Is this effort worthwhile for the tenants?

Hi,

quick question for the experts: we might want to rent out our hobby room as a granny flat later on. The room is located in the exposed basement level, with floor-to-ceiling windows. We are planning all the connections for electricity, bathroom, etc. What’s bothering me now are two things. The granny flat itself and the wall thickness. The exterior wall is 24cm concrete + 12cm perimeter insulation. The interior walls, which basically separate the granny flat from our main entrance and the utility room, have now been planned as 24cm brick. That seems a bit much to me. We are already losing a few square meters of living space because of that. How thick does the wall really have to be? Wouldn’t 17.5cm be enough, for example?

We don’t even know if we will ever rent out the granny flat. Because of its size (about 30m²), it’s really only an option for students anyway. We just wanted to be prepared, either for our own children or for renting to family members / students. Maybe we will live abroad for a few years and thought it would certainly be an advantage to have two sources of rental income then.

I’m just wondering if the effort is even worth it, considering the room size. The room will be very bright, but the separate entrance door with certain security features alone already cost us €2500. The connections cost another €5500, bathroom construction, etc. So we are easily at €10,000.

Only if we don’t do it, we might regret it sometime. We definitely do not want to rent to strangers as long as we live in the house. At most, as mentioned, to student family members or then when we are abroad for a few years. In old age it could supplement the pension if needed. But currently renting to strangers while we live here is no option, only family.

Well, the connections are being installed now anyway. That’s okay. Even for the hobby room, a kitchen corner and a toilet are very useful.

Still, I’m interested in your opinion. And how thick do the interior walls really have to be (for rental)? 24 or is 17.5 enough? Or even less?

Hello Stefan,

Nevertheless, I am interested in your opinion. And how thick do the interior walls (for rental) really need to be? 24 or are 17.5 enough? Or even less?

In your place, I would be less interested in the opinions of forum users and more in your structural engineer's. 24 cm walls are usually the load-bearing walls.
Otherwise, to my knowledge, there is no clear regulation. However, I would stick with the 24 cm walls.

If the connections are being laid straight, how can the wall thickness still be an issue? Or in the floor slab?

As Joche said, a structural engineer has to assess that - he specified it after all. We always have 17.5 cm load-bearing bricks - but KS, so it's possible then ;).

Hello!

I don’t believe you will ever be able to recoup the costs in this constellation. When an overseas stay is imminent, the entire property is either sold or rented out so that there is only one point of contact and one billing. When renting within the family, it is questionable whether anyone studies in S or the surrounding area at all, and if so, whether they pay a market price. Probably not. However, a room rented within the family (!) does not need to meet the standard of an official separate apartment (certificate of separability/second front door, etc.).

If you actually need additional income in old age – do you then want to rent out a 30-year-old bathroom? Probably not, or only on rather bad terms, ergo generally uneconomical. If you keep that in mind, lay the connections and build the standard so (low) that it is sufficient for personal use and family purposes. If renting does become necessary, renovations, a new bathroom, etc. must be done anyway, which can also be achieved with an additional small external apartment.

Your architect should also clarify which requirements are necessary for a certificate of separability. If this is linked to a certain wall thickness, you need to consider whether it is worthwhile. If statically required, the discussion is settled anyway.

Basically, renting out single units/in-law apartments is associated with high risk, as all losses affect the single unit. I had originally considered this as well but have completely backed away from it. If you look at it economically, you have to rent out permanently; otherwise, it is a nice-to-have investment that will most likely not pay off. Then the 10,000€ for the refurbishment have to be completely irrelevant to you or you have to be aware that you first wear it out and then adapt it to the situation again in 25-30 years.

Best regards
Dirk Grafe

Interesting perspective, Dirk. I haven’t seen it that way before. So the 24 cm wall is probably structurally necessary. Nothing can be changed there. The connections are floor penetrations. We’re not doing the bathroom for now. We’re just having the walls and connections built, and tiling and sanitary fixtures will come when needed. Well, now it’s too late to do without the separate entrance door. The basement is currently being poured and I guess we can’t revise that anymore. So we’ll have to live with it now. You never know what will come. Maybe someday we’ll have to accommodate a family member. I don’t hope so, but at least now we would have the option.

If you are already at it, then you have financially planned for it anyway. I would simply have the connections installed. They won't do any harm. What you do with them can still be decided later.