MOISTURE PROBLEMS: Paint and Stucco Will Interact -

Moisture can cause peeling paint on the lower part of stucco or other masonry walls. Water entering the ground can be absorbed into masonry, then migrate upward and, warmed by the sun, create water vapor pressure on the back side of the paint film. This problem is often accompanied by a white crystalline deposit called efflorescence on the paint and a general decomposition of the masonry itself.

Applying a waterproofing compound to the surface of the paint will NOT help. Water must be stopped before it enters the masonry below ground. Excavating and coating below grade surfaces with a coal tar or asphaltic coating will help.

Improving the drainage of the water away from the structure will also help. This problem of water wicking also occurs with wood in contact with the ground or areas of high moisture concentration (piled snow, siding adjacent to rain water, down spouts, etc.), causing the grain to swell. This in turn causes the paint to peel from the surface.

Two of the major causes of painting failure on exterior wood surfaces are either moisture passing through the substrate from the interior, or exterior sources of moisture getting behind the painting film. These may result from faulty flashing, lack of adequate ventilation in the house itself (i.e. ridge vents, soffit vents, attic vents), allowing trapped moisture to evaporate, improper or inadequate caulking, or a porous or cracked painting film, among others.

A clean surface is extremely important to both interior and exterior painting. To clean most surfaces prior to painting, use a mild detergent solution to remove accumulated dirt, chalk, and grime. Pressure washing with a portable high pressure washer and adding a chemical injection is excellent for removal of dirt, surface contaminants, chalk, flaking and peeling paint from almost any exterior surface.  After washing, rinse the area thoroughly with water and allow to completely dry before painting with primer or finish coat.

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