Case 1

Remedial (see also Remedial)

Clean the surface thoroughly before repainting. The affected areas should be washed cleaned with pressure jet and an abrasive cleaning agent. Washing should begin from the top. Repaint with paint system of weather resistant quality.

Removal of Efflorescence

-If efflorescence exists on an existing surface, the best method of cleaning or removing it, would be to use an acidic cleaner. These salts and minerals would readily dissolved in these acidic cleaning agents.
-Care should be taken when using these acidic agents which may be corrosive in nature.
-Occasionally, the cleaning and removal process can become more difficult if latex or chemical transmission occurs at the same time as the salts and minerals surfaced. These latex or comparable chemicals are often found in the more recent and advanced cementitious adhesives and grouts available and can form a protective layer which defends the efflorescence from direct contact with acidic cleaning products.
-To help solve this problem, select an acidic product that has cleaning agents in it (acid and cleaner in one single product). Another recommendation would be to use a high alkaline restoration cleaner to break down the latex protective coating, rinse well and then proceed with the acidic cleaning.

Repair: Application of Water Repeller

This type of solution act as a hydrophobic surface by penetrating into the pores of the bedding or screed layers and tightening the pores such that the water is not allowed to penetrate through.

It allows vapour to escape and prevent any development of hydraulic pressure caused by the retained moisture.

Repair: Application of Water Proofer (Silicate based)

This kind of solution reacts with the free lime in cementitious materials and seals the pores and cracks in the surface. In fact, as long as moisture and free alkali is present, the reaction will continue by sealing pores. This can also be referred to as “active” repair.

Repair: Application Water-based Clear Coating (with polymer particles)

In this treatment the floor is ponded with the solution and allow the super fine polymer particles to penetrate into the porous structure to form a permanent and continuous plug.

Constant maintenance of the external rendering is one method of keeping the staining at minimal level. Stained paints and plasters are usually cleaned with high-pressure water jet. However if the stains are too serious and large, it is more appropriate to remove the affected surface coatings, sand, clean and redo the coating

However, main consequences of staining can be kept low by adopting good design practices which will discourage the accumulation of dirt particles on the surface of external rendering.

Table 1: General Cleaning for painted surface