Two-family house new construction - Which costs to calculate?

Report on your experiences, gladly also via PM.

I have no experience with that. I just browsed the website and spoke with a colleague who is apparently going to build together with this company in 2016. She finds their layouts and designs so great – and the prices are supposedly quite close to what is advertised on the website. But as I said, no solid information here.

From my own experience, I can only advise you to think about an architect sooner or later. At the latest when you are also considering an additional granny flat, i.e. planning 3 residential units.

But the architect doesn’t work for free. Or can I just go there and say, "Hey kid, make me a plan, but I don’t know yet if I’ll ever build because I don’t even know if it’s financially feasible"?

Don't forget that the KFW loan only runs for 10 years. That means after 10 years, the follow-up financing must be taken care of. And if you finance two residential units at 100,000 each, there will still be a large sum left after 10 years, since KFW loans are generally not paid off that quickly. And since market-standard interest rates or worse usually follow, the burden can increase significantly. This has already broken the neck of many.

That is not entirely correct. He is referring to the new conditions from 04/2016. And there will also be a 20-year fixed interest rate.

After having looked at a few plots of land, I at least have a somewhat better idea of what my future house could look like. I am not an expert when it comes to reading development plans, but if it says 2 full floors, wall height 7.50m, ridge height 12m, and floor area ratio 0.4, then I understand that for a plot of 550m² (20m*27.5m) - I am allowed to build on 40% of the plot, so 220m², with a maximum of 2 floors. That should be enough for a house with my requirements and a double garage.

What exactly does full floors mean here? If the maximum heights are used, 7m wall height would not allow more than 2 floors anyway. Assuming 2.50m ceiling height and 50cm ceiling construction, a third floor is out of the question. But I could still convert the attic. If I calculate 3m height for one floor, and then the roof with about 1m knee wall, then I can basically still use the "attic" as a full floor - but this does not count as a full floor - right?

What would a basement roughly cost compared to building a utility room (which costs living space) otherwise? Doesn't a basement save energy in the long run because the living spaces are better insulated from below? Or is that a myth?

Would it make sense to integrate the garages into the basement so that the basement area is not quite so large?

At what point is it sensible to consult an architect to discuss something like this? They don’t have to make exact plans yet, just show what is feasible within which budget and what is not. But do they work for free for me hoping that they will eventually get a commission from me?

And according to which criteria does one choose such an architect? Would it make sense to commission a large company where everything is already coordinated? Or should one rather give "smaller" ones the chance to plan and let them organize everything as well?

Hello,

It’s about development plans, but when it says 2 full storeys, wall height 7.50m, ridge height 12m, and floor area ratio 0.4

What exactly does full storeys mean here? If the maximum heights were fully used, with 7m wall height no more than 2 floors would be possible anyway. Assuming 2.50m ceiling height and 50cm floor thickness, a third floor is out of the question. But I could still convert the roof. So if I calculate 3m height for one floor and then the roof with about 1m knee wall, I could practically still use the "attic" as a full floor – but this would not count as a full storey – right?

**According to the NRW building regulations, a full storey is a storey that protrudes more than 1.60m above the average ground level and is at least 2.30m high, measured from the top edge of the floor to the top edge of the floor of the storey above or the top edge of the roof covering of the storey above.

The following are not considered full storeys:

[*]Storeys used exclusively for housing technical building equipment and heating systems

[*]Top storeys where the height of 2.30m exists over less than three quarters of the storey below.

The following are disregarded:

[*]Voids between the top floor and the roof, whose clear height is less than that required for habitable rooms according to the state building code (2.20m over at least half of the floor area, parts of the room with a clear height up to 1.50m not counted)

[*]Mezzanines up to a floor area of 20 m².

# This varies slightly between federal states, but the gist remains the same.

The wall height here marks the external height of the outer wall from the fixed reference point NN at the intersection of the rising roof covering including a possible knee wall, unless another reference point is mentioned in the development plan/the textual specification. To achieve a clear finished height of the interior rooms of 2.50m on the ground floor and upper floor, you can roughly assume a raw structural clear height of 3.00m (sometimes less depending on provider). Depending on NN and permitted roof pitch (DN), a well usable attic can therefore be created in your example.

How much more would a basement roughly cost compared to building a utility room (which counts as living space)?

What is the floor area of the two-family house?

Doesn’t a basement save energy in the long run because the living spaces are better insulated from below? Or is that a myth?

A basement is usually built as a utility basement; without heating. Only the utility room must be additionally insulated according to the energy saving regulation.

Would it make sense to integrate garages into the basement so that the basement area is not quite as large?

That entails additional costs regarding separation from the other basement/ground floor rooms as well as the required ventilation. Moreover, it is advisable to additionally heat the driveway to the integrated basement garage.

At what point does it make sense to consult an architect to discuss something like this? They don’t have to make exact plans yet, just show what is feasible within what financial scope and what isn’t. But do they work for free for me in the hope that they will eventually get a commission from me?

From the moment you are sure that building the house or the building application is only conceivable for you with an architect. Most architects offer free initial consultations where both parties can get to know each other. But beware: a simple "just do it" closes the contract, and all subsequent services must be paid for according to HOAI.

Edit: however, you should already have purchased a plot; unless you involve the architect in the property search.

And by what criteria do you choose such an architect? Would it make sense to commission a large company where all the parts already mesh? Or do you rather give "small" ones the chance to plan and let them organize everything?

For example: drive through residential areas and look at the architectures; ask homeowners about their experiences; ask friends and acquaintances; look at architects’ websites to see if you like their work – almost every architect can be recognized by their designs.


**Source: my website

Rhenish regards

The floor area of the house is still not entirely clear to me... I just want everything to fit as much as possible within the financial framework, but still fulfill our wishes as much as possible..

You mentioned some numbers a few posts ago, and if I add up everything discussed afterwards, without a basement, it comes to an estimated 630K€ (with the construction method "side by side"). Where would we get to with a basement?

I want the following "wishes" to be considered:

- Apartment for parents, everything (~100m²) on one level, only storage room and utility room/HAR could be on a different level
- Apartment for the parents on the lowest level because of age. A granny flat would also be conceivable if the size is appropriate... Although I somehow can’t imagine a difference between an apartment and a granny flat...
- Apartment for my family preferably divided over 2 levels (a total of ~150m²), a study room (but only this one) could also be in the attic (thus 3rd level), if you can move around properly there (currently I have it like this too, but the attic almost has no area with more than 1.5m height)
- A balcony would be nice on the upper floor
- At least a double garage, but better would be a garage that fits 3 vehicles and a trailer

So if I keep the floor area as small as possible (100m²), the parents’ utility room would have to be in a basement. Or is it cheaper to do without the basement and instead have about 20m² more floor area for a utility room?

If the bedrooms should be located at most on the first upper floor, then almost the entire apartment has to be on this level. But since this is larger than the apartment on the ground floor, something doesn’t add up...

Maybe my way of thinking is just completely "nonsense".