ᐅ Exterior walls made of aerated concrete, interior walls of calcium silicate bricks – yes or no?

Hi,

There are many different opinions online, but I wanted to ask specifically here. Our house is planned to be built with 42cm (17 inches) aerated concrete blocks (lambda 0.08). Since I like to listen to music loudly and we also have two children, the idea came up to use calcium silicate blocks for the interior walls. The building company would include the calcium silicate blocks in the offer at the same price and said that cracking is not to be expected.

What is your opinion on this? In principle, aerated concrete and calcium silicate are compatible because of their similar shrinkage behavior. But there is still a residual risk, right? Nevertheless, large companies often use this combination as standard (e.g., Arge Haus).

What do you think?

(No, we will not be using soundproof interior doors).

Interior walls made of sand-lime bricks are, to my knowledge, the only type of masonry (regardless of whether the exterior wall is made of the same or a different material) exempt from the usual requirement to be tied into the exterior walls. Therefore, sand-lime bricks as a material for interior walls effectively allow the exterior and interior walls to be built as completely separate processes, which is extremely valuable, especially since large-format blocks are commonly used for exterior walls. As a result, sand-lime brick is a very popular and widely used material for interior walls.

I assume that it is quite common to find interior walls traditionally built with mortar beds, even when the exterior walls consist of thin-bed adhesive "glued" planer blocks. Given the widespread use, any related problems would likely be well known. I would even expect that specific products have been developed for this situation, for example, special adhesive layers for wallpaper at transition corners where interior walls meet exterior walls. However, I have never heard of such products.

It is also not uncommon to see a switch from aerated concrete blocks to sand-lime bricks in reveal areas of porous brick walls, and I am not aware of any related issues such as plaster cracks. Therefore, I assume that this combination of materials does not cause any particular problems.

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We also use aerated concrete on the exterior and calcium silicate bricks on the interior, and have had several general contractors offer this combination directly. I see no concerns with this.

We are building exactly like this: 42.5 cm (17 inches) aerated concrete on the outside and 24–11.5 cm (9.5–4.5 inches) calcium silicate brick on the inside.
However, we also have wall ties between the calcium silicate brick and the exterior wall.

So far, no structural issues—except for chasing and milling slots in the calcium silicate brick.

Sound is noticeably absorbed during the shell construction phase. So far, I can recommend it.

@truce what do you use 24cm (9.5 inches) sand-lime bricks for indoors? Is it by special request? A 24cm (9.5 inches) sand-lime brick wall is typically used for exterior basement walls.

As a load-bearing wall, we have the 24cm (9.5 inches) calcium silicate brick wall in the middle of the house. Otherwise, inside there are only 11.5cm (4.5 inches) partition walls, and one 17.5cm (7 inches) wall between the utility room and the hallway.

As a layperson, I assumed this was correct.