ᐅ Solid Wall House: Which Type of Block? Poroton, Liapor / Expanded Clay, Ytong?

Good evening,

EveundGerd schrieb:
I vaguely remember that it’s best to stick to one type of masonry rather than using different kinds.

You remember correctly.

Mixed masonry should be avoided if you want to prevent cracks and thermal bridges. The building materials differ in their specific properties as well as in their shrinkage and creep behavior. This results in stress on the plaster base, and due to differing thermal conductivity values, condensation can form on the interior walls.

Best regards, Bauexperte

The building expert was faster. 

We were advised against the above-mentioned combination.

We are now building with Ytong. The walls are either load-bearing and correspondingly thick or 17.5cm (7 inches). Only two walls were built with 11.5cm (4.5 inches) thickness (shower room/laundry room and office/bedroom on the upper floor). Now that the interior plaster is applied, there is hardly any echo. The drywall on the ceiling of the upper floor is still missing and will be installed only after the screed is laid and dried.

Therefore, we do not expect major issues with sound insulation.

maximax schrieb:

I have had difficult experiences with Poroton blocks concerning sound insulation and thermal bridges. If you simply screw a window or door frame into Poroton or aerated concrete, the frame itself may be insulated, but this creates a significant thermal bridge around it, which can lead to mold risks. With calcium silicate bricks, although there is more heat loss at specific weak points in the insulation due to their higher thermal conductivity, the wall generally does not cool down locally, so mold is less likely. Typically, window frames are integrated with the external thermal insulation composite system (ETICS) with overlaps. This doesn’t mean you can’t get good results with Poroton or Ytong; it just requires special attention to these details.

I would be interested to know if Poroton and aerated concrete are really as problematic as described here?

Bauexperte schrieb:
Different thermal conductivity values can cause condensation on the interior walls.

You’ll have to explain that to me. It’s clear that different mechanical behavior can cause cracks. However, I suspect that mechanical stresses can also develop within a single building material (for example, due to uneven loads, varying relative humidity, or differing average temperatures in the exterior walls).

But if I build an interior wall of calcium silicate blocks onto an exterior wall made of aerated concrete, where would the condensation come from? The interior surface of the exterior wall is roughly 1°C (2°F) cooler than the indoor air. The calcium silicate wall is about as warm as the indoor air (assuming there are no thermal bridges at the floor slabs), and thanks to its good thermal conductivity, the interface between the interior and exterior walls is also close to room temperature. So there is only about a 1°C (2°F) temperature difference and, accordingly, no condensation. It would be a different case if I built an interior aerated concrete wall in front of a calcium silicate exterior wall.

Hello,

first of all – the language used on the internet is informal (“you”).

maximax schrieb:

You have to explain that to me ... But if I build an inner wall of sand-lime brick onto an outer wall of aerated concrete, where would the condensation come from?

I purposely wrote “can,” because, on the one hand, I think a complete answer includes that possibility. On the other hand, there are different types of aerated concrete, porous clay blocks, and sand-lime bricks with varying thermal conductivities (depending on bulk density). If you want more detailed explanations, you’ll find plenty of information online; for example, on Chemie.de, the Fraunhofer Institute, or Ruhr University Bochum. I’m not a natural scientist myself and don’t really connect with that rather complex language; “legalese” is a breeze for me by comparison.

From our practical experience, I can assure you that we always try to avoid mixed masonry; the main goal is to prevent cracking. If someone insists on using sand-lime brick, in my opinion, they should fully commit to that choice and accept an insulated outer wall. On the other hand, if you prefer a monolithic wall structure and are sensitive to sound transmission, you can rely on proven lightweight construction in the attic, which also makes future remodeling easier. With a 36.5cm (14.4 inches) thick outer wall—whether aerated concrete, porous clay, pumice, or expanded clay—hopefully, sound insulation is no longer an issue.

To be honest, I don’t really understand this whole discussion about mixing materials.

Best regards, Bauexperte

Bauexperte schrieb:
If you want more detailed explanations on this, you can find plenty of information online; for example on Chemie.de, the Fraunhofer Institute, or the University of Bochum. I am not a natural scientist at the moment,...

And I am a natural scientist and sometimes wonder about how unnecessarily complicated some technical applications are formulated.

On the other hand, since there are aerated concrete, Poroton, and sand-lime bricks with different thermal conductivity (depending on bulk density)

You will almost always have higher thermal conductivity for interior walls than for exterior walls, and the (insulated) exterior wall will almost always have an indoor surface temperature close to room temperature. Therefore, I cannot see how condensation would form there. In addition, Poroton usually uses a denser clay brick on the interior side, which has better thermal conductivity. The only construction where condensation could deliberately be caused by an interior wall in direct contact (a butt joint, as we are talking about, I thought) would be if a thick aerated concrete or Poroton wall were abutted against a thin, uninsulated sand-lime brick or clay brick exterior wall. This could at best happen if someone installs aerated concrete inside a bathroom during a renovation of an old building.

I can assure you, regarding our work, that we always try to avoid mixed masonry; with the main focus on preventing cracking.

But a silly question: What about non-load-bearing interior walls? Those can be decoupled, right? And theoretically, lightweight partition walls are also a form of mixed masonry.

If someone insists on using sand-lime brick, in my opinion they should fully commit to it and accept an insulated exterior wall.

Which, in my amateur opinion, is the most consistent building method anyway (ideally combined with a ventilated curtain facade, of course a bit more expensive), because then you can best avoid thermal bridges.

On the other hand, if someone prefers a monolithic wall design and is sensitive to noise, they can rely on proven lightweight construction in the attic, which also makes future remodeling easier.

Or at least when using Poroton inside, walls should be built with plan bricks with a thermal conductivity coefficient (RDK) of 1.4 or better yet acoustic protection bricks with RDK 2, and not skimp on load-bearing walls either—unless you want to share acoustically everything from music, sneezing, coughing, and toilet use to intimacy with all the other occupants.

With a 36.5 cm (14.4 inches) exterior wall—whether aerated concrete, Poroton, pumice, or lightweight expanded clay aggregate—hopefully nobody still questions the sound insulation.

At least not for the exterior walls in a quiet residential area.

A silly question I don’t quite understand: Why do people always talk only about mass when it comes to sound insulation? Ultimately, the damping effect of the material and the overall build-up also matter. Regarding the latter: If I have a load-bearing ceiling across the entire width of the house, structure-borne sound spreads much better than if there is a load-bearing interior wall. And a very stiff wall transmits sound better than a more damped material; a decoupled double-leaf wall transmits much less (can’t this at least be done in lightweight constructions, with separate stud frameworks on both sides?).