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Moisture in Our Environment as a Serious Threat to Building Durability
Moisture is a constant presence in our surroundings and poses a significant threat to the longevity of buildings. Walls, foundations, and roofs are nearly always exposed to water from both external and internal sources.
Internal Sources
Moisture from inside a building typically takes the form of water vapor produced during daily activities such as washing, cleaning, cooking, breathing, and occasional events like plumbing failures or flooding.
External Sources
Rain, snow, and fog impact the building externally, while groundwater exerts additional pressure on foundations, potentially leading to damp walls.
Freeze-Thaw Cycles
In our climate, the freezing and thawing of water within walls further exacerbate the issue. Water exposure is not unusual and is a year-round phenomenon affecting all types of buildings. However, negative effects only occur when a building lacks proper protective measures.
Moisture problems affect not only older or historic buildings but also newly constructed ones. The question arises: where does moisture in walls or on basement floors come from?
Identifying Causes
Before addressing the issue of moisture, it is essential to identify its source. Water in walls can cause damage to the structure and negatively impact the health of its inhabitants. Salts present in building materials, migrating with moisture, are hazardous to walls and can lead to their deterioration. These salts also result in unsightly stains.
Consequences of Damp Walls
Wet walls create ideal conditions for mold and mildew growth, which can cause health risks. Additionally, they lead to significant energy loss. In spaces where people live and work, walls and basements must remain dry and well-sealed to ensure safety and comfort.
Causes of Moisture Penetration Beyond Household Water System Defects and Leaky Roofs
Moisture issues can arise due to various phenomena, often independent of obvious household malfunctions.
The Most Common Causes Include:
- Rainwater and Splash Water Load
Moisture penetrates the wall due to the absence or malfunction of base sealing. - Hygroscopic Moisture
Salts present in walls have the ability to absorb moisture from the air and surrounding environment, depositing it within the building material (hygroscopic properties). - Condensation
Water vapor condenses into liquid water on cold surfaces, typically resulting from thermal bridges within the wall structure. - External Moisture Penetration
Moisture infiltrates walls or floor slabs due to missing or improperly functioning external waterproofing. - Capillary Moisture Wicking
Moisture enters the wall due to the absence or failure of horizontal damp-proofing and/or external waterproofing, then rises through the material via capillary action.
Harmful Salts
Along with penetrating water, dissolved salts harmful to the structure also enter the walls. Additionally, chemical reactions (acidic exhaust gases + binder = salt) can create salts within building materials. Moist partitions transport water containing salts to the outer layers of the wall. There, the water evaporates, leaving behind salts that form characteristic unsightly efflorescence. This recurring process increases salt concentration and consequently hygroscopicity, which enhances the absorption of moisture from the surroundings.
Is it Efflorescence or Mold?
Salt efflorescence is often mistaken for mold. How can you distinguish between them? To differentiate salt deposits from mold, scrape off a bit of the residue from the wall and dissolve it in water at about 20°C. If it dissolves completely, it is definitely salt.
Efflorescence forms when dissolved salts in water emerge onto the wall's surface from the mortar and bricks. The water evaporates, leaving unattractive residues on the surface. These residues can range in color from snow-white, orange, red, to dark gray. They often appear as colorful stains or crystalline growths on the wall.
Unfortunately, salt crystallizing on the wall's surface is not easy to remove. The deposits will keep reappearing as long as the wall remains damp.
Where Do Harmful Salts in Walls Come From?
- Sulfates, e.g., from gypsum.
- Chlorides, e.g., from deicing salts.
- Nitrates, e.g., from urea.
What Damage Can They Cause?
- Mechanical damage due to salt crystallization and water deposition (hydration).
- Mechanical damage caused by freezing and thawing cycles within the material.
- Increased moisture in the wall and floor slab.
