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How should landlords best tackle damp and mould?

mould on a wall and in the corner of a ceiling

The tragic death of two-year-old Awaab Ishak in 2020, due to black mould in the flat his parents rented from Rochdale Boroughwide Housing Association, underlined just how important it is for landlords to take damp and mould seriously. As well as potentially being bad for physical health, damp and mould are often very distressing, and can adversely affect mental health.

Most landlords will encounter damp and mould in their rental properties at one time or another. Although damp and mould are so common, it can be really difficult for landlords to get to the bottom of it, as there may be multiple causes which might not immediately obvious.

Damp and mould won’t go away by themselves, and will require intervention to stop them getting worse. Condensation mould is notorious for coming back a year or so after the room has been treated and nicely redecorated, so it’s important to know how to break the cycle.

This is a very practical and comprehensive blog post to help landlords, tenants and letting agents alike understand where damp and mould come from, how to remove mould and prevent the damp conditions that make mould come back again. It draws on my own experience in tackling damp and mould as a landlord, as well as advice from experts. There are lots of links to useful guides for further research.

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What is damp and how common is it in the private rented sector?

Put simply, damp is the build up of moisture in a property. It doesn’t just affect the fabric of the building (eg walls, floors, ceilings and even the foundation), but it can also affect what’s inside the property. This includes carpets, curtains, furniture and clothing.

Damp often comes with a characteristic musty smell, and can lead to the growth of mould.

According to modelled data in the English Housing Survey published in December 2022, 11% of the housing stock in the private rented sector has a “problem” with damp. Damp is considered to be a “problem” if it’s significant enough to be considered a “hazard” when surveyors make Housing Health and Safety Rating System (HHSRS) assessments. This definition excludes “minor issues of damp”, and the number of properties with more minor problems will be far greater.

>> Related Post: What are HHSRS Hazards?

>> Related Post: Landlords’ Repairing Obligations

The different types of damp

condensation on a window
Condensation is easy to see on windows and window frames; less easy on permeable surfaces like walls

There are a number of different types of damp, with different root causes. When faced with damp in a property, it’s important to figure out which type of damp it is, whilst being aware that there may be more than one cause and type of damp.

For instance, a patch of damp may be caused by a leaking roof and made worse by condensation due to inadequate ventilation. If you fix the leak and redecorate, the mould will come back if the condensation hasn’t been addressed.

That’s why it can sometimes seem like a continuing Whac-a-Mole arcade game. No sooner have you got rid of one cause, another pops up! It might seem to have disappeared over the summer, but up it pops again when the temperature drops.

Here are the different types of damp:

1. Condensation damp

Condensation damp is the most common form of damp, and can be a problem in a property of any age. It’s often worse in properties that have been retrofitted to improve energy efficiency, this might have reduced ventilation and the natural circulation of air. Alternatively, in older properties there may insufficient insulation, inadequate heating or a reluctance to open windows to reduce moisture levels due to the cold.

It occurs when warm moisture vapour that is created inside a property (say from breathing, cooking, showering, drying washing) cools and condenses into water when it comes into contact with colder parts of the buildings such as cold outside walls and windows.

Condensation can occur well away where the moisture is produced. For instance, water vapour produced in the kitchen or bathroom may spread through the property into a cold bedroom, where it condenses on cold walls.

Condensation is easy to spot on impervious surfaces like the glass on windows, as in the image above, where the condensation may show on the glass and pool on the window sill. However, it’s less easy to spot on permeable surfaces like wallpaper and plaster, where the water is absorbed into the material. Slightly damp wallpaper, without an obvious leak, is a sign of condensation, and an early warning of mould.

Often the presence of the moisture is only revealed when dark patches of mould start to grow where the moisture collects in corners and low points on walls, perhaps behind sofas or wardrobes on outside walls.

It tends to be worse in the winter when the outside temperature drops, which causes the temperature of the external walls of the building to fall.

2. Penetrating and traumatic damp

damage from misaligned downpipe causing penetraing damp
This misaligned downpipe caused the mortar between the bricks to wash away, and damp on the inside

Penetrating and traumatic damp are both caused by water.

With penetrating damp, it occurs when water gets into the building from outside due to defects in the walls, roofs, windows or floors. A common cause is blocked gutters and misaligned downpipes, as you can seen in the above photo, which I took in viewing a house that I bought and renovated. Penetrating damp can get into the property through the gaps provided by the missing mortar.

Traumatic damp usually involves water from inside the property. For instance, leaking waste and heating pipes, broken seals around showers and baths, overflowing baths, leaking radiators, leaking sinks and burst pipes.

Damp caused by flooding from outside of the property (for instance, when a river bursts its bank) is also categorised as traumatic damp.

3. Rising damp

image of rising damp that has breached the damp proof membrane

Rising damp occurs where moisture from the ground rises up through the pore structure of building materials such as brick and mortar by capillary action, similar to the way as oil travels upwards through the wick of a lamp.

This means that the water is effectively sucked up through the bricks or concrete, and may rot plaster and the timber found in joists, floorboards and skirting boards. The water brings salts from the ground, which travel up through the wall, and can be diagnosed by chemical testing. Black mould cannot grow where salt is present, so if there’s black mould, it’s not rising damp.

This water contains salts that also travel up through parts of the buildings that are in contact with the ground, esp. walls and floors. It’s often due to defective damp proof courses and membranes, or (say) where the ground is higher than the damp proof course.

Rising damp only occurs on the ground floor, so if the problem is on the first floor, it will be another damp problem such as condensation or penetrating damp. Tide marks on the ground floor walls showing where the water has reached are another tell-tale sign of rising damp.

To tackle rising damp, it’s vital to seek the advice of a qualified surveyor to find out the right course of action.

Landlord guide to black mould

black mould in a corner or a room

What causes black mould?

Black mould is a fungus that thrives in damp and dark places. Fungal spores are present everywhere in the air, inside and outside, looking for a suitable place to land and grow. Black mould loves the wet conditions caused by condensation, when warm moist air comes into something colder like a cold external wall or a window, which makes the moisture condense. Over time a small mouldy spot can turn into brown or black patches, growing on the surface of the wall, ceiling or skirting board.

The key causes of condensation are poor ventilation and/or inadequate heating. Black mould isn’t caused by rising damp, as mould can’t grow where salt deposits are present. It can only grow in clean water, which is produced by condensation.

Black mould can grow incredibly quickly, seeming to come from almost nowhere. it often begins in the corners of rooms and ceilings, growing behind wardrobes and cupboards, and along the top of the skirting board where moisture is collected. You may also find it behind furniture that’s up against an external wall in a. bedroom. Black mould is also often found in kitchens and bathrooms.

Smaller room sizes also contribute to the growth of mould from condensation as small rooms can cope with less moisture (Source: HHSRS Operating Guidance, p. 58).

Black mould can also be caused by leaky pipes, rain entering through cracks or damage to roofs or windows, ie penetrating and traumatic damp.

>> Useful Resource: Dealing with damp and condensation by National Energy Action

>> Related Post: What are HHSRS Hazards?

>> Related Post: Landlords’ Repairing Obligations

How to get rid of black mould

Ronseal 3-in-1 mould killer on a decorator's bench
Specialist products like Ronseal 3-in-1 Mould Killer are effective at removing mould

It’s important to clean off black mould as soon as possible, moving furniture to check along skirting boards and at the bottom of walls. As well as natural solutions like baking soda and vinegar, there are many specialist products that can remove the mould.

Two specialist products that are popular with landlords are Ronseal 3-in-1 Mould Killer (see above) and HG Mould Remover Spray, which are designed to effectively remove the mould and stains on most surfaces. You can buy them at DIY stores (the links above are for Homebase). As they are very potent, it’s wise to wear a mask and gloves when using them (click here for guidance on what to wear). Do read the instructions on the bottles.

It’s always important to remove the mould before redecorating; painting over mould will not kill the mould.

If the mould is on wallpaper, it’s important to strip off the wallpaper (as in the photo above), and ideally paint the prepared walls with anti-mould / anti-condensation paint, such as Ronseal Anti-Condensation Paint. Anti-condensation paint raises the temperature of the wall and helps prevent condensation.

Practical tips for landlords and tenants to prevent condensation mould

While cleaning off mould can be fairly straightforward, preventing mould that is caused from condensation from coming back is more difficult and needs regular attention. This is something where the landlord or agent will need to sit down with the tenant and explain sensitively how to minimise condensation in the future, and keep on top of any new mould.

Even if mould caused by condensation is removed, it may well come back again if the levels of moisture in the property are not reduced. Mould grows when the indoor relative humidity is persistently at least 70%, so reducing the internal humidity is key.

Here are some practical tips to prevent mould, which break the cycle of condensation / humidity that causes black mould to form:

1. Maintain an optimum temperature

  • The AMIP Guide to Condensation Mould recommends that to avoid major condensation problems, the temperature of rooms should not drop below 14oC.
  • While this may be a difficult message during a cost of living crisis, the landlord can help by increasing insulation (and ventilation) in the loft, and fitting thermostatic radiator valves to radiators.
  • They also recommend that the property is ready for when the occupants are active, suggesting that the heating is set to come on 30 minutes before they get up in the morning and before they return in the evening.

2. Ventilate and bring in dry air from the outside

  • The quickest and cheapest way of preventing condensation is ventilation. This means brining in dry air from the outside first thing in the morning to allows moisture that has built up over night to dissipate.
  • A simple way of doing this is by opening the window for about 10 minutes.
  • There’s no need to air the room for long periods; 10 minutes is enough time to bring in dry air.
  • Kitchens and bathrooms should have extractor fans fitted that are vented to the outside, to reduce condensation.
  • The Housing Health and Safety Rating System (HHSRS) Operating Guidance recommends there should be continuous low-level of background ventilation. Trickle vents should be left open if they are present in UPVC windows, and airbricks / vents should not be covered over or blocked.
  • Sometimes mechanical ventilation is needed with the installation a positive input ventilation (PIV) system in the loft in order to eliminate or significantly reduce condensation.

3. Other practical tips to prevent mould from condensation

Here are some other tips to help prevent mould:

  • Leave a gap of at least 10cm between furniture and external walls to help air circulate.
  • Don’t dry clothes in bedrooms – it’s best to dry them outside or in a tumble dryer that is vented to the outside. If that’s not possible, drying them on an airer over the bath with the extractor fan on or the window open is a good option.
  • Use anti-condensation paint like Ronseal Anti-Condensation Paint.
  • Wipe condensation from windows and window sills each morning. This rechargeable condensation vacuum is brilliant for making it easy to clear off and dry condensation from windows – it costs about £25 on Amazon. If you prefer using a cloth, do wring it out and don’t put it on a radiator to dry as that will only increase the moisture in the air.
  • Close internal doors when cooking or showering.
  • Open a window in the bathroom after showering.
  • Use a dehumidifier in rooms that are prone to condensation
  • Clean off any signs of mould on walls, ceilings, skirting boards, bathrooms and kitchens, with specialist products.

>> Useful Resource: AMIP Guide to Condensation Mould in Tenants’ Homes by Geoff Hunt, Chartered Building Surveyo

5 tips on how landlords and tenants can stop mould in bathrooms

Mould in bathroom showing black mould on grouting behind tap
Mould can be a real problem in bathrooms

With all the hot water and steam, bathrooms can provide ideal conditions for mould to flourish. It’s important to manage it actively both to remove mould and to stop it coming back.

Here are 5 tips on how to stop mould in bathrooms:

  1. It’s important to clean any signs of mould off the walls, tiles, sanitary wear and ceiling, using a specialist product like HG Mould Remover Spray that you can buy at DIY stores, or even the standard Dettol Mould and Mildew Spray sold by supermarkets. The type of mould shown above can usually be controlled in bathroom if cleaning products are used to remove it regularly. This means the tenant needs to clean the bathroom regularly to keep on top of the mould. They should wear a mask and gloves.
  2. Landlords should install extractor fans in bathrooms with a run on timer to stay on for at least 15 minutes after the lights are turned off to remove the damp air (Source: PEATA Guidance).
  3. Landlords should use Anti-Mould Condensation Paint in bathrooms to make it more difficult for mould to breed.
  4. Tenants should close the door to the shower or bath when using them, and open the window for at least after they have finished.
  5. Tenants should not leave wet towels on the floor, as they can start to breed mould within 24 hours. Wash and dry towels regularly.

10 ways for landlords and tenants to stop mould in bedrooms

Condensation mould can be a particular problem in bedrooms where it can lurk behind wardrobes and furniture.

Here are 10 practical tips for landlords and tenants to get rid of mould in bedrooms:

  1. Remove mould off the walls and ceilings with cleaning products, pulling out the furniture and looking for it on the top of skirting boards and in the corners.
  2. Tenants should wipe down the window sills regularly if water pools there from condensation.
  3. Tenants should avoid putting furniture on outside walls. If you must, try to leave a gap of at least 10cm to allow air to flow.
  4. Leave the trickle vents open if the windows have them.
  5. Open the window each morning for at least 10 minutes to bring dry air into the bedroom.
  6. Keep the temperature of the bedroom above 14oC.
  7. Use a dehumidifier to remove moisture from the room.
  8. Don’t block air-vents or ventilators.
  9. Clean the bedroom regularly, pulling away the furniture from the walls and clean away any new mould that appears. Vacuum the carpet regularly, moving the furniture away from the walls.
  10. Landlords should use Anti-Mould Condensation Paint in bedrooms where mould is a problem to raise the temperature of the wall, and make it more difficult for mould to breed.
  11. If the room is cold, despite the heating being on, the landlord could replace the radiator with a more powerful one.

As a final tip, indoor plants like peace lilies, tillandsia, and ferns are all moisture absorbers and just need a bit of indirect sunlight to grow. They can help to reduce moisture levels.

Why there is mould around window frames and how to stop it?

black mould around window

Unless there’s a leak, mould around windows is usually due to condensation formed when warm moisture-laden air meets the cold glass and/or exterior wall, and condenses into water. If it’s not wiped away, mould can grow in the water.

The first step in preventing mould around windows is first of all to remove the mould with a suitable product like HG Mould Remover Spray, and wipe it down so it’s dry.

The second (repeated) step is to wipe down the condensation using a squeegee each day. A simple one will do, but a water collecting one is even better. Then wipe away any moisture.

By removing the moisture around the window, there will be nowhere for the mould to grow.

Are landlords solely responsible for damp and mould in rental properties?

If damp and/or mould are present in a rental property, it’s the responsibility of the landlord to identify the underlying causes of the problem, so that they can be properly addressed. All landlords should read the Government Guidance on Damp and Mould published in September 2023 as it gives useful information on landlords’ responsibilities.

Where the damp is penetrating or traumatic (see above), caused by water from leaks or disrepair, it is the landlord’s responsibility to fix this. For instance, misaligned downpipes, blocked guttering, leaking waste pipes.

Tenants on the other hand are responsible for keeping the property in a “tenant like manner”.

>> Related Post: What does “tenant-like manner” mean?

All rental properties must be free of serious hazards, be fit for tenants to live in and not contain conditions that are harmful to health.

According to the Government Guidance, Landlords must take damp and mould seriously, assess the underlying causes with urgency, take appropriate action and keep tenants informed.

Landlords are responsible for maintaining the fabric of the building, and removing the source of the moisture to reduce the risk of damp and mould. From a practical perspective, this means that landlords should fix the following causes of penetrating or traumatic damp:

  • leaking internal pipes such as waste pipes, water pipes, and pipes to radiators.
  • leaks due to baths and showers that are not adequately sealed, eg missing grouting or silicone.
  • broken boilers and heating systems.
  • leaking roofs, missing roof tiles, faulty and/or blocked guttering or downpipes.
  • cracks in walls, leaks from rotten window frames.
  • damaged plaster, skirting boards or flooring.
  • faulty damp proof course.

If a property is unfit to live in due to an absence of (say) insulation in the roof, the landlord will need to increase the insulation, even if the property is already an EPC E.

The landlord should redecorate the room(s) after the remedial work has been done, if need be. It may be appropriate to use anti-condensation or anti-mould paint to reduce the likelihood of mould recurring.

When it comes to preventing mould from condensation, it would be reasonable for landlords to do the following:

  • Investigate the causes of the condensation, taking advice from a suitably qualified expert if the cause is not obvious.
  • Install extractor fans that are vented to the outside in kitchens and bathrooms.
  • Explain sensitively to the tenants why condensation mould grows, how to improve ventilation and control moisture control, and the importance of cleaning away mould to break the cycle.
  • Ask the tenants to alert the landlord or letting agent if the mould comes back, or if they notice any leaks, so that the landlord can investigate further.

Finally, landlords should inspect the property at least 6 weeks after remedial work has been carried out, to ensure that the issue has been fixed and that the damp and mould have not come back. Sometimes damp and mould will seem to disappear over the summer, only to come back with a vengeance when the weather turns cold. It’s a good idea to inspect the property again in 6 months time, as sometimes tenants are reluctant to report problems.

If damp and mould reappear, landlords should investigate further, and take professional specialist advice from a damp and mould expert.

>> Related Post: Landlords’ Repairing Obligations

What a landlord should do when a tenant reports damp and / or mould?

If a tenant reports damp or mould, landlords (and property managers) should take it very seriously, investigate the causes promptly, determine whether remedial work needs to be carried out to tackle the underlying causes, and keep the tenant informed.

This is what the Government Guidance says about how landlords should respond

When a tenant or another professional notifies a landlord that there is damp and mould in a property, it is crucial that the landlord takes the concern seriously, assesses the issue with urgency to identify its severity, and ensures that they always identify and tackle the underlying causes promptly, and with urgency when concerns have been raised about tenant health. Tenants should be informed about what is being done to resolve the issue and what the likely timescales for the work will be.

What are tenants’ responsibilities for damp and mould?

Tenants are required to act in a “tenant-like manner”. When it comes to damp and mould, here are 10 things that are expected for tenants for them to comply with this responsibility:

  1. Keep the property adequately heated, which means over 14oC.
  2. Keep furniture at least 10cm away from external walls.
  3. Wipe away the condensation from windows and open bedroom windows for at least 10 minutes every morning.
  4. Don’t dry clothes in bedrooms. Tumble dryers should be vented to the outside or condensing ones. If the tenant is unable to dry clothes outside, the best choice is using an airer over the bath with the door shut, the window open and the heating on.
  5. Cover saucepans with lids when cooking, and put the extractor fan on (if there is one).
  6. Put the extractor fan on (if there is one) when having a bath or shower, open the window for at least 10 minutes after finishing, and close the bathroom door behind so the moisture doesn’t spread to the rest of the property.
  7. Clean mould away with anti-mould products if it re-appears, and keep a close eye for mould in bathrooms, kitchens and bedrooms.
  8. Check for mould regularly behind furniture, and on the tops of skirting boards.
  9. Let the landlord or letting agent know if the mould comes back or if they are unsure sure what they need to do.
  10. Report any new leaks promptly.

Final thoughts

The presence of damp and mould can have devastating consequences on health, especially young children. It’s not always easy to “solve” damp and mould, but there are a lot of practical things that both landlords and tenants can and should do to remove mould and stop it coming back.

I’ve had instances of damp and mould in two of my rental properties. One was due to a leak, and the other was due to a mixture of a leak and condensation. Unless the cause of the damp and mould is obvious, having been through it myself, I recommend having an expert inspect the property and advise on an appropriate course of action.

Landlord Guide to successfully tackling damp and mould

3 thoughts on “How should landlords best tackle damp and mould?”

  1. I was surprised to find out that the presence of salt may prohibit black mold from spreading. Still, it would be better for me to employ an inspector right away. My basement might’ve been impacted by salt dampness recently and I don’t know what to do.

  2. Great summary Suzanne. With all the rain we’ve had through the 23/24 winter, I’ve had a few more issues than normal, so this information is a great resource.

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