Mold in the Apartment: Identifying Causes, Proper Removal, and Long-Term Prevention

Mold in the Apartment

Mold in the apartment is more than just an aesthetic problem – it can have serious health consequences and lead to legal disputes between tenants and landlords. Whether it’s black spots on the walls, a musty smell in the bathroom, or health complaints without an obvious cause, the signs of mold infestation are diverse.

In Switzerland, around 20% of all apartments are affected by mold, especially in older buildings or after energy-saving renovations without adequate ventilation concepts. Causes range from incorrect ventilation and construction defects to water damage. But who is responsible? How can mold in the apartment be removed? And which preventive measures are truly effective?

This comprehensive guide answers all key questions about mold and provides practical recommendations – whether you are a tenant or owner in Switzerland.

Chapter 1 - What is Mold and How Does It Develop?

Definition and Types of Mold

Mold fungi are microorganisms that belong to the group of fungi. They reproduce through spores, which are constantly present in the air. Only under certain conditions do these spores start to grow and form visible mold colonies.

The most common types of mold in Swiss apartments:

Type of Mold	Color	Typical Locations	Health Risk
Aspergillus niger	Black	Walls, window reveals	High
Aspergillus fumigatus	Greenish-gray	Damp corners, basement	Very high
Cladosporium	Black/Olive green	Textiles, wood	Medium
Alternaria	Dark brown/Black	Bathroom, kitchen	Medium
White Mold	White	Basement, behind furniture	Medium

The Three Main Causes of Mold Growth

1. Moisture (most important factor)

Relative humidity above 60%
Water damage (pipe leaks, leaky roofs)
Rising damp from the ground
Condensation on cold surfaces
High humidity due to föhn weather or in Alpine valleys

2. Insufficient ventilation

Too infrequent or incorrect ventilation
Missing or defective ventilation systems
Air stagnation behind furniture on exterior walls
Post-renovation issue: New tight windows without adjusted ventilation behavior

3. Structural defects

Thermal bridges (formerly: cold bridges)
Insufficient insulation (especially in older buildings)
Defective seals
Cracks in masonry
Problems in historical buildings with heritage protection

Chapter 2 - Health Risks from Mold

General Health Effects

Mold exposure can trigger various health problems, especially in sensitive individuals. Common symptoms include:

Allergic reactions (sneezing, runny nose, itchy eyes)
Respiratory problems (cough, shortness of breath, asthma attacks)
Skin irritation (rashes, itching)
Fatigue and headaches
In severe cases, infections in immunocompromised individuals

Who is Most at Risk?

Certain groups are more susceptible to mold-related health problems:

Children and infants
Elderly people
People with respiratory diseases (asthma, COPD)
Individuals with weakened immune systems
Allergy sufferers

Indoor Air Quality

Prolonged mold exposure can reduce indoor air quality and may even contribute to "sick building syndrome." It is therefore crucial to identify and remove mold early.

Important Links

Swiss Federal Office of Public Health – Mold Information

Chapter 3 - Mold Prevention and Remediation

Preventing Mold Growth

Preventing mold is always better than treating it. Key strategies include:

Maintain indoor humidity below 60% (ideally 40–50%)
Ensure proper ventilation in kitchens, bathrooms, and basements
Fix leaks and water damage promptly
Use mold-resistant building materials when possible
Regularly clean and dry areas prone to moisture

Identifying Mold Early

Signs of mold include musty odors, discoloration on walls or ceilings, and condensation buildup. Early detection prevents serious damage and health risks.

Safe Mold Removal

Small areas of mold can often be cleaned with soap and water or specialized mold cleaners. For larger infestations, hire professional remediation services to avoid exposure to spores.

Important Links

U.S. Environmental Protection Agency – Mold Cleanup Guidelines

Chapter 4 - Mold Remediation in Different Living Areas

Kitchen

Kitchens are prone to moisture from cooking and dishwashing. Tips to prevent and remove mold:

Ventilate while cooking using exhaust fans or open windows
Wipe down wet surfaces and counters daily
Check under sinks for leaks and moisture buildup
Use mold-resistant paint or materials in cabinets

Bathroom

Bathrooms have high humidity. Mold prevention strategies:

Use exhaust fans during and after showers
Keep tiles, grout, and shower curtains clean and dry
Fix dripping faucets and plumbing leaks immediately
Consider water-repellent coatings for shower walls

Basement

Basements are particularly vulnerable to dampness:

Install a dehumidifier to maintain humidity below 50%
Check for cracks in walls and floors and seal them
Ensure proper drainage around the foundation
Store items off the floor to prevent moisture accumulation

Important Links

Chapter 5 - Professional Mold Remediation and Health Considerations

When to Hire a Professional

Professional mold remediation is recommended in the following situations:

Large areas affected (over 10 square feet / 1 m²)
Mold caused by contaminated water (sewage or flooding)
Persistent or recurring mold despite DIY efforts
Presence of sensitive individuals (children, elderly, immunocompromised)

Health Risks

Mold exposure can cause various health issues:

Respiratory problems: coughing, wheezing, shortness of breath
Allergic reactions: sneezing, runny nose, red eyes
Skin irritation: rashes or itching
Long-term exposure may exacerbate asthma or other chronic conditions

Choosing a Professional Service

Look for certified mold remediation specialists (IICRC or equivalent)
Check references and reviews from previous clients
Request a detailed remediation plan and cost estimate
Ensure proper containment and safety measures are in place

Important Links

Chapter 6 - Maintenance and Prevention Strategies

Regular Inspection

Inspect your home regularly for signs of moisture and mold:

Check basements, bathrooms, and kitchens for damp spots
Look behind furniture and under sinks for hidden mold
Monitor areas near windows and roofs for leaks

Moisture Control

Controlling moisture is key to preventing mold growth:

Fix leaks immediately
Use dehumidifiers in damp areas
Ensure proper ventilation in bathrooms and kitchens
Maintain gutters and downspouts to prevent water intrusion

Cleaning and Maintenance

Regularly clean surfaces with mold-resistant products
Replace or dry water-damaged materials promptly
Keep HVAC systems clean and use filters
Trim vegetation near the home to improve airflow

Emergency Preparedness

Have a plan in place for unexpected water events:

Know how to shut off water quickly
Have cleaning supplies and protective equipment ready
Document property for insurance purposes

Chapter 7 - Professional Mold Remediation and Restoration

When should you call a professional?

Hire a specialist if:

Infestation area over 0.5 m² (according to SIA 180)
Mold in the apartment in load-bearing structures
Infestation in the floor or behind walls
Residents with health vulnerabilities
Unknown cause
Recurring mold after self-treatment

Process of professional remediation

Phase 1: Analysis (1-2 days)

Identify cause
Damage mapping
Material samples
Airborne spores measurement
Thermography (thermal imaging camera)

Phase 2: Remediation (depending on extent)

Set up dust containment system
Remove affected materials professionally
Eliminate causes (sealing, insulation)
Disinfection using specialized methods
HEPA filtration of indoor air

Phase 3: Restoration

Install new materials
Apply anti-mold coating
Final inspection with air spore measurement

Costs in Switzerland (indicative):

Assessment: CHF 800-2,000
Small remediation (< 5 m²): CHF 1,500-4,000
Medium remediation: CHF 4,000-15,000
Comprehensive remediation: CHF 15,000-80,000

Choosing the right specialist in Switzerland

Quality criteria:

Certification (e.g., SVGW-approved, SIA-certified)
Membership in professional associations (e.g., Gebäudehülle Schweiz)
References and reviews
Detailed offer including cause analysis
Guarantee on the remediation

Warning signs:

Generic remote diagnoses
Immediate remediation without identifying the cause
Extremely cheap offers
No written documentation

Tip: Always get at least 3 quotes and compare not only the price but also the services offered.

Swiss professional associations and certifications:

FAQ - Frequently Asked Questions about Mold in the Apartment

What to do in case of mold?

For mold in the apartment, you should:

Document: Take photos, note extent
Determine the cause: Measure humidity, check ventilation habits
For small infestations (< 0.5 m²): Treat yourself with alcohol or mold remover
For larger infestations: Hire a specialist
As a tenant: Notify landlord in writing (registered mail)
Eliminate the cause: Adjust ventilation habits or fix structural defects

Where does mold come from?

Main causes of mold in the apartment are:

High humidity (over 60%) due to incorrect ventilation
Structural defects: Thermal bridges, poor insulation, leaks
Water damage: Pipe bursts, leaking roofs, rising moisture
Insufficient heating: Cold walls promote condensation
User behavior: Drying clothes indoors, too many plants, insufficient ventilation
Swiss peculiarity: After energy renovations with new tight windows without an adapted ventilation concept

Often it is a combination of multiple factors.

How can I remove mold?

For small areas (under 0.5 m²):

Wear protective gear (FFP3 mask, gloves, goggles)
Spray 70-80% alcohol or mold remover
Let sit for 10-15 minutes
Wipe with a damp cloth
Dispose of materials immediately in a plastic bag
Important: Eliminate the cause!

For larger areas: Hire professional mold remediation. Specialists have special equipment and disinfectants.

Products available at: Coop Bau+Hobby, Migros Do it, Jumbo, OBI Schweiz, Bauhaus Schweiz

Why do I have mold in the shower?

Mold in the shower arises from:

High humidity: Up to 2.5 liters of water vapor produced during showering
Poor ventilation: Especially in windowless bathrooms
Silicone joints: Ideal breeding ground for mold
Insufficient drying: Residual moisture remains in joints and corners
Limescale deposits: Additional nutrients for mold fungi

Solution: Ventilate immediately after showering, squeegee tiles, clean joints regularly, and renew every 2-3 years.

Mold in the apartment: What are my rights as a tenant?

Under Swiss Code of Obligations (OR), tenants have the following rights in case of mold:

Rent reduction from knowledge of defect (5-100% depending on extent, Art. 259d OR)
Right to defect removal by landlord (Art. 259a OR)
Health risk: Deposit of rent (Art. 259g OR)
In extreme cases: Extraordinary termination (Art. 257f OR)

Important:

Report mold immediately in writing to the landlord (registered mail)
Pay rent reduction under reservation
Mediation is mandatory before lawsuit
Consult tenant association (www.mieterverband.ch or www.asloca.ch)

You must prove you ventilated and heated sufficiently. The burden of proof for incorrect user behavior lies with the landlord.

How to prevent mold?

Best mold prevention includes:

Proper ventilation:

3-4x daily shock ventilation (5-10 minutes)
Ventilate immediately after showering, cooking, sleeping
No tilt ventilation!
Prefer cross ventilation

Proper heating:

Heat all rooms to at least 16-18°C
Keep doors between rooms with different temperatures closed
Maintain base temperature even when away

Reduce humidity:

Keep indoor humidity under 60% (ideal: 30-50% according to SIA 180)
Do not dry laundry indoors
Use a hygrometer

Structural measures:

Keep furniture 5-10 cm from exterior walls
Regularly check joints and seals
Improve insulation if needed (funding via Das Gebäudeprogramm)
Consider ventilation system with heat recovery (according to MuKEn standard)

Use Swiss funding programs: