ᐅ Semi-detached house within a building plot measuring 8.5 m by 15 m (width x depth)

Dear housebuilding forum,

After several years of searching, we have finally purchased a plot of land (with an existing building to be demolished) in our desired location. This also marks the end of my many years of purely passive participation in this forum. Since we were primarily looking for renovation projects rather than new builds, we naturally have some initial questions.

The plot, approximately 500 m² (5,400 sq ft), lies within the scope of a development plan that was last updated 20 years ago.

Basic data about the plot and development plan:

• Building is permitted from 3 meters (10 ft) to 18 meters (59 ft) depth (so 15 m (49 ft) for the house)
• After deducting setback areas, a width of 8.5 meters (28 ft) is possible
• Slight slope across the building envelope with a rise of approximately 2.2 meters (7 ft)
• 3 full floors permitted
• Site occupancy index (ground coverage ratio) 0.4
• Floor area ratio 1.2 (cannot be fully utilized due to the aforementioned building envelope)
• Roof pitch 35–45°
• Knee wall (dormer wall) height 60 cm (24 in)
• Base (plinth) max. 60 cm (24 in) above the midpoint along the width of the access area, which is itself 30 cm (12 in) lower than the start of the building envelope
• General residential zone
• Open building style (detached buildings, no shared walls)
• Covered terraces allowed up to 1.5 meters (5 ft) outside the building boundary, provided the site occupancy index is not exceeded
• Roof indentations and structures permitted up to half the eaves length and at least 1 meter (3 ft) from the gable wall
• Fencing with native hedges. Along the street, an additional fence up to 1.2 meters (4 ft) high is permitted.

The development plan places no restrictions on, among other things:

• Building type
• Number of residential units per building
• Height limits
• Basements
• Parking spaces

The plan is to build a semi-detached house with another family. Both families have two children each and require two home offices, resulting in a need for six rooms per semi-detached unit. If we make progress here, I will create another thread in the floor plan forum and fill out the questionnaire.
Since the building envelope width of 8.5 meters (28 ft) is too narrow for semi-detached units side by side, they would have to be arranged one behind the other. Garden access and terraces would then be located on the narrow sides (one facing the street and one facing the main garden at the rear). This type of semi-detached house is quite rare. I have looked around in real life but have not found any examples. Only the Büdenbender semi-detached house Gemello SD 135 roughly corresponds to this layout (though not to the measurements).

I have had some informal discussions with an architect I know (who now only works on office buildings) and the building authority, without encountering any fundamental contradictions so far.

I have already applied the @11ant basement rule, according to which a basement seems obligatory because there is more than 2 meters (7 ft) of height difference within the building envelope. However, I do not understand how this relates to the “base (plinth)” restriction of max. 60 cm (24 in) in the development plan. My layperson assumption would be that one floor (the ground floor? the lowest residential floor? the lowest full floor?) may start a maximum of 60 cm (24 in) above street level.

My first questions for you:

• Are you familiar with similar houses, possibly with names for Googling or similar?
• Would you approach this topic differently?
• What does the rule about the base (plinth) mean?

Thank you in advance,
Gregor

You seem to interpret the base correctly. However, if you want to place a complete duplex on just one of the four building plots within the building envelope, I don’t see that as feasible. At least, from the small excerpt of the development plan, I don’t read any prohibition against positioning the building ensemble with the gable facing the street. Functional semi-detached houses (see among the "usual suspects," Büdenbender does not count) typically measure 6 m (20 feet) in half of the eave length and 12.5 m (41 feet) in gable depth, with roof pitch around 35° or 38° (roof pitch angle), and offer about 140 to 145 square meters (1,500 to 1,560 square feet) excluding basements, which are rare in this area. With 7.5 by 8.5 m (25 by 28 feet), you can only replicate that if the basement is converted into a livable lower ground floor. Where are the parking spaces supposed to be or allowed to be placed?

---

https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/

Hello, could you please mark your plot on the site plan?

Please also provide the dimensions of the plot.

If you plan and build together with the other semi-detached house, you can save a lot of money.

Plans for semi-detached houses on a slope are rather rare online. You will then have the garden at the basement level.

Placed lengthwise means that for the second house, the basement is completely built into the slope, while in the front house, the basement is a fully usable floor.

Otherwise applies

hanghaus2023 schrieb:

Could you please mark your plot on the site plan?

Please also provide the dimensions of the plot.

And maybe a slightly better scan so the contour lines can be seen more clearly?

GregorBerger schrieb:
Slight slope over the building plot with an increase of about 2.2m (7.2 feet)

I would also appreciate a site plan with dimensions, and please mark the building plot and the slope.

GregorBerger schrieb:

Do you know of any similar houses, possibly with a name to look up on Google or something like that?

In our area, there is a very narrow plot that was developed like this:
At the top (north) is the street with parking spaces, the entrances are on the east side, and the gardens are on the west side. They are attractive houses. The entrances are set in bay windows, which are allowed by the regional building regulations. On the west side, there are two dormer windows for two bedrooms each. The plot is flat.

GregorBerger schrieb:

The development plan does not specify requirements regarding the following:

• Type of building
• Number of housing units per building
• Height restrictions
• Basements
• Parking spaces

There is always a textual regulation with a development plan. WA stands for general residential area, which you can look up to understand the details. Each federal state has its own parking regulations and building code. Anything not regulated is free to decide.

GregorBerger schrieb:

Because the building envelope is 8.5 meters (28 feet) wide, too narrow for semi-detached houses to be placed side by side, they would have to be arranged one behind the other.

GregorBerger schrieb:

• Construction is allowed from 3 meters (10 feet) to 18 meters (59 feet) depth (so 15 meters (49 feet) for the house)
• Minus setback areas, 8.5 meters (28 feet) width is possible

Luckily, you can do some calculations with the few parameters available. A 500 sqm (5,382 sq ft) lot, 8.5 m (28 ft) plus 2x3 m (2x10 ft) setbacks equals 14.5 meters (48 ft) width, and about 34 meters (112 ft) length. The building envelope is definitely 8.5 by 15 meters (28 by 49 feet), allowing 127.5 sqm (1,372 sq ft) to be built over. With exterior walls 40 cm (16 inches) thick, that leaves about 109 sqm (1,173 sq ft) of usable living space, so including the dividing wall, about 53 sqm (570 sq ft) of living area per unit. (This essentially forms our open-plan space.)

This is only possible if the front setback of 3 meters (10 feet) is not exceeded. On the left and right (driveway/access and garden) there are also 3 meters (10 feet) each. Question 1: Where will you park?
Question 2: How will you divide the plot conceptually? Who gets the back half, which is essentially the premium part despite the slope, because the front half is basically a small area (house plus 3 meters (10 feet) all around, although certainly no terrace can fit within those 3 meters (10 feet). This also quickly brings you close to a floor space ratio of 1.2.

So: 3D modeling isn’t necessary. A bit of calculation will suffice. I would keep it as a semi-detached house, no matter which way. You probably won’t be happy otherwise.