Cost estimate single-family house 165m², NRW, fully basement

Hello everyone,

here is a quick question whether the cost estimate is correct.

We are planning a single-family house with 165m² of living space (living floor and attic floor, knee wall at 1m height, a total of 10 rooms including the two hallways on the living and attic floors). Additionally fully basemented (due to the slightly sloping plot, the basement is at the back in the hillside, at the front it is at ground level) with 90m² of usable space. The plot is available, normal amount of window areas, clear and simple structure without frills. Air heat pump for heating, no special KFW energy standard, double garage in the basement with double sectional door.

The enclosed volume is 1,075m³, which is built at 320€/m³ --> 344,000€ (plus additional costs: architect, connections, sewage system,...) I personally find (with my amateur knowledge) the m³ somewhat unfortunate. For example, by adding one more row of bricks in the attic/basement, the cubic meters increase quite significantly, which does not necessarily reflect the "small" additional costs of this one more row of bricks. As a first reference point, however, it is probably one of the best options.

My question: Is the cost estimate about right? It seems somewhat high to me. Of course, it is good to have a buffer, but from a pure feeling, the whole thing seems relatively high priced.

The costs were broken down according to a percentage key to the individual trades, here are the largest items:

Total costs: 344,000€ 126,000€ masonry and concrete work (50% material, 50% labor) 23,000€ heating 22,000€ interior plaster 25,000€ windows, doors, shutters 18,000€ exterior plaster 32,000€ carpentry and roofing work 20,000€ installations 15,000€ tiles, window sills 15,000€ joinery, doors 8,000€ earthworks 9,000€ electrical 9,000€ flooring 22,000€ rest (insulation, plumber, locksmith, painting work)

Own work is planned within a certain scope. It is difficult to say to what extent, we assume about 10% of the construction sum.

If any relevant data is missing: just let me know. Many thanks in advance.

Best regards

344k including the garage?

Yes, the garage is included (directly in the basement)

I say, roughly. We pay 320k including garage. Living area around 140m², fully basemented but in "living space quality". However, no floor coverings are included (no tiles, no parquet, nothing). So 344k I can imagine could be very tight.

The 320€ per m³ seems very cheap to me. So far, we have always been offered ready to move in for around 380€ per m³. (Bayern)

With ~35k€ own contribution, you practically do the interior finishing almost completely yourself, but it doesn’t sound like you intend to do that, does it?

Personally, I find (with my layman's knowledge) the m³ a bit unfortunate. For example, adding one more row of bricks in the attic/basement directly increases the m³ quite significantly, which does not necessarily reflect the "small" additional costs from that one more row of bricks.

Well, you want a cost estimate, you need some kind of reference point for that. You can also calculate it based on m², but then in the cost estimate, costs for heating, bathroom, etc. are included as flat rates; with more m² you don’t necessarily need more bathroom or heating. Keep in mind in your calculation that with 165m² according to your information you have 10 rooms. That’s a lot of "bricks" used, which in cost calculations based on m³ does not differ from a house of the same size but only 5 rooms....

I think the best way is to calculate the costs using the keys m² and m³, then you have a realistic range in which your costs will fall. From gut feeling, your calculation does not seem unrealistic but rather on the low side. As already mentioned, 35k of personal contribution is quite a lot. Saving this in labor costs means, at 50€/h, a total of 700h of personal work, assuming your skills and tools are comparable to those of the tradesman.