House construction costs realistic? Please provide an assessment!

Hello everyone,

I would still consider myself a layman when it comes to construction, but we (my wife and I) plan to build (have built) a detached single-family house in RLP next year. The living area (ground floor and upper floor) should be about 155 sqm, and there will also be a basement. We have now received an offer from a company with Liapor prefab walls and find it difficult to assess whether the costs are realistic. The company generally only provides the refined shell construction but also offers the house turnkey.

The offer we have received looks as follows:

Refined shell construction - includes:
155 sqm living area plus basement (white tank)
Windows (triple-glazed, about 20 pieces, approx. 30 sqm, all with electric shutters)
Soil survey
Basement as white tank
Roof including insulation
Concrete stairs
Chimney (room air-independent)
Preparation of building services (empty conduits and approx. 130 empty boxes)
Complete architectural and engineering services as well as construction management

This should cost 198,000 € - I hope I have listed all essential points.

For a turnkey house, the following items were listed (which are each specified individually - so these are estimates from the consultant):

Electrical installations 10,000 €
Heating (gas condensing boiler with solar and underfloor heating (also in the basement)) 23,000 €
Sanitary installations (rough and final installation) 12,000 €
Screed 6,000 €
Full thermal insulation (14 cm mineral wool) plus exterior plaster and basement insulation 27,000 €
Front door 4,000 €
Interior doors (15 pieces) 6,000 €
Interior window sills 1,000 €
Tiling work (stairs and approx. 90 sqm including materials) 10,000 €
Cladding of collar beam ceiling and inserted staircase 7,000 €
Stair railing 4,000 €
Floors and walls (DIY - materials only) 8,000 €

These would then be additional costs of 118,000 €, totaling 316,000 € for a KfW-70 house. Interior plastering is not required for Liapor walls, so it is not listed. The walls have a U-value of 0.17 with the mentioned insulation.

Of course, the usual additional construction costs for earthworks, connections, building permits, surveying, etc., as well as kitchen, garage, and outdoor facilities, would still be added.

Are the above costs realistically estimated, are any essential items possibly missing? And how should the price for the refined shell construction be assessed? Possibly too high? We are grateful for any advice and assessments.

Best pre-Christmas regards
Carsten

Hello Carsten,

I would rather still describe myself as a layman when it comes to construction,

And then you choose exactly the self-assignment of trades? Who supervises the trades?

The living area (ground floor and upper floor) should be about 155 sqm and there will be a basement added. We now have an offer from a company with Liapor prefabricated walls and find it difficult to estimate whether the costs are realistic. The company generally only supplies the refined shell, but also offers the house turnkey.

The offer we have now looks as follows:

...

the cost is supposed to be 198 T€ - I hope I have listed all the essential points.

Normally, exterior plastering is also included in a refined shell; therefore, I assume you just forgot to list this item.

For a turnkey house, the following items were listed (which are each tendered individually in each case – so these are estimates from the consultant):

---

This would then be additional costs of 118 T€, totaling 316 T€ for a KfW-70 house.

A “normally” built, solid house of this size should cost around 320 - 330 T€ including a living basement. The cost savings due to prefabrication of the walls are therefore limited, if your question is aimed at this.

The interior smoothing is omitted for the Liapor walls, so it is not listed. The walls have a U-value of 0.17 with the insulation mentioned.

That is not correct. Smoothing work is definitely required – the ceiling joints and wall elements must be sealed. Furthermore, it critically depends on which supplier you choose; some deliver only one side smooth!

Of course, the usual incidental construction costs for earthworks, connections, building permit, surveying, etc. as well as kitchen, garage, outdoor facilities would be added.

Typical incidental construction costs: 35-40 T€
Reserve for additional foundation costs: 8 T€ (removal of topsoil should be guaranteed by the shell suppliers)
Painting/floor coverings: 15 T€
Outdoor facilities: 15 T€
Finished garage 3 x 9 incl. sectional door: 11 T€
Kitchen: "x" T€
Reserve for extras: 10 T€

If you have not chosen any extraordinary design for the shell – e.g. offsets in the house, stepped floor, or similar – the sales price for the refined shell seems too high to me. The entire profit of the provider is probably included there in my opinion.

Kind regards

Hello construction expert,

Thank you for your response. Yes, my knowledge is limited to one year of intensive research, various professional consultations, and expert lectures. Hence the deliberately modest designation "layman." Anything else would be presumptuous towards the various professional groups regarding the complex matter of construction.

The construction management for the trades still to be tendered would be included in the offer. So we wouldn’t have to do it ourselves; it would be the company’s responsibility.

The costs for the exterior plaster are deliberately not listed because they are included in the item "thermal insulation composite system (14 cm mineral wool) and exterior plaster and basement insulation – 27,000 €." Perhaps the term "refined" shell construction deviates a little from the conventional definition here. And the filling and smoothing work you mentioned is already included in the price of the shell construction, and the walls are smooth on both sides of the formwork. I wouldn’t have thought of that on my own.

So far, we have only had offers with a final price, so it is difficult for us to assess the now individually listed items more closely. It will not be an architectural marvel, so the costs refer to a fairly simple building style. Gable roof, knee wall on the first floor of 1.80 m. I also think that the company’s profit margin lies solely in the mentioned 198,000 €, as this is also the only fixed price. They may possibly earn various surcharges for tendering the other trades.

So perhaps another question, were the listed costs for the other trades estimated sufficiently or even set too high in the calculation? Or was something essential even forgotten? Of course, there is no upper limit, but we will more likely stay within the standards. What are the experiences here?

I can only compare the total costs of previous offers and only with some reservations because of differing descriptions of construction services. And the above-listed offer is rather in the middle in comparison, so not noticeably higher or lower than conventional solid construction.

Thank you in advance for your help.

Best regards, Carsten