Technical Guide
Waterproofing External Walls
Often external walls develop wet spots and leakages. Causes are generally the absorptive nature of the plaster, due to age and degradation (or otherwise) as also the absorptive nature of the brick-work or block work behind the plaster. These walls need to be waterproofed effectively.
Case I
If the dampness is not widespread this can be remedied by the following method, using Polymer based chemicals with good quality cement paint.
Method:
a) Clean the surface thoroughly to remove all loose material, fungus, old paint etc. and moisten with water.
b) Mix Polymer based chemicals in the water used for preparation of the cement paint. Mix thoroughly to a uniform consistency. For the first coat use 20% Polymer based chemicals by weight of (dry powder) cement paint. For the second coat add only 5% Polymer based chemicals
c) Cure the paint after 24 hours.
d) Follow all the usual steps taken in painting using cement paints
(powder form).
Case II
If walls are extensively damp and plastering is deteriorating, replastering would be called for. In this case following steps are recommended:
Method:
1. Remove the old plaster, remove all the loose particles, and dust etc. and wash with a jet of water.
2. Prepare a mortar mix 1:4 [cement : sand], or as directed by the engineer-in-charge, and admix thoroughly 3% Polymer based chemicals by weight of cement in this mortar.
3. Provide a first coat plaster using the mortar in item 2 above. Keep its surface rough to receive the second coat. Apply the second coat after the first coat has hardened.
4. Cure as usual as per regular construction practice.
5. External walls may be finished further as per method in Case I
Case III
If walls are extensively damp and plastering is deteriorating, replastering would be called for. In this case following steps are recommended:
NEW WALLS
Once the plastering is completed, cured and dried out (to the extent possible) external painting with Polymer based chemicals can be taken up.
Please follow the detailed instructions in the literature on Polymer based chemicals for 'Instructions for use'.
In case it is desired to finish the exteriors using a cement paint only, then use Polymer based chemicals to improve several qualities of the cement paint coating. The combination of Polymer based chemicals and good quality cement paint upgrades the ultimate performance of the decorative finish to a plastic-emulsion or acrylic type of finish to provide an effective water proofing & long lasting service.
The details as in case I may be followed for application.