Floor slab, masonry, and insulation okay?

Hello,

I would like to hear your opinion on an offer we have received. Beforehand: the developer is "quite" affordable compared to the industry standard, so I understand that we have not been offered the absolute best. Nevertheless, I would like to know if the offered is basically okay for today's house building standard. Therefore, below are some excerpts from the construction description


Regarding earthworks
...The topsoil in the area of the building body will be removed up to 30 cm deep and stored on the property for reuse on site. Filling sand up to 30 cm thick will be placed and compacted in the excavation pit. The trenches for the strip foundations will be dug out, and the excavated soil will be stored on the property. Additional earthworks required due to local conditions are to be agreed upon and paid for separately.

Foundation and drainage
The wastewater pipes will be laid under the base plate from KG pipes with an average diameter of 100 mm along the shortest route to the exterior of the house.
The foundation will be a shallow foundation with a reinforced concrete base slab including continuous, unreinforced strip foundations. The base slab is 20 cm thick, reinforced with two layers of steel reinforcement mesh Q 257A, and made with concrete of quality class C 20/25. A stud membrane will be installed as a cleanliness and capillary breaking layer.
A foundation earth conductor made of galvanized strip iron will be installed according to VDE regulations.

Masonry
The exterior walls with plaster facade will be constructed with a total thickness of approx. 33.0 cm as follows: masonry made of 17.5 cm hollow bricks (brand Unipor) and approx. 15.5 cm thermal insulation composite system including white colored, textured facade plaster.
The exterior walls with facing masonry will be constructed with a total thickness of approx. 45 cm as follows: masonry made of 17.5 cm hollow bricks (brand Unipor), approx. 14 cm core insulation made of mineral fiber, 2 cm finger joint gap, and 11.5 cm facing bricks. The window and door lintels are covered with galvanized steel angles. Standard format with a material price of up to €600.00/1,000 pieces including VAT is planned. The joints of the facing masonry will be raked out and subsequently pointed with cement gray mortar.
The knee walls, if present, will be constructed massively in masonry or reinforced concrete according to planning and statics.
The interior walls on the ground and upper floors will also be massively built from hollow bricks. The clear rough construction height on the ground floor is approx. 2.64 m and approx. 2.665 m on the upper floor.

Damp proofing against ground moisture
The horizontal damp proofing against rising ground moisture under the rising masonry will be made with bitumen sheets. The remaining area of the base slab will be sealed with bitumen welding sheets.
All outer surfaces of the enclosing walls will be sealed against lateral moisture up to 30 cm above ground level. In the case of facing masonry, the sealing takes place behind the facing on the outside of the backup wall.

Drywall work
The ceilings and roof slopes on the upper floor are insulated with mineral wool according to the thermal protection certificate, sealed with a vapor barrier foil, and clad with gypsum plasterboards on the rafter sheathing.
The knee walls are also clad with gypsum plasterboards on a metal stud framework. The gypsum plasterboards will be filled and smoothed in the joints and fastening areas in standard quality level Q2 to accommodate a woodchip wallpaper. The connection joints between individual components, e.g., gable wall and ceiling, are to be made elastically with acrylic by the painter.

Screed work
A calcium sulfate screed will be installed level and smooth. On the ground floor, thermal insulation according to the thermal protection certificate and approx. 80 mm impact sound insulation in the upper floor will be installed. The total height of the floor construction on the ground floor is approx. 19 cm and approx. 14 cm in the attic.

Do the above-mentioned properties at all represent a KFW-55 house?
I would be grateful for any tips :)

Do the above-mentioned features even represent a KFW-55 house?

Your energy consultant or the builder will definitely tell you that. We cannot. Which windows, which heating, which ventilation, which roof insulation, etc.?

I am currently in contact with property developers

the property developer is "quite" inexpensive compared to the industry standard,

You mean a construction contractor (here probably a general contractor). From a construction developer you would only get the complete bundle house and land, no construction on your land. Choose one who is especially well regarded in terms of reputation – these are mostly found locally or regionally.

will be excavated up to 30 cm deep and [...] fill sand up to 30 cm thickness will be applied and compacted.

Reading this with a layman’s perspective says: "great, that much is included" – professionally read, however: "30 cm are included – what does it cost from the 31st cm onwards?" Skimming through, the quoted offer is within the usual range. Offering two wall structures (essentially one for the meat fans and one for the fish fans) is very usual, and the described variants are average in the sense of no particular feature "upwards or downwards". Technically speaking, I do not read in your description any reason to warn you (or to congratulate you on a great offer). Basically, you can be advised here with an accuracy that is causally connected to how much or how little we know about your project (so currently: quite little).

Briefly skimmed... - Earthworks are a common clause. You will have problems if 30cm are not sufficient, whether due to slope, soil bearing capacity, or frost protection. - Drainage may be suboptimal under certain circumstances. The shortest way to the outer edge is not necessarily in the direction of the sewer shaft, and from the outer edge onwards it is presumably your responsibility. It would be better to combine everything and run a pipe towards the shaft. - Are you building with clinker or plaster façade? 60c per clinker seems a bit too little to me, a quick Google search tells me that you should rather calculate about 1€ per brick. - Room height is the rough construction dimension, so you have to deduct the floor construction everywhere. - The different floor heights for the upper floor and ground floor confuse me a bit. Exactly where is the thermal envelope on your side? Apparently the base slab itself is not insulated and this is compensated by a high floor construction?

Different floor heights in the upper floor and ground floor are normal. In the upper floor, no thermal insulation is required under the screed, only impact sound insulation, to which the underfloor heating is also stapled. In the ground floor, thermal insulation is added underneath, apparently 5cm here.

There are no problems with the foundation, it just becomes a bit more expensive. But that would also be the case if you use a general contractor who includes the foundation, then in the form of a higher house price.

The insulation overall does not seem to me to be sufficient to meet the KfW-55 standard (as far as I know mandatory from 01.01?). Even the Building Energy Act is very tight. But I could be wrong. It could also be that their person responsible for the thermal protection verification calculates precisely and does not work with flat rates, in which case often less insulation is needed.

A dimpled vapor barrier sheet is laid as a cleanliness and capillary break layer.

That was done the same way for me, but I had to be told "in the shopping center around the corner" that this does not comply with the Eurocode (which, however, is not mandatory either). Your slab is probably not a structural element (this is said to be cheap construction). However, no one there could explain to me how many years earlier my house will now collapse.

I recommend a good expert who also looks at the construction service description before signing the contract.