Designing hillside property - Earthworks / Retaining wall cost options

Hello everyone,

after having read here in the forum for a long time, I would now like to get in touch with my concerns.
We have bought a 600m2 sloping plot in a new development area and are currently in final negotiations with a prefabricated house supplier.
However, I realize that the plot is not so easy to design, and therefore the plot/garden planning should ideally be considered from the very beginning.

I would be interested to hear what you think about our concept and how you would proceed.

I have attached 2 pictures of the plot (one from below, one from above) and one visualization with rough height specifications for the plot planning.

1. The plot has 600m2 and is roughly square with 25x25m. It has a slope from west (street side) to east of approx. 4m and a slope from north to south of approx. 1.5m.
2. The gable roof house will be 9x10m (2 storeys) offering 140m2 plus a full basement. The basement faces west (street side) and is about half exposed, and the rooms there will be developed as living space.
3. The house should be moved to the north/east side to free up as much garden as possible in the south and west.
4. The house entrance should also be in the north because we do not want to enter the house through the basement. The northern side will therefore be a driveway with a carport in front of the front door.
5. The single-family house is fixed according to the development plan. With the lowest point of the plot normalized to 0m (north/west), the single-family house will thus be at approx. 3m.
6. If I subtract 50cm for the ceiling, 30cm space between ceiling and upper edge of the window, 90cm window height and another 30cm for distance from the floor to the bottom edge of the window, this results in approx. 2m that the basement must be exposed compared to the single-family house.
7. This means there is a height difference of 2m in our garden between the west side (in front of the basement) and the south side (our terrace).
8. I am now wondering whether it makes sense to introduce 3 levels (as in the picture), or whether one should extend the 3m height from the south side up to the street and then have a relatively large 2m difference to the rest of the garden. This would probably be significantly cheaper, as we would have to pay much less landfill/earth transport due to embankment. However, this would require a higher retaining wall at the street.
9. According to the development plan, the retaining wall may be max. 80cm high. Max. 2 one after another with an 80cm distance. This can be designed as a slope with a ratio of 1:1.5.
10. For a height difference of approx. 2m, approx. 1.6m depth with 2 retaining walls is therefore needed.
11. The retaining wall towards the east will probably be the most complex, since almost 2m height must be retained over the entire length here.

Questions:

1. How would you design this? Does my very rough visualization fit or does it make no sense?
2. What costs would you estimate for the retaining walls (especially towards the east, the street side would also be 1.5m if you draw the height from the south garden to the street)?
3. Would you discuss these issues with the architect of the prefabricated house company (with whom we have not yet had contact, still before contract signing) or directly with a garden and landscaping specialist? I want to avoid starting the planning too late and having things get messed up later because of incorrect house positioning.

Thanks!!

Best regards
Florian

Welcome to the forum, Please indicate the north arrow in your sketch. A prefabricated house could become more expensive, the general contractor starts his house from the top edge of the basement, and until then you first have to come to terms with the costs. This could be more expensive with the earthworks than the catalog price of the house.

Do you have a site plan with contour lines?

What about parking spaces? The 2.5 m drive will probably not be sufficient for the parking space regulations.

Hello everyone, my graphic was already oriented to the north. The site plan with contour lines attached. Our property with a purple frame. Yes, construction costs have unfortunately risen quite a bit ... the basement in the offer is at 70k (white tank, 2.62m shell height, perimeter insulation). But still without interior finishing. With interior finishing, it is certainly about over 100k included in the current offer. The meter specifications in my upper illustration are the elevation. That means the carport is 2.5m above the street. It will probably also be tricky to design that on a 14-15m driveway. The width of the carport/house entrance will be about 4.5m. PS: The carport can be either in the window drawn or in the building window. We will put it in the building window since we will want the garden to the south.

I somehow can't follow the explanations and the approach. You have a hillside property and buy a “piece of house” and a “piece of basement” and now want to somehow optimally place that on the property? :rolleyes: Before there are any offers for house/basement, all of this must be planned together on the property. Especially because of access from above/north, driveway, carport, etc. What has been planned so far? Of course, a prefabricated house provider can plan everything completely, but if I read that there have been no talks yet, then where does the basement come from? Or did you decide on house X and inform the basement builder that for the house we need a basement in the hillside with living spaces? Kanitverstan. :oops: What drawings/plans are there?