Expertise & Advice
An overview of mold, moisture, and building physics

In this section, we share our knowledge about moisture, mold, and structural damage.

The content is based on the daily assessment practice of certified expert Michael Trübswetter and takes into account the requirements of DIN standards, the German Federal Environment Agency (UBA), and the WHO.

The aim is to provide owners, managers, and specialist companies with clear information on identifying the causes of typical building damage, assessing it, and repairing it.

Mold & Interior Hygiene

Mold develops when moisture comes into contact with organic materials—such as wallpaper, plaster, wood, or dust—over a prolonged period of time.

The causes are often thermal bridges, inadequate ventilation, construction defects, leaks, or water damage.

Condensation on cold wall surfaces or in poorly ventilated areas creates ideal conditions for mold growth.

Yes. Mold can cause allergies, respiratory irritation, asthma, or headaches.

According to the UBA and WHO, all visible mold should be removed professionally, regardless of the type.

There is no such thing as a “safe” amount of mold.

Children, allergy sufferers, and people with weakened immune systems are particularly at risk.

According to the guidelines issued by the Federal Environment Agency, a distinction is made between three categories of damage:

  • Category 1: minor, superficial infestation – local cleaning possible.
  • Category 2: moderate infestation or hidden areas – professional remediation recommended.
  • Category 3: Extensive or deep infestation – remediation by a specialist company with free measurement required.

From category 2 onwards, an expert should be consulted.

The distribution of costs depends on the cause:

  • Construction or design defect: Owner or developer
  • Incorrect ventilation/heating: Tenants
  • Burst pipe/water damage: usually covered by building insurance

An expert opinion helps to clarify the cause objectively and avoid disputes.

If you commission an expert opinion, the costs are always borne by the client initially. The extent to which the costs can be passed on to the other party depends on the individual case.

    The basic principle is: stop moisture = stop mold. Without moisture, mold cannot grow.
    To prevent mold growth permanently, the cause must be identified. The most common causes are:

    • thermal bridges
    • Incorrect ventilation and heating behavior
    • Insufficient heating
    • construction defects
    • Water damage repaired improperly

    There are no standard values for proper ventilation or humidity. The rule of thumb is that at a room temperature of 20°C, the maximum relative humidity should not exceed 60%. This applies to modern buildings constructed since the early 1990s. For older buildings, other lower humidity values may apply.

    Moisture & building physics

    Building moisture refers to the moisture contained in building materials that has entered the material through diffusion, capillary action, or water ingress.

    A certain moisture content is normal – it becomes critical when the equilibrium moisture content is exceeded and damage, mold, or salt contamination appears.

    Preservation of evidence & expert opinions

    Preservation of evidence is the objective and comprehensible documentation of the condition of a building or damage at a specific point in time.

    It serves to avoid subsequent disputes about causes, responsibilities, or the course of damage.

    The result is legally admissible evidence of the actual condition.

    Preserving evidence is always recommended when:

    • Construction work takes place near existing buildings,
    • Risse, Setzungen oder Feuchtigkeitsschäden bereits sichtbar sind,
    • Renovations or modernizations are planned,
    • or legal disputes/insurance issues are to be expected. It can be carried out before the start, during, or after the completion of construction or renovation measures.

    Practice & Case Studies

    An on-site appointment serves to objectively assess the current state of damage.

    The affected rooms and building components are systematically inspected, measured, and documented.

    The process follows a fixed, transparent pattern:

    1. Welcome and introduction
      • Introduction of the expert, brief clarification of the purpose of the investigation.
      • Explanation of the procedure and the measurement methods used.
      • If desired: Participation of the client or representative (e.g., tenant, property manager).
    2. Inspection and visual inspection
      • Recording of the affected rooms and building components.
      • Documentation of abnormalities, damage, signs of odors, or moisture.
      • Production of overview and detailed photos.
    3. Measurements and technical recording
      • Moisture measurements (capacitive or resistance) at representative points.
      • Surface and room temperature measurements, thermography if necessary.
      • Measurement of indoor humidity, outdoor climate data if applicable.
      • Comparison with reference values.
    4. Interim evaluation / on-site meeting
      • Brief explanation of initial observations.
      • Information on possible causes or further investigations.
      • Keine rechtliche Bewertung oder Sofortgutachten – nur technische Einschätzung.
    5. Überprüfung der Messergebnisse und Fotos.
      • Review of measurement results and photos.
      • Preparation of a brief report or expert opinion with evaluation and, if necessary, recommendations for action.
      • Shipping to the client (digital).

    Note:

    The on-site appointment forms the basis for every expert opinion.

    It represents the condition at the time of inspection and serves as objective evidence for later evaluations or comparisons.

    In the case of mold or moisture damage, the damage pattern can change after just a few days—which is why prompt assessment and documentation are crucial.