Basement for a small recording studio, or rather an extension?

Hello everyone!
My family and I intend to build in the near future. The plot has already been purchased, an architect has been found, and many components are already relatively clear to us. We will build using solid wood construction. We don’t have many requirements: besides an open ground floor with kitchen, living room, utility room, shower bathroom, and work area, there should be a master bedroom and two children’s rooms on the upper floor. So far, so simple.
The following point is more complicated: I am a musician and would like to integrate my small recording studio into the house. I work alone in it, so it is not a studio with through traffic. Music is also to be made and practiced in the room. The room should be about 30 sqm in size. We had long considered an acoustically separated extension, but our architect suggested that a basement might be more sensible. For cost reasons, we actually wanted to do without one. But the architect is right: an extension naturally causes very different costs than a basement.
Moreover, the soil in the first 2 meters is very humus-rich, so we would have to remove 2 meters of soil and refill it with sand anyway if we didn’t build a basement. In that respect, it does make sense.

By the way, the soil expert recommends a white tank. We will have a ground area of about 9x9m, so the basement will be around 80 sqm in size. As a living basement, it must also be insulated. I also want natural light in the studio, so the idea is to design the basement as a high basement and to take advantage of the slightly sloping plot by terracing it to the south, so that the basement is at ground level on the south side.

Now my question to you: does this make sense to you in terms of costs? Or can you imagine a cheaper realization for the room? Considering all these mentioned points (terracing, insulation, white tank, high basement, ...) could a realization as an extension still be cheaper? Integrating the room into the upper or ground floor is difficult in terms of space, as the floor area is hard to expand due to a rather low building window (with an extension it would be possible, since the plot is triangular and a smaller building body would fit beside it). The house can also only be built as 1.5 stories, so using an attic is also not an option. Do you have experience with providers of prefabricated basements?
So, I would appreciate your opinion!
Best regards,
Willem

Hello Willem,

The room should be approximately 30 sqm. We had long considered an acoustically separated extension, but our architect pointed out that a basement might make more sense. For cost reasons, we actually wanted to do without it. But the architect is right: an extension naturally causes very different costs than a basement.

That is not fundamentally correct. Realizing a ground-level extension is always cheaper than sinking expensive money into a basement.

In addition, the soil in the first 2 meters is very humus-rich, so we would have to remove 2 meters of earth anyway and fill it with sand if we didn't build a basement. So it does make sense.

Well, gravel is not that expensive.

By the way, the soil surveyor recommends a white tank (waterproof concrete structure).

How expensive this will be ultimately depends on the shape of the adhesive sealing recommended by the surveyor. It will certainly be around TEUR 5.

Now my question to you: does this make sense cost-wise for you? Or can you imagine a cheaper realization for the room? Considering all these mentioned points (excavation, insulation, white tank, raised basement, ...) could a realization as an extension be cheaper?

One thing is certain – either way, there will be additional costs for you, because acoustic separation upwards (from the basement perspective) or to the side (from the extension perspective) certainly does not come cheap. I don’t think egg cartons, like we used to, will be sufficient.

Integrating the room into the upper floor or ground floor is technically difficult in terms of space, as the floor area is hard to expand due to a rather low building window (with the extension it would be possible, as the plot is triangular and a smaller building body would fit next to it). The house can only be built 1.5 stories high, so utilizing an attic wouldn’t work either. Do you have experience with providers of prefabricated basements?
So, I would appreciate your opinion!

I would – as a living partner – certainly not tolerate the recording studio in the house; I know how loud it gets and how often doors open and close once the music junkies get going. Eventually, the cola will find its way outside.

It’s difficult to answer your questions because I lack prices for gravel in HB. I would therefore recommend having your architect calculate; I can then adjust the cost estimate – excluding soil replacement – to realistically expected values.

A basement will cost you about TEUR 35. The fact is that the basement, finished as a liveable basement (insulation, underfloor heating everywhere, etc.), will cost around TEUR 15; in addition, adhesive sealing according to DIN haumichtot about TEUR 5, and one or two floor-to-ceiling window elements another TEUR 2.5 to 4.5 depending on size and whether electric or manual shutters. Masonry exposed due to excavation has to be plastered as well; assuming one cross side and a bit left and right, that adds another TEUR 2.5. The big question is what the gravel costs and what quality it must have. Quickly, I found a price indication of €13.00/cubic meter/gravel/sand mix. This would mean that soil replacement accounts for about TEUR 2.1; however, you have to have this done anyway.

A ground-level extension costs – with 30 sqm and a simple gable roof – about TEUR 42; naturally plus soil replacement €780.00.

Both in the basement and extension, additional measures must be taken so that the sound does not spread uncontrolled; or the bass does not drive the residents or neighbors crazy. What this might cost – I unfortunately have no idea.

Even if the above numbers are “only” approximate – and additional costs for soundproofing will be added – you can already see that the basement – with all the difficulties you described – is still quite a swallow from the bottle in comparison to the extension.

As I said, have your architect calculate and then you’ll see; some numbers you already have now.

Best regards from the Rhineland

Quick question to construction expert: How do you come to use gravel as filling material? You use "good" sand, right, or was I given the wrong explanation? We partly have gravel/crushed stone on the property, which has to be removed separately...?

Quick question for the construction expert: How do you come to use gravel as filling material? You usually use "good" sand, or was I misinformed?

In most cases it is a gravel mixture; the soil expert will specify the quality.

We partly have gravel/crushed stone on the property, which has to be removed...?

How should I know? You have to check your soil report to see what it says.

Rhenish greetings

What should you know? Didn’t have a question anyway

Soil survey, what is that

Soil survey, what is that

Your warranty for the stability of your house - without a survey there is no warranty