Condensation and Mould Guide for Landlords and Tenants

Condensation and mould can quickly become stressful. Tenants worry about health and comfort. Landlords worry about damage, compliance and disputes. The truth is that mould is rarely caused by one single factor. It is usually a mix of ventilation, heating, moisture and the way a property is lived in.

This guide sets out what we see most often in Hemel Hempstead and across Hertfordshire, plus practical steps that help resolve issues early.

What condensation actually is

Condensation forms when warm, moist air meets a cold surface, such as windows, external walls or corners of rooms. That moisture then sits on the surface and, if it is repeated and not dried out, mould can begin to grow.

Common signs to look for

These are the early signals that a problem is developing.

• Water droplets on windows most mornings
• Black spotting in corners or behind furniture
• Musty smells in bedrooms or cupboards
• Damp patches that worsen in colder weather
• Peeling wallpaper or flaking paint near external walls

Typical causes in real homes

Everyday moisture

Cooking, showers, drying clothes indoors and even breathing add moisture to the air. In a busy home, moisture levels can rise quickly.

Insufficient ventilation

Extractor fans not being used, vents being closed, or windows never being opened can trap moisture inside.

Intermittent heating

Homes that are warmed briefly then allowed to cool can create the perfect conditions for condensation. Steadier heat often helps more than short bursts of high heat.

Cold spots and blocked airflow

Large furniture pushed tight to external walls can stop warm air circulating and create cold, damp corners.

Practical steps that usually help quickly

• Use extractor fans during and after showers and cooking
• Open trickle vents if your windows have them
• Keep lids on pans when cooking where possible
• Dry clothes with ventilation and avoid drying directly on radiators
• Maintain a consistent background temperature where possible
• Leave a small gap behind furniture on external walls
• Wipe away window condensation each morning

When it might be more than condensation

Some damp issues are caused by factors beyond lifestyle. If mould is persistent despite sensible ventilation and heating, or if you see tide marks, bubbling plaster, or damp that worsens after rainfall, it may indicate a building related issue.

At that point it is important to investigate properly rather than repeatedly treating the symptoms.

Advice for tenants

If you notice early signs, raise it quickly in writing and include photos. Most issues are easier to resolve before mould becomes established.

Keep a brief record of what you are seeing, where it appears, and what steps you have taken. This helps everyone focus on solutions rather than blame.

Advice for landlords

Fast response matters. Even when condensation is a contributing factor, good communication and clear guidance helps prevent problems escalating.

Make sure extractor fans work properly, ventilation points are open and the property has no obvious maintenance issues that could be feeding moisture into walls.

Download the full guide

The full guide covers prevention, practical checklists, and what steps to take when mould keeps returning.

Disclaimer: This guide is general information only and does not constitute legal advice. If you have health concerns, seek appropriate professional guidance.