Wall Water Migration, What causes wall water migration

Wall water migration speaks to what is wall water migration, what is wall water migration.

They are the forces that cause moisture to move through the exterior walls such as gravity, momentum, surface tension, capillary action and air currents.


This is a factor in pulling water through a wall only if the wall contains an inclined plain that slopes into rather than out of, the building. It is usually a simple matter to detail the exterior wall system so that no such inclined plains exist, though sometimes a loose gasket or an errant bead of sealant van create one despite the best efforts of the designer.


The momentum of falling rain drops can drive water through a wall only if there is a suitable oriented slot or hole that goes completely through the wall. Momentum is easily neutralized by applying a cover to each joint in the wall or by designing each joint as a simple difficult path.

Surface Tension

The surface tension of water, which causes it to adhere to the underside of a cladding component, allows water to be drawn into the building. The provision of a simple drip on any underside surface to which water might adhere will eliminate the problem.

Capillary Action

This occurs when the surface tension effect that pulls water through any opening that can be bridged by a water drop. It is the primary source that transports water through the pores of a masonry wall. It can be eliminated as a factor in the entry of water through the pores of a masonry wall.

It can be eliminated as a factor in the entry of water through a wall by making each of the openings in a wall wider than a drop of water can bridge or if this is not feasible or desirable by providing a concealed capillary break somewhere inside the opening. In porous materials such as brick, capillary action can be counteracted by applying an invisible coating of silicone based water repellant, which destroys the adhesive force between water and the walls of the pores in the brick.

Air Currents

The solutions described in the four preceding paragraphs are easy to implement. With relatively straight forward geometric manipulations of the joint, the possibility of leakage caused by four of the five forces that move water through an opening in a wall can be eliminated.

The fifth force, wind currents, is the force most difficult to deal with in designing a wall for water tightness. We can neutralize it by employing pressure equalized wall design.

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