It’s that time of the year again when the days are getting shorter and colder and that means that your house is more susceptible to mould growth. Mould growth is caused by either building defects, which wets building elements, or by condensation. Mould growth will develop on walls, furnishing, and clothes once dampness is present for a period of time. Mould fungus needs three conditions to grow (infection, nourishment and a damp environment) and these will be present in a dwelling once a damp environment is established for a period of time. It is considered by some that the presence of mould within buildings can contribute to serious health risks. Toxic moulds can cause a range of symptoms including headaches and a wide range of skin lesions and rashes. The areas where mould is located need to be treated using a suitable fungicidal wash. But this is a temporary cosmetic solution and the cause of the appearance of the mould, the damp environment, needs to be dealt with prior to redecorating. A damp environment can also cause rot in timber and we will cover that in a later post.
Condensation occurs when warm moist air meets a cold surface. Its more likely to occur in winter because the building surfaces are cold and because windows are opened less, thus trapping the moist air.
Condensation is caused by a combination of:
-Unheated and poorly insulated rooms.
-Excessive moisture in the air, i.e. from gas heaters, drying clothes indoors etc
– Excessive moisture on the building element itself because of defects in the building and/or flashings.
A. Mould remedial action necessary, based on building use
- Maintain reasonable background heat levels in the property. If a room is allowed to cool the door into it should remain closed to prevent warm damp air entering from the remainder of the dwelling, and condensing in the room.
- Limit the drying of clothes internally and if clothes are dried inside they should be dried in well-ventilated rooms (with windows open) and with the doors closed to other parts of the dwelling.
- Limit the use of movable gas heaters, as this type of appliance releases large amounts of water vapour into the air, if they are used an external window should be left ajar in the room to allow fresh air to enter and the moisture produced to escape quickly.
- After using the bath the windows should be kept open/ or extract fan on and the door closed until all the moist air is removed.
B. Mould remedial action, based on building defects
Remove mould from all surfaces where present by washing the surface with a suitable fungicidal solution and allow it to drying. A dehumidifier can be used to aid the drying. Do not attempt to brush the mould off the walls, as this will just spread it.
Increase ventilation to rooms.
Engage a specialist to inspect roofs, walls, balconies etc for leaks in water proofing membrane and flashings. Perhaps a DPC (damp proof course) or DPM (damp proof membrane) is missing or damaged. Bear in mind that water entering a leak can penetrate in one place, track along a surface and exit in a remote spot.
Provide additional insulation to avoid cold spots on walls, floors and ceilings.
Provide a mechanical extract fan to ‘wet’ rooms i.e. bathroom.
Finally, the building should be regularly maintained by:
- Checking, maintaining and clearing gutters, drains, gullies and downpipes.
- Removing weed and plant growth from the building facades.
- Carrying out regular inspections and repairing any damage to downpipes, roofs and gutters promptly.