100-110m² bungalow: How much living space is possible in the attic? What are the costs?

Hello everyone

We are considering, if we get approval for a plot of land, to build a second time.

Even though we are both only 30, we really like the idea of a bungalow that is built as age-appropriate as possible (1 meter doors, walk-in shower, etc.).

Now the idea came up to build a bungalow with about 100-110m² and over the course of the year after moving in to finish the entire upper floor ourselves and create partition walls as a lightweight construction system.

So, generally asked first: How many m² of living space can you expect in such a attic ("usual" building plan regulations, ridge height max. 9.5m) with 100-110m² living space on the ground floor?

What do you think such a roof would cost as an additional price compared to the lightweight construction variant? The plan is to have screed including underfloor heating directly in the upper floor.
Can someone roughly say what a bungalow, solid construction, brick-faced with a maximum roof pitch + screed in the upper floor including all additional costs would cost?
According to my calculation, I come to about €170,000, without kitchen, without garden, and without land/notary/property transfer tax. The plot will cost about €80,000 including notary/property transfer taxes. €30,000 is then planned for kitchen/garden.

Many thanks for any advice

Do you want to build a 110 sqm bungalow, or a classic one-story single-family house with a converted attic? If the development plan allows it (9.5 m ridge height is quite something), I would also consider a two-story construction and any knee wall height in between.

We have 2 bungalows among acquaintances - one of them has a Nagebilnderdach with cross and diagonal braces - there is no way to convert that. The other one does have a walkable roof, but it is not designed to bear the load of a normal living floor.
Our attic, for example, is statically designed for only 1.6 kN/sqm (160 kg). Screed, insulation and flooring already weigh about 165 kg/sqm on the ground floor ceiling. Of course, you would choose a different floor structure there, but it must be urgently considered in the planning.

We assumed that we would come out a bit cheaper if we first build a bungalow with 100-110m² and later fully develop the attic. A normal 1½-story gable roof house is of course also an option. But there, a steep roof pitch and a second staircase would also be necessary to convert the attic into a sewing room/storage room. The question is what is cheaper, plus a bungalow always has the advantage that you can easily live on the 100-110m² on the ground floor in old age.

Screed in the attic is not a must, but unfortunately with flow temperatures of 30-35 degrees, you cannot heat the upper floor without underfloor heating in the screed. We currently have a fairly large radiator installed in the attic of our semi-detached townhouse villa, which according to the heating installation should be sufficient at 30-35 degrees. No chance, it doesn’t work at all.

Of course, I haven’t yet thought about the ceiling load caused by the screed and the consequently even higher costs. I would now naively have assumed that you pay about ~10,000€ upfront for the bigger roof, another 4x 750€ for 4 roof windows, 5000-6000€ for the screed and the underfloor heating, and that would be it. Electrical work/attic development would be done on our own.

A building expert can probably say more about this - but I think that a gable roof house without a finished attic and without a knee wall is not significantly more expensive than a bungalow - gable walls, however, mean less roof area and - I believe - also a somewhat simpler roof.

110 sqm living space. The ground floor, however, is not as cozy as one might think, but rather quite large.... somewhere around Viebrockhaus Maxime 495 Z. We have something similar - about 105 sqm on the ground floor and 85 sqm on the upper floor - and it turned out to be a master bedroom with bathroom on the ground floor and otherwise just the usual rooms (by the way, we now do sleep in the attic, since sleeping downstairs felt weird )

But back to the basics: you have a house and want to move out - why? So why no longer does it meet your requirements? What are your requirements? Do you want to have children?
Thinking about age is a good thing - we did that too - but to severely limit yourselves now (or to build a house that is way too big) seems nonsense to me. You can still climb stairs well for at least 40 years. If the development plan allows it, you should also consider a two-story house - that can surely also be done with drywall on the upper floor or at least not executed yet.

P.S.:
When expanding, you should make sure to heat the part of the house from the beginning, otherwise you risk being surprised by mold there.

P.P.S.:
Conclusion: I would either build a real bungalow - then according to your requirements; if with children's rooms rather around 140 sqm or alternatively normally with an attic or two stories.

We currently live in a semi-detached house, unfortunately a city villa was built here due to the quite low floor area ratio of 0.25 (approx. 300m² plot).
With small city villas (ours has 110m² without the attic), the ground floor is extremely small compared to a normal gable roof house.
As a result, we have a "only" 26.5m² living room, which would not be the biggest problem; by now, the utility room with its approx. 4m² is simply far too small, the stroller is standing in the already small hallway, and so on.
In addition, due to building law (building boundaries), no carport/garage can be built, if at all then in the middle of the already small plot.

The second essential point is: our current loan has an interest rate of 4.2%, and expires in 6 years. The plan was to rent out the old house for at least 6 years, possibly sell it afterwards and completely repay the expensive loan with a small profit. Basically, according to the plan, we would acquire a larger, detached house with a much bigger garden on a fixed 25-year loan.
Electricity, tiles, attic conversion, garden landscaping, painting work, etc. would be done by ourselves.

The question is whether all the wishes can be realized for a maximum of €280,000 (80,000, up to a maximum of 95,000 would be the cost for the plot including property transfer tax/notary) including kitchen, stones for paths/driveway, garden house, etc.

We assumed that we would come off a bit cheaper if we first build a bungalow with 100-110m² and later fully expand the attic.

It still remains a classic single-family house; a bungalow has only one level: the ground floor and maybe some basement as storage space.

A normal one-and-a-half-story gable roof house is of course also an option. However, that would require a steep roof pitch and a second staircase to convert the attic into a sewing room/storage room. The question arises what is cheaper, moreover a bungalow always has the advantage that you can easily live in the 100-110m² on the ground floor in old age.

A real bungalow – that is, one level – is always more expensive than a classic one-story house. Before you can expect a reliable answer, you have to decide what you really want. One-story single-family house or bungalow? Rhenish regards