How does mold affect building materials?

Satunnainen

Mold is a microscopic fungus that grows in moist, poorly ventilated environments. Once it gets a foothold in a building's structures, its effects vary depending on the material and how long it has been exposed to moisture, but the results are consistently harmful: weaker structures, worse indoor air, and unpleasant odors.

Effects of mold on wood materials

Wood is one of the most common building materials, and it is particularly prone to mold growth. Mold can cause wood to rot, which weakens its structural strength; rotten wood loses its load-bearing capacity and can lead to serious structural problems. Mold can also discolor wood and cause a persistent, unpleasant odor.

Effects of mold on concrete and brick

Concrete and brick are less prone to mold growth than wood, but they are not immune. Mold can grow on the surface of concrete and brick if they stay constantly moist, leading to discoloration and surface erosion. Over the long term, sustained moisture can also weaken the durability of these materials.

Effects of mold on plasterboard and insulation

Plasterboard (gypsum board) is very prone to mold growth, especially in humid conditions, and mold can spread quickly across its surface and into the board itself. Repairing the damage usually requires replacing the whole board. Insulation materials such as mineral wool and cellulose wool can also suffer from mold: it weakens their thermal performance and can spread from the insulation to other materials and to the indoor air.

Effects on the structure and indoor air

Beyond the material itself, mold growth weakens the structures it lives in and lowers indoor air quality. Mold spores can trigger allergy symptoms and respiratory problems, and mold growing inside structures often causes a persistent, unpleasant smell that affects living comfort.

Prevention and control

Preventing mold growth is essential for protecting building materials and keeping indoor air healthy. The most important measures are:

  • Good ventilation
  • Managing humidity
  • Protecting building materials from moisture
  • Regular inspection and maintenance

If mold damage is found, it should be addressed as quickly as possible: this typically means removing the mold, replacing the damaged materials, and fixing the source of the moisture.

More information: Finnish Institute of Occupational Health: Mold and indoor air

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