Part 1: Understanding the Problem
To fix damp and mould, you first need to know what you're dealing with.
What Are Damp and Mould?
Damp is too much moisture in your home. Mould is a fungus that loves damp conditions. You might see it as fuzzy black, white, or green patches, or notice a musty smell.
The most common cause is condensation. This happens when warm, wet air hits a cold surface, like a window or an outside wall. The air cools and drops the water, forming condensation.
Know Your Numbers: Ideal Humidity
A healthy home should have a relative humidity (RH) between 40% and 60%. In winter, aim for 30% to 50% to stop condensation on windows. Your humidity monitor helps you track this.
2-Minute Explainer Video 🎥
🌡️Try Our Tool: Condensation Calculator
Use our calculator to find out if your home's conditions could lead to damp forming on your walls and windows.
Go to Calculator →
A Serious Risk to Health
Mould isn't just unsightly; it's a health risk. Exposure can cause a range of problems, from common allergies to more persistent issues sometimes called 'mould illness', especially for vulnerable people.
How Mould Affects Your Body
Mould releases substances that can cause harm in three main ways:
- Allergens: Inhaling or touching mould spores can trigger allergic reactions like sneezing, a runny nose, red eyes, and skin rashes.
- Irritants: These can directly affect your eyes, skin, and respiratory system, causing irritation.
- Toxic Substances (Mycotoxins): Some moulds produce poisons called mycotoxins. With long-term exposure, these can lead to more widespread health issues.
Common Symptoms of Mould Exposure
Symptoms can range from mild to severe and may include:
- Coughing, wheezing, and shortness of breath
- Worsening of asthma
- Sneezing, runny or blocked nose
- Watery, red eyes or skin rashes
- Chronic fatigue or brain fog
- Headaches and sinus congestion
- Muscle and joint pain
- Digestive issues
Who Is Most at Risk?
Some people are more sensitive to the effects of mould, including:
- Babies, young children, and older people.
- Individuals with weakened immune systems.
- Those with existing allergies, severe asthma, or chronic lung diseases.
Finding the Root of the Problem
Is it your daily habits or a problem with the building? Often, it's a mix of both. Landlords must provide proper heating and ventilation and can't just blame a tenant's "lifestyle." Use this table to identify the type of damp you have.
| Type of Damp |
What it Looks Like |
Cause & Responsibility |
| Condensation |
Water droplets on windows; dark mould spots, often in corners or behind furniture. |
Caused by moist air from daily life plus poor ventilation. Shared issue: Residents manage moisture, landlords must provide adequate heating and ventilation. |
| Penetrating Damp |
Damp patches on walls or ceilings that get worse after rain. |
Water leaking in from outside (e.g., bad roof, broken gutters). Landlord's responsibility to fix. |
| Rising Damp |
A 'tide mark' up to one metre high on ground floor walls, with crumbling plaster. |
Groundwater soaking up through the walls due to a failed damp-proof course. Landlord's responsibility to fix. |
Step 1: Put Less Water into the Air
A family of four can produce several litres of water vapour a day. These simple, no-cost habits can make a huge difference.
🍳In the Kitchen
- Cover Pans: Always use lids when cooking to keep steam in.
- Use Extractor Fans: Use them every time you cook. They are very cheap to run.
- Close the Door: Keep the kitchen door shut to stop moist air from spreading.
🚿In the Bathroom
- Keep the Door Shut: This contains the steam in one easy-to-ventilate area.
- Ventilate After: Use a fan or open a window for 15-20 minutes after a shower.
- Wipe Down Surfaces: Use a cloth or squeegee to wipe water from tiles and screens.
🧺Tackling Laundry
- Dry Outside if Possible: This is the best way to remove moisture from your home.
- If Drying Indoors: Put laundry in one room, open a window, and keep the door closed.
- Avoid Radiators: Don't dry wet clothes on radiators, as this pumps moisture into the air very quickly.
Step 2: Take Water Out of the Air
As well as making less moisture, you need to remove the moisture that's already there.
The Power of Fresh Air: Ventilating Your Home
Ventilation simply means swapping stale, moist indoor air for fresh, drier outdoor air. It's the most important way to control condensation.
- Open bedroom windows for 15-60 minutes every morning to clear moisture built up overnight.
- Keep 'trickle vents' (small slots at the top of windows) open as much as possible.
- Leave a small gap between furniture and outside walls to let air circulate.
How to Ventilate in Winter Without Losing All Your Heat
Open windows wide on opposite sides of your home for just 5-10 minutes. This creates a quick through-draught that swaps the air but doesn't cool down the walls and furniture. Your home will warm up again quickly.
Good to know: Drier air is cheaper to heat!
It takes less energy to heat dry air than damp air. By ventilating, you make your heating system work more efficiently, which can save you money on bills.
💨Try Our Tool: CO₂ Simulator
See how ventilation affects indoor air quality. Use the CO₂ simulator to understand how room size, occupancy, and ventilation impact the air you breathe.
Go to Simulator →
Heating and Insulation
A warm home is a drier home. Warm air can hold more moisture, and warm surfaces don't attract condensation. Keeping a low, constant background heat (around 15°C if possible) is often better than short bursts of high heat.
If you're struggling with energy bills, organisations like Citizens Advice and the Energy Saving Trust can offer free advice on grants and support.
Using Appliances to Help: Costs vs. Benefits
Electrical appliances can help, but it's important to know the running costs. This chart shows typical costs per hour, based on an electricity price of around 25-26p per kWh.
Step 3: Cleaning Mould and Getting Help
Once you're controlling the moisture, you need to deal with any existing mould and know your rights as a tenant.
📸Try Our Tool: AI Mould Inspector
If you have mould, our AI Mould Inspector can analyse a photo of the problem area. It provides a full action plan, including safe cleaning instructions, and lets you download a report to share with your landlord or a professional.
Go to Inspector →
A Guide for Renters: When It's Not Your Fault
You have legal rights. Landlords must fix problems that cause damp, like leaking roofs, broken heating, or poor ventilation. They cannot just blame your lifestyle without investigating.
Your 3-Step Plan for Action:
- Report it in Writing: Email your landlord or letting agent as soon as you see a problem. Describe the issue and its impact on your health. Keep a copy. Shelter has free letter templates you can use.
- Allow Access: Let your landlord in to inspect the problem and do repairs.
- Escalate if Needed: If your landlord does nothing, contact the Environmental Health department at your local council. They have the power to order your landlord to do the repairs.
Where to Get Free, Expert Help
You are not alone. Contact Shelter or Citizens Advice for free, confidential advice on your housing rights.
Your Humidity Monitor: An Early Warning System
Your monitor is a powerful tool. Use it to check if your actions are working.
- Aim for a humidity level between 40% and 60%.
- If you see the level creeping above 60%, it's a sign to increase ventilation.
- If the level stays high no matter what you do, it's strong evidence of a building problem that you can show to your landlord or the council.
