Yes, data can settle most of the argument. When a tenant says the house is damp and the landlord says it is how they live, both are usually guessing. Measuring the humidity and temperature in the home over a couple of weeks, and checking that the ventilation is working properly, replaces opinion with evidence. It shows whether the building is the problem, whether habits are, or whether it is a bit of both, and that is the only way to fix it without blame.
In the latest episode of The Healthy House Podcast, Aaron Worrall talks to Ramona Hirschi about what it takes to run rental homes profitably now that the Renters' Rights Act is changing the rules. It is a long conversation about rents, paperwork, structure and tenants, and near the end it turns to damp and mould, which is where both of them agree that landlords and tenants most often fall out.
This post takes that part of the conversation and adds what we would want any landlord or tenant to know as damp and mould specialists. If you rent out a home, or live in one, it should help you work out what to do when mould appears and nobody agrees why.
🎙️ What Did The Podcast Say About Damp And Mould In Rented Homes?
Aaron hosts the show and Weather Wise Solutions presents it. What follows is what was said, put into our own words. These are paraphrases, not quotes, and they are the speakers' views and experience. They are not WeatherWise's advice, and Ramona doesn't recommend or endorse WeatherWise.
Damp and mould needs both sides
Around the 55 minute mark, Ramona said damp and mould is one of the issues that causes the most friction between landlords and tenants. Her reasoning was that a dripping tap is easy, because the landlord just fixes it, but damp and mould is harder. Sometimes it is the fabric of the building, and sometimes it is how the heating is used in an older house, and often there is more than one thing going on. She said it takes both sides to work together to find the source.
Get the property up to a sensible standard first
Aaron's advice to landlords, shortly afterwards, was to keep on top of maintenance, such as leaking gutters and taps, and to stop jumping to the conclusion that the tenant is to blame. His suggestion was to look at the property first. Older housing stock should be brought as close as it can be to the ventilation standard in Part F of the Building Regulations, so that a tenant doesn't have to do anything unrealistic just to live there.
Data loggers and fans
Aaron said there is technology now that helps, including data loggers and ventilation fans. His point was that once a home is properly ventilated and the loggers are in, and a tenant still has a problem, you can start to look at living habits, because the data tells you what is happening. Ramona agreed that a warmer, better ventilated house means the chances of damp and mould drop, even if a tenant doesn't know how to use the heating or open a window.
Why drier air is easier to heat
Aaron used a simple picture. If someone threw a cold wet blanket over you, you would get cold quickly and it would take a long time to dry. Without it you feel fine. He said air works the same way: the drier you can keep it, the easier it is to heat and the better it stays warm. His message to everyone was ventilation, ventilation, ventilation.
Boiling pans and everyday moisture
Both of them described homes where pans had been boiling for hours, with water running down the kitchen walls and tiles, and extractor fans that were never switched on or weren't understood. Aaron said housing stock isn't built for that amount of moisture, and that in cold weather a single-brick extension will reach dew point on the wall. Ramona added that different cooking and lifestyle habits can come into it, and that the extractor fan is often the thing nobody has explained. Aaron's answer was that a logger lets you see it, and then it is a conversation about the facts.
Stop the water getting in first
In the closing minutes, Aaron said the biggest cost he sees is a lack of simple maintenance. Water saturates things, so look after the gutters and the brickwork and stop it getting in, and it can save thousands. Ramona noted that our damp climate means homes here have to work harder to stay dry.
🤝 Why Do Landlords And Tenants Argue About Mould?
They argue because the same patch of black mould can honestly look like two different things. A landlord sees a tenant who dries washing indoors and doesn't open windows. A tenant sees a cold, damp bedroom that they can't afford to heat. Both can be partly right.
Without evidence, each side defends its own view. The tenant feels blamed and stops reporting problems. The landlord feels accused and delays. The mould carries on growing in the meantime, and that is bad for the building and for the people living in it.
Aaron's point in the episode was that the way out of this is to take the guesswork away. Check the property first, then look at habits with real numbers in front of you. That order matters. If you start with habits, you risk blaming the tenant for something that is a building fault. If you start with the building and find nothing wrong, the conversation about habits is much easier to have.
🌡️ What Can A Data Logger Actually Tell You?
A data logger is a small device that sits in a room and records the temperature and relative humidity at regular intervals, day and night, for days or weeks. It doesn't judge anyone. It simply shows what the air in the home was doing.
That record can answer questions that are hard to settle by looking at a wall.
- Is the room too humid, and when? A spike every evening points to cooking, showering or drying washing. A high reading that never drops points to poor ventilation or a source of moisture in the building.
- Is the room too cold? Mould likes cold surfaces. A bedroom that sits at a low temperature all day gives moisture somewhere to settle, even when the humidity isn't extreme.
- Does the humidity fall when someone ventilates? If it drops after a fan runs or a window opens, ventilation helps. If nothing changes, the fan may not be doing its job.
- Is it the same in every room? If one room is far worse than the others, look for a local cause, such as a leak, a cold wall or a blocked extractor.
A logger does not tell you why the numbers are what they are. That still needs someone who understands buildings to read the data alongside the property. It is a tool for a surveyor, not a verdict on its own.
💨 Why Does Ventilation Matter So Much?
Every home produces moisture. Breathing, cooking, showering, drying clothes and even a kettle all add water to the air. If that moisture has nowhere to go, it settles on the coldest surfaces, which is usually a window reveal, a corner of an outside wall or the back of a wardrobe, and mould follows.
Ventilation is how that moisture leaves. In a modern building it might be a mechanical extractor in the bathroom and kitchen, trickle vents in the windows or a whole-house system. In an older building it may be nothing more than gaps, a chimney and a window you open. Part F of the Building Regulations sets the standard for ventilation in new work and in many alterations, and it is the benchmark Aaron mentioned for getting a property to a reasonable level.
The common faults we see are simple ones.
- An extractor fan that is too weak, too small, or ducted badly so that it doesn't move much air.
- A fan with no timer or humidity sensor, which tenants understandably turn off because of the noise.
- Vents that have been painted over, taped up or blocked.
- Rooms with no extraction at all, such as a kitchen that relies on a window.
- A tumble dryer that is vented into the room, or no vent for it at all.
Fixing these is usually cheaper than treating mould again and again. Our guide to mould in a rental property explains who is usually responsible and what to do next.
🏠 What Should A Landlord Do When A Tenant Reports Mould?
It helps to have a sequence, so that you aren't reacting from emotion. This is a practical order that fits what Aaron described.
- Take the report seriously and reply quickly. Acknowledge it, agree a time to look, and keep a written record.
- Look for a building cause first. Check gutters, downpipes, roof, pointing, plumbing and any wall that feels cold or damp to the touch. Fix what you find.
- Check the ventilation. Is there a working extractor in the bathroom and kitchen? Is it strong enough? Does it run when needed?
- Look at heating and insulation. A home that can't hold heat will be prone to condensation however careful the tenant is.
- Measure. If the cause isn't obvious, record the temperature and humidity in the affected rooms for a couple of weeks.
- Share what you find. Show the tenant the results and explain the fix. Most people want a solution more than they want an argument.
- Talk about habits only once the building is sorted. Then it can be a friendly conversation about drying washing, using the extractor and keeping the heating on low rather than off.
- Follow up. Check that the problem hasn't come back, and keep the record.
The rules on rented homes are changing. We are surveyors, not solicitors, so we won't set out the law here. The practical point is the one both speakers made: act early and keep records.
🧑🤝🧑 What Can A Tenant Do?
If you rent, you don't have to prove anything alone, but a few steps put you in a good position.
- Report mould and damp to your landlord or letting agent in writing, and keep a copy.
- Take dated photos of the affected areas, including the wall, the window and any damaged belongings.
- Use extractor fans while cooking and showering, and keep any trickle vents open.
- Keep furniture a few centimetres away from outside walls so air can move behind it.
- Wipe condensation off windows in the morning, and dry washing outside or in a ventilated room if you can.
- Keep a steady low level of heating rather than short bursts, if you can afford to. Aaron mentioned in the episode that fuel costs are a real worry for many households, and we know that is true.
None of this means mould is your fault. Whether the building is doing its job is a separate question, and it is the landlord's side of the argument to look into.
🔍 Where Does A Ventilation Inspection Fit In?
When the cause isn't clear, a ventilation inspection gives a landlord or letting agent something concrete to work from. WeatherWise offers a Ventilation Inspection and Report for £349. It is a written report, so the findings are on paper and can be shared with a tenant, an agent or a contractor.
If you are considering one, it is worth asking what is included, for example whether any monitoring is part of it, so there are no surprises. Many of our other surveys are free, for landlords as well as homeowners, and we are open about the ones that aren't: the Home Buyer Quote is £349 and the Full Damp and Timber Report is £449.
Visits to a rented home are arranged with the landlord or their letting agent. If you want to know more about how a survey works, our guide to what a damp survey is sets it out, and our page on damp and mould surveys for landlords covers what is available.
💷 Does Fixing The Building Pay For Itself?
This part of the episode was about money, because it is a business podcast as much as a property one. Aaron's view was that if you invest in your property and do what is required, the headaches tend to go away. Ramona's view, in a different context, was that a property that is compliant and well looked after sells for more, and that buyers tend to take off more than the work actually costs.
We can't speak for the sums involved in your property, and we won't invent figures. The principle is sound, though. A home that stays dry needs less redecoration, loses less of its fabric and gives you fewer difficult conversations. Repeatedly cleaning and repainting a wall that is wet for a reason is the expensive route.
🪵 When Is It More Than Condensation?
Ventilation and habits explain a lot of mould, but not all of it. Some signs suggest that something else is going on and need a proper survey.
- A tide mark or salt crystals on a wall low down.
- Damp patches that stay put whatever the weather or the heating does.
- A musty smell with no visible mould, particularly under floors or in a cupboard on an outside wall.
- Soft skirting boards, springy floors or crumbling plaster.
- Stains that appear after rain, or below a window or a roof junction.
- Mould that returns quickly even though ventilation and heating have improved.
These can point to rising damp, penetrating damp, a leak or rot. Our guides to rising damp and penetrating damp show how they differ, and the sooner a cause like that is found, the cheaper it generally is to put right.
✅ What Was On The Healthy House Checklist?
Every episode ends with a short list of things anyone could do. For this one, the guest's five things were aimed at landlords and were mostly about the business side: look at your rents, check your compliance, think about the tenants you have, decide what to do if you want to sell, and manage your finances and ownership actively. She also made the point that landlords should consider having a letting agent review their paperwork.
On the damp and mould side, the most useful takeaway came from the discussion rather than the list. Get the building right, measure what is happening, and keep both sides talking. Aaron added that if you see a problem, it is better to deal with it early than to wait.
📋 What Is The Quick Answer?
- Mould in a rented home often comes from a mix of the building and how it is used, and guessing which is which causes arguments.
- Check the building first: water getting in, ventilation, heating and insulation.
- A data logger records temperature and humidity over days or weeks, which shows what the air in the home is really doing.
- Ventilation that works, such as a properly sized extractor with a timer or humidity control, takes pressure off everyone.
- Talk about habits only after the building has been put right, and use the data to do it.
- Signs such as tide marks, soft timber or mould that keeps returning need a proper survey.
- Landlords should reply quickly, keep records and fix small faults early.
🔬 How Does WeatherWise Look At Mould In A Rented Home?
We start with the cause, not the stain. We look at the outside of the property, then the inside, take moisture readings, check how the rooms are ventilated and tell you what we think is going on and what the sensible fix is. If it is a job for a plumber, roofer or electrician, we say so.
Our surveying team includes professionals holding the Level 3 Award in Damp, Mould and Condensation in Buildings (L3 Award DMCB), which is the qualification behind our condensation and mould work, alongside the Certified Surveyor of Timber and Dampness in Buildings (CSTDB) qualification. You can read more about who we are on our surveyors page.
If you would like to hear the whole conversation, listen to the full episode of The Healthy House Podcast.
📞 Dealing With Mould In A Rental Property?
Whether you are a landlord who wants a clear answer, a letting agent with a tenant complaint, or a homeowner with mould of your own, we can come and find out what is causing it. Many of our surveys are free, and we are open about which ones aren't: the Ventilation Inspection and Report is £349, the Home Buyer Quote is £349 and the Full Damp and Timber Report is £449.
We're members of the Damp Proofing Association, the Federation of Damp and Trust a Trader, and we're CHAS accredited and Google Guaranteed. WeatherWise's staff have over 40 years' combined experience, and we are a family and friends run business.
Book your free survey with Weather Wise Solutions on 01782 901101, or send us a message.