Number of stories - second full story only if it forms the attic

Hello everyone,

I am Christian and relatively new here in the forum. We are currently in the middle of planning our single-family house in Porta Westfalica (NRW). I have first listed the basic regulations from the development plan here:

Development plan/restrictions
Size of the plot: 923m²
Slope: yes
Floor area ratio: 0.3
Floor space index: 0.6
Building window, building line and boundary: see attachment
Edge development: n/a
Number of parking spaces: n/a
Number of floors: 2* (*the second full floor is only permitted if it forms the attic)
Roof type: 28°-45°
Style: no specifications
Orientation: no specifications
Maximum heights/limits: bases are only permitted up to a height of 0.80 m

We plan to build a house with a gable roof measuring 9x13m (no basement). If possible, we wanted to build the house with the 2 full floors permitted according to the development plan (knee wall with a minimum clear room height of 2.0m) in order to be able to easily place cupboards along all walls. We plan to have the gable run from northwest to southeast. If possible, we wanted to avoid dormers/gables.

The problem we are now facing is the restriction from the development plan that a second full floor is only permitted if it at the same time forms the attic.

But when is a floor an attic? I would interpret the whole thing so that in this floor (somewhere) the roof slope must start. Is that correct? Or are there "minimum heights"?

Is it then still permitted to have an attic/loft above the second full floor (i.e. the attic)? Are there any restrictions/guidelines regarding the loft, in terms of size or height, so that in the worst case it might again be counted as a new floor? What roof pitch would be recommended?

Best regards, Christian

The problem we are now facing is the restriction from the development plan that a second full storey is only permissible if it simultaneously forms the attic storey.

No, from my point of view, you do not have a problem – at least not a significant one.

But when is a storey an attic storey? I would interpret it so that the roof slope must start (somewhere) in this storey. Is that correct? Or are there "minimum heights"?

That is the problem others in your position have: they need to understand and apply the full storey definition. You don’t. You are allowed to build an upper floor as a full storey. Even with "full room height as knee wall."

Is it still permissible to have an attic/loft above the second full storey (i.e. the attic storey)? Are there restrictions/guidelines regarding the attic, in terms of size or height, so that in the worst case it might again be counted as a new storey? What roof pitch would be recommended?

I understand the restriction such that above this upper floor there may either be nothing more (i.e. no loft, accordingly open roof undersides) or at least no further residential storey: two full storeys, site coverage 0.3 and floor area ratio 0.6 would otherwise mean that—for example with consumed site coverage 0.25 and floor area ratio 0.5—there would still be 0.1 floor area ratio "left over" for a non-full storey above. At least that is excluded here. But: you are allowed to build with a knee wall as high as the eaves height allows—for that you will be envied by many.

Maximum heights/limits: Base walls are only allowed up to a height of 0.80 m

This means that to prevent a deeply projecting basement being inserted underneath, the ground floor should start no lower than 80 cm above ground level. What is already used up by ground slopes should fit together well with that. In this respect I read this restriction as probably insignificant.

We plan to build a house with a gabled roof measuring 9x13 m (no basement). If possible, we want to build the house with the 2 full storeys permitted according to the development plan (knee wall from min. 2.0 m clear room height) to be able to place cabinets easily against all walls. We plan the gable to run from northwest to southeast. We want to refrain from dormers/gablets if possible.

That seems quite feasible to me. If the ridge direction (= apex line between the gables) is required or not specified at all, then that fits. You don’t need dormers/gablets: "Full storey" practically allows you to have the straight wall height all the way up to the ceiling.

Slope: yes Site coverage: 0.3 Floor area ratio: 0.6 [...] Number of storeys: 2* (*the second full storey is only permissible if it forms the attic storey) Roof shape: 28°-45°

So I would also provide the walls in the upper floor on the eaves side with normal facade windows, with roller shutter boxes and ring beams, thus practically as a straight storey all the way up. If my suspicion is correct that nothing more should come above, I would then continue with open roof undersides (thus without a "ceiling"). But with at least 28°, that is unlikely—rather it means having zero residential storeys above. Then a loft would be possible, i.e. also with a ceiling an ordinary "straight" storey.

At 28° there would already be 2 m standing height over about 1.5 m width in the loft, at 34° it would be 3 m width.

Hello 11ant,

Thank you first of all for your reply. That would already reassure me a bit.
I also consider the option with the open underside of the roof to be unrealistic, but with some planners you really don’t know what they had in mind when creating the development plans.
We would definitely need an attic because we are building without a basement and of course parking spaces are scarce.

Is there a definition of when the attic counts as a separate floor?

So can I understand it this way, that the top floor is automatically regarded as the attic if there is no further floor above it, so that a sloping roof is not necessarily required on the top floor?

Is there a definition of when the attic is considered a separate floor? So can I understand it as the top floor automatically being regarded as the attic floor if no floor is above it, so that a sloping roof is not necessarily required on the top floor?

You are allowed to build the second floor as a full floor, i.e. without a sloping roof - on the condition that there is no floor above it at all (this probably means: none with living space - utility room, storage room or the like are a different matter). Normally, development plans only specify the number of full floors. You can then build more floors above, but these may no longer be full floors. This means you then add an attic floor with sloping roof, with or without knee wall - but in such a way that (depending on the state building code) certain room heights are allowed on a maximum of 2/3 or 3/4 of the floor area (measured based on that of the floor below). Your development plan is nice: it saves you, the one-and-a-half stories, from fiddling with knee walls, dormers, etc., and simply allows you outright a full second story without any ifs or buts. Hence also the floor space index of 0.6 compared to the site coverage ratio of 0.3. This way you can stack full 30% property area twice. In return, you are not supposed to pile any extras above, but be satisfied with the two full portions. That is a (envyingly rare) fair deal. To ensure that no one thinks, "well, then I'll just give my house more sitting height and let the basement stick out a bit," a limit is also set on the plinth height. Basically, so the deal remains fair on both sides. Those who want to build without a basement, i.e. who don't want a guest room or home office below anyway, are not bothered by this. So everything is in the green zone. What can now limit your "knee wall" is the eaves height. Suppose you have to use the 80 cm plinth due to the slope: then you would need 6.5 m eaves height for two flat roofless floors. The roof pitch is also very nice, 28 to 45 degrees is a pleasant range of variation. With 20 or 25 degrees, the attic would have been flatter. But with 28° you have 2.40 m at the ridge (or 2 m standing height over one and a half meters width), and with 45° 4.50 m at the ridge (in the example, 11 m ridge height would be required for that) or 5 m width of the 2 m high area.

You are allowed to build the second floor as a full floor, i.e. without a sloping roof - on the condition that there is no floor above it at all (this presumably means: none with living space - technical room, storage room or the like are a different matter).

: your statements are incorrect!

I would interpret the whole thing so that the sloping roof has to start somewhere in this floor. Is that correct?

That is correct.

Is it then still permissible to have an attic/loft above the second full floor (i.e. the attic)?

yes

Are there any restrictions/guidelines regarding the attic in terms of size or height, so that in the worst case it might again be counted as a new floor? What roof pitch would be recommended?

§ 2 Building Code NRW:
(5) Full floors are floors whose ceiling upper edge protrudes on average more than 1.60 m above the ground surface and which have a height of at least 2.30 m. A top floor recessed relative to the exterior walls of the building (setback floor) is only a full floor if it has this height over more than two thirds of the floor area of the floor below. A floor with inclined roof surfaces is a full floor if it has this height over more than three quarters of its floor area. The height of the floors is measured from the top edge of the floor to the top edge of the floor of the ceiling above; for floors with roof surfaces, up to the top edge of the roof covering.

: your statements are wrong!

I agree with that.

That's right.

Do you mean without minimum requirements, so that for example a 5cm roof slope would already be sufficient? I would have this confirmed by the local city planners, as I am not aware of any definitions of an attic in laws and regulations. I think it is similar to the case with clipped gable roofs, which are often used to reduce the distance areas. There is no exact definition here either. In practice, a limit was drawn at some point as to when a clipped gable roof is no longer a clipped gable roof.

Is there a definition of when the attic counts as a separate floor?

The attic is a floor, just not a full floor. Your neighboring properties are already built on. What does it look like there?