Mouldy Flat?

Mould can be a serious health hazard. But before you complain to your landlord you need to make sure you aren’t creating the problem. 

Water in the air gets there through normal things like showering, cooking, and breathing. Dampness on your walls and windows is caused by that water in the air of your nice warm flat meeting the cold outside parts of your flat (like windows), and turning back into water – which makes a great environment for mould to grow.


Things You Need To Do To Avoid Growing Mould:

Windows: These need to be opened for at least a few minutes each day (even on cold days) to get rid of your humid inside air. Ideally you should leave bedroom windows slightly open overnight. Ask you landlord about security latches that allow this if there’s none. This ventilation can be more important in warm insulated flats than drafty old villas.
If you have condensation on your bedroom windows in the morning wipe it off; your towel after a morning shower is ideal.

Cooking: When you cook it releases water into the air, so you should always have a window open while cooking and for a while afterwards; or use the range-hood or extractor-fan if you have one. Use lids on pots when cooking.

Showers & baths: Use the extractor fan and heater when you’re showering or bathing. Always have a window open during a shower or bath (even if it’s cold). Always leave the window open after use and keep the door shut (and the fan and heater for a short while). If moisture is still a problem, you should also wipe down any excess moisture on the walls and windows afterwards.

Washing: Do not dry wet washing and towels inside if it can be at all avoided. Clothes should be removed immediately from the washing-machine and hung outside or dried in a dryer. If you do have to dry washing inside, give it a double spin in the washing-machine or ring out as thoroughly as you can first, and you must ventilate the flat during and after drying.
Obviously you can’t always dry clothes outside in Dunedin, but it’s not the landlord’s fault if your house is damp because you dry clothes or towels inside and don’t ventilate. If this is only occasionally a problem laundrettes have drying facilities. If it’s a constant problem, ask your landlord to consider installing a clothes-drier.

Heat-pumps: Is yours set too high? If you have it cranked-up all the time you are increasing the differential between your warm inside and the cold outside making condensation more likely. Note the World Health Organisation recommends 18 degrees as a suitable healthy minimum temperature for occupied rooms (or 20°C if you’ve got vulnerable people like young children, the elderly or the ill), and 16°C for overnight.

Gas-heaters: If you use a non-flued (ie portable) gas-heater you must ventilate the room. Not only do they produce water, but they produce monoxides which can kill you in big doses.

Leaks: You flat should be totally free of any leaks from water from the outside or from the water pipes. If you have a leak – tell your landlord as soon as possible. Not only do they have to repair it so you have a liveable flat, but it may also be causing damage to their property.

Furniture: Keep a 10cm gap between larger furniture items and the external walls of the flat (especially if poorly insulated and cold) so air can circulate behind them.

Plants: If you have a moisture problem you might need to reduce the number of plants, or move plants outside.

Clean: Wash off any mould when it first appears. A detergent solution will work fine (bleaches should be avoided if you need to clean mould regularly as they produce nasty gasses). Wear rubber gloves, and don’t breathe it in obviously; ideally use a face mask, especially if there’s a lot of mould.

Chemical moisture-absorbers: Chemical salt products, like DampRid, are available to help take moisture out of the air. These can help, but they are not a substitute for proper ventilation or a dehumidifier. They are best used for smaller specific problem areas like wardrobes and cupboards. Smaller moisture absorbing products are available for drawers etc. Tip: Asian grocery stores often sell these products cheaper than the supermarket.


What Landlords Can Do:

Many Dunedin flats have more people living in them for more hours than they were ideally designed for, so the built-in ventilation in some is inadequate.

While tenants need to ventilate their flat by opening windows etc, it is not reasonable to expect them to have windows open in occupied rooms over winter. It your flat needs that level of ventilation to keep mould free you should consider other measures like below.

Shower lid: Put a lid on the shower cubicle if practical. These are available to fit many common showers.

Windows: Fit security latches to windows so tenants can leave windows open without fear of the flat being broken into or intruded on. Ideally ones that have enough flexibility to allow the window to be secured slightly ajar are best (especially for bedrooms).

Extractor-fans: These remove damp air from the kitchen, bathroom and laundry areas when in use.

Dehumidifiers: These can help to avoid dampness in rooms that are not adequately ventilated. Please ensure these are suitable for the task; ie it must be able to process enough liquid for the room size and dampness it’s being asked to deal with. Dehumidifiers that have moisture sensors are more efficient (ie they only operate when there’s moisture present). Ensure tenants know to empty their container regularly.

Clothes-dryers: It’s often too cold and wet in Dunedin to dry clothes outside, especially in shady damp areas. Landlords may want to consider putting a dryer in the flat so tenants aren’t forced to dry their clothes inside. Ensure driers are vented to the outside – even the ones that claim not to need exterior venting create moisture; lots of moisture.

Information: Provide your tenants with information about how they might avoid excess moisture and condensation in the flat. Perhaps leave notes in relevant areas of the flat if you have specific concerns.

Maintenance: Between tenants ensure all the fixtures associated with preventing moisture are working: eg drier and extraction fans are working and venting outside with no leaks, dehumidifiers are working, clean and up to the task. Clean and drain heat-pumps where necessary. Give the washing-machine a good clean (eg some hot cycles with bleach and white vinegar, and rinse). Check property for damp areas and smells.

Paint: When repainting problem or wet areas like bathrooms and laundries consider using a mould resistant paint.

Insulation: Where possible insulate the external parts of your property. Poorly insulated walls, ceilings and floors are cold and attract condensation. Remember to retain adequate ventilation though.

Explore all unexplained moisture: You might have a roof, window or plumbing leak, or unsealed foundations causing capillary action in masonry, or rising damp slowly ruining your house.

Home ventilation systems: You might need to consider a home ventilation system if the above measures do not prevent dampness in your property. Seek professional independent advice.


If your flat has mould issues you can not resolve, get in touch with

• Your students’ association: OUSA
• Tenancy
• DCC Environmental Health


Potential flats:

If you’re looking at flats to rent don’t forget to check for potential mould, think about how well vented the flat is, is it in a shady damp area, and is there a clothes-drier or suitable clothes-line outside? A damp smell or feel is a bad sign.

The STARS flat rating scheme at is handy indicator of how good a flat is. (and it’s free to use).

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