I am so tired...
I have been dealing for over a year with drawings, the building committee, neighbors, etc. Always with Ytong blocks in mind as building material.
Finally found a mason who seems good, but he advises against plastered aerated concrete as the plaster will likely crack and let in water, which would be a "catastrophe" for the wall. I didn't think to ask in what way, maybe the rest of the plaster freezes and breaks apart?
I've searched the internet without finding a single piece of information about this. My neighbor's house is a Serponit-plastered aerated concrete house from the early 50s, as far as I know, never facade-renovated or even repainted. A bit grayish in color but otherwise with a perfect facade!
The mason suggested instead 25 cm Leca with plastered foam plastic outside, something I feel strongly skeptical about for various reasons.
( One of the less scientific reasons is an old optimist dinghy that my father-in-law had lying around, with polystyrene between the hulls as a flotation element. When this beauty was launched a few years ago after a long rest on land, it turned out that most of the polystyrene was gone; eaten or just transported away by the thousands of ants that had settled there! I feel that I will never really be able to relax after this if my house exterior walls consist of this, or similar material... )
Has anyone here ever heard of aerated concrete houses where things went wrong after moisture got in through the plaster (assuming you don't use acrylic paint or other diffusion-tight paint as a surface treatment)? I'm thinking of lime-cement plaster and I'm considering Optiroc's scratched plaster or CD-sprayed plaster as surface plaster.
PS How do you get the smileys in??
I have been dealing for over a year with drawings, the building committee, neighbors, etc. Always with Ytong blocks in mind as building material.
Finally found a mason who seems good, but he advises against plastered aerated concrete as the plaster will likely crack and let in water, which would be a "catastrophe" for the wall. I didn't think to ask in what way, maybe the rest of the plaster freezes and breaks apart?
I've searched the internet without finding a single piece of information about this. My neighbor's house is a Serponit-plastered aerated concrete house from the early 50s, as far as I know, never facade-renovated or even repainted. A bit grayish in color but otherwise with a perfect facade!
The mason suggested instead 25 cm Leca with plastered foam plastic outside, something I feel strongly skeptical about for various reasons.
( One of the less scientific reasons is an old optimist dinghy that my father-in-law had lying around, with polystyrene between the hulls as a flotation element. When this beauty was launched a few years ago after a long rest on land, it turned out that most of the polystyrene was gone; eaten or just transported away by the thousands of ants that had settled there! I feel that I will never really be able to relax after this if my house exterior walls consist of this, or similar material... )
Has anyone here ever heard of aerated concrete houses where things went wrong after moisture got in through the plaster (assuming you don't use acrylic paint or other diffusion-tight paint as a surface treatment)? I'm thinking of lime-cement plaster and I'm considering Optiroc's scratched plaster or CD-sprayed plaster as surface plaster.
PS How do you get the smileys in??
Hello!
Hmmm... it makes you a bit thoughtful when you read the mason's comment about lightweight concrete + plaster. What I understood is that one of the good advantages of this construction method is that the walls are not completely sealed, allowing moisture to move back and forth. This way, you never have problems with trapped moisture in the construction.
Does the paint applied to the plaster act as a moisture barrier?
What have I missed???
Best regards, Stefan
PS The smileys can be found above the window when you write a new message. Just click on the one you want to paste in! DS
Hmmm... it makes you a bit thoughtful when you read the mason's comment about lightweight concrete + plaster. What I understood is that one of the good advantages of this construction method is that the walls are not completely sealed, allowing moisture to move back and forth. This way, you never have problems with trapped moisture in the construction.
Does the paint applied to the plaster act as a moisture barrier?
What have I missed???
Best regards, Stefan
PS The smileys can be found above the window when you write a new message. Just click on the one you want to paste in! DS
I would definitely not use foam boards when you already have a stone wall. Firstly, foam boards are quite a soft material. What happens when you hit the wall or want to hang something?
Here you have a handbook on ytong-plaster and surface treatment
http://www.yxhult.se/lattbetonghandboken/index.html
Otherwise, you can order ready-made blocks of pre-plastered concrete walls like we did. All we had to do was choose how it should look. Then you just paint with silicate paint. ;D
Here you have a handbook on ytong-plaster and surface treatment
http://www.yxhult.se/lattbetonghandboken/index.html
Otherwise, you can order ready-made blocks of pre-plastered concrete walls like we did. All we had to do was choose how it should look. Then you just paint with silicate paint. ;D
... sounds more like a poor excuse from the mason for why he doesn't want to take on the job.Jena said:
Building with lightweight concrete blocks is nothing new. And plastering it is standard. However, there are many different materials and methods for plastering, some better than others.
Check out Lovskog's page, where you can find a ton of great ideas. He built the house with lecablock and applied plaster.
http://husbygget.lovskog.com/
It's the same with Ytong; just apply plaster directly.
We also considered building with Ytong, and I called Yxhullt, where they manufacture the blocks.
He said it was just a matter of plastering directly on the blocks.
Recommendation: change your mason if you want plaster that lasts ;D ;D
http://husbygget.lovskog.com/
It's the same with Ytong; just apply plaster directly.
We also considered building with Ytong, and I called Yxhullt, where they manufacture the blocks.
He said it was just a matter of plastering directly on the blocks.
Recommendation: change your mason if you want plaster that lasts ;D ;D
Sounds rather undramatic when you just mention that you plastered, plus in passing that you do it yourself and for 20,000 SEK! Unfortunately, I don't think I'm in the same league. :-[
Sweli: I've studied your walls a bit but haven't really been captivated, don't ask me why: Maybe it's because I'm attracted to a homogeneous, heavy, and thick wall. Perhaps it's the lightweight concrete floors (but maybe you can fix that somehow with your system too?).
Stefan: If I've understood correctly, the plaster should let through water vapor (which dense paints don't do) but not pure water (which pure lightweight concrete does).
I've called around a bit:
- Ytong says it's absolutely no problem, as long as you have a solid foundation, use the right plaster, and plaster according to the instructions (is anyone surprised by that answer?..).
- The claims adjuster at our insurance company had heard of the problem but since it was never an insurance case, he didn't know much more. He didn't seem to be able to relate it to different plaster systems, e.g., if you could encounter it with a KC thick plaster system such as Serporoc.
- Optiroc said that it can probably happen with lightweight concrete and naturally drifted into promoting their own Leca as a building material...
- Other masons consulted don't rule out the possibility; if you want a "safer" facade, brick is what's needed. For a couple hundred kronor more per sqm.
- The architect thinks I'm being a bit too nervous and fussy; of course the plaster will work.
- Personally, I don't think I've ever seen a thick plastered house with major damage, and I find it hard to imagine foam with acrylic paint and already have a brick wall from the early 60s that's eroding away at a rapid pace. I will probably continue on the outlined path according to Ytong's recommendations and decide to use the optimal surface in the future IF the plaster causes issues: Aluminum; weather-resistant, maintenance-free, and cheap! That it's ugly, I (and maybe the wife) will overlook the day I'm standing there with an exorbitantly expensive, peeling plaster!
Sweli: I've studied your walls a bit but haven't really been captivated, don't ask me why: Maybe it's because I'm attracted to a homogeneous, heavy, and thick wall. Perhaps it's the lightweight concrete floors (but maybe you can fix that somehow with your system too?).
Stefan: If I've understood correctly, the plaster should let through water vapor (which dense paints don't do) but not pure water (which pure lightweight concrete does).
I've called around a bit:
- Ytong says it's absolutely no problem, as long as you have a solid foundation, use the right plaster, and plaster according to the instructions (is anyone surprised by that answer?..).
- The claims adjuster at our insurance company had heard of the problem but since it was never an insurance case, he didn't know much more. He didn't seem to be able to relate it to different plaster systems, e.g., if you could encounter it with a KC thick plaster system such as Serporoc.
- Optiroc said that it can probably happen with lightweight concrete and naturally drifted into promoting their own Leca as a building material...
- Other masons consulted don't rule out the possibility; if you want a "safer" facade, brick is what's needed. For a couple hundred kronor more per sqm.
- The architect thinks I'm being a bit too nervous and fussy; of course the plaster will work.
- Personally, I don't think I've ever seen a thick plastered house with major damage, and I find it hard to imagine foam with acrylic paint and already have a brick wall from the early 60s that's eroding away at a rapid pace. I will probably continue on the outlined path according to Ytong's recommendations and decide to use the optimal surface in the future IF the plaster causes issues: Aluminum; weather-resistant, maintenance-free, and cheap! That it's ugly, I (and maybe the wife) will overlook the day I'm standing there with an exorbitantly expensive, peeling plaster!
I grew up in a Ytong house (built in 79/80) and there are absolutely no problems. The facade consists of mortar mixed with stone, basically a really thick and coarse mixture, covering the entire house like a blanket and then spray-painted white.
My father is a hyper-perfectionist and has built everything himself (or at least controlled everything that was done) and the foundation was so perfect that there isn't a single wedge in the entire house.
My experience (in more areas than just house building) is that if you do a perfect groundwork, you benefit from it multiple times all the way to the final result—which also becomes more durable.
I have never heard of anyone having the problems with lightweight concrete that you, Jena, describe.
My father is a hyper-perfectionist and has built everything himself (or at least controlled everything that was done) and the foundation was so perfect that there isn't a single wedge in the entire house.
My experience (in more areas than just house building) is that if you do a perfect groundwork, you benefit from it multiple times all the way to the final result—which also becomes more durable.
I have never heard of anyone having the problems with lightweight concrete that you, Jena, describe.
1)
Does anyone know if Optiroc's system, where you have a layer of mineral wool + reinforcement mesh + plaster, is practically better than plastering directly on a lightweight concrete façade? In theory, it should be an advantage that the rainwater is kept away from the wall a bit and cannot penetrate directly into the structure (cf. the air gap inside the outer wall panel on wooden houses). The mineral wool should also provide slightly better insulation (perhaps negligible).
2)
To deviate slightly from the topic: You discussed floor joists in ytong earlier. What do these approximately cost per m2? What is the advantage compared to wooden joists?
Does anyone know if Optiroc's system, where you have a layer of mineral wool + reinforcement mesh + plaster, is practically better than plastering directly on a lightweight concrete façade? In theory, it should be an advantage that the rainwater is kept away from the wall a bit and cannot penetrate directly into the structure (cf. the air gap inside the outer wall panel on wooden houses). The mineral wool should also provide slightly better insulation (perhaps negligible).
2)
To deviate slightly from the topic: You discussed floor joists in ytong earlier. What do these approximately cost per m2? What is the advantage compared to wooden joists?
Idalind: Thank you for those words. No, I haven't been able to find a single concrete example of the bricklayer's concerns either. However, there are several thin-plastered houses of different construction where the plaster has flaked off in large patches after a couple of years. At least one of these, I know, was plastered dangerously close to the frost season. Your father's plaster; is it a thick layer that is then painted? No mesh, then?
hasse_f; regarding lightweight concrete floors, you can go up to just under 6 meters in span, you avoid mice scampering in the floor and the sweetish smell throughout the house for a few weeks when a little rascal has taken its last breath there. Additional advantages are fast assembly, fire resistance, and (I imagine) better sound insulation, at least with a suspended ceiling below, but then we have the mice again... Furthermore, I appreciate the feeling of a hard subfloor. The price is probably the biggest disadvantage; I think you have to account for about 800 kr/sqm.
hasse_f; regarding lightweight concrete floors, you can go up to just under 6 meters in span, you avoid mice scampering in the floor and the sweetish smell throughout the house for a few weeks when a little rascal has taken its last breath there. Additional advantages are fast assembly, fire resistance, and (I imagine) better sound insulation, at least with a suspended ceiling below, but then we have the mice again... Furthermore, I appreciate the feeling of a hard subfloor. The price is probably the biggest disadvantage; I think you have to account for about 800 kr/sqm.
hasse_f: Regarding your first question, I've been thinking about it a bit, especially considering that you can get a significantly better U-value.
However, I've skipped the idea because I feel it defeats the whole concept of a simple, homogeneous wall.
It becomes much more sensitive with mineral wool behind the plaster, the windows are relatively further in (I appreciate deep window niches), and fastenings of all kinds become more complicated and vulnerable if you have to go through a thick layer of mineral wool before reaching a solid wall. Then there's also my phobia of all our little friends who appreciate spaces with soft cozy materials where they can build a nest...
I'd rather go for thicker aerated concrete, and after all, it doesn't seem like the plaster should be a problem.
However, we will use the mineral wool variant on the old house, which has a 32 cm (!) thick, uninsulated brick wall, so maybe I can come back in a few years with a comparison.
However, I've skipped the idea because I feel it defeats the whole concept of a simple, homogeneous wall.
It becomes much more sensitive with mineral wool behind the plaster, the windows are relatively further in (I appreciate deep window niches), and fastenings of all kinds become more complicated and vulnerable if you have to go through a thick layer of mineral wool before reaching a solid wall. Then there's also my phobia of all our little friends who appreciate spaces with soft cozy materials where they can build a nest...
I'd rather go for thicker aerated concrete, and after all, it doesn't seem like the plaster should be a problem.
However, we will use the mineral wool variant on the old house, which has a 32 cm (!) thick, uninsulated brick wall, so maybe I can come back in a few years with a comparison.
Jena: Regarding "my childhood home," the outer walls there consist of 7 cm Ytong + 16 cm cell plastic + 7 cm Ytong. The Ytong blocks are 60 cm wide. U-value 0.24.
The plaster consists of a mixture made of yellow clay mixed with cement (about 30%), fine sand, and 16mm crushed stone. This was left in the cement mixer for ages and then the mixture was "thrown" onto the wall. It required a perfect mix and considerable skill to get it right, according to my father.
Then the whole thing was spray-painted white.
There is also "plaster with stone" (coarse plaster) with stones up to 8 mm. This was used when we sprayed an industrial building (also in Ytong) of about 800 square meters. This only took 2 days. You can do a house in one day.
The plaster consists of a mixture made of yellow clay mixed with cement (about 30%), fine sand, and 16mm crushed stone. This was left in the cement mixer for ages and then the mixture was "thrown" onto the wall. It required a perfect mix and considerable skill to get it right, according to my father.
Then the whole thing was spray-painted white.
There is also "plaster with stone" (coarse plaster) with stones up to 8 mm. This was used when we sprayed an industrial building (also in Ytong) of about 800 square meters. This only took 2 days. You can do a house in one day.