Understanding moisture movement from exterior walls

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Understanding moisture movement from exterior walls


Moisture movement through all exterior walls is possible. There are many different types of moisture movement. Some are due to building defects allowing gross water entry. Others are the result of pressure and thermodynamic forces which push or pull moisture through the walls themselves, independent of the type of wall. In general, there are these types of moisture movement.

  • Gross water entry
  • Vapor pressure movement
  • Capillary action

The slides in the slider to the right display some of these dynamics. Brick exterior walls, particularly at the basement level on a concrete slab, are always suspect for gross water entry at the floor level.

Examples of foundation and exterior wall moisture intrusion


Mold and Moisture

Water damage from foundation water intrusion

Note water staining and paper buckling

This is subtle but may indicate a large wall cavity problem with mold

Hidden Mold

A terrible mold situation between vinyl wallpaper and sheetrock backing

This is a large bathroom with a strong exhaust fan

The exhaust fan created a negative pressure environment

Moisture was sucked through the sheetrock from the exterior wall

Moisture could not pass vinyl wallpaper.

So water condensed between the two surfaces - hence mold growth

Hidden mold on sheetrock

Another example of mold growth on back of vinyl wall paper

Moisture seeped between the seams and wet the sheetrock

Water stained sheetrock

This is a painted concrete foundation wall

Moisture moved through the concrete and wet the back of dried paint

Mold grew on the back of the paint and bled through to surface

Foundation Moisture

Moisture movement can be seen as efflorescence behind paint

Note paint bubbling, scaling and flacking off

Exterior moisture and mold

Removed insulation disclosed extensive mold growth on exterior wall

This is not an uncommon finding particularly in basements on slab

Rain water entered at the base and wicked up the paper

Paneling water damage

Obvious foundation moisture entry and paneling damage

Self Help Recommendations


To identify possible moisture intrusion around your home, carefully inspect the perimeter of your foundation from the outside. Look for areas where the earth ground looks to have settled next to the foundation. Landscaping by planting trees and bushes next to the house usually results in a loose and permeable soil.  Overtime this loose soil will settle resulting in a downward (or negative) slope towards the house.This allows rain water runoff to saturate the soil next to the home hence the foundation.

Also, inspect the interior of your home. Look for signs of moisture movement particularly at the floor level.


  • Inspect entire exterior perimeter

  • Check the gutters and downspouts

For detailed consultation on your particular moisture intrusion challenges, please call Dr. Kraemer at 770.321.6653
By |2017-04-03T23:21:23+00:00April 3rd, 2017|Building Defects, Investigation, Mold|