The optimal masonry? Ytong or sand-lime brick?

Hello everyone.

We intend to have a semi-detached house built.
The builder said: "We only build solid. Exterior and interior walls completely made of Ytong."

So Ytong certainly has its justification for exterior walls in quiet new residential areas. For interior walls regarding sound insulation, especially when you have children, certainly not. Or is the sound insulation of Ytong interior walls better than that of exterior walls?

Since the area is not particularly noisy, I could possibly live with Ytong exterior walls if the windows are suitable. However, I would clearly like the interior walls to be made of sand-lime brick.

I am now wondering whether klinker slips on a Ytong exterior wall improve sound insulation? Currently, we would like klinker slips because there is no roof overhang, so the facade remains visually appealing for as long as possible.

If klinker slips on Ytong do not bring better sound insulation, the next question is: How thick does the mineral wool (no polystyrene or such!) have to be in an exterior wall made of sand-lime brick to meet the current KfW standards?

Thanks!

Regards

Allow me, before I simply answer your question, to draw your attention to a danger:

We intend to have a semi-detached house built.

I have marked the error in the quote with an underline, and I recommend that besides my post "A semi-detached house has TWO halves," you also familiarize yourself here with the Goalkeeper thread and the forum search keywords Mitkellerer / Ohnekellerer, Unterfangung and Hausprofil.

The builder said: "We only build solid. Exterior and interior walls completely made of Ytong"

And here is also my keyword "11ant Steinemantra." Your builder probably does not want to use ETICS but to build monolithically - this is no longer allowed with sand-lime brick (or would require extremely massive fortress-like walls).

Since the area is not particularly noisy, I might be able to live with Ytong exterior walls if the windows fit. However, I would clearly prefer the interior walls to be made of sand-lime brick.

You can certainly do that, and I suspect your builder will have little objection, as the market-leading suppliers of aerated concrete and sand-lime brick even belong to the same holding and market their products "jointly." However, I offer two points to consider: first, it will bring you little — I have explained here several times why the simplistic thinking about the heavy "door guardian stone" is naive. And second, it entails additional structural engineering effort, which can be quite costly, especially if the possibilities to coordinate the walls among each other are limited. There are more clever options, including the cladding of lightweight walls with "Silentboard" (TM).

I now wonder whether clinker slips on a Ytong exterior wall improve sound insulation? Currently, we would like clinker slips because there is no roof overhang, so that the facade stays looking good for as long as possible.
If clinker slips on Ytong do not provide better sound insulation, the next question is: How thick must the rock wool (no polystyrene or such!) be on an exterior wall made of sand-lime brick to meet current KfW standards?

I have to disappoint you again a bit here: the dream from plaster advertising about the always neat clinker facing is much less radiant in reality. Acoustically, a clinker facing is neutral. However, as slips, you will not be able to install them on rock wool but would have to build a full facing shell.

Just for background, the left neighboring house has been standing for years. We are now building onto it. So we do not need to coordinate with the neighbor about whether he/we want to build with/without a basement or who/how/when will do what. We are building without a basement.

Why shouldn't clinker bricks be applied on stone wool? To my knowledge, that's not unusual. Of course, the surface should be plastered with mesh before the clinker bricks are applied.

Then asked differently: Which walls/facade would you have chosen?

We intend to have a semi-detached house built. The builder said: "We only build solid. Exterior and interior walls completely made of Ytong"

If you want to build with Ytong, go ahead. If you want a different masonry, find a general contractor who only does that, but don't force any general contractor to deviate from their standard.

Just for background, the left neighboring house has been standing for years. We are now building onto this one. So we don’t have to coordinate with the neighbor about whether he/we want to build with/without a basement and who/how/when does what. We are building without a basement.

Then the advice remains: pay attention to the house profile at the "seam side".

Why shouldn’t you put facing bricks on stone wool? To my knowledge, that is nothing unusual. Of course, first plaster with mesh before applying the facing bricks.

I can’t really imagine that. I would keep my distance from that.

Then asked differently: which walls/facade would you have chosen?

Here clearly aerated concrete, see stone mantra. Does your question apply to me as a construction advisor or my personal taste? - plaster is sufficient for me, I might take facing bricks for accents. And for the sake of completeness: I answer the material question individually for each interior wall.

Just to ask bluntly, where can I find the Steinemantra? The search function only shows posts where it is mentioned, but not linked...