Hello, we have built a prefabricated basement and I plan to start the plastering work eventually. I have a question about the internal and external corners:
How would you plaster the internal corners (the typical room corners)? Currently, they are filled with foam. Would you embed a corner bead here or just seal it with acrylic?
We also have an external corner. The concrete wall is chamfered here. Are there corner beads designed for embedding in this case?
Thanks in advance for your answers.
How would you plaster the internal corners (the typical room corners)? Currently, they are filled with foam. Would you embed a corner bead here or just seal it with acrylic?
We also have an external corner. The concrete wall is chamfered here. Are there corner beads designed for embedding in this case?
Thanks in advance for your answers.
It is a basement made of precast elements. These are filled with concrete from the inside after being positioned. The joints obviously need to be sealed to prevent the concrete from leaking out.
As far as I know, there are different systems for this.
I’m not an expert, though. The foam does not go from the outside to the inside, of course. Also, I don’t think it is standard PU foam.
In our precast basement, the corners were also foamed with something.
Inside, in the utility rooms, we didn’t do anything at all—just painted the walls white. So far, no foam has pushed out there.
In the two “living-use rooms,” the plasterer applied it. I just quickly checked but couldn’t find any photos from the plastering work in those rooms.
However, I strongly assume that corner profiles were integrated there.
As far as I know, there are different systems for this.
I’m not an expert, though. The foam does not go from the outside to the inside, of course. Also, I don’t think it is standard PU foam.
In our precast basement, the corners were also foamed with something.
Inside, in the utility rooms, we didn’t do anything at all—just painted the walls white. So far, no foam has pushed out there.
In the two “living-use rooms,” the plasterer applied it. I just quickly checked but couldn’t find any photos from the plastering work in those rooms.
However, I strongly assume that corner profiles were integrated there.
Hello,
I will answer the question anyway:
It is not possible to say whether it is a problem or not (that is the issue with foam). Of course, the joints need to be sealed to prevent concrete from leaking out, but this must be done using formwork that is flush with the surface to ensure the concrete cross-section meets the minimum required thickness everywhere. The problem with foam (regardless of the type) is that you cannot control how far it penetrates into the interior of the component. This unintentionally reduces the thickness of a waterproof concrete component at its most critical point—the joint.
From what it looks like here, the foaming was done fairly properly, so one can initially assume that nothing will happen.
However, there is a reason why the waterproof concrete guidelines (WU guidelines), especially concerning waterproof construction with precast wall elements, have been tightened significantly and are still a matter of ongoing discussion.
In my opinion, this is simply not proper professional practice, which is why I am pointing it out. The answer that it is often done this way does not change that.
To respond directly to your question:
1. The foam must be removed.
2. At internal corners, I would avoid installing profiles if possible and instead use sealants, as we expect annual movement that can cause cracking. With sealants, it is easier to repair and refresh the area.
3. For the internal external corner, I would like to see how the elements meet there to assess where the crack is most likely to occur.
Good luck with your project!
I will answer the question anyway:
It is not possible to say whether it is a problem or not (that is the issue with foam). Of course, the joints need to be sealed to prevent concrete from leaking out, but this must be done using formwork that is flush with the surface to ensure the concrete cross-section meets the minimum required thickness everywhere. The problem with foam (regardless of the type) is that you cannot control how far it penetrates into the interior of the component. This unintentionally reduces the thickness of a waterproof concrete component at its most critical point—the joint.
From what it looks like here, the foaming was done fairly properly, so one can initially assume that nothing will happen.
However, there is a reason why the waterproof concrete guidelines (WU guidelines), especially concerning waterproof construction with precast wall elements, have been tightened significantly and are still a matter of ongoing discussion.
In my opinion, this is simply not proper professional practice, which is why I am pointing it out. The answer that it is often done this way does not change that.
To respond directly to your question:
1. The foam must be removed.
2. At internal corners, I would avoid installing profiles if possible and instead use sealants, as we expect annual movement that can cause cracking. With sealants, it is easier to repair and refresh the area.
3. For the internal external corner, I would like to see how the elements meet there to assess where the crack is most likely to occur.
Good luck with your project!
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