Who's responsible for mould in a rental property? Landlord Blog

By Shannon Hall

Mould In A Rental Property – Who’s Responsible?

Mould in a rental property can cause serious health issues and therefore, should not be ignored by either landlord nor tenant.  The mould fungi have been identified as the source of many health risks such as asthma, allergies, infections and sinusitis. Moulds produce allergens, irritants, and in some cases, toxins that may cause reactions as well as being unsightly. And, it’s not uncommon – according to a recent housing survey by Shelter, 61% of renters have suffered damp, mould or leaking roofs.

The laws and rules surrounding the management of mould in a rental property aren’t clear cut, so when it comes to deciding who’s responsible for removing the mould and fixing any afflicted areas, it can result in disputes between landlords and tenants.

What causes mould to appear?  

The main causes of mould include; water leaks, penetrating or rising damp, wet or damp basements or crawl spaces, condensation, excessive water vapour or steam being generated through cooking, washing, bathing, showering and clothes drying, inadequate ventilation and/or heating.

Who’s responsible for dealing with mould in a rental property?

For mould to be the landlord’s fault, it will usually have been caused by something that’s wrong with the build of the house, such as structural defects, leaking pipes, or ineffective damp-proofing. This may be different in commercial properties where the tenant may take on repairing responsibilities.

The most common cause of mould is through condensation and this is typically caused by the tenant’s lifestyle. For example, lack of proper ventilation, not opening windows or using heating. They should be regularly airing the property to prevent the growth of mould.

What can landlords do to prevent mould in a rental property?

Looking from the outside of the property, a landlord should first check for obvious structural defects, that the walls are not suffering from rising damp, is there a presence of a damp-proof course?  Check that any wall cavities are clear of debris and that airbricks are clear and perhaps consider fitting additional airbricks to ventilate under suspended floors. Ensure that the roof tiles are in good condition and no leaks are present. Inspect the guttering and down pipes, make sure that they are carrying the water away from the property or into adequate drains.  Solid concrete floors are prone to damp so may require a damp proof membrane.

What can tenants do to prevent mould?

When checking a tenant into a property, we always advise going through the inventory with them room by room.  At this point, it is a good idea to educate them on the causes of mould and how little lifestyle choices can make a big difference to their living conditions, health and comfort.

For starters, after a bath or shower, the room should be ventilated to the outside, not to the rest of the house – just opening a window (and closing the door) will help.   You as the landlord may also wish to fit an extractor fan.

Advise tenants to dry clothes outside on a line (if possible) or in a cool area of the property (although this may take longer, less moisture will be held in the air at any one time).  If the tenant chooses to dry clothes indoors, they should ensure that there is plenty of ventilation in the room. If they are using a tumble dryer, the dryer should ideally have external air extraction.  When people come in with wet coats and umbrellas, they should be hung or placed outside the living area to dry – like the porch.

Difficulty finding proof

The problem with mould in your buy-to-let property is the difficulty of identifying the person at fault. It can be tough to prove whether the mould was caused by a structural defect or simply a lack of ventilation.

In particularly difficult cases, a damp expert can be called in to assess the property and make a report that can be used as proof of the party at fault. They can also recommend the best ways to remove the mould and prevent it from growing again.

About Shannon Hall

Shannon HallShannon joined LettingaProperty.com in 2015 and has proven to be an exceptional Valuations Manager by supporting new landlord clients in switching to our digital platform. Not only is Shannon an experienced landlord herself, she has achieved professional qualifications in Residential Lettings & Property Management, holds a NFOPP Technical Award and has completed a Diploma in Business Management.


    February 13, 2020 REPLY

    hi im living in a property that has serious black mould issues on the wall in the back room and under the kitchen sink a few months ago when we had the heavy rainfall happened water came in through the top of the bay window .the landlord sent in some builders to put a sort of seal around the door and also they were supposed to do some pointing but the landlord told them not to , is it the landlord or ourselves responabilty to sort out damp proofing thanks K P Daniel

    July 17, 2019 REPLY

    Mould can not survive on a saline solution. Rising damp and penetrating damp both result in salts deposits on the surface of the internal plaster which would prevent mould growth. There are circumstances where the mould is protected by a paint film or wallpaper but these are rare. On solid wall structures, penetrating damp that is in its early stages as a result of damage or erosion of the water resistant brick face, can partially penetrate a solid wall causing significant increases in heat loss. This will promote condensation internally but the water from the penetrating damp is not the direct cause.

    Mould can only grow on pure water and that water has only two potential sources. A water leak or condensation. In 95% + of the buildings I have surveyed in the last 25 years, this is due to condensation. Cold surfaces reduce the air temperature below the dew point in relation to the humidity inside the property, and clean water droplets form on the surface which allows mould spoor to become established. In all instances where this is the case, the problem is the balance between the heating, the insulation and the levels of humidity in the air in relation to available ventilation. Some instances of mould can be dealt with by improving the ventilation and the use of antimould paints. However, in most serious cases we have found the need to insulate using Thermal board or Ultratherm insulation. Ventilation almost always involves improvements to the bathroom extractor fan and the installation of insulated air bricks. The tenants themselves can do very little to prevent condensation in poorly designed buildings. Pre cavity buildings were designed to be ventilated by 1000s of cubic feet of air rushing up chimneys in the winter drawn through drafty windows. We block the fireplaces and add double glazing and totally eradicate the proper ventilation. Early cavity wall designs had woeful levels of cavity insulation if any at all. Again ventilation was poor as its benefits were not understood.

    Air can only support a given amount of water dependent on the air temperature. This is called relative humidity (RH) . On average 60-70% of what we breath is actualy water. Air at 60-70RH we are comfortable. Much below 50% we will be complaining of sour throat’s and dry lips and getting static shocks. 70% + is the danger zone. A room with say 80% humidity at 18 degrees centigrade only needs to drop to 15 degrees citigrade for the water vapour to turn into physical water. So any cold external wall will act as a heat sink and attract condensation.

    Warm moist air has a higher vapor pressure than cold air. So ventilation allows the high pressure warm air to vent through air bricks of similar ventilation. However if the ventilation is not insulated, tenants tend to either not use it, or block it in a misguided attempt to save heat and money. Opening windows is in this category and in most instances leaving windows open is not safe for security reasons. Drying clothes on radiators is often given as a reason for mould. As I always ask, unless theres a condensing tumble dryer or a laundry room in the rented property, where else are tenants in properties without gardens going to dry their clothes?

    In my 10 rental properties, I endeavour to use antimould paints on all redecorations and refurbishment projects. On the worst properties I will insulate all external walls with thermal board to a minimum of 30mm, sub carpet or laminate insulation on solid floors and I provide top quality high powered humidity controlled extractors in the bathrooms. As a result my only condensation issues are on single glazed windows in GII listed properties where these can not be changed. In all bedrooms I will install Passi Vents which are insulated air bricks. On cupboard built against external walls, I line the back of the cupboard with Jablite insulation. All internal doors are air gaped at the bottom to promote through ventilation.

    I hope this helps

    Mark Chase CTIS CRDS CSRT

      July 17, 2019 REPLY

      Hello Mark, thanks for taking the time to contribute such an informative comment. Some brilliant tips and explanations.

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