Plaster, skim coat or slurry?

[Helle WIlliams]

Hi,

I am completely at a loss as I can't find the answer and those I ask give different responses.

I have torn out a sauna in the basement and built an internal wall with concrete blocks to divide a larger room into two. There is waterborne underfloor heating and we drained last year. The basement is constructed of lightweight concrete, then plastered and painted with silicate or lime paint. Where there has been moisture penetration, the plaster is porous and crumbles like chalk.

The walls have a very rough texture today, and now that I've knocked down everything that was loose, I'd like to achieve an even surface. The room is supposed to be for my 15-year-old son, so I don't want it to feel like a basement.

However, there are some places where larger holes appeared when I knocked down the loose parts. (see pictures)

What I want to achieve is a surface as smooth and even as possible, which I can then paint with silicate paint.

See the pictures to get an idea.

Questions:
1. Should I skim coat, render, or plaster, or should they be done in different stages?
2. What material should I use?
3. What is the fastest?
4. What is the cheapest yet correct?
5. Do I need to sand down all existing paint?
6. Do I need to prime? If so, with what?

Thanks in advance!

 

[Stefan N]

If you want silicate, all the paint must be removed, and then you can slurry which should be the fastest. You shouldn't use filler.

 

[mexitegel]

You get less of a basement feeling and less work if you frame with metal studs and put drywall on the outside instead, but keep in mind that you should have the space ventilated.