Sealing and painting a mouldy ceiling?

[SRJDIY]

Hi all. I have a patch of mould on my bathroom ceiling that I want to get rid of and prevent coming back. However, there's a few things I'm not sure about.

I'm planning on doing the following:

1.) Cleaning off the existing mould with an anti-mould spray
2.) Applying a stain sealer to stop any remaining stains showing through
3.) Painting the ceiling with a mould-resistant paint

However, the wall is covered in plastic cladding, with what looks like hard grout where it meets the ceiling (see attached picture). Is it best to remove/treat the grouting before painting the ceiling? I'm concerned that if I paint first, then dealing with the grouting might mess with the paint job. Also, does it look like the grouting would need replacing entirely, or can it be treated with one of those grout refresher pens? I'm not sure how well they work.

Also, can certain paints only be used over certain types of stain sealer? I've seen Zinsser BIN and Zinsser bullseye 123 recommended as stain sealers; apparently one is shellac-based and one is water-based, but I'm not sure what that means when it comes to painting over them. Also, can you apply stain sealer over just the area with stains, or do you have to cover the whole ceiling with it to avoid it showing through the paint?

And one final newbie question - whats the best way to clean stain sealer off your brushes/roller? I'm assuming water if it's water based and white spirit if it's not?

Thanks for reading all of this and for any advice you can offer! :)

[Scotty001]

I can't really answer the questions you have posed but the first thing I would address is the ventilation in the bothroom. Mould in bathrooms is mainly due to lack of ventilation and condensation building up and not clearing away.

Do you have an extractor fan?
YES (automatically comes on with the lights)
Does it work?
NO - fix or replace it.
YES - is there a gap between the bathroom door and the floor to allow air to circulate?
NO - you need to trim the door a little to provide a gap and allow ait circulation
YES - it may not be powerful enough to circulate the correct volume of air, you may have a speed setting within the unit, if not then you may need a stronger more powerful unit.

YES (pull cord to turn it on manually)
do people keep forgetting to turn it on / it doesn't work?
YES - make it so they don't forget / rox or replace it.
NO - see above re air circulation.

If you don't have an extractor fan is there a window in the bathroom?
YES - make sure people open the window a little to allow for air circulation before they turn the hot water on and keep it open for at least 15/20 mins after the hot water has been sent down the plug hole.
NO - WITHOUT either an extractor fan or a window managing the condensation that builds up and eventually causes the mould is going to be tough and mould is likely to re occur.

[SRJDIY]

I can't really answer the questions you have posed but the first thing I would address is the ventilation in the bothroom. Mould in bathrooms is mainly due to lack of ventilation and condensation building up and not clearing away.

Sorry, I should have clarified this! There is an extractor fan that comes on when either the light is turned on and remains on until around 5 mins after the light is turned off. This means it is always on when someone is in the shower. We also make sure to keep the window open when we shower, and there is also a slight gap under the bathroom door.

The house used to be a rented proporty and the fan was only upgraded to be this powerful a couple of years ago. I suspect that mould formed previously and the tenant or landlord just painted over it without actually removing it properly, which is why it's coming back now.

[Neelix]

I agree with scotty above but would add that with the window shut you need to able to feel the air flow under the door, if you can’t then you need to shorten the door.

Also, if you leave the window open all year, all the fan will do is suck air from outside into the room - this isn’t good as you will be mixing more cold air with steamy air. You really should shut the window when it’s cold outside

[Tom d'Angler]

Clean the mould off thoroughly using something like Dettol Mould and Mildew remover and then see my reply on your other thread about Dulux Easycare for my opinion on painting a mildewy bathroom...

[London mike 61]

I often do various jobs in rental properties from time to time and here are some observations and remedies

Most tenants go to work so after they shower they often shut the bathroom door and all the moisture and damp towels stay in the room until next morning, and the moisture has to evaporate into the room and condense.
This is worse in winter where there is no ambient heat to disperse moisture and no air flow through the property.

My advice
1. Open the window whilst in the shower and leave it open until you leave for work or leave the property
2. Try to dry towels elsewhere in the property to help spread moisture levels
3. I’ve used a few stain blockers over the years and my go-to is Zinsser coverstain, it covers normally in one coat but really dark stains may take two.
4. Before using the stain block, spray areas with a diluted bleach solution, leave for 5 minutes then wash off and allow to dry. Make sure all areas such as floor, basin and toilet etc are covered up while doing this.
5. Use a 4 inch mini roller to apply the stain block then throw away ( it’s not worth cleaning it )
6. Apply mould resistant paint
7. In winter, there is nothing wrong with using a dehumidifier to remove unwanted moisture from vulnerable areas on a regular basis.

I hope that helps

Mike