A few tips about mould and its causes.
Just a few tips to remember when sorting out mould problems, there are plenty more reasons than shown here as to why mould appears, but the basic starting point is dampness, caused by whatever means possible. Condensation occurs when the humidity reaches 70%, keep the humidity a bit lower by venting etc then the chances are that there will not be a problem. Also remember that one adult breathes out roughly half a bucket of moisture from their mouth a night, just consider how much moisture is in a building when a family is in there, a few animals and cooking as well as showers or baths are taking place when there is not ventilation. Just something to think about.
Mould is a symptom of a cause, find the cause and cure the symptom. It is that easy, the problem is recognising the cause in the first place.
Once the cause has been found it needs to be urgently addressed so as to prevent further contamination.
Often the smallest water ingress or damp area can produce a massive mould problem.
I often hear about people being told to open a window when showering, this is fine if you like to stand in a cold draught in the winter.
I hear about opening a window and use the extractor fan, fine if you want to suck in cool damp air from outside just to push it back outside via the fan.
I hear so many stories from people that just do not understand damp ingress and mould try very hard to convince me that they are doing everything possible to solve the problem, whereas a lot of the time they are making the situation worse.
I could write a book on causes, symptoms, excuses etc but I wont delve into that side of the problem, however I will cover a few simple solutions etc.
If you have a damp problem do not immediately think dehumidifier, these will work very well if they are used at the correct setting and in a sealed room, they work on the principle od dry a room out then open the door and let that dry room act as a piece of blotting paper to soak up the moisture from other areas. This idea is fine as long as there are no external doors, vents or windows open or else the machine is drying out the outside atmosphere.
The other method I have tried myself but am not convinced work well is the ceiling mounted pressure system or ceiling dehumidifiers. These are ok in larger commercial properties, but again require warm air from the loft space to blow it around the building creating a higher air pressure within the building and then letting it escape through window vents or similar. As these units are similar to air curtains it is important to mount them where air can flow into all rooms, whilst ensuring that the air pumped into the room can also escape, or else a pressure is built up to a degree that the airflow is zero. This in turn can make the whole reason for having such a unit worthless. Also it has to be turned on 24 hours a day, and also remember that in the winter months the loft space is colder than indoors, and as such if the unit does not have heaters built in only cold damp air will be pulled into the building.
If the shower or cooking area has steam being produced it is better to have the doors closed and an extractor fan sucking the moisture out of the building, NEVER into a loft space as the condensation will certainly create damp and in turn mould.
If there are black lines of mould across the ceiling this is almost certainly cold bridging caused by lack of insulation between the joists in the loft space, which will allow cold air to touch one side of the ceiling whilst warm air is touching the other side, hence condensation and mould. Remedy re-lay the insulation.
General DIY treatment for mould once the damp air has been eliminated is to use Cillit bang mould treatment, this item has an HSE number which means that the chemical which is bleach dries at the same speed as the water that carries hence the rooting system of the mould is not fed with water. Whereas if household bleach is used the bleach chemical will discolour the black mould and give it the appearance of being sorted, whereas all the bleach has done is to discolour the black and feed the roots with water which means that very soon after treatment the mould will return.
There are lots of people out there that will tell you that this or that works but from years of experience I can assure you that most of them do not. It is always find the cause to cure the symptom but always without a shadow of doubt do not cut corners, nor be in denial.