ᐅ We are planning to build a house. Is what has been offered to us acceptable?
Created on: 15 Apr 2015 19:47
L
LittleWulf
Hello, we would like to start building our own home this year with a general contractor, a complete package.
Since I am not very knowledgeable about this topic despite a lot of research and cannot properly assess such matters, I wanted to ask what you think about the offer we have received. We are currently strongly leaning towards this provider.
We are curious whether this is more or less "standard" or if it is rather on the lower end. Also, what could possibly be improved without immediately having to pay several thousand more.
First of all, many items are listed as “insulated,” such as the lowered ceiling in the bay window, the roller shutter boxes, or the solid knee wall.
Floor:
Reinforced concrete slab foundation including frost protection edge strip and waterproofing against rising damp instead of strip footings. Thickness about 20cm (8 inches) and concrete quality C 20/25.
Steel reinforcement and slab thickness according to the assumed ground pressure as per the homeowner’s specification sheet (I can provide that if needed). A foil is laid under the slab as a clean layer.
Walls:
The exterior walls are executed with a total thickness of about 44.5cm (17.5 inches) as follows:
1.5cm (0.6 inches) fine plaster
17.5cm (7 inches) masonry of porous, fired clay brick
14cm (5.5 inches) cavity insulation, thermal conductivity class (WLG) 035
approx. 11.5cm (4.5 inches) facing brickwork
Interior walls on ground and attic floors are constructed with brick (Poroton).
(Now the addition for KfW 70)
The piping for the warm water underfloor heating is designed for a supply temperature of 35°C (95°F) by installing the pipes closer together.
Extension of roof insulation to 26cm (10 inches) with WLG 035
(Credit of 4,216,- if omitted)
[Is that reasonable for slightly better insulation and closer pipe spacing?]
For an upgrade to KfW 55 (20k-21k):
Different heating system with more solar input.
Ventilation system.
8cm (3 inches) insulation with WLG 035 under the slab.
Exterior walls then apparently no longer face brick but rendered, consisting of:
1.5cm (0.6 inches) fine plaster
17.5cm (7 inches) masonry of porous, fired clay brick
20cm (8 inches) external thermal insulation composite system (ETICS) with WLG 032 including silicate facade plaster.
Now my question is: since I would like a ventilation system, should I improve the insulation somehow even if I do not aim for KfW 55? And isn’t the masonry thickness of 17.5cm (7 inches) rather thin?
I skimmed a forum where this exact wall build-up (by the same contractor) was heavily criticized.
Since I am not very knowledgeable about this topic despite a lot of research and cannot properly assess such matters, I wanted to ask what you think about the offer we have received. We are currently strongly leaning towards this provider.
We are curious whether this is more or less "standard" or if it is rather on the lower end. Also, what could possibly be improved without immediately having to pay several thousand more.
First of all, many items are listed as “insulated,” such as the lowered ceiling in the bay window, the roller shutter boxes, or the solid knee wall.
Floor:
Reinforced concrete slab foundation including frost protection edge strip and waterproofing against rising damp instead of strip footings. Thickness about 20cm (8 inches) and concrete quality C 20/25.
Steel reinforcement and slab thickness according to the assumed ground pressure as per the homeowner’s specification sheet (I can provide that if needed). A foil is laid under the slab as a clean layer.
Walls:
The exterior walls are executed with a total thickness of about 44.5cm (17.5 inches) as follows:
1.5cm (0.6 inches) fine plaster
17.5cm (7 inches) masonry of porous, fired clay brick
14cm (5.5 inches) cavity insulation, thermal conductivity class (WLG) 035
approx. 11.5cm (4.5 inches) facing brickwork
Interior walls on ground and attic floors are constructed with brick (Poroton).
(Now the addition for KfW 70)
The piping for the warm water underfloor heating is designed for a supply temperature of 35°C (95°F) by installing the pipes closer together.
Extension of roof insulation to 26cm (10 inches) with WLG 035
(Credit of 4,216,- if omitted)
[Is that reasonable for slightly better insulation and closer pipe spacing?]
For an upgrade to KfW 55 (20k-21k):
Different heating system with more solar input.
Ventilation system.
8cm (3 inches) insulation with WLG 035 under the slab.
Exterior walls then apparently no longer face brick but rendered, consisting of:
1.5cm (0.6 inches) fine plaster
17.5cm (7 inches) masonry of porous, fired clay brick
20cm (8 inches) external thermal insulation composite system (ETICS) with WLG 032 including silicate facade plaster.
Now my question is: since I would like a ventilation system, should I improve the insulation somehow even if I do not aim for KfW 55? And isn’t the masonry thickness of 17.5cm (7 inches) rather thin?
I skimmed a forum where this exact wall build-up (by the same contractor) was heavily criticized.
L
LittleWulf15 Apr 2015 21:54No, no ^^ I only mentioned excerpts that relate to the insulation.
We have a 12-page customized offer, based on a rather densely written 7-page client specification document. Unfortunately, some points are not described in enough detail, but I don’t think I can get much more for the individual contract since I would have to discuss every single point and also know where more details are needed.
We have a 12-page customized offer, based on a rather densely written 7-page client specification document. Unfortunately, some points are not described in enough detail, but I don’t think I can get much more for the individual contract since I would have to discuss every single point and also know where more details are needed.
T
toxicmolotof15 Apr 2015 23:27So, the scope of work provided by our architect for the insulation covered the structural builder, the exterior plasterer, and the roofer, and included only about 1.5 to 2 pages for the insulation layer itself. And that was ONLY the insulation layer with the corresponding conditions and details.
B
Bauexperte15 Apr 2015 23:30BeHaElJa schrieb:
I believe Bauexperte is against it because of the lack of long-term experience (material compression). As far as I know, there are no reliable data at all—neither short-term nor long-term—because no homeowner who has insulated beneath the slab has, after 5 years, had a surveyor come back to re-measure the ridge height. Only this would, in my opinion, conclusively prove what under-slab insulation actually achieves.
In our latitudes, there is a frost line at 80cm (31.5 inches) that must be observed for all foundations to prevent frost heave of the concrete. Therefore, a layer of gravel is typically laid under buildings as frost protection. This diverts rainwater so that freezing does not cause soil swelling. This also means that significant cold cannot rise beneath a properly founded house. Downward, it becomes warmer anyway, meaning that at basement level, the temperature does not drop below 0 degrees Celsius (32°F); after all, we are not living in Siberia.
But yes, fundamentally I favor insulation above the foundation slab; I prefer to have the warmth "in" the house and not underneath it.
BeHaElJa schrieb:
Depending on the house, that can account for part of the heat loss. On paper, with "assumed" values; paper is famously patient, after all.
Best regards, Bauexperte
B
Bauexperte16 Apr 2015 02:09LittleWulf schrieb:
Exterior walls will probably no longer have brick cladding but will be finished with plaster Apart from the fact that this statement is simply incorrect – what is the explanation behind it?
LittleWulf schrieb:
I skimmed through a forum where they completely tore apart this exact wall construction (same developer) I can understand that.
Regards, Bauexperte
L
LittleWulf16 Apr 2015 09:01Bauexperte schrieb:
I can understand that
Regards, BauexpertePlease provide more details, this is my main question. What value does this exterior wall construction have? Is this a thinner brick? Should it be thicker? Is it thick enough? Does the thickness alone not say anything?
The stone must meet the structural requirements – in my opinion, it is not too thin. It serves a load-bearing function and, in your case, also provides some insulation as well as sound and heat protection. The insulation is handled by the mineral wool. The facing brick is a bonus.
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