ᐅ Single-family house construction project, 140 sqm with basement

Dear community, first of all, a big compliment for the very helpful tips here. I have been planning—or rather trying to plan—our house for half a year now. We have already consulted an architect and want to build with solid construction. How do you assess our project in terms of cost?

- Single-family house with 140 sqm (1507 sq ft) and full basement
- Standard according to energy-saving regulations
- Refrigerator with external thermal insulation composite system (ETICS / WDVS)
- Square, practical design, without dormers, bay windows, etc.
- External dimensions 7.49 * 11.49 meters (25 * 38 feet)
- 1 bathroom upstairs, 1 guest shower room downstairs
- Ground floor open living area with chimney (not really necessary, but we want the coziness of a stove)
- Upper floor with 3 bedrooms
- Basement with 1 finished room as an office, 3 storage/technical/utility rooms
- Planned is an air-to-water heat pump and underfloor heating
- Controlled ventilation with heat recovery system
- Triple-glazed windows with external blinds
- Soil according to geotechnical report is simple sandstone, so excellent conditions, no rising groundwater pressure

Now, the architect gave us a rough estimate and said we should calculate about 400 Euro per cubic meter (796 m³). This seems rather high to us. To be prudent, we will structure our loan accordingly since someone could get sick or have delays.

However, we want to contribute a lot of DIY work ourselves. Heating, electrical work, roof structure installation, plumbing, floor laying, and gypsum/plaster work will be done by us.

Do you think it could be possible to manage around 200k, if everything goes optimally? This is only about the construction costs; everything else like landscaping, garage, and terrace will be contracted separately.