Sources of Building Moisture

One of the first steps in renovation work is identifying the source of moisture. What are the possible causes?

• Groundwater impact – moisture penetrating walls due to the absence or damage of horizontal and vertical insulation.
• Rainwater exposure – both direct and indirect effects.
• Floodwater infiltration – water accumulating around the building.
• Water and moisture from plumbing and sewage systems – leaks from internal installations.
• Condensation moisture – caused by insufficient thermal insulation of walls, often combined with poor ventilation.
• Hygroscopic moisture absorption – materials drawing moisture from the air.

How to Identify the Source of Moisture?

Observation is the key to detecting the cause of dampness. Different sources of moisture result in different visible effects, and the intensity of damage varies depending on the cause.

1. Terrain formation (soil layers and slope) directs rainwater toward the building.

   • Effect: Stains on masonry walls.

2. Capillary moisture absorption.

   • The ability to absorb moisture depends on soil conditions, material type, and capillary size.
   • Effect: A continuous damp zone at a consistent height.

3. Bypassing of insulation.

   • If ground usage changes (e.g., paving around the building), existing hydro-insulation may become insufficient.
   • In some cases, asphalt layers used for sidewalk repairs can bypass the building’s horizontal insulation.
   • Effect: Moisture increases over time, accompanied by harmful salt deposits.

4. Rainwater impact.

   • Effect: Irregular damp patches on external walls.

5. Condensation moisture due to poor thermal insulation.

   • In winter, warm air condenses on cold walls.
   • In spring and summer, warm external air condenses when it meets a cooler internal surface.
   • Effect: Moisture can appear throughout the building or in isolated areas.

6. Hygroscopic moisture absorption.

   • Building salts attract moisture from the air, dissolve, and cause dampness.
   • Effect: Irregular wet stains that appear and disappear depending on weather conditions.

7. A combination of multiple moisture sources (e.g., splash water, hygroscopic absorption, and capillary action).

   • Capillary moisture absorption is rarely the sole cause of dampness, so it is impossible to determine the exact source by visual inspection alone.
   • A horizontal damp line suggests capillary absorption.
   • Irregular dark stains indicate hygroscopic moisture from salt deposits in plaster.
   • Dirt and stains at the lower part of the wall above ground level signal splash water exposure.