Plaster basement walls (advice?)

[JoGi]

OK, so it's time to tackle the basement walls... Need some basic tips. Here's what I'm thinking.

(1) The walls are painted with some kind of silicate paint and in some places with a denser paint. Where the paint is dense, I thought I’d scratch up the surface a bit before proceeding...

(2) Plaster mesh is nailed (does the nail have to be stainless? Is galvanized sufficient in the basement?)

(3) Coat the base and plaster mesh with "cement slurry" (Anyone have a good recipe?)

(4) Plaster with some KC mortar (class C1). Should I use "Putsbruk C" like SERPO 224? What is the cheapest and easiest to work with? (I have my own mixer and lots of plaster sand...) Planning to apply about 10mm.
I saw that you can also plaster with "Optiroc Gullex Murbruk B", "is it good - or"? Normally this is used for Leca block masonry...

JoGi

 

[JoGi]

Silly me ... Smooth-rendered (lime-rich render?) concrete block from -45.

JoGi

 

[Fasting65]

Why use render mesh if the substrate is concrete?

Go with a lime-cement render directly on the concrete... Then paint with silicate paint.

 

[Eld]

If it is rendered at -45, it is likely pure lime plaster. Old lime plaster usually has low strength and may not hold if you apply KC plaster on top. Try tapping on the wall; if the plaster is loose under the hard surface, I would consider either of the following two options:

1. Repair damages with lime plaster SERPO 142, but do not plaster the entire surface.

2. Remove all the old plaster and apply new. Choose a plaster system and stick to it. You don't need a mesh on concrete block, but make sure to prime.

 

[JoGi]

Thanks for the "help"... I'm afraid you're right. I called Optiroc and got equally sensible answers. Their recommendation was to chip away the lime, apply a red base coat, and use something like "Sepro 224" (or a self-mixed lime cement + sand).

Huh, it's going to be a bit more work than I initially thought... and above all dustier. Not so fun on the exterior walls where I have Siporex underneath (there I'll probably need to use a mesh).

JoGi

 

[TN]

I have heard that you cannot plaster over silicate paint, and that it must be removed first. But I am not completely sure about this, so it should be checked if you don't take down the plaster first.

 

[Fasting65]

Check out my project website under the diary, June. There are pictures of an excellent tool - the concrete grinder. It is actually made to sand down casting seams, but it works ridiculously well for tearing down old plaster from the walls.

Scraping with a paint scraper was really hard work. The hammer drill did more harm than good.

This is what the machine looks like:
http://hem.spray.se/fasting65/byggdagbok/dagboken/juni/slipmaskin.jpg

http://hem.spray.se/fasting65/byggdagbok/dagboken/juni/nina_slipar_golv.jpg