Exterior Paint Chalking - Causes & Solutions

How many times have you touched the outside wall of a painted house, and when you lifted your hand you found that your fingers and palm were covered with a chalky substance? This is the best example of exterior paint chalking.

Causes

Chalking is most commonly seen with cheaper exterior paints that contain excessive amounts of pigment extenders or lower quality binding agents. Over time, moisture and UV radiation, as well as temperature extremes, will cause the binding agents to begin breaking down and the pigment will begin separating from the paint surface in the form of a powder.

Severe Chalking

As chalking becomes more severe, rain or mist often cause the pigment powder to run or bleed onto nearby surfaces. If the nearby surfaces are wood, brick or concrete, this often results in unsightly staining that can prove quite difficult to remove.

Prevention

The easiest way to prevent exterior paint chalking is to use a high quality UV-resistant paint. However, small amounts of chalking often still occur with most paints, especially in hot and dry areas. In such cases, occasionally washing the painted surface and treating it with UV-resistant sealant can help extend the life of the paint.

Solutions

Depending upon the types of paint pigment involved in the chalking, sometimes the best solution is to simply wash and/or sand down the surface and repaint with a better quality product. In less severe cases, you can remove chalking with commercially available cleaning agents, and rinse the surface afterward with water.

As with many other household projects, preventative maintenance almost always saves time, work and expense further down the road. It is often far wiser to invest in higher quality and more durable paints at the start, in order to avoid having to address a larger and potentially more expensive problem later on.

Primers and Finishes

A penetrating primer is essential to seal off any remaining chalk.
Select a top quality exterior paint in the color and sheen of your choice.

Substrates, Primers

Substrate: Wood
Primers: 239 Kel-Bond II Surface Conditioner
Finish Coats: 1240 Acry-Shield Exterior Flat Finish
1245 Acry-Velvet Ext. Low Sheen Finish
1250 Acry-Lustre Ext. Semi-Gloss Finish
1235 Seasons Ext. 100% Acrylic Flat
1236 Seasons Ext. 100% Acrylic Low Sheen

Substrate: Metal
Primers: 1711 Kel-Guard Rust Inhib. Primer
Finish Coats: 1240 Acry-Shield Exterior Flat Finish
1245 Acry-Velvet Ext. Low Sheen Finish
1250 Acry-Lustre Ext. Semi-Gloss Finish
1235 Seasons Ext. 100% Acrylic Flat
1236 Seasons Ext. 100% Acrylic Low Sheen

Substrate: Masonry
Primers: 239 Kel-Bond II Surface Conditioner
Finish Coats: 1240 Acry-Shield Exterior Flat Finish
1245 Acry-Velvet Ext. Low Sheen Finish
1250 Acry-Lustre Ext. Semi-Gloss Finish
1235 Seasons Ext. 100% Acrylic Flat
1236 Seasons Ext. 100% Acrylic Low Sheen

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