I have noticed that the walls in the basement, especially the laundry room, are crumbling at the bottom.
The basement is from the late 50s, maybe early 60s.
Does anyone know what this could be due to? I measured the humidity to be 80% when it was the warmest and have bought a dehumidifier that aims to keep it at 65%
The basement is from the late 50s, maybe early 60s.
Does anyone know what this could be due to? I measured the humidity to be 80% when it was the warmest and have bought a dehumidifier that aims to keep it at 65%
Ok, do I have to remove the old paint? How do you do that?
What can I use to repair the walls?
What can I use to repair the walls?
I used a concrete grinder (like a heavy-duty angle grinder) with a diamond blade (the kind with "blocks") to grind off paint and loose plaster. Warning, it creates an infernal amount of dust, even though I rented a machine that was connected to a shop vacuum. Then I replastered the walls with plaster mix C and painted with silicate paint. It's holding up nicely so far, although it's only been almost 2 years, so I can't comment on how it will look in 20 years.
Okay, that sounds fun 
So is it plaster mortar C that you fill with? Or is it only for the surface layer?
So is it plaster mortar C that you fill with? Or is it only for the surface layer?You should not "fill in" anything. You should remove all the paint, which usually results in having to replaster the entire wall. The surface layer is the paint, and there you should use something that breathes (e.g., silicate), just as b8q writes.
However, the paint should not be applied within 2 months from when you plastered, as the plaster must be completely dry.
However, the paint should not be applied within 2 months from when you plastered, as the plaster must be completely dry.
The easiest way to remove the paint is to "flex" the wall, just don't forget to rent a vacuum cleaner intended for the machine. You can read a thread about it here:fulingbusen said:
http://www.byggahus.se/forum/grund-markarbeten/175663-slipa-bort-faerg-fran-betongvaegg-golv.html
If you're going to repair holes, etc., in the old plaster, you should use the same type of plaster that's there now. (Definitely do not apply cement plaster to lime plaster, for example.) Finally, you paint with a silicate paint.
Ok, but there are quite deep "wounds" in some places so I guess it's more than plaster? Admittedly, it's a thinner wall that doesn't seem to be load-bearing (slab above) but the walls consist of more than just plaster anyway, right?
Can I determine what type of plaster/material I have without bringing in an expert?
Here comes a larger image that should be clickable:
Can I determine what type of plaster/material I have without bringing in an expert?
Here comes a larger image that should be clickable:
Very difficult to say just by looking at a picture, but generally, lime plaster is a porous material that is reasonably easy to "scratch" while concrete plaster is much harder.
I would suggest starting by knocking down some of the plaster so you can also see what the wall might be made of. Since it's late 50s early 60s, it could be anything from lightweight concrete blocks, like blåbetong, siporex, or ytong, to concrete elements. If it's lightweight concrete, you can see it by the wall being built, if it's concrete elements, you can see it by the wall having long vertical joints.
Edit: What do you mean by "platta över"?
I would suggest starting by knocking down some of the plaster so you can also see what the wall might be made of. Since it's late 50s early 60s, it could be anything from lightweight concrete blocks, like blåbetong, siporex, or ytong, to concrete elements. If it's lightweight concrete, you can see it by the wall being built, if it's concrete elements, you can see it by the wall having long vertical joints.
Edit: What do you mean by "platta över"?
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"slab over" means I have a ceiling in the basement that is cast. You can see the knotting in the ceiling from the formwork.
This is what the basement looks like, it is the thin (120mm) wall above/beside the washing machine that has deteriorated the most:
This is what the basement looks like, it is the thin (120mm) wall above/beside the washing machine that has deteriorated the most:
If the wall is as thin as you say, and there is a cast slab over it, I would spontaneously say that the wall is constructed of concrete elements, but chip away some plaster to confirm this.
Have you checked that the drain by the washing machine is not leaking? Concrete absorbs water, and over time waterlogged concrete deteriorates.
Have you checked that the drain by the washing machine is not leaking? Concrete absorbs water, and over time waterlogged concrete deteriorates.
No, I haven't checked that, but the floor in the laundry room is a bit higher than the other floors and has cracked in some places.
How can I check if the drain is leaking? That drain is used quite frequently because of the washing machine.
How can I check if the drain is leaking? That drain is used quite frequently because of the washing machine.
If the floor in the laundry room has also cracked, I can almost swear that the drain is leaking. You probably have an old cast iron drain that has rusted through. The connections to this are probably also cast iron and of poor quality. Open the drain cover and shine a light down, scrape the interior with a screwdriver or similar tool. You will easily notice if it is made of iron and seems "rotten." If it is, it must be replaced.
Now I have checked the well but I'm none the wiser.
It was filled with old mortar, lint from the washing machine and old gunk, but once I managed to remove all the dirt and hacked through the old mortar or whatever it was, it looked decent. I didn't see any holes anywhere even though it's not in new condition.
I don't know what to think, that a drain or sewer pipe might be broken sounds reasonable and could perhaps explain the sewage smell I sometimes sense, but since the humidity was so high before I installed the dehumidifier, I'm wondering. Below is a picture of the cracks in the laundry room floor.
That I have similar, though slightly smaller, damages in the other wall with the same thickness but at the other end of the house (the small room at the bottom of the drawing) also makes me think that it's due to humidity.
The house hasn't been drained since it was built, but I have quite a steep slope on the plot after the house, so I imagine that it shouldn't be a major concern.
It was filled with old mortar, lint from the washing machine and old gunk, but once I managed to remove all the dirt and hacked through the old mortar or whatever it was, it looked decent. I didn't see any holes anywhere even though it's not in new condition.
I don't know what to think, that a drain or sewer pipe might be broken sounds reasonable and could perhaps explain the sewage smell I sometimes sense, but since the humidity was so high before I installed the dehumidifier, I'm wondering. Below is a picture of the cracks in the laundry room floor.
That I have similar, though slightly smaller, damages in the other wall with the same thickness but at the other end of the house (the small room at the bottom of the drawing) also makes me think that it's due to humidity.
The house hasn't been drained since it was built, but I have quite a steep slope on the plot after the house, so I imagine that it shouldn't be a major concern.