Anyone done this - any tips on products to use, methods of removing or prepping the painted surface?
Do you know what it's painted with? If it's sound you could probably use an SBR slurry to aid adhesion before self levelling.
I've helped a carpet fitter mate screed a few floors. He used a latex screed and mixed it up in a big tub with a plasters mixing paddle.
As for floor prep we just floated the screed over the top of old carpet glue. If the paint is well adhered to the base then just cover over it.
How thick is the levelling or screeding? If it is quite thin then you really need to bond it and that means getting rid of the paint. That will be a big job. Even then you'll risk cracking especially if there will be heavy loading like a car.
It's been painted with a solvent-based grey floor paint and the screed will be no thicker (at max) than 5mm. The garage is for storage/working on bikes and will see very occasional loading from a parked car.
Run a kango all over it
It'll be noisy and dusty but not too much hard work... look to rough the surface, making a key for the screed, you'll not have to get up every last spot of paint.... Still use bonding.
Good luck
I'd get that paint off if I was you.
It will be a dusty job but so worth it. If you have an air compressor, you could use a needle gun (Normally used for descaling steel)
If in the future the paint lifts, then the screed will lift as well.
You WILL be slightly annoyed.
You could prime it with a latex primer before a SLC produxt, but I'd want the floor to absorb water before doing so.. which means roughing up per above.
All these products have prep instructions though. Worth following to avoid a sh*t show later.
I faced the same dilemma 18 months ago. Did loads of research, spoke to loads of experts etc and the consensus was it could easily go wrong if not done properly.
Ended up chatting with a very experienced builder mate who swore blind that Arditex NA would do the job. I took him on his word and got in x bags, mixing bucket and a spiked roller. Did the area (3 rooms and a hallway) in no time at all. Put the heating on to dry overnight (as winter was kicking in). Next day = job done. Laid down some acoustic underlay followed by laminate of choice. Sorted.
Bottom line IMHE = Arditex NA