Planning single-family house - construction of exterior wall

Hello dear forum members,

we are currently planning our single-family house. We are in the preliminary planning stage and have already had the first conversations with an architect and potential builders. A single-family house with 2 residential units (granny flat), gable roof, 1.75 stories (knee wall at 185 cm), 2-layer wall construction in Kfw 40 standard will be built.

Our architect is nice and kind, but somehow I have a weird gut feeling... (Different topic).

An example of the outer wall construction. Our architect has planned a 525mm wall structure as follows:

- 11.5 cm outer shell (clinker brick)
- 10 cm core insulation (032)
- T9-30 cm Poroton
- Lime interior plaster
U-value: 0.149 (0.154 required for KFW)

Two builders have offered/suggested the following wall structure:
- 11.5 cm outer shell (clinker brick)
- 16 cm core insulation (032 or 035)
- T14-24 cm Poroton
- Lime interior plaster

-> U-value: 0.145 / 0.151
-> Better sound insulation

Same wall thickness. The material costs are 40% lower than the architect's proposal.

Here I became a bit suspicious. I have not won the lottery and as the builder I also have to watch the costs. Is there any flaw in this wall construction from my side or the builders'? The builder also advised me against filled bricks with perlite or mineral wool, as they are way too expensive, even if I could then save the core insulation between bricks and outer shell. By the way, the latter was also an alternative suggestion from the architect...

I would be grateful for some feedback!

Gable roof, 1.75 stories (knee wall at 185 cm)

Why a knee wall at 185? – for that I recommend the search term "Fensterscheide" here.

Our architect is nice and kind, but somehow I have a weird gut feeling... (Different topic).

Which different topic (?) – you have so far only this one thread here.

Is there any flaw in the wall construction from me or the construction company?

For that I recommend the search term "Steinemantra" here.
Regarding the wall construction with total thickness 525 – thus deviating from the standard dimension – another search term would be "Pfuschertaschen" (if you want to keep the facing brick in the standard dimension and therefore offset the structural wall shell); otherwise, befriending a brickwork in a random bond is recommended.

How does it already come to talks with a general contractor – are you writing out despite having an architect’s plan?

I can't tell you which setup is the most sensible. But something for the experts

Here I became a bit suspicious. I didn't win the lottery and as the builder I also have to watch the costs.

The doctor prescribes a high-quality and expensive medication. At the pharmacy around the corner, you are asked if you would also agree to a product that is only half as expensive, then without co-payment for the patient, but everything is 100% identical.
At the online pharmacy, the original costs only 2/3, but it is a reimport.

Whatever the patient buys – it has nothing to do with the doctor's competence. You can't accuse him of wasting money either.

The disability insurance otherwise recommends what his bricklayer always installs. Usually, of course, inexpensive, because he needs customers who can pay for his house.
Talking to the architect helps! What does he say?

Why a knee wall of 185? - For this I recommend the search term "Fensterscheide" here.

Which other topic (?) - so far you only have this one thread here.

For this I recommend the search term "Steinemantra" here. For the wall construction with a total thickness of 525 - so stepping from the standard dimension - another search term would be "Pfuschertaschen" (if you want to keep the cladding in the standard dimension and therefore offset the structural wall shell); otherwise I recommend getting used to a clinker bond in the wild pattern.

How does it come to conversations with a general contractor - do you not tender despite architectural planning?

Yes, we do tender. Our two neighbors are building contractors or also build turnkey; they get the tenders anyway. So the contact already exists.

I do not quite understand "Pfuschertaschen". The exterior wall thickness is not the decisive point here. Rather, it is the height and width of the house... The knee wall height in the shell construction measure is 187.5 cm. Due to interior plaster, it's about 185 cm afterwards.

@ 11ant: Oh, now I understand. I was just a bit slow. The grid dimension is not being adhered to with the clinker bricks. If you take a 9 cm clinker brick and leave an air gap of 1 cm between the insulation and the clinker, you would have a total build-up thickness of 50 cm. That would fit again.

We have a few other strange suggestions from the architect. I haven’t reported those yet. Might come later ectl. We are also considering changing the architect.

But we do issue tenders. Our two neighbors are construction contractors or also build turnkey; they get the tenders handed to them anyway. So the contact already exists.

What is to be offered is what has been tendered. That is then no longer variable; otherwise you have the apples and pears one tries to avoid, and the effort of the quantity calculations would have been for nothing. Reasonably, the involvement of bidders in the wall construction discussion takes place before the tender and comes from the architect.

I don't quite understand botched pockets. The exterior wall thickness is not the decisive point here. Rather the height and width of the house...

The height of the house has nothing to do with it, and not directly the width either. Botched pockets are caused in planning by walls or wall shells being torn out of the octameter grid. In a double-shell wall, this happens when the shells do not follow each other in rhythm (in the discussed case with a deviation of 2.5 cm). The exterior wall thickness is therefore absolutely causal here. If you do not want to restore the rhythm, I recommend making the adjustment in the facing shell, which as mentioned means coming to terms with a wild bond (which many building owners prefer anyway). However, this inevitably results in the use of masons also for the facing shell (popularly, contractors like to get by here with general construction helpers).

The knee wall height in raw building dimensions is 187.5 cm. Due to interior plaster, later about 185 cm.

No way, little Peter. Including floor construction, nowadays you rather lose around twenty centimeters. But even a knee wall height of 165 would still be unfavorable as a window divider.

I just got stuck on that. The grid dimension is not observed with the clinker. If you take a 9 cm clinker now and leave an air gap of 1 cm between insulation and clinker, that would be a total build-up of 50 cm. That would fit again.

Aside from my doubts about such constructions with a 1 cm "finger gap": where do you want to get a "9 cm clinker" from, which by the way would rather replace one complication with another? No, with wall thicknesses "impure" in terms of the octameter grid, it is better to make one of the wall shells the master shell; for that I recommend choosing the structural wall shell - with the mentioned consequence.

We still have a few other comical proposals with the architect. I haven't reported those yet. Might come later. We are also considering changing the architect.

Yes, please not salami-style, but all en bloc on the table. In which service phase are you? Probably 3?