42.5 cm aerated concrete and 400 cm wide windows and venetian blinds

Hello everyone,

we hopefully want to start our single-family house construction project this year. We are building single-story and I would like to build monolithically with 42.5cm aerated concrete, meaning without additional thermal insulation.

My father is very involved and, as an old "construction phase" person, is very skeptical because for him only 36.5cm perforated bricks + ETICS is acceptable and he sees many problems with the roller shutter / venetian blind boxes in connection with thermal bridges and plaster cracks.

I would like to understand the topic better and have therefore informed myself with the following result:

42.5cm thick wall, into which two fixed-glass windows of 400cm x 250cm will be installed.
Directly above the window, for example, finished insulated venetian blind boxes can be installed. These are (if I understand correctly) exactly 42.5cm deep and insulated. The maximum width up to 5000mm seems to fit – does anyone know if these really are delivered custom-made in 400cm length, or if we are talking about 2x 200cm here?



A = 42.5cm
B = 29.0cm

It seems there are no ready-made, load-bearing aerated concrete lintels over a 4m span.
Since we only want to build single-story and only the wooden flat roof rests on the wall at the end, could we then directly use aerated concrete U-blocks (42.5cm deep, 49.9cm wide) to create a ring beam, which in the case of the window openings also serves as a lintel?

Then in the end you would achieve that there are no material changes – except in the area of the venetian blind boxes.

But one would nevertheless incorporate reinforcing mesh at these transitions anyway to counteract plaster cracks caused by different expansion of materials, correct?

Thanks for a few explanations – I just want to understand the whole topic.

But one would work in these changing reinforcement fabrics anyway to counteract plaster cracks caused by different expansion of the materials, correct?

You want to do it yourself?

I just want to understand the whole topic.

Or do you have a BU - doesn't it explain it to you?

I am always very skeptical when building owners know exactly what is good without knowing whether it is even the material used by companies in the region.

Hey,

no, I don’t want to do anything myself regarding the shell construction. What I want after some research is to build monolithically with aerated concrete. My builder (the one who constructs the shell) is fine with that, has built a lot with it (and with everything else) in the past, and supports the decision.

I didn’t say that I know exactly what is best. I said that I get different information from various sources. Therefore, I want to form a comprehensive picture to understand things and possibly question them. I hope this is the right place for that.

And regarding material used in the region – we are building around Leipzig. In the immediate neighborhood as well as in the future building area, you see everything, really everything. There is no specific material that everyone uses. Sand-lime brick, precast concrete parts, clay bricks, aerated concrete, ETICS of all kinds.

Edit: I have already experienced in this forum that concrete questions about execution, materials, practices, etc., are often dismissed with “Don’t you have a builder?” or “You don’t want to do that yourself!?” or “There is such and such a person who has to take care of that..!” The reality unfortunately is that you repeatedly see construction defects or homeowners curse wrong decisions, even when “professionals” were on the job. Therefore, it must be valid for a prospective homeowner to inform themselves about “house building” as best as possible in a “house building forum,” right? If I ask something about car repair in Motor-Talk, no one says “Go to a garage!” - a bit strange..

I understand your father, who would prefer the tried and tested, just as much as I understand you, who want to go different ways. However, the question for me is why you chose exactly this brick and what advantage it brings you. Not far from you, it was like this with us: I would have liked to build with Liapor (I had already used bricks once and it was simply a matter of feeling). The general contractor then told me a few days before the start that we would build with Poroton after all, because he had to change the structural shell company (in our case the permanent excuse was Corona) and they only build with Poroton. We didn’t want further delays, so we agreed and the house was built. Now, after living here for 3 years, I claim that I wouldn’t notice any difference with another wall construction. In your place, I would be more interested in the quality of the insulation overall, because that actually has an impact on your living quality. We also have blinds and I know that the installation was not carried out optimally and we had to significantly improve the insulation in that area. But I think both options would be possible here, otherwise they wouldn’t be offered, so for me it would be rather insignificant which brick we choose, and I would rather question concretely the things that determine my later well-being in the house. We chose a wooden facade out of necessity because the plasterer was sick for the umpteenth time, unreachable or something else, just like with many other trades; at some point we simply wanted to get through it and at the same time we had a reliable carpenter on hand. For this facade, we have the suboptimal brick or wall construction, but the house stands and WE feel very comfortable in it TODAY. My questions in your place would be rather: maximum insulation of the house, controlled residential ventilation, climate, shading, room feeling; the brick doesn’t really matter and will have zero impact on your living experience.

Thank you for your answer!

I personally prefer the monolithic construction method based on my own research due to the simplicity and speed of construction. Simple is better for me than a combination of stone xyz + additional material and work steps for a second shell. More "mess" can happen there, the manufacturing is more complex, and in the end, you combine different materials again to achieve various effects. The thermal insulation is relatively minor anyway – we have very many, very large windows. In the living room alone, there are four windows measuring 400cm x 250cm each – so it really doesn’t matter what kind of thermal insulation those few walls in between have; respectively, the thermal insulation of the 42.5cm aerated concrete blocks is completely sufficient and the difference to a double-shell wall structure is negligible. In addition, I am an allergy sufferer and have only heard positive things regarding aerated concrete.

Regarding soundproofing, we have no special requirements – the plot is in a residential area in a forest location.

I have lived in two hollow brick houses and hated the noise sensitivity in the house – if someone plugs something into the socket, I heard it next door – "you can hear the walls." Also, there were sometimes drafts from the sockets (yes, maybe work was not done correctly and cleanly here, etc.) – what is often done here? Use insulation again, special boxes, spray construction foam everywhere – I don’t think any of that is okay.

In processing, my shell builder also finds them poor because you cannot cut them as precisely as aerated concrete and the bricks are not exactly 1:1 in size. In the end, you smear everything with mortar and adhesive again and often need the ETICS just to prevent plaster cracks. Of course, there are also perlite-filled bricks that could also be used for monolithic construction.

That means I am clear about the material properties and everything fits. Now it is about what to pay attention to during construction – even as a builder, it doesn’t hurt to know what is important and not always rely solely on others.

we have a house made of filled expanded clay bricks, local, 42.5cm. Have you heard of the Oktameter in solid houses, little sawing, no botched pockets, almost no plaster cracks. Do you really want to live in a greenhouse? Think about the windows, 4m windows are already very heavy to open