ᐅ Additional Costs for Residential Units

Hello,

I am currently planning a new build (my first), which is intended to have 2-3 residential units and will likely aim for an energy efficiency rating of 40+. Essentially, it could be called a multi-generational house. Initially, only 2 units will be developed (one on the ground floor and one on the upper floor), but in the future, a third unit is planned for the attic. I would like to leave the attic unit as a shell at first, but have all the connections, wiring, and so on installed. The goal is to avoid any further construction work later so that it can be used as a separate unit.

As far as I know, a separate residential unit requires the following conditions:
- Its own lockable entrance
- Its own electricity meter
- One kitchen connection each
- One bathroom connection each (toilet and shower)
I hope I haven’t missed anything here. If so, please let me know.

Now to my question: To plan a bit better, I would like to get an idea of how much an additional residential unit costs in terms of installing connections for an extra kitchen and an additional bathroom, as well as setting up a separate electrical circuit with its own electricity meter in the utility room. In other words, the extra costs you should budget for when turning a standard single-family house into a house with 2 or 3 units.

For now, I am only interested in the cost of the connections—that is, the potential for an additional unit—not the cost of the kitchen or bathroom fixtures themselves.

I hope you can help. Many thanks in advance for any comments and explanations!

Felix85 schrieb:

I hope you can help me. Thanks in advance for all comments and explanations!

Try searching using keywords like accessory apartment and KfW. You will see that there are FAQs where you can repeatedly read that acting as a landlord for a quantity of "one housing unit" is often a zero-sum game or much ado about nothing, and that the KfW efficiency level 40 as a target is viewed critically and controversially.

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Hello,

thank you in advance for your reply! I have indeed already searched the forum. It’s possible I missed some relevant threads, but mostly I just found posts accusing other forum members of “overbuilding” and “trying to get subsidies.” Sorry, that wasn’t helpful for my question. My concern isn’t so much about financing (I’m not really worried about the money, though of course I don’t want to pay more than necessary).

My question is more technical and budgeting-related: roughly what should one expect to plan for to provide connections for a kitchen, bathroom, and a separate electricity meter on an additional floor? Are there other significant costs involved when creating an additional residential unit?
Further questions would be along the lines of: Can these costs be reduced (for example, by placing the relevant rooms stacked vertically)? Or are there general tips on designing a house with multiple residential units to keep it as cost-effective as possible?

The fundamental question is whether three residential units are permitted on a single plot within the planned building area. Considerations should also include requirements such as necessary parking spaces for cars, etc.

Only the connections shouldn’t be too expensive if they are already in place and just need to be extended to an additional floor.

A shell construction intended for "future expansion" does not qualify for KfW funding: sanitary installations must be present, and residential units generally need to be completed to receive subsidies. Planning for future expansion alone is not sufficient.
It is also not enough to declare a space or attic with a drain, shower head, and wiring with an outlet for a stove as a separate dwelling unit.
So: do whatever you want. But don’t expect official approval for a future plan.

kbt09 schrieb:

Considerations also include things like the required parking spaces for cars, etc.

The property will have three parking spaces. However, I wasn’t aware that this is mandatory. Is it required to provide parking spaces in order to classify a residential unit as such?

kbt09 schrieb:

Are three residential units allowed on one plot in the planned development area?

This is currently being clarified. A friend has also pointed out to me that this might not be allowed.
A follow-up question: Are secondary apartments assessed differently than residential units? For example, would there be one main unit and two secondary units rather than three equivalent residential units? Has anyone been in a similar situation and had experience with this?

ypg schrieb:

Only the connections shouldn’t be that expensive if they already exist and just need to be extended to another floor.

Could you give a more specific estimate of the costs per residential unit/floor? Is the separate electricity meter, which I understand is also required for each residential unit, a significant cost factor? Or is it basically straightforward to install one meter per floor in the utility room without major difficulty?

ypg schrieb:

A shell construction for “later finishing” is not eligible for KfW subsidies: sanitary facilities must be installed, and residential units generally have to be completed to qualify for funding. Planning for future finishing alone is not sufficient.
It’s also not acceptable to declare a room or attic with a drain, showerhead, and wires with an outlet for a stove as a secondary apartment.

That’s interesting. Is there an official regulation or guideline specifying exactly what must be in place for KfW to recognize a residential unit as such? A few years ago, an architect/developer assured me that for KfW, the mere potential of a residential unit was enough, since the goal is to provide energy-efficient living space for more people. Of course, all wiring and connections must be present, but by the end of construction the kitchen does not need to be installed and the bathroom furnished. The loan would already have been paid out by then, meaning the subsidy was already granted. Or is it the repayment grant that would then be denied?
A full attic conversion is not crucial for us in terms of space at this stage, so I would like to do that later, but at the start create all the prerequisites so that I would only have to do the interior finishing (tiles, flooring, wallpaper, furnishings) later when the unit is occupied.

ypg schrieb:

So: do as you wish. But don’t expect official approval for a future plan.

I’m certainly not expecting official approval from a forum 😉 No worries. What I hope for are some information and general exchange with more experienced home builders.