Dampness and mold are common issues for landlords and tenants, regardless of the rental property's age. It's crucial for both parties to understand the causes and the best prevention methods to stop these problems from worsening. |
Condensation
Condensation occurs in a dwelling when warm, moist air produced by everyday activities such as showering or cooking meets a cold surface, like an external wall or window. If the air is not ventilated, the moisture-laden air will remain inside and gravitate towards the nearest cold surface where it condenses.
Moisture is naturally present in the air and, as temperatures drop, this moisture is released in droplet form—a process known as reaching the dew point. Condensation typically occurs during cold spells of weather and appears on cold surfaces. It also forms in microclimatic areas with little air movement, such as behind cupboards. This often leads to mould growth, particularly in the corners of rooms, inside cupboards, or on north-facing walls, which are generally the coldest areas.
Could dampness be caused by something else?
Yes. Condensation may not be the only factor when mould growth occurs.
Rising damp can occur if the damp proof course or membrane within the walls or floors of your dwelling has been breached. Prevalent in ground floor flats as well as houses due to damp proof course failure, something that generally occurs over a long period of time.
Penetrating damp. Rain may also seep through cracks in brickwork or through missing tiles on external roof surfaces.
Blocked guttering may also mean water spills over and saturates external walls.
External plumbing which is cracked may allow seepage into internal parts.
It can be difficult to be certain of the exact cause of any dampness and so unless you are sure it may be wise to contact an RICS qualified surveyor or an experienced contractor who has experience working in this particular area.
Condensation will not be limited to certain areas and may cause growth in different areas of a room and you may also notice furniture and clothing becomes affected.
Examples of condensation
Lack of insulation at construction
Properties constructed during certain eras did not have the more stringent construction and insulation levels now required in new development. As a consequence, they are potentially more susceptible to the development of condensation than modern buildings.
Areas, where this can occur, are areas of a property that were difficult to insulate at construction such as above or below balconies or undercrofts.
Insulation causes a warming effect which helps to counteract the conditions under which condensation can develop.
Cold spots/bridging
Certain construction elements such as concrete beams by their very nature are cold and insulating them to bring them up to modern standards can prove to be difficult. As a consequence, many properties have cold spots or suffer from thermal bridging. Equally, when properties are refurbished insulation can be removed which increases the possibility of cold bridging and the like becoming a problem.
Lack of ventilation
The development of condensation can be controlled in part by increasing ventilation throughout the dwelling. In tenanted properties, there is a preconception that ventilation means higher heating bills and as such there are growing examples of condensation which is exacerbated by the blocking up of trickle vents (vents within window frames) or traditional air vents which are found individually within rooms.
Remedies and Precautions
How to avoid condensation
With the correct balance of heating and ventilation, condensation should be avoided. The heating helps keep the property warm and the ventilation will enable excess moisture-laden air to escape.
TIP: Improving ventilation (opening windows, trickle vents).
Using the thermostat. Set it on for long periods on a low setting or have it switched to operate automatically on shorter periods for at least seven hours a day. Do not adjust the thermostat manually when set but trust the system to regulate itself for you. Make sure there are no cold zones in the home by turning all radiators on.
TIP: Improving heating (constant temperature space heating).
Landlords and agents should tell tenants how to best manage any problems and provide the information below:
How to combat moisture production
Always cover saucepans when cooking to minimize moisture release.
Dry clothing outdoors whenever possible instead of using radiators.
Quickly wipe away condensation as soon as it appears to prevent moisture buildup.
Keep window trickle vents open at all times and ensure windows are opened regularly, especially after cooking or showering, to maintain good air circulation while balancing room temperature.
Maintain adequate heating by keeping rooms at a minimum of 20°C, paired with daily ventilation, to reduce moisture accumulation.
Test extractor fans to ensure they are working efficiently by holding a sheet of tissue paper against the fan and checking if it sticks.
When filling a bath, run the cold water first to reduce steam production when hot water is added.
Close doors in areas prone to moisture, such as bathrooms or kitchens, to prevent humidity from spreading to other rooms.
Position furniture, such as cupboards and drawers, against internal walls whenever possible to reduce the risk of damp.
Interesting fact How much moisture is typically produced in the home?
• Drying clothes produces ten pints of water in an unvented tumble dryer. • Having a bath produces two pints of moisture. • Washing clothes produces one pint of moisture. |
Fighting mould
Remove mould growth by wiping down walls and windows with a fungicidal wash recognised by a Health and Safety Executive ‘approval number’. Follow the manufacturer’s instructions precisely. Dry-clean mildewed clothes and shampoo carpets. Take care because disturbing mould can increase the risk of respiratory problems.
After treatment, redecorate using good quality fungicidal paint to help prevent mould recurring.
Ensure insulation to external walls is in place.
For landlords who want to take more intrusive measures to deal with structural problems consider:
Increasing insulation (EWI, IWI, cavity fill, double glazing)
Improving ventilation (fan installation, opening windows, trickle vents, Passyfier Dehumidifier Vents)
Improving Heating (constant temperature space heating)
By understanding the causes and implementing these prevention strategies, landlords and tenants can work together to create a healthier living environment and reduce the risk of damp and mould in rental properties.
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