For exterior surfaces it is very important to undertake repairs of any wall imperfections before commencing painting. The most common problem with exterior walls specially old constructions is cracks in the wall. Avoid applying putty or filling compound while painting exterior
surfaces. Fill up cracks with a 1:3 cement and sand mixture. All external drainage pipes must be checked for rusting or leakage. Any faulty plumbing must be rectified.
Special attention must be given to the roof. Check for cracks near the edges and close to the water reservoirs. Proper masonry or waterproofing work on the ceiling will enhance the performance of the painted surfaces.
- Newly plastered surfaces must be allowed to cure for at least 35 to 45 days before painting.
- To ensure long protection, the surface to be painted should be free from dust, grease and any loose materials.
- Remove any fungus and algae growth thoroughly by brushing it vigorously with wire brush and then cleaning it with bleaching powder solution in water (dissolve 10% bleaching powder in 1 litre of water, filter the solution and apply with a brush or sponge). This treatment should be done with greater care on the top of the awnings, sunshades, parapets and other horizontal surfaces where water is likely to accumulate during monsoon.
- Previously oil painted surfaces, should be sanded thoroughly to remove loose particles and made dull and matt for better adhesion. Exterior rough surfaces, previously coated with cement paint, should be wire brushed and washed with water thoroughly and dried completely. Before painting, ensure that the surface is free from chalking.
- The exterior surface should not be affected by water and constant dampness should be avoided . If you are painting during the rains allow for 2-3 days of total sunshine for the surface to dry out completely and before commencing painting.
- Apply a liberal coat of Exterior Wall Primer using recommended method.
- Apply two coats of top coat paint at recommended dilution. You can use Apex Weather Proof Exterior Emulsion or Apex Textured Exterior Emulsion or Ace Exterior Emulsion as top coat.
- A gap of 4 to 6 hours must be given between two coats.
- It is recommended that horizontal surfaces like the tops of awnings and Parapets must be given an additional coat for greater protection.
Content retrieved from: http://www.probcguide.com/finishing-works/painting/external-wall-paint/.