwise choke the pumps during spraying.
Spraying Equipment
Pump which is used for spraying insecticides and pesticides for crop protection is suitable for asphalt spraying also. Highly efficient spraying is achieved with a nozzle orifice of 2 to 2.5 mm diameter and a discharge rate of about 5 kg/mm.
Surface Preparation
It is advisable to repair the cuts and holes and apply a coat of mud-cow dung slurry onto the wall to seal off all the cracks on the surface before spraying. The wall should be allowed to dry fully before spraying begins. Old walls should be brushed with a wire brush to make the surface rough.
Application
The prepared material should be sprayed twice or thrice, depending upon the porosity of the surfaces, at an interval of at least four hours on a sunny day, allowing the previous coat to be absorbed fully. The spraying should move horizontally, starting with the top of the wall. Spraying on the wall directly exposed to the sun should be avoided as otherwise it will evaporate without being absorbed at all. Two persons can spray an entire two-roomed rural house in a day. The black colour can be overcome by applying lime-wash mixed with animal glue.
Cost
Each square metre of the wall surface requires 1 kg of the water proofing material; and including white washing will cost Rs. 40/- per m2. Thus, a small rural house can be made water proof by spending Rs. 160/-. But the process will have to be repeated after every 3 years.
Precautions
Inspite of the application of the above methods of water proofing, a mud house may fail due to the following reasons :
- Driving rain and water logging at the base level are the common causes of deterioration of mud walls, and the base should be made of conventional brick work in cement mortar or of stone masonry, if necessary.
- Water seeping through the top of the wall is another source of failure of the wall. The thatched roof should, therefore, be of 30' slope (or more) to quickly drain off the rain water.
If you are in need of spraying equipment, whether it is for residential or commercial purposes, you will certainly need to know what exactly your options are going to be like. There will be numerous types of sprayers to choose from, including utility 3-point sprayers which come in a variety of sizes. Before you make a final decision of any kind on one of these products, you will need to take into consideration what your own needs are.
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