Understanding damp and mould
Condensation
Condensation occurs in a dwelling when warm moist air produced by ordinary activities such as showering or cooking meets a cold surface such as an external wall or window.
The moisture laden air will remain internally if ventilation does not occur and will gravitate towards the nearest cold surface where it condenses.
Moisture is also naturally occurring in the air and when air temperatures drop it will release this water in droplet form. This is known as the dew point.
Condensation generally occurs during cold spells of weather. It will appear on cold surfaces and also in microclimatic areas where there is little movement; for example behind a cupboard. This will often lead to the formation of mould growth and mainly occurs in corners of rooms, in cupboards or on north facing walls, as these are generally the coldest.
Ben Burlikowski says:
“Damp and mould is a common problem area for landlords and their tenants, regardless of the age of the rental property.
“It’s important that both parties understand the causes and best ways to prevent the problems from worsening. RICS accredited Surveyors Walker Management have written this useful guide to help both landlords and their tenants deal with the causes of the damp and mould.”
Could damp 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 under crofts.
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 that 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.
Protect your deposit today
If you have taken a cash deposit, you must protect it in a government authorised scheme within 30 calendar days
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 heating (constant temperature space heating)
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.
Landlords and agents should tell tenants how to best manage any problems and provide the information below:
How to combat moisture production:
- Cover saucepans.
- Dry clothing outside rather than on radiators.
- Wipe away condensation as quickly as it’s spotted.
- Keep window trickle vents open constantly and open windows as much as possible (especially after cooking or showering) to allow a through flow of air whilst maintaining a heat balance.
- Ensure extractor fans are operational, you can test pull by holding a sheet of tissue paper against it and seeing if it sticks.
- Turn on the cold tap of the bath first so that when the hot water hits its doesn’t produce as much steam.
- Close doors in wet areas to stop the spread of moisture to other rooms.
- Where possible position cupboards and drawers etc. against internal walls.
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 a 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 Vents)
- Improving Heating (constant temperature space
heating)