The Hidden Cost of Mildew

Mildew is a fact of life in the Lower Mainland of BC. As I keep reminding our clients, we live in a rainforest. But is the slimy scum just an unsightly nuisance?

The short answer is no.

But doesn’t exterior paint contain mildew resistant components? Yes, but the mildew does not grow and build within the paint film. It begins on the top.

Mildew is made up of live organisms that feed off of organic materials that settle on top of surfaces. Dew and slow moisture evaporation is the key element in mildew growth, which is why it is most commonly found on white and lighter coloured surfaces that don’t absorb as much heat, and in areas where the sun reaches less often. Mostly on the north facing elevations of buildings. This doesn’t mean that it won’t grow on darker colours, it just takes longer to build up.

The presence of mildew means moisture. It will hold moisture on the surface of paint or other surfaces which will wick into the substrate through the most microscopic holes, cracks and gaps in protection. If left unchecked, the moisture and mildew will wick and etch itself into the surface.

On powder coated metal or factory finished vinyl surfaces it will eat in and leave unsightly permanent stains.

On painted wood, it will cause delamination of the paint coating, leaving the wood exposed and vulnerable to premature wood rot, costing more in the long run to repair, replace and repaint. If left long enough on painted wood, washing the mildew off will also remove the paint, forcing a repaint project prematurely.

In addition to the damage, an unmaintained complex costs in curb appeal. Owners that choose to sell in a complex that is not well maintained are potentially giving up percentages of what their unit "could" sell for, reducing the property values for all residents.

The best practice for strata complexes is to budget for regular cleanings. The more prone a complex is to mildew growth, the more often it should be cleaned. This simple step will extend the life of a paint coating by up to 50%. Allowing mildew to remain on a painted surface can cut the life of the paint coating in half, or more if mildew growth is really aggressive.