ᐅ Exterior walls made of 15 cm calcium silicate bricks (also known as sand-lime bricks)

Hello building experts,

We are planning to purchase a semi-detached house with three floors and no basement. The exterior walls will be constructed with calcium silicate blocks, wall thickness 15 cm (6 inches), compressive strength class 2.0. I looked it up online and found the following: "A thickness of 17.5 cm (7 inches) is the minimum wall thickness allowed for load-bearing walls."

My question is: Is this something I should be concerned about, for example regarding the structural strength of the house or the possibility of cracks developing in the future? I know that in Germany everything is regulated and no building permit / planning permission is granted if the necessary building codes are not followed. However, I would also like to get an expert opinion from here.
Thank you.

It is probably very unusual. Exterior walls with 15cm (6 inches) thickness do not exist. Regardless of the building material, it should be 36cm (14 inches), or possibly 24cm (9.5 inches) with insulation. The energy efficiency regulations specify the required insulation value here. Additionally, I consider a 15cm (6 inches) exterior wall to be structurally questionable, but I am not a structural engineer.

I only know sand-lime brick as a 17.5cm (7 inch) exterior wall (which is standard, with external thermal insulation composite systems (ETICS) or brick veneer plus insulation applied) and 11.5cm (4.5 inch) for non-load-bearing interior walls.
Most likely the "7" is simply missing and it is a typo.
To my knowledge, 15cm (6 inch) bricks do not actually exist. Other sizes would be 24cm (9.5 inch) or 30cm (12 inch) bricks.

@ Vicky Pedia: A minimum thickness of 36cm (14 inch) regardless of the building material is complete nonsense. For sand-lime brick, you typically use 17.5cm (7 inch) and then, for example, from 18cm (7 inch) upwards, ETICS.

Large-format calcium silicate blocks from Bonava, formerly NCC, have an exterior wall thickness of 15cm (6 inches). They are also installed widely in Germany, almost like on an assembly line.

Mycraft schrieb:

Large-format calcium silicate blocks from Bonava, formerly NCC, have a thickness of 15cm (6 inches) as external walls. They are also installed in Germany on a large scale.

That's correct, I just looked into it. However, they are then used as party walls (double-layer). So, they could still be suitable for the semi-detached house.

Vicky Pedia schrieb:

Also, I consider 15cm (6 inches) as an exterior wall to be structurally questionable, but I’m not a structural engineer.

Neither am I, and personally, I would never even consider using a load-bearing interior wall as an exterior wall. However, others have been doing this tens of thousands of times in recent years – and if 17.5cm (7 inches) of the aerated concrete blocks, which are often dismissed here as crumbly, suffice structurally, then 15cm (6 inches) of the limestone sandbrick, which is mostly praised here as a miracle material, should be at least equivalent.

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