ᐅ Gentle slope: Building with a basement or a slab-on-grade?

Created on: 21 Jan 2018 18:46
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Wüstling
Hello everyone,

We have finally found a plot of land that we really like in terms of location, size, and price. Unfortunately, it has a slight slope. We originally planned to build only with a slab foundation because the plots are more expensive than expected and, of course, our budget is limited.

My question now is: Would it be possible to build on this plot (see attachment) using a slab foundation? The plot extends all the way to the edge of the curb.

My idea was to keep the parking space at street level, aligned with the neighbor’s retaining wall blocks, and then create a kind of embankment from the street down to the house so that the house would be 1–2 meters (3–6 feet) below street level (if even that much would be necessary). The embankment could be planted as a front garden, and a staircase could lead from the parking space down to the house entrance.

The alternative would be a walk-out basement, since we want to have level access to the garden, but that will probably be quite expensive.

What do you think would be sensible and feasible in this situation?

Thank you in advance.

The Wüstlings

Outdoor view of a detached house with a red tiled roof in a rural setting, clouds in the sky.
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ypg
22 Jan 2018 13:20
I would also find a very simple split-level design interesting. A basement halfway (at the front), the living area on the garden level, and the sleeping area above the basement. But as I mentioned before, when building on a slope, you should always involve an architect and not just a construction planner from a general contractor.
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haydee
22 Jan 2018 13:48
I would put the living spaces in the so-called basement. This way, they face the garden and have direct access to it.

In my opinion, using the basement only for building services and storage is too expensive.

We have a sloped lot and no basement at all. (Most of the earthworks were unnecessary because the property had already been built on.)

Friends of ours enter their house on the sleeping level and have the living spaces in the lower ground floor with garden access.

Neither our ground floor nor the lower ground floor of our friends resembles the damp, dark rooms that people used to associate with basements.
11ant22 Jan 2018 19:44
It is a myth that omitting a basement always saves money. This is generally only true for plots that are as level as the concrete slab. When there is an almost "basement-high" difference in elevation within the building footprint, leaving out the basement can end up costing nearly as much as building one. This is simply because the additional fill, slope stabilization, and so on are not inexpensive either. In the end, you might spend the same amount of money and just have no storage space in return.

A plot shaped like a slide with the house at the lower end also means, in turn, a sewage lifting station if the street is at the top.

Concrete slab houses belong on plots suitable for concrete slabs.
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Zaba12
23 Jan 2018 06:20
11ant schrieb:
It is a myth that skipping a basement automatically saves money. This generally only applies to plots that are as flat as the slab itself. When there is practically a "basement-high" elevation difference within the building footprint, omitting the basement ends up costing nearly as much as building one. Simply because the added fill, slope stabilization, and so on are not free. In the end, you might spend the same amount of money but end up without the additional storage space.

A plot shaped like a slide with the house at the lower end also means a sewage lifting system if the street is at the upper end.

Slab-on-grade houses belong on plots suitable for slab foundations.

That exactly is the right comment regarding the photo posted by the OP.
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Wüstling
26 Jan 2018 09:00
Hello,

We had a meeting with our builder yesterday. He said that for this sloped site, a strip foundation could be used, and from the terrace or terrace door, there would be about three steps down into the garden. The slab foundation is basically already included in the purchase price. He has now estimated additional foundation costs of 10,000 €.

I have read online that a strip foundation is quite feasible for sloped sites. Do you think this would be possible for the property? I’m not really sure if 10,000 € would be enough.

Thanks and best regards
Wüstling
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Zaba12
26 Jan 2018 09:17
Wüstling schrieb:
Hello,

we had a discussion with our general contractor yesterday. He said that with this sloped site, a strip foundation could be used, which would mean going down about 3 steps from the terrace or terrace door into the garden. The slab foundation is basically included in the purchase price. He has now estimated additional foundation costs of €10,000.
I read online that a strip foundation is feasible on sloped sites.
Do you think this is possible for this plot? I'm not really sure if €10,000 would be enough.

Thanks and best regards
Wüstling

It's funny how the answers from the general contractors are similar. We also spoke to a general contractor in a similar situation. He said the extra costs would be around €7,000.

Since I was a bit skeptical about that, I asked an experienced architect. He said from experience, either you spend at least €30,000 here or use the extra costs for a basement. You also have to keep in mind that you will have to level the garden for tens of thousands of euros.

Going down 3 steps to the garden means a height difference of 30–40cm (12–16 inches). Looking at your site, it’s at least 1.5m (5 feet) down to the start of the garden. After that, it continues to slope further down.