Cost calculation - We are curious about your feedback

Hello everyone,

this year we are planning to build a house with the goal of obtaining a KfW40+ subsidy. Our goal was not to build a KfW40+ house. It is rather the fact that our list of requirements covers many things necessary for a KfW40+ house. Sand-lime brick with an external thermal insulation composite system (ETICS), photovoltaic system with energy storage, ventilation system, etc.

We plan to build without a developer, since some family members work in the construction industry. As an option, however, an expert should additionally ensure the quality.

We are now trying to roughly estimate the costs to find our price range and to see if we can even achieve a KfW40+ standard. There are some key figures on how to calculate costs based on the living area, but we wanted to be more precise and get a better overview of the individual trades. Also where savings can possibly be made by own work and how much savings, for example, a KfW55 house would bring. Without a bill of quantities it is not possible to determine costs exactly, that is clear to us, but as said, this is a rough plan and the detailed planning can only start when it is clear which plot we will get. There is time pressure when awarding the plot and we want to be well prepared when the time comes and not only then consider whether a KfW40+ is feasible for us at all.

We have now spent several weeks/months researching (internet, acquaintances, developers, specialist companies, etc.) and at the same time have become somewhat better informed. So there were positive side effects. The calculation as a first reference point is now done and we would like to show it to you in the hope that you can confirm or correct the costs. As mentioned, these are approximate values and we have estimated rather conservatively. Better to have some buffer at the end.

A few basic ideas about the planned house:
- 200m² living area
- 2 full stories
- 2.70m wall height
- hip roof
- sand-lime brick with ETICS
- slab on grade (no basement)
- no garage
- house budget 400k
- plot 200k (the plot will probably be cheaper)
- west of Frankfurt

Additional construction costs
€10,200 - property transfer tax
€1,600 - notary
€2,800 - land registry entry
€2,000 - building permit (0.5% of construction sum)
€500 - construction water
€500 - construction electricity
€2,500 - disposal of excess soil
€1,000 - sidewalk protection (may be omitted)
€1,000 - construction road (may be omitted)
€300 - insurance
Sum: €22,400

Site development
€1,500 - soil survey/geotechnical report
€2,500 - surveying
€1,500 - electricity connection
€2,750 - drinking water and wastewater
€560 - media provider (fiber optic connection flat rate from municipal utilities)
Sum: €8,810

Architect (planning)
This block is currently either not or hardly quantifiable for us. We have only a total amount here
€3,800 - draft planning
?€ - approval planning (building application, description of works, thermal protection certificate, structural engineering, site plan)
?€ - execution planning
?€ - preparation for awarding contracts (bill of quantities, schedule)
€1,000 - blower door test
Sum: €31,000

---
House construction

Civil engineer
€10,890 - civil engineering work for slab on grade (90€/m² // 200m² living area results in a slab approx. 11x11m)
€18,000 - insulated slab on grade (150€/m² // uncertain for concrete (140€/m³) and pouring (40€/m³))

Mason
€26,400 - masonry work (50€/m² for sand-lime brick // assumption: 4 exterior walls, 4 interior walls = 8x11m x 6m (two stories))
€34,000 - facade/ETICS (150€/m² incl. plaster and paint (50€) // unfortunately only styrofoam, as Multipor is too expensive)

Upper floor
€4,950 - floor slab (150€/m³ concrete; 15€/m³ reinforcement // would be "only" 5k at 25cm thickness, a figure of 10k is often assumed including plastering and filling)
€4,000 - ceiling plaster (40€/m²)
€5,000 - underfloor heating (50€/m²)
€3,000 - screed (30€/m² incl. mesh, impact sound insulation and grinding)

Interior plaster
€9,000 - base plaster (15-20€/m²; 450m² wall area)
€5,400 - top plaster (8-12€/m²)

Electrical
€15,000 - electricity, SAT, telephone, internet (according to company approx. 10-15k)
€15,000 - smart home (myGekko: heating, photovoltaic, battery, blinds, alarm system, door)

Sanitary
€11,000 - fresh water, wastewater
€10,000 - fixtures (WC, washbasin, ...)
€6,000 - fixture installation

Heating
€15,000 - air-source heat pump (ASHP, alternatively ground-source heat pump with ring/coil)
€10,000 - ventilation system (60€/m² // acquaintance paid 5k for the device + installation)
€25,000 - photovoltaic (2.6 kWp incl. storage // 8 kWp from Sonnenbatterie)
€0 - energy storage (already included above)

Carpenter
€25,000 - windows (19 windows; 8 floor-to-ceiling, 7 regular, 4 narrow)
€12,000 - blinds (€800 per window // 15 pieces // electric; should be controllable via smart home)
€5,000 - doors (10 doors)
€7,000 - front door (incl. installation)

Carpenter/Roofer
€18,000 - roof frame (60€/m² gable roof, 90€/m² hip roof; approx. 200m²)
€12,000 - thermal insulation (60€/m² gable/hip roof)
€10,000 - roof covering (50€/m² gable/hip roof)

Tiler
€6,500 - bathrooms (110€/m² incl. materials // 1 guest WC, 1 children's shower bathroom, 1 master bathroom // 30m² floor // 75m² wall)
€1,320 - utility room (110€/m² for 12m²)

Painter
€0 - exterior painter (already included in the facade)
€4,500 - interior painter (10€/m² // 450m² wall area)

Stairs
€5,000 - concrete stairs

Cistern
€2,500 - concrete cistern

Floor covering
€3,000 - labor (15€/m²)
€13,000 - materials (60€ + 4€ cork roll + 1€ moisture barrier/m² // 160m²)

Sum: €351,460
---
Sum (house + architect + site development): €391,270

What do you think? Theoretically, we are still under 400k (excluding additional construction costs), but the buffer of 8k is too small for me. In case, for example, we have forgotten a cost item. Especially since we cannot yet quantify the architect’s services more precisely and there were also differences in internet data on individual items and we have prudently calculated with the higher values. We know ourselves and would rather opt for higher quality things, so better to calculate more. For example, entrance door. I think €7k is an amount where you can also easily come cheaper.
It is also unclear how many solar modules will fit on the roof/need to fit, although I have already set the costs rather high here, but in my opinion reasonably. As said, your feedback/quality check etc. would interest us very much.

Thanks in advance. We are looking forward to it

In total, it doesn't sound so unrealistic at first. It might still fit upstairs. But painter, stairs, cistern tiles, floors are, I think, set MUCH too low. Feel free to calculate double for each. And the expert naturally costs extra as well.

I believe you are underestimating the requirement of the KfW regarding a 40+ house in terms of "we want to build monolithically." With our KfW55 house, we have to build 30% better in all positions (exterior walls, windows, roof/floor insulation) than the current reference value of the Energy Saving Ordinance. For 40+ it is even 45%. You will have to calculate with the U-values very precisely. It is not timber frame construction where you almost get the 40s for free.

Regarding your numbers: many positions are estimated 500-2000€ off. From the gut, I would say add another 40-60k€, then you will be in the right range.

In addition, the outdoor facilities are completely missing. The costs for the groundworks are only accurate if the plot is level with the street edge like a mirror.

The item Development completely for 9,000 also seems too inexpensive to me.

Do you have the figures from the fee schedule of the utility company?

Overall, in total, it might be possible, but kFW40+ and the simplest equipment (because that's probably what the price ultimately comes down to) don't really fit together.

I think it will be 50,000 EUR more expensive.

Regarding individual items, I picked out the photovoltaics. Who plans 2,600 kWp on a 200 sqm house with later 4? residents? In my opinion, the full 9.99 kWp belongs on it. And the battery only if you really want it. Economically, it has never really been worthwhile before.