Plaster and paint walls in basement!

[Lärkan8]

Hello everyone here, now asking for tips and help.

We have a laundry room in a basement that we are going to spruce up a bit. The house was built in 1947 and the walls in the basement, at least the exterior walls, are made of some stones that on this forum seem to be called concrete hollow blocks. Can that be right if you look at the pictures? The wall you see is an exterior wall and on the outside, there is a staircase that goes down to a basement door. Some years ago, a roof was built over the staircase so now not as much moisture (rain and snow) comes down into the staircase, which then seeps in through the wall. What I have knocked loose from the wall, as you can see in the picture, is all the loose plaster, and the paint had also started to peel off completely or bubble. I assume that they painted with the wrong type of paint before (like plastic paint, indoor paint, acrylic, latex) and therefore the paint has come off.

Now I am thinking of applying some sort of plaster to the wall where it has come off, it is not an easy task but at the same time, I think it doesn't need to be perfectly smooth either since it's in a basement, it can't get worse than it is now Do you have any tips on which plaster to use and how to proceed to get it right? I have previously used tile adhesive which is cheap at jem&fix and adheres fantastically well when plastering; I usually first wet it with a brush and then apply a loose mix, I don't know if that's what is called 'slamming', and then throw on the tile adhesive and smooth it out, does that sound completely crazy?

Then we come to the actual paint, the walls should be white and I usually buy my paint at Happy Homes, namely Beckers. When I did the workshop, which didn't have as much moisture attack on the walls, they said I should use the same paint as in the house, that is, Beckerplast 7 http://beckers.se/Inomhus/Vara-produkter1/Vagg/Beckerplast-7/ but in hindsight, maybe one should have used a silicate paint that breathes better, is it more expensive though? http://beckers.se/Utomhus/Vara-Produkter/Putsfasad--Betong/Silikatfarg/ The question now is whether one should opt for this paint on all basement walls then. The problem is, well, that you shouldn't paint with this over old acrylic or latex paint? Do you then have to remove all the old paint and what's the best way to do it?

I got a little crazy idea just as I was writing, could one remove all the plaster on that wall so that only the stone remains and then just point the joints and then paint with a white silicate paint over it, it would probably look pretty nice but the question is if you lose too much insulation ability in the wall? Exciting idea though...

We will then paint the floor with Floor Paint + http://beckers.se/Inomhus/Vara-produkter1/Golv/GOLVFARG-PLUS/ and then lay plastic tiles from Jula, as they breathe better than tiles, can that be good, you think?

Thanks in advance for your tips and ideas!

 

[Helioz]

I would have stripped down all the old plaster and then, if possible, pressure-washed the wall to remove any potential mold. I would have also checked the joints. After that, I would have applied a red primer to slow down water penetration and maximize adhesion for the plaster. Then, I would have used mesh and plastered with B-bruk since it's concrete block and a harder mortar is suitable. Finally, I would have painted with a silicate paint to make it diffusion-open.

Preferably, do not plaster with tile adhesive or any other product, use only regular plaster (it's also cheaper) and do not underestimate the benefit of using mesh.

 

[Lärkan8]

Thanks for the tip....what is rödgrunda and what function does it serve?

I'm not completely used to plastering as I mentioned, how do you attach the mesh and is it like chicken wire?

 

[Helioz]

Rödgrund is a type of slurry that seals against direct water penetration, evens out the suction capacity in the underlying material, and increases the adhesion of the plaster. Available from all major manufacturers. Here is from Weber for example: http://www.weber.se/uploads/tx_weberproductpage/weber.base103rodgrund_datasheet.pdf It can be sprayed on with a pneumatic funnel sprayer or applied by hand with a lime brush. It is usually applied the day before plastering so that it doesn't set too much for optimal adhesion. If you don't apply rödgrund and paint with a diffusion-open paint, there is a risk that the joints between the concrete blocks will show through when the wall is damp.

Plaster mesh (installed after rödgrunding) looks like this and is attached with staples, staple guns, nail plugs and washers, or special nails depending on the substrate: http://www.bygghemma.se/utomhus/bygg/mura-och-gjuta/tillbehor/putsnat-combimix-rulle-25-m/p-186696

Here you have a complete fastening package: http://www.bygghemma.se/utomhus/byg...nfastningspaket-combimix-for-putsnat/p-186700

 

[Lärkan8]

Thanks for the great answer! Are there any others who have any tips?
//Herman

 

[Magnus_Andersson]

Isn't it a bit overkill with plaster mesh and round foundation indoors? I had exactly the same problem. Old lime plaster that started to come off, partly due to plastic paint. I knocked off all the plaster and cleaned the concrete hollow block. Then I plastered with plaster and mortar C, and finally painted with silicate paint. It's still holding up after 2 years at least. Plastering is heavy work, and a bit tricky to get it straight and nice, in my opinion. The first wall turned out quite poorly, the fourth and last was fairly okay, but not perfect.

 

[Helioz]

Basecoat and mesh are important in this case to maximize adhesion to the concrete hollow blocks, which can be difficult to plaster against. It also extends the plaster's lifespan up to 25 years, whereas if you plaster directly, it might last around 8-10 years in the worst case. It is very little extra money and work when you are going to plaster anyway for a potentially more than doubled lifespan. The mesh also keeps the plaster in place; if there is a bit hollow behind, it prevents the type of damage seen in the picture.

If you have a wall in, for example, Leca, you can choose to only use mesh around windows and doors because the plaster has better adhesion to Leca's porous structure.

If you want a smoother result, you can choose to apply a 2-5mm thick final layer with 1mm Putsbruk C and float it. With this method, you can also conceal the mistakes made in the layer below.

 

[Magnus_Andersson]

It also extends the lifespan of the plaster up to 25 years, whereas if you plaster directly it might last around 8-10 years in the worst case.

My lime plaster had been in place for 60 years, so it must have been fantastic then! I concede when it comes to the plaster mesh. It might be a good idea. It will probably be easier to get the plaster to stick too. Sometimes it wanted to fall off a bit when it got too thick. Maybe I should try plaster mesh next time.

 

[Lärkan8]

No more wise answers!