Hello dear forum members,
We are currently planning our single-family house. We are in the preliminary planning phase and have already had the first discussions with an architect and potential builders. The house will be a single-family home with two living units (a granny flat), a pitched roof, 1.75 stories (knee wall at 185 cm (6 ft 1 in)), and a double-layer wall construction built to KfW 40 standards.
Our architect is kind and nice, but somehow I have a strange gut feeling... (a different topic).
Here is an example of the exterior wall construction. Our architect has planned a 525 mm (21 inch) wall assembly as follows:
- 11.5 cm (4.5 inch) facing brick layer (clinker brick)
- 10 cm (4 inch) core insulation (lambda 0.032)
- T9-30 clay brick
- Lime interior plaster
U-value: 0.149 (0.154 required for KfW)
Two builders have offered/suggested the following wall assembly:
- 11.5 cm (4.5 inch) facing brick layer (clinker brick)
- 16 cm (6.3 inch) core insulation (lambda 0.032 or 0.035)
- T14-24 clay brick
- 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.
This made me a bit suspicious. I have not won the lottery and as a client, I also have to watch the costs. Is there a flaw in the wall construction concept either from my side or from the builders? The builder also advised against using bricks filled with perlite or mineral wool, saying they are far too expensive, even though I could save on core insulation between the bricks and the outer wall this way.
Incidentally, this was also an alternative suggestion from the architect...
I would appreciate some feedback!
We are currently planning our single-family house. We are in the preliminary planning phase and have already had the first discussions with an architect and potential builders. The house will be a single-family home with two living units (a granny flat), a pitched roof, 1.75 stories (knee wall at 185 cm (6 ft 1 in)), and a double-layer wall construction built to KfW 40 standards.
Our architect is kind and nice, but somehow I have a strange gut feeling... (a different topic).
Here is an example of the exterior wall construction. Our architect has planned a 525 mm (21 inch) wall assembly as follows:
- 11.5 cm (4.5 inch) facing brick layer (clinker brick)
- 10 cm (4 inch) core insulation (lambda 0.032)
- T9-30 clay brick
- Lime interior plaster
U-value: 0.149 (0.154 required for KfW)
Two builders have offered/suggested the following wall assembly:
- 11.5 cm (4.5 inch) facing brick layer (clinker brick)
- 16 cm (6.3 inch) core insulation (lambda 0.032 or 0.035)
- T14-24 clay brick
- 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.
This made me a bit suspicious. I have not won the lottery and as a client, I also have to watch the costs. Is there a flaw in the wall construction concept either from my side or from the builders? The builder also advised against using bricks filled with perlite or mineral wool, saying they are far too expensive, even though I could save on core insulation between the bricks and the outer wall this way.
Incidentally, this was also an alternative suggestion from the architect...
I would appreciate some feedback!
stjonas schrieb:
Gable roof, 1.75 stories (knee wall at 185 cm (6 ft 1 in))Why a knee wall at 185 cm (6 ft 1 in)? – I recommend searching for the term "Fensterscheide" here.stjonas schrieb:
Our architect is kind and friendly, but somehow I have an uneasy feeling... (another topic).What other topic (?) – so far, you’ve only started this one thread here.stjonas schrieb:
Is there any mistake in the wall structure that I or the builders might be making?For that, I suggest searching for the term "Steinemantra". Regarding the wall structure with a total thickness of 525 mm (21 inches) – deviating from the standard dimension – another useful search term is "Pfuschertaschen" (if you want to keep the facing bricks within the standard dimension and shift the structural wythe of the wall); otherwise, consider using a brick pattern with irregular bonding.
How is it that you are already negotiating with a general contractor – are you not putting the project out to tender despite having architectural plans?
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
I can’t tell you which construction method makes the most sense.
But a few words about the experts
The doctor prescribes a high-quality and expensive medication. At the local pharmacy, they ask if you would also accept a medicine that costs only half as much, without any co-payment for the patient, but it is 100% identical.
At the online pharmacy, the original costs only two-thirds, but it is a parallel import.
Whatever the patient buys, it has nothing to do with the doctor’s competence. You cannot accuse them of wasting money.
The builder’s merchant usually recommends what his bricklayer always uses. Usually, this is cost-effective because he needs customers who can pay for his houses.
Talking to the architect helps! What does he say?
But a few words about the experts
stjonas schrieb:
This made me a bit skeptical. I didn’t win the lottery and as a builder, I also have to watch the costs.
The doctor prescribes a high-quality and expensive medication. At the local pharmacy, they ask if you would also accept a medicine that costs only half as much, without any co-payment for the patient, but it is 100% identical.
At the online pharmacy, the original costs only two-thirds, but it is a parallel import.
Whatever the patient buys, it has nothing to do with the doctor’s competence. You cannot accuse them of wasting money.
The builder’s merchant usually recommends what his bricklayer always uses. Usually, this is cost-effective because he needs customers who can pay for his houses.
Talking to the architect helps! What does he say?
11ant schrieb:
Why a knee wall height of 185? – I recommend searching for the term "Fensterscheide" here.
What other topic (?) – so far you only have this one thread here.
For that, I suggest the search term "Steinemantra".
For a wall assembly with a total thickness of 525 – based on the standard dimension – another useful search term would be "Pfuschertaschen" (if you want to keep the facing masonry at the standard dimension and shift the structural wall layer); otherwise, consider getting familiar with a brickwork pattern laid in a random bond.
How did talks with a general contractor come about – are you not tendering despite having architect plans? We are tendering. Our two neighbors are general contractors or also build turnkey; they will get the tenders anyway. So, contact already exists.
I don’t quite understand "Pfuschertaschen." The exterior wall thickness is not the deciding factor here. It’s more about the height and width of the house...
The knee wall height in the shell construction measurement is 187.5cm (74 inches). Due to interior plaster, it will be about 185cm (73 inches) afterwards.
@ 11ant: Ah, I see now. I was a bit slow to understand. The module size isn’t being followed for the facing bricks. If you use a 90mm (3.5 inches) facing brick and leave a 1cm (0.4 inches) air gap between the insulation and the brick, the total wall thickness would be around 50cm (20 inches). That would fit again.
We also have a few other strange suggestions from the architect. I haven’t mentioned those yet. I will share more later. We are also considering changing the architect.
We also have a few other strange suggestions from the architect. I haven’t mentioned those yet. I will share more later. We are also considering changing the architect.
stjonas schrieb:
But we put it out to tender. Our two neighbors are contractors or also build turnkey; they get the tenders anyway. So the contact already exists. What is offered is what was put out to tender. This is no longer flexible; otherwise, you end up comparing apples and oranges, and the effort put into the quantity calculations would have been wasted. Reasonably, bidders’ involvement in the wall construction discussion takes place before the tendering phase and is initiated by the architect.
stjonas schrieb:
I don’t quite understand 'botched work pockets.' The exterior wall thickness is not the decisive factor here. Rather, it’s the height and width of the house… The height of the house does not play a role here, and the width not directly. Botched work pockets are caused by planners when walls or wall layers are removed from the octameter grid. In a double-shell wall, this happens when the layers do not follow each other uniformly (in the case discussed, a deviation of 2.5cm (1 inch)). So the exterior wall thickness is absolutely the cause here. If you do not want to restore the grid, I recommend adjusting the facing layer, which, as mentioned, means accepting a random bond pattern (which many owners prefer anyway). However, this inevitably requires skilled masons for the facing layer as well (contractors often settle for general construction helpers here).
stjonas schrieb:
The knee wall height in the shell construction dimension is 187.5cm (74 inches). Due to interior plaster, it will be about 185cm (73 inches) later. No way, little Peter. With the floor structure, you nowadays lose closer to 20cm (8 inches). But even a knee wall height of 165cm (65 inches) as a window separation would still be unfavorable.
stjonas schrieb:
I just realized. The module dimension is not maintained with the facing bricks. If you take a 9cm (3.5 inch) facing brick and leave a 1cm (0.4 inch) air gap between insulation and facing brick, the total wall build-up would be 50cm (20 inches). That would fit again. Apart from my doubts about constructions with a 1cm (0.4 inch) “finger gap”: where are you going to get a 9cm (3.5 inch) facing brick? Which by the way would complicate things rather than solve them. No, with exterior wall thicknesses that do not align with the octameter grid, it is better to designate one of the wall shells as the master layer; I recommend choosing the structural shell for this — with the consequences mentioned.
stjonas schrieb:
We have a few other comical suggestions with the architect. I haven’t reported those yet. That will probably come later. We are also considering changing the architect. Yes, please don’t drip-feed them, but put everything on the table at once. Which project phase are you in? Probably phase 3?
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
Similar topics