Rough estimate of the cost for an extension per m²

Unfortunately, there is the next snag: everyone (they all agreed on this) told me that the additional square meters become relatively cheaper, so it is rather not worthwhile to do without them.

I understand that this is difficult, especially in a forum like this, but my expectation is that several architects should be able to give a more or less similar estimate after an initial consultation of about two hours.

Maybe someone with a similar project and real experience will still be found. If not, I just have to accept that my expectation is unrealistic.

Tendentially, I would rather say that 50 sqm extension per sqm is more expensive than 150 sqm complete new build. Considering pure construction costs, since services such as site logistics, screed pump, excavator, etc. are not cheaper because of fewer sqm, but the costs are divided over fewer sqm.

Of course, every construction site has setup costs that are distributed over the square meters. The larger the building, the lower the setup costs per sqm. An extension is often logistically more difficult than a new build. Be that as it may. As a builder, I want a good solution that meets my demands – a few sqm more or less – and at a budget I can comfortably afford. Living space is not a value in itself.

Maybe someone with a similar project and real experience will still be found. If not, I'll just have to live with the fact that my expectation is unrealistic.

At friends’ place, an extension burned down at the beginning of the year. It was still quite new and was to be rebuilt identically. The offers differed by up to 50%. The cheapest offer, which seemed particularly attractive to the insurer (oh wonder), was missing several items. A fixed-price agreement was then reached. The extension is standing again.

Hello el_horst,

we are currently also expanding our single-family house by about 80m² (3 rooms) plus a covered terrace through a house extension plus a "inserted" cuboid.

See under

We had the same question and were initially also surprised by the first offers. Comparison offers have shown that an extension is simply significantly more expensive than a new build (everywhere there are small quantity surcharges, dismantling costs, risk surcharges, increased planning effort). We started 3 weeks ago, so far everything is running smoothly, and according to the offer we are at about €2,600 / m². We are building in Bavaria, and it was quite difficult to get offers at all. Many were rather in the direction of €3,000 per m², sometimes more. As you can see from the construction description, we also have no luxury fittings planned, rather everything standard.

We wanted to build turnkey. In the end, we commissioned a construction company that obtained the offers for us on a fee basis and also carries out the construction management on a fee basis. This way we have a negotiated fixed price offer transparently available for each trade. Billing is done via the construction company, which thus also assumes the entire warranty. That was the cheapest and best solution for us.

Ultimately, it is also a question of alternatives. A new build was not an option for us at land prices of around €1,000 / m²; we searched for existing properties for two years and did not find any in comparable locations and quality. The only choice left was between extending or doing nothing at all....

Where are you building, and what is the current status with you? Do you want to upload a building plan?

Best regards,
The Extender

Hi,

Due to the unclear condition of the spiral collectors of the ground source heat pump, we are currently trying to get information from the construction company involved at that time. If that doesn't work, we will have to use ground-penetrating radar first. We haven’t progressed further yet.
The location is the eastern Ruhr area.
We are currently on the move, I can give more details when I have a proper keyboard.
We will probably end up around 180" for 60m^2. There are no offers yet, only a rough preliminary plan and initial cost estimate.
We have chosen an architect. The supposedly cheapest one, but not for that reason.

Your project looked quite interesting at first (phone) glance. However, we will only build a single story extension and either simply slide the structure under the existing roof or connect it to the existing roof.

Greetings
./el_horst./

Currently (as of 22.07.2019) between 3,000 - 4,000€/sqm are charged for an extension with us, depending on the equipment desired or the effort required.

Location: City in RLP