When is a slope a slope? Basement vs. slab

Our slope is about 12-14% (not evenly sloping), from corner to corner (the slope runs diagonally across the property) we have about 5m height over 35m length.

This results in almost exactly one floor height difference. Our "basement" therefore consists of half living spaces.

The additional cost of the basement is mainly because the living spaces require windows, doors, installations, and heating compared to simple basement rooms.
In our case, the above-ground part of the basement is built of masonry and the other part is made of waterproof concrete.

We are located below the street. Due to an easement registered in the land register, we can drain our wastewater down to the next street and receive fresh water from above from "our" street.

Otherwise, we would have had to install a lifting system (10,000€ one-time + follow-up costs, maintenance, and regular cleaning) or not install water consumers in the basement (e.g., toilet, sink).

If you were to build "above" the street, that would not be a problem. In that case, almost everyone in our building area builds an integrated garage in the house, parking their car as "in" the hill.

For that purpose, we planned a driveway next to the house and partially basemented it (= garden tool room).
This "bunker" (without a driveway) with a window and door cost about 15k.

On the other side, we want to have a terrace, which is supposed to have a concrete retaining wall about 2.60m x 3.00m in size (L-shaped stones can possibly tip over slightly over time). Estimated cost from the construction company about 2k.

Many construction companies initially calculated about 20k additional costs for earthworks.
However, due to the slope, only about 50% of the basement volume had to be excavated, since the rest is above ground.

We had the excavation material placed in one spot right away, which then only needed to be slightly compacted, and we already have our terrace area filled (at no extra cost, because "excavation plus side storage plus spreading the excavation on the property at the end" is generally always included in the bid price and this actually means less effort for the construction company in our case).

Hello everyone, thank you very much for the useful tips and also for the specific numbers, you have really helped me a lot!

Best regards

Bo

If you are watching costs: As flat as possible. As little slope as possible. I’ll give you an example: Our soil: topsoil, underneath clayey and gravelly. Our plot: 30 m deep at the widest point, at the narrowest 24 m. Slope from street level to the back post, 1.2 m. Slope in the house area, house 10.5 m wide, - 1 m, house 5 m behind street boundary. Concrete slab laid so that at the front 0.5 m sticks out, at the back 0.5 m goes into the ground.

Quick question, since it looks similar for me. From the street to the back part of the house about 1 m incline. I would be about 50 cm above the street in the front and 50 cm in the ground at the back, which then has to be excavated. I wanted to ask how you solved this with the garden. Did you have the entire plot excavated up to the boundary or only a part, then use a small slope to get back up the remaining 0.5 m? If possible, I would appreciate a photo of how it was solved, especially the situation regarding the neighboring plot.

Wanted to ask how you solved the garden.

See house pictures thread, page 115 (post #685) - click on the arrow in the quote box:

And the garden landscaper piled up the dyke, against the flood from the mountain.

In the same thread and in the time frame around that post you will also find the context.

Are you sure you want to be 0.5m above the street? I’m glad that it almost didn’t happen with us by chance.

Originally, I thought that everything that was removed could be piled up elsewhere.
But I didn’t take the gravel into account; we don’t have good topsoil, and therefore everywhere the terrace is supposed to go as well as in front of the house, gravel was laid, and more soil had to be removed for that.
In the end, we had quite a bit of soil left over, more than expected.

Down at the back part, where a terrace is also supposed to go, we will create a plateau up to the end of the boundary or leave a slope shortly before the boundary or work with retaining walls.
If you have everything removed all the way to the back, wouldn’t you have to come out again on the turf because of the slope?

If you have a small slope back up behind the terrace, there is a risk that rainwater will collect on the terrace, which I would avoid; it’s better if the water can continue to drain away.

This is how it looks here. In front of the planting rings under the gravel drainage.