Bathroom Paint Cracking Issues Help!

[elfie]

We are first time home owners with little experience of decorating. However, we need to redecorate our bathroom as the walls are in a poor condition. We have two main issues on two different coloured walls in our bathroom. My question is, how do I prepare these walls before painting them?

1. The light blue paint is cracking all over in a pattern - see photo. We know (from finding the can in the shed!) that this paint was not a bathroom paint and so we're guessing this cracking has occurred due to the paint not being able to withstand moisture. The bathroom is well ventilated with an extractor fan and window, and we haven't had any issues with mould.



2. The teal paint was a bathroom paint and does not have the same patterned cracking. However on this wall there are some large cracks, some of which are quite deep and seem to show the plaster underneath. (There is at least a layer of bright pink paint between the plaster and the current colour, which can be seen in the cracks on both walls)


There were also some large holes in the wall where a shelf fell down and so we have filled these in with polyfiller.


My question with both of these walls is what do I need to do to prepare them before painting? Do I need to sand either/both walls? Or prime them? Do I need to fill the deep cracks in with something? Is it okay to paint over the polyfiller?

We are complete novices when it comes to decorating as this is our first property so any advice would be very much appreciated!

 

[misterhelpful]

1. There is an adhesion issue between the paints which has caused the crazing, either caused by surface contamination of grease/soap/dirt, etc, or if a matt emulsion has been used on top of a bathroom/silk emulsion.

2. Scrape away the loose material, apply a diluted coat of emulsion to the bare areas of plaster before filling (this will stop too much moisture being absorbed from the filler which can cause it to crumble as it dries or when it is sanded). Once filler is dry, sand flush and apply another coat of diluted emulsion over the filler to seal it.

3. It would be a good idea to give the whole area a good wash down and rinse, then lightly sand all of the existing paint with 120 grit sandpaper to provide a key for the next coat. You don't have to remove any paint when doing this but just need to take the sheen off the surface. This isn't so essential when applying a bathroom paint, although still wise, but would be absolutely necessary if you intended to use a matt emulsion (which is not a good option for the majority of bathrooms), otherwise you'll end up with the scenario you have in your first two pictures.

You can, of course, do all of the cleaning and sanding before you do the filling mentioned in point #2.

 

[elfie]

Wow thank you Misterhelpful - you're definitely living up to your name! I just want to clarify a couple of things:

1. I suspect the second of your suggestions is the issue - that the pink underneath was a silk emulsion. Should I follow your advice in step 3 (i.e. wash down and sand) but sand all of the light blue matt emulsion off, then sand the pink underneath to take the sheen off of it?

2. Is the diluted coat of emulsion just water and the paint we plan to repaint the walls in? We're planning on using a Dulux bathroom paint in a soft sheen finish. Or another type of emulsion? And roughly what ratio of water to paint would you use?

Sorry for the ignorance! Right, on with my cleaning, filling, sealing and sanding!

 

[misterhelpful]

If the paint on top of the silk is adhered well enough, there shouldn't be any need to remove it all and just remove whatever is loose around the cracks and holes. If, however, you try to apply fresh paint and it starts to lift, total removal will probably be required, but I think this would be a worst case scenario. Keying all types of paint is never a bad thing so I would still recommend a light sanding. The worst areas of crazing can be addressed with a good quality fine surface filler.

The diluted coat can be just whatever you are using to repaint, or just some plain old white emulsion that you have lying around, because all you are doing is satisfying the porosity of the bare plaster and filler before you use your finish coats. This will help all of the patches to blend quicker, with less coats required, but don't be tempted to put the diluted coat on too heavily because that could end up causing patches to show through too. Just adding around 20% water to the paint will be enough for the patches.

There is always the option of using something like Gardz to bind down loose areas, but I would prefer to try the filling and sanding route in this instance.

 

[elfie]

Brilliant, thank you so much for all of your advice. I'm now hopeful that we can have beautifully smooth bathroom walls by the end of the week!