ᐅ Aerated concrete on the outside and calcium silicate bricks on the inside?

We would like to have the exterior walls made with aerated concrete PPW2 0.35 (probably 36.5 or 42.5). For the interior walls, we could choose between PPW6 or calcium silicate blocks, and we tend to prefer calcium silicate blocks. The builder has already pointed out that there are some important details to consider when connecting the exterior walls to the interior walls, but that it is basically feasible. I have also often read that using aerated concrete on the outside and calcium silicate blocks on the inside is not a problem, and since the builder knows about the necessary considerations for the connections (unfortunately, I didn’t fully understand exactly what needs to be done on short notice), this should work out, right?

Compared to PPW6 interior walls, calcium silicate interior walls would offer higher thermal mass, meaning they can store cold in summer as well. They also provide better sound insulation. That’s why we prefer to use calcium silicate blocks for the interior walls. Additionally, it is easier to fix items to them.

Where is the question?

Mixing aerated concrete on the outside with calcium silicate bricks on the inside—if the company knows what they’re doing, not a problem? Or is it better to stick with PPW6 and stay within the system? What exactly is important when combining aerated concrete on the outside and calcium silicate bricks on the inside?

Hello,

I did it exactly like this in my house: 360mm (14 inch) aerated concrete exterior walls and 240mm (9.5 inch) sand-lime brick interior walls. Since I have my office in the house and soundproofing was important to me, all the interior walls are 240mm (9.5 inch). For structural reasons, 170mm (6.7 inch) or 110mm (4.3 inch) would have been sufficient.

You need to be careful with the connection between the walls. Normally, the walls are interlocked. However, with mixed masonry, the walls are butted flush so that the materials, which expand and contract differently, do not cause cracks. Also, because sand-lime bricks have a high thermal conductivity, the spots where they interlock with the exterior wall would affect the insulation and create thermal bridges.

Since interlocking contributes to structural stability, when butting flush, a connection has to be made instead. For this, wall ties are placed in the mortar joints. That’s basically all there is to it.

Interlocking with mortar is often not very effective anymore... however, a lot is mixed here – so aerated concrete on the outside and calcium silicate brick on the inside.

So, we have 40cm (16 inches) aerated concrete external walls, load-bearing walls made of 24cm (9.5 inches) sand-lime brick, and the remaining walls made of 11.5cm (4.5 inches) aerated concrete.