In this method the surface exposed to moisture is treated by providing a thin film of water-repellent material over the surface. Such a surface treatment may be external or internal. Generally the external treatment is more effective in damp prevention when compared to internal treatment.
Surface treatments include pointing, plastering, painting, distempering, etc., Lime-cement plaster mix (1 cement:1 lime:6 sand proportion) is more effective.
Materials used for surface treatment are sodium or potassium silicates, aluminium or zinc sulphates, barium hydroxide and magnesium sulphate, soft soap, linseed oil, coal tar, soap, bitumen, remix and gums, etc., applied in alternate layers with suitable combination depending on the climatic conditions.
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