Exterior wall brick + interior walls lime sandstone

Hello,

our single-family house is being built monolithically with exterior walls made of brick. It was originally agreed that the interior walls should also be made of brick, as certain disadvantages apparently can occur with the "red-white" combination. However, the interior walls have now been built with calcium silicate blocks. I am now wondering whether this supposed rule that you should combine either "red-red" (brick-brick) or "white-white" (aerated concrete-calcium silicate), but not mix "red-white," is just a common misconception, or whether there are indeed real disadvantages and medium- to long-term problems (cracks???) to be feared. We are still in the shell construction phase; in principle, with considerable effort, many things can still be changed. However, the ceilings have already been concreted. Therefore, the effort to replace the interior walls would not be so simple.

Thank you very much for your assessments

Augustus

Hello Augustus,

"Agreed" is quite nice, but what does the contract say? There must be something like a construction description that says more than just "1 piece house," right?

KS is not devil's stuff, but it has different properties than bricks (I assume Poroton). If the interior walls are decoupled (slip joint) and not interlocked with the exterior walls, different expansion has no negative consequences. That is a matter of construction. KS generally - without knowing the specific stones - has better sound insulation due to the greater mass, but worse thermal insulation. However, what was contractually agreed is decisive.

If there were already such "misunderstandings" there, what about the masonry technique? Was it dipped or laid in thin bed mortar? What does the stone manufacturer specify? Basically, the construction company is obliged to comply with the "basic rules of technology," which also includes proper processing. Do you have an expert on site?

Regards Allrounder

Hello Allrounder,
thank you very much for the answer; I just realized I had formulated it incorrectly.
It is stated in the contract that the load-bearing interior walls are made of brick, and the non-load-bearing ones are executed as gypsum board walls.
Yes, the exterior walls are made of Poroton. Interior walls and exterior walls are not interlocked, only these metal strips (I don’t know what they are called) are installed, which are supposed to hold the two walls together.
What do you mean by sliding joint?
We had considered an expert.
However, after having "some collisions," to put it mildly, with one we engaged for a recently constructed project, we refrained from doing so for this project. The additional input the expert was able to provide was quite limited. When I then received the offer for the requested supervision of the current project, the decision was made quickly.

So far so good, the problem now is that the ceilings are already resting on the load-bearing walls ...
I will hardly have the walls torn out anymore, especially since structurally it would never be the same again as when the ceiling is cast on the wall (you can never achieve the vertical compression prestressing in the load-bearing wall anymore).
I am currently trying to get an idea and make an assessment of how hard I should "lay it on thick."
On the one hand, I do want to set an example that at least from now on all contractual agreements are adhered to.

Regards,
Augustus

morning Augustus, only these metal strips (don’t know what they are called) are installed: that will be exactly the sliding joints!

I don’t understand the part about the ceiling resting on something: it should actually only be non-load-bearing interior walls involved here, meaning that nothing should rest on them. Because gypsum boards as load-bearing walls would be questionable. For the load-bearing walls made of KS instead of Poroton, no changes should be possible anymore.

Compared to KS, gypsum has better moisture storage/regulation capacity. Either you have the non-load-bearing walls knocked out again or make some kind of deal, e.g. thicker interior plaster as compensation for the above-mentioned worse properties of KS + compensation payment. That is up to your negotiating skills. After all, the company did not comply with the contract.

Regards Allrounder

Hello all-rounder,

so, contractually fixed is:
load-bearing interior walls made of brick (these are already standing, but are now constructed of sand-lime bricks)
non-load-bearing interior walls as gypsum board walls (these are still to be installed).
of course, the load-bearing interior walls (real: sand-lime brick) were built, the ceiling was laid on them and concrete was poured, since the ceiling rests load-bearing there.

Regarding the wall connection:
about 15 mm wide metal strips were laid into the joints of the exterior brick wall, which then engage into the joints of the sand-lime brick wall. I guess the simple reason for this is to fix the interior wall against tipping over. (Although I actually believe that it won't go anywhere anyway, and if it wanted to, it wouldn't be stopped by these few strips)

What I took from your first answer, and which also makes immediate sense, is that the joint must be separated when plastering.
That could then happen as follows: The inside of the exterior wall is plastered, and ends in the first step at the interior wall.
In the next step, then (of course once the above-mentioned plaster is firm), the interior wall is plastered, but where the plaster of the interior wall meets the plaster of the exterior wall, a separating joint is laid. There is some material for this, of which I don’t have the term at hand right now, looks a bit like cork.

I think then nothing more should happen with cracks. Or are there even systems made of plaster rails etc?

Regards, Augustus

Hello Augustus,

There are about 15 mm wide metal strips laid into the joints of the brick outer wall, which then engage into the joints of the sand-lime brick wall.

As already mentioned, these are the sliding joints I referred to for decoupling the walls.

The plaster can be separated in different ways, either the profile protrudes slightly in plaster thickness so that plastering is done only up to that point, or an elastic joint is formed, or simply a scraping cut is made. Your bricklayers should know this better.

If you no longer want to do anything about the KS stones that violate the contract, you should at least supervise the installation of the gypsum boards. KS is not so optimal for the indoor climate in that case (see my previous answer comparing KS:Gypsum).

Regards Allrounder