Did you ever wonder why sand on the beach is cool and moist above the height of the tide? Today we explain how capillary action flows moisture upward even to the handle of a paintbrush. And for that matter makes the legs of your trousers damp up to your ankles, when you walk across a sopping wet lawn.
What Is Capillary Action in Non-Scientific Terms?
Capillary action is a natural force that makes water flow through a horizontal tube, or even uphill in defiance of gravity! The primary drivers of this process are:
1… The ‘sticky’ nature of water holds individual molecules together.
2… Water has an innate ability to attach to many other substances.
3… But this action ceases when gravity overcomes surface tension.
Did you ever wonder why liquid spreads up a paper straw, but not up a lift shaft? This is because a paper straw has a sufficiently small diameter to support those forces. We can plot this relationship on a graph as follows:
How Capillary Action Can Reach Roof Timbers
We now understand how capillary action flows moisture upwards through a tube. However, the same phenomenon manifests in cloth, paper, and even porous wood. That’s why we seal exposed building timbers with paint, and other oil-based products. However, some roofers seldom do because they believe their roofs will keep the supporting timbers dry.
Unfortunately, this insurance policy cannot hold if rain or sleet, even mould penetrates past the roof, soffit, or fascia. That’s because porous woods absorb the liquid, although the rate slows as saturation approaches. Moreover, the rate of evaporation reversing this depends on temperature and humidity.
Damp Rot Strikes as Capillary Action Makes Moisture Travel
Damp roof timbers are susceptible to wet rot after prolonged exposure to damp. This encourages a variety of fungal species. Some of these organisms feed on cell walls of timber breaking them down. This weakens the wood, and affects the structural integrity of the roof if left unattended.
This information comes to you from Valiant Exteriors Limited trading in Calgary. We are a small, family business keen to take care of all your roofing concerns.
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Deck Timber after Prolonged Water Exposure (Image Øyvind Holmstad)