Assessment of construction costs for a single-family house in the Rhine-Main region

Hello everyone,

we are currently in the planning and contractor selection (GU) phase. For this, we have various manufacturers in closer consideration.

One manufacturer has already given us a first rough offer of the construction costs based on a more "individual" scope of work description. Here are some brief summarized key data (of course, much more detailed information is available in parts – I can gladly provide further info).

Location: Rhine-Main area
Construction site equipment: WC, construction electricity (except drying), construction fence, construction crane included
House length: 11m x 8.36 (net)
Living area: 140 sqm
Roof: gable roof 40°
Basement: white tank and waterproof shafts with 5 windows
Shell construction heights: 2.75m ground floor, 1.30m knee wall attic, basement 2.50m
Windows: dual-color plastic windows RC2 (basement, ground floor, attic) + shutters (specified brands), ground floor: sliding door + fixed elements; attic: 2x floor-to-ceiling windows + 5 roof windows (specified brands)
Floor slab: C25/30, perimeter insulation 99mm
Exterior walls: Poroton 36.5cm
Heating: specified brand from Viessmann for air-water heat pump including performance – underfloor heating for ground floor and attic in all rooms
Ventilation system: decentralized system (brand and quantity specified)
Sanitary: specified brands from Hansgrohe and Villeroy & Boch (toilet, washbasin, towel holder, shower partition, additional towel radiator, etc.), 60x60 cm tiles for €50/sqm (tiling for wet rooms included), washing machine connection, utility sink in basement
Electrical installation: brands specified, one room as example: living/dining 25 sockets plus an additional 20 extra sockets for free distribution
Sun protection: aluminum shutters
Front door: value €5,500 including installation
Interior doors: brand specified including sliding doors
Stairs: 2 reinforced concrete stairs from basement to ground floor and ground floor to attic (plus pull-down ladder for roof)
Roof: colored roof covering Braas

The construction costs were calculated at €580,000.

From my point of view, roughly estimated, that would already be €3,400/sqm (with 140 sqm usable area) – given the basement costs about €100k.

I have pointed out that I am simultaneously obtaining offers for a soil survey and will have it carried out. We have also already commissioned a surveyor. I think this will only help gain more clarity about procurement.

What else concerns me?

[*]Earthworks and rainwater drainage within the work area are completely self-performed. The work only starts from the top edge of the filter layer. I have not seen this with any other manufacturer so far. Here I have currently roughly set ancillary costs at €60k (GU €30k) – I am even rather worried that it could become more. Would you negotiate to have at least part of this covered by the GU?
[*]Currently, no flooring and painter work is included (except wet room tiles). I consider this quite fair for the price and it could be brought into the price negotiation. How do you see it?
[*]Additionally, we are considering installing venetian blinds. These would also be negotiable for me.
[*]The request to further break down the €580,000 was only fulfilled after I said that I want to compare several providers for the trades and otherwise the discussion will not progress here.
[*]Are there any other points you would pay attention to from your perspective?

I can gladly also provide a supplementary ancillary cost estimate.

Many thanks in advance.

Here are the key data briefly summarized (of course, there are partly much more detailed information available – I can gladly provide more info if needed).

Well, the problem or the additional services that must be provided on the construction side are almost only to be read hidden in the details. Roughly, daxgar doesn’t bring anything.

Basis of a "more individual" construction service description

To be honest, I am also somewhat skeptical. Good construction service descriptions are (for the general contractor) mature and practically indisputable, as they are approved by the legal department or lawyer. Any spontaneous change carries trouble and uncertainty for both sides.

The request to further break down the €580,000 was only complied with after I said that I wanted to compare several providers on the trades and otherwise the discussion here would not proceed.

You are confusing a general contractor with an architect’s firm.

Earthworks and rainwater drainage are fully done as own work in the work area. The service only starts from the top edge of the filter layer. I have not seen this before with any manufacturer.

Yes, that’s how it is and not an exception, but standard practice. Slab-on-grade houses are usually offered with 30cm earthworks. This basically always means additional costs. And this is because it concerns the plot, i.e. is the responsibility of the builder, it is not part of the house offer.

Of course, you can negotiate everything. However, I would ask myself what kind of general contractor depends on having to change everything. Are you their only client? Ultimately, €3400/sqm is completely within range.

except wet room tiles

Google what wet rooms are. Only rooms with floor drainage, i.e. walk-in showers with floor rails, are wet rooms. Nothing more.

Residential ventilation system: Decentralized system (make and number specified)

Regardless of the fact that the construction costs for the plot are within a "normal" range, a decentralized system is not up to date for new buildings. I hope you just made a typo.

we are currently in the planning and contractor selection phase (GC). For this, we have various manufacturers in closer consideration.

So you are looking for a general contractor who is willing to carry out a house construction including the "necessary architectural services" (Note, the restriction "necessary" is meant very seriously!)? Why not a freelance architect at least for the preliminary draft, and awarding after tender including a GC?

The request to break down the €580,000 was only fulfilled after I said that I wanted to compare several providers on the trades and otherwise the discussion here would not move forward.

If you have sent around a self-design with the price attached and want to find the cheapest bidder by the "layman compares with Excel table" method, you might as well flip a coin.

Good construction performance descriptions are (for the GC) mature and virtually incontestable, since approved by legal department or lawyer. Any spontaneous change entails trouble and uncertainty on both sides.

The bigger the GC, the more strictly applies: services are not negotiable at all – features are negotiable, whereby the euro in upgrades is only worth eighty cents (and in downgrades or removals even only sixty to fifty).

Slab-on-ground houses are usually offered with 30cm earthworks. This basically always means additional costs. And this is because it is related to the property, i.e. by the client, it does not belong to the house offer.

Thirty centimeters is a popular, because commonly not questioned by men, symbolic measure for "guaranteed sufficient" – but means nothing other than that from the 31st centimeter every excavator bucket is gilded. A division of earthworks into those for the house footprint and those around it (esp. by a different contractor) is an excellent shifting of blame for additional costs. At least you don’t also make the slab-on-ground "by client."

decentralized systems are not contemporary in new construction.

Decentralized controlled residential ventilation systems are (in new buildings) only for buildings that are not intended to be continuously equipped with one (and thus actually for people who are neither pro nor con convinced and consider lazy compromises the golden middle way). When you have understood controlled residential ventilation, you also have an opinion on it (which can be fondness or aversion), but you do not use it decentrally without cause. One provider who – wordplay alert – never belongs to the core of my bidding field prefers the decentralized version.