ᐅ Basement Height: 1 Meter vs. 60 Centimeters – Cost Perspective

Hey,

we are working with our architects on a well-advanced design and are about to apply for the building permit / planning permission.

One of the final decisions is whether the basement (with a waterproof concrete tank) should extend 60 cm or 100 cm (24 inches or 39 inches) above ground level.

According to our architects, choosing 100 cm (39 inches) might save a little money, but it wouldn't be significant. They also consider earthworks and the waterproof concrete tank as major cost factors.

From my understanding, earthworks and the waterproof concrete tank should be noticeably cheaper if we go for 100 cm (39 inches) height above ground (less excavation, less concrete for the waterproof tank, less volume that needs elaborate moisture protection). Visually and regarding the terrace, 100 cm (39 inches) would be fine for us.

Is it worthwhile to go for the 100 cm (39 inches) basement height? What are your thoughts?

CheoRatharsair schrieb:

According to our architect, saving on 100 cm (40 inches) is possible, but it would hardly be worth mentioning.

I agree with that.

CheoRatharsair schrieb:

As I understand it, earthworks and the waterproof concrete shell (white tank) should become noticeably cheaper if we reduce the depth by 100 cm (40 inches) (less excavation, less concrete for the shell, less volume requiring extensive moisture protection).

This doesn’t save a huge amount of cubic meters of earthworks. And since the basement will be completely constructed as a waterproof concrete shell, it doesn’t matter whether it is fully underground or sticks out by one meter (40 inches). Everything is concreted regardless. And the moisture protection itself isn’t that complicated, especially since you are already building the waterproof shell.

CheoRatharsair schrieb:

Is it worth going for a 100 cm (40 inch) tall basement? What do you think?

What is the site situation and the building plan? You might save some money on the basement, but you could end up spending it again on modifying the terrain. The main entrance will then be one meter (40 inches) above ground level—creating a level entrance or stairs will both require additional expenses. Does the total building height still comply with the zoning regulations (building permit / planning permission)? How will it look overall? Personally, I find a terrace that high quite inconvenient for just stepping into the garden.
If there is no good reason to have the basement stick out above ground, dig it normally and enjoy what is likely a nicer and more practical house. This will also save you the significant extra costs for the entrance and terrace. Your potential savings might even be an illusion.
These are just assumptions since you haven’t introduced your building project yet, and in my opinion, your question can be answered in isolation but the answers can vary widely and be either right or wrong.

Thank you, Jens, for your assessment, that already helps me a lot.

jens.knoedel schrieb:

What is the situation with the plot and the building planning?

jens.knoedel schrieb:

since you haven’t introduced your house building project to us at all

Sure, I can gladly provide that:
Single-family house, two adults, currently one child, potentially two children in the future
Plot about 750 sqm (8,070 sq ft), located approximately 0.5 m (20 inches) below street level, in Baden-Württemberg, Karlsruhe district
House: basement, ground floor, upper floor (75% of ground floor area), total 190 sqm (2,045 sq ft)

Does that help?

In terms of costs, it is quite tight for us because, for various reasons (both working from home, children, low knee wall on the upper floor and limited upper floor space → we need a large ground floor to have enough room upstairs) we want/need to build relatively large. Therefore, if it’s even feasible, we plan initially to build only the house itself—not the garage, balcony, garden, etc.—and if possible and sensible, to partially finish the basement or certain rooms only.

Hence the question whether it might help financially to have the basement protrude 1 m (3 ft) above ground level (which the development plan would allow). This is purely a financial consideration.

I hope you are referring to an architect—and not just a draftsman for the building application, as many builders mistakenly call them. Given the presentation (at least as I read it), which seems primarily aimed at inflating the overall size of the house so that the attic does not qualify as a full floor, I still question whether the floor plan has been thoughtfully designed. It would also be helpful to see the nearly finalized plans, as I understand they are almost ready to be submitted.

First of all, congratulations on being open to a raised ground floor (this is often considered unacceptable nowadays by many homeowners, who want level access to the garden). I’m glad to read that the zoning regulations support this approach as well. Otherwise, I’ll keep it brief and simply express my agreement with the previous comment.

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Yes, we planned everything with a professional architect. The zoning plan states that the upper floor can only be 0.75, which basically means that the upper floor tends to be too small and the ground floor too large.

Is it common to post plans here? Personally, I don’t mind, but I’m not sure offhand whether this is allowed according to the contract with the architects. Do you have any experience with this in the forum?

Couldn’t you then convert the basement into fully functional living spaces? In that case, you wouldn’t need a finished upper floor, and the ground floor might not have to be that large either.