ᐅ Floor Plan Planning – Extending a House – What Costs Are Involved?

Hello dear house building forum,

Since three detached single-family homes are going to be built just around the corner from where we currently rent, we got into conversation with the builder.

He planned to build three identical single-family houses.

Key details:

KfW 55 energy-efficient house in Bavaria (rural area)

approximately 8.3m x 10m (27 ft x 33 ft) plus plot
no basement, 2 full floors, unfinished attic + garage 6m x 6m (20 ft x 20 ft)
insulated exterior walls
insulated ground slab
concrete ceiling on the 2nd floor
underfloor heating + heat pump
electrical and sanitary installations all completed
also exterior plastered and painted
owner only needs to finish flooring, painting, and landscaping
He would ask for €240,000 for such a house.
I hope these details are sufficient to answer my question.

However, since we need 3 children's rooms, such a house would be too small for us.

Therefore, the builder offered to extend the house by 2 meters (8.3m x 12m / 27 ft x 39 ft), so that on the upper floor instead of a storage room there would be a children's room plus storage, and on the ground floor a pantry would be added and the kitchen would be about 5m² (54 ft²) larger.

For this version, he would ask for €300,000.

Now to my question:

Is the additional cost justified?
€60,000 more for 2 meters (6.5 ft) of house length?

Many thanks in advance for your answers and your effort...

Best regards,
Andreas

A 2m (6.6 feet) extension adds roughly 32 sqm (344 sq ft) more floor area on the ground and upper floors, let’s say 30 sqm (323 sq ft) additional living space.
This means the 60,000 euros correspond to the often mentioned 2,000 euros per sqm (186 per sq ft).
At least it does not seem entirely unreasonable.

You should double-check the offer of 240,000 ... does that really include the land, etc.? Make sure to carefully verify the scope of services.

The 2,000 per square meter (sq m) cost includes all the expensive building services; additional space tends to be somewhat cheaper. On the other hand, it doesn’t really matter whether the extra cost for something you don’t need is high or low – in the end, only the final price in the bottom right counts. For example, if I want to buy a California, I don’t decide based on the price of a Golf and the difference between them. I’m much more interested in how it compares to the Marco Polo.

New plans and new structural calculations need to be prepared.
I don’t find the 60,000 unreasonable.

In my opinion, this is somewhat plausible. In the initial post, does the house measure 8.3m x 10m (27 ft x 33 ft) including the plot or excluding the plot?

The land cannot be included in the price.