Construction costs single-family house bungalow

Here is our offer
Shell construction is a fixed price from the construction contractor.
The finishing trades are from different companies with cost estimates.
It will be a bungalow with 164 sqm without a basement.
Heating air heat pump with complete underfloor heating.
Masonry Poroton T10 in 36.5 without additional insulation.

What do you think of the offer?

Shell construction
Architect, energy saving ordinance, static 7,000 € site setup 5,000 € earthworks, base slab 25,200 € shell construction including chimney 52,300 €
Finishing works
Windows, front door, exterior window sills 21,500.00 €
Heating / sanitary 30,500.00 €
Carpentry work 18,000.00 €
Roofing and roof plumbing 20,000.00 €
Drywall including inset staircase 12,000.00 €
Interior plaster 7,500.00 €
Interior window sills 1,000.00 €
Screed 2,500.00 €
Interior doors 3,500.00 €
Tiling work 7,000.00 €
Electrical installation 9,000.00 €
Exterior plaster 14,000.00 €

Floor coverings 3,000 material
Painting work 2000 € material
Construction costs 251,000.00 €

Incidental building costs / notary / property transfer tax 5,000.00 €
Development costs (HA - costs)
Electricity 2,500.00 €
Telecom 500.00 €
Water 1,000.00 €
Wastewater, sewer 2,000.00 €

Outdoor facilities 5,000 € material
Plot of land 35,000.00 €

The land price shows that it is a structurally weak region. The prices are also extremely cheap.

The prices are realistic and comprehensible. You should not expect any major surprises, except maybe +5000-10000€. Possibly a bit higher if there are problems with the ground.

But for the price, there is only a low standard for all trades. You need to be aware of that. Are you adding any upgrades, such as better sockets, tiles, sanitary ware, windows, doors, etc.? Or are you taking everything off the shelf as stated in the [Bauleistungsbeschreibung des BUs]? If not, it will certainly become more expensive.

We built our bungalow for a similar amount of money. So it could be about right. But what you really need to look at again is the connection costs. They can easily be twice as high. A house entry is often not included in the price. It costs up to €1000 (depending on the version). Whether the earthworks are suitable for you can only be determined by the soil survey. For my part, I would consider them a bit tight.

But for the price, there is only a low standard in all trades.

Well, what does low standard mean? In Germany, the "low standard" is already completely sufficient.

What I still miss in the offer: ventilation (no matter what it looks like). Or will you be able/want to ventilate several times a day?

Well, what does low standard mean? In Germany, the "low standard" is already completely sufficient.

What I still miss in the offer: Ventilation (no matter what it looks like). Or will you be able/want to ventilate several times a day?

You answered that yourself. That won't be included at that price. Apparently, ventilation is already part of your standard :-). 7k€ for tiles including material is not much either. The OP treated themselves to something nice for the windows alone. Since the offer is relatively high, 3000-4000€ more. Either they are not plastic windows or made of wood.