Mould & Damp: What to do about it?

In a wet, cold British winter, damp and mould flourish.

Even the best-maintained properties can develop damp. Damp and mould can damage your property’s structure, cause health problems for your tenants and cost you money in repairs and void periods.

Black mould is particularly damaging and can cause allergies, asthma and fungal infections. It’s classed as a category one hazard by the Housing Health and Safety Rating System. That means that it’s something you must deal with as quickly as you can.


There are two types of damp. Both can cause mould.

Rising Damp

Rising damp is caused by a structural fault in a property. Damp rises through the brickwork and seeps into beams and floorboards. If you have stained patches on the walls and crumbling plaster, you might have rising damp.

It’s relatively rare, but it is serious. If you think you have rising damp, you need to get a professional to look at it as quickly as possible. It often means the damp course has failed.


The majority of damp in British houses is condensation. Though it’s very common, too much condensation can lead very quickly to black mould developing.

Condensation happens when wet air hits a cold surface, such as a window or wall. Rather than staying in the air, the dampness forms wet beads that sit on the surface. You’ll also find condensation in warm, wet spots where the air doesn’t circulate, such as behind a wardrobe.

Condensation is often worse in new, well-insulated homes as there’s nowhere for the wet air to escape to, as there is in a draughty, single-glazed older property.

Causes of condensation

Condensation can be caused by the way tenants use a property, but it can also be caused (or at least exacerbated) by the layout or features of a property.

Common causes of condensation are:

  • Washing being dried inside.
  • Windows not being opened often enough (or at all), especially in kitchens and bathrooms
  • Heating is turned up high.
  • Extractor fans not being used or faulty.


While it might seem as if there’s little you can do about condensation, it’s important to work with your tenants to avoid it. Long-term damp will damage your property and cost you money, regardless of who caused it.

Dealing with damp and mould management is part of your landlord’s responsibilities. Section 11 of the Landlord and Tenant Act 1985 states that the “structure and exterior of the dwelling-house”, “the supply of water, gas, and electricity” and “heating and heating water” need to be maintained and repaired where necessary. For tenancies that began after October 2015, you must respond to a reported problem within 14 days.

It’s important to be realistic about how far tenants can change their habits without support from you. For example, washing can’t be dried outside in winter, so if there’s no tumble dryer, it’s inevitable that people will use radiators. And few people will be willing to leave their windows open in winter.

With this in mind, you could:

  • Install a tumble dryer if possible (this is especially important in HMOs, where there are multiple tenants all trying to dry washing).
  • Make sure there are working extractor fans.
  • Install vented windows so air can circulate without windows being opened.
  • Make sure the heating has a thermostat and that this is working.


If you already have mould, it can be relatively easy to get rid of. It can also be extremely difficult, and if it is, removing it is a professional job.

Before you start, make sure you’re not missing any mould patches. It often appears on walls and ceilings, but also look under carpets, in cupboards, and behind furniture.

Small areas of mould on walls caused by condensation can often be removed with soapy water. For more stubborn mould, look for specialist mould cleaning sprays. These are strong, bleach-based sprays. You can also make your own with one part bleach to one part water (never use neat bleach as it can damage walls). Whichever method you use, wear a mask, goggles and long gloves to protect yourself from the mould spores.

If you have a large area (over one square metre) of mould or mould caused by a flood or sewage, then you’ll need to get a professional mould cleaning company to help. They can often respond to callouts within a day.

Damp and mould are hard to avoid during the winter. It’s pretty much inevitable that your property will suffer from damp in some form for at least part of the year, but there is much you can do to avoid or minimise it.

We regularly publish practical advice for landlords. Keep in touch by following @IAMinventories on Twitter

Edited and originally read at

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People and property are my passion, and I love it when they work together in harmony, especially when it involves a binding legal agreement that provides an accurate written record of the condition, contents, and cleanliness of a property at the beginning, during and end of a tenancy. My role is to share insights, knowledge, skills, and know-how with people invested in property. Read more about the evolution of IAM Inventories.