Capillary Action
The movement of liquid through narrow spaces against gravity, driven by surface tension. In building materials, water travels through the pore network of masonry and concrete this way.
On an actual building
It explains why water rises up walls, why crystalline waterproofing chemicals can be carried into concrete by pre-wetting, and why penetrating repellents work by lining pores rather than blocking them.
What we most often have to correct
That water only travels downward. Capillary movement carries it upward and sideways through the pore structure.
Terms that come up alongside this one
- Rising Damp
Ground moisture drawn upward through the pores of masonry by capillary action, typically producing a horizontal tide mark and salt deposits..
- Breathability (Vapour Permeability)
The ability of a material to let water vapour pass through it while still resisting liquid water..
- Crystalline Waterproofing
A cementitious system carrying reactive chemicals that penetrate concrete and grow insoluble crystals within its capillary pores, blocking water paths inside the material..
Capillary Action — questions we get asked
What does capillary action mean in waterproofing?
The movement of liquid through narrow spaces against gravity, driven by surface tension. In building materials, water travels through the pore network of masonry and concrete this way.
Why does capillary action matter on a real project?
It explains why water rises up walls, why crystalline waterproofing chemicals can be carried into concrete by pre-wetting, and why penetrating repellents work by lining pores rather than blocking them.
What do people commonly get wrong about capillary action?
That water only travels downward. Capillary movement carries it upward and sideways through the pore structure.
Have a building showing this?
If a term on this page describes something you are looking at, a site inspection will tell you how far it has gone and what it needs. It costs nothing.
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