ᐅ Which masonry is best? Aerated concrete blocks or calcium silicate blocks?

Hello everyone,

We are planning to have a semi-detached house built.
The builder said, "We only build solid constructions. Both exterior and interior walls are completely made of Ytong."

Ytong certainly has its advantages for exterior walls in quiet new residential areas. However, for interior walls in terms of sound insulation—especially if you have children—it probably doesn’t perform as well. Or is the sound insulation of Ytong interior walls better than that of exterior walls?

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

I am now wondering if applying brick slips to a Ytong exterior wall would improve sound insulation? Currently, we want brick slips because there is no roof overhang, and we want the facade to remain visually appealing for as long as possible.

If brick slips on Ytong do not improve sound insulation, the next question is: How thick does the mineral wool insulation (no polystyrene or similar!) need to be on an exterior sand-lime brick wall to meet the current KfW standards?

Thank you!

Best regards

Allow me, before answering your question in a simple way, to draw your attention to a potential issue:

MustermannNRW schrieb:

We intend to have a semi-detached house built.

I marked the mistake in your quote by underlining it, and I recommend that, besides reading my post "A semi-detached house has TWO halves," you also check out the Goalkeeper thread https://www.hausbau-forum.de/threads/reihenendhaus-mit-gue-in-eigenregie-bauen.31198/ and search the forum for the keywords basemented/non-basemented, underpinning, and house profile.

MustermannNRW schrieb:

The builder said: "We only build solid walls. Exterior and interior walls entirely from Ytong."

And here comes my keyword "11ant stone mantra." Your builder presumably wants to build not with external insulation composite systems (EICS / EIFS) but monolithically – this is no longer permitted with calcium silicate blocks (sand-lime brick) or would require extremely thick walls like castle walls.

MustermannNRW schrieb:

Since the area is not particularly noisy, I could probably live with Ytong exterior walls if the windows are suitable. However, I would clearly prefer calcium silicate blocks for the interior walls.

You can definitely do that, and I suspect your builder won’t object much. The market-leading suppliers of aerated concrete (autoclaved aerated concrete) and calcium silicate blocks belong to the same holding company and even market their products "jointly." However, I have two points to consider: first, it will not bring you much benefit—I have explained several times here why the naive “heavy doorframe stone” thinking is misguided. Second, it will involve additional structural engineering effort, which can get quite expensive, especially if the possibilities to coordinate or interconnect the walls are limited. There are more clever alternatives, including the use of drywall partitions clad with materials like "Silentboard" (TM) for sound insulation.

MustermannNRW schrieb:

I now wonder whether brick slips on a Ytong exterior wall improve sound insulation? Currently, we would like brick slips because there is no roof overhang, and we want the facade to remain attractive for as long as possible.
If brick slips on Ytong do not provide better sound insulation, the next question is: how thick does the mineral wool (not polystyrene or something like that!) need to be on an exterior wall made of calcium silicate blocks to meet the current KfW standards?

Here I have to somewhat disappoint you again: the housewife’s dream from plaster advertising about a permanently neat brick cladding is noticeably less radiant in reality. In terms of sound insulation, a brick slip cladding is neutral. However, as brick slips, you won’t be able to apply them directly to mineral wool insulation; instead, you would have to build a complete ventilated cavity wall (full brick veneer).

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

Why shouldn’t you apply facing bricks to stone wool insulation? As far as I know, that’s not unusual. Of course, you should plaster over the insulation with a reinforcing mesh before installing the facing bricks.

Let me ask differently: Which walls/facade would you have chosen?

MustermannNRW schrieb:

We plan to build a semi-detached house.
The builder said: "We only build with solid construction. Exterior and interior walls entirely made of Ytong"

If you want to build with Ytong, go ahead.
If you prefer a different masonry, find a general contractor (GC) who specializes in that, but don’t force any GC to deviate from their standard practice.

MustermannNRW schrieb:

Just to provide some context, the neighboring house on the left has been there for years. We are now building an extension onto it. So, we don’t need to coordinate with the neighbor about whether he or we want a basement, or who does what, when, and how. We are building without a basement.

Then the recommendation stands: pay attention to the house profile at the “joint side.”

MustermannNRW schrieb:

Why shouldn’t there be brick slips on mineral wool insulation? To my knowledge, that’s not unusual. Of course, first apply a reinforcing mesh and render before fixing the brick slips.

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

MustermannNRW schrieb:

Let me ask differently: Which walls/facade would you have chosen?

Clearly aerated concrete here, see the “stone mantra.” Is your question directed at me as a building consultant or just my personal preference? For me, plain render is sufficient. I might use brick slips only for accents. And for completeness: I answer the material question individually for each interior wall.

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Just a simple question: where can I find the stone manual? The search function only shows posts where it is mentioned, but there are no links to it...