ᐅ When Is a Slope Considered a Slope? Basement vs. Slab Foundation
Created on: 23 Jun 2017 00:17
B
Bobinho
Hello everyone,
My family and I are currently looking for a plot of land. In a prospective new development area, where the sale of plots will begin soon, I have identified a few spots (the plots have not yet been officially surveyed) that we really like. However, all of these locations have more or less significant slopes.
Attached is a screenshot from the development plan, which includes some elevation details. I do not yet have any information on the soil conditions.
In the upper part, you can see that the plots have a slope of about 4 meters over 20 meters (approximately 13 feet over 66 feet), and the slope decreases further down.
We actually want to build without a basement on a slab-on-grade foundation (for cost reasons). This raises the following questions, and I would really appreciate your input:
- Is this feasible in the upper area with additional costs remaining reasonable compared to a flat plot?
- What about in the lower area?
- To avoid starting the same thread with other plots next week, how much slope can a plot have before the extra costs for a slab foundation become excessive and a basement becomes advisable?
- Can the additional costs be roughly defined now (for example, can we reasonably assume clay soil)?
- Would building a basement, possibly partially or fully open on the slope side, incur significantly higher costs compared to a basement on flat land?
- I assume I should have a soil survey done before purchasing? Would a report from a nearby site be insufficient?
Thank you very much in advance!
Bobinho
My family and I are currently looking for a plot of land. In a prospective new development area, where the sale of plots will begin soon, I have identified a few spots (the plots have not yet been officially surveyed) that we really like. However, all of these locations have more or less significant slopes.
Attached is a screenshot from the development plan, which includes some elevation details. I do not yet have any information on the soil conditions.
In the upper part, you can see that the plots have a slope of about 4 meters over 20 meters (approximately 13 feet over 66 feet), and the slope decreases further down.
We actually want to build without a basement on a slab-on-grade foundation (for cost reasons). This raises the following questions, and I would really appreciate your input:
- Is this feasible in the upper area with additional costs remaining reasonable compared to a flat plot?
- What about in the lower area?
- To avoid starting the same thread with other plots next week, how much slope can a plot have before the extra costs for a slab foundation become excessive and a basement becomes advisable?
- Can the additional costs be roughly defined now (for example, can we reasonably assume clay soil)?
- Would building a basement, possibly partially or fully open on the slope side, incur significantly higher costs compared to a basement on flat land?
- I assume I should have a soil survey done before purchasing? Would a report from a nearby site be insufficient?
Thank you very much in advance!
Bobinho
We were offered a so-called hillside house for a similar plot. From the street view, it has two full floors, with the upper floor at the back opening level with the garden, while the rear wall of the lower floor is embedded in the sloping terrain.
In our case, the ground rises about 180cm (71 inches) over 10m (33 feet) in depth within the building area, and about 7m (23 feet) over 44m (144 feet) in total depth. By the way, the direct neighbor built with a slab foundation and started cutting into the slope there. For us, it would only be necessary to cut into the slope on the right and left sides of the house, each about 3m (10 feet) wide.
We have not bought the plot yet and are currently waiting to review the house cost estimate.
In our case, the ground rises about 180cm (71 inches) over 10m (33 feet) in depth within the building area, and about 7m (23 feet) over 44m (144 feet) in total depth. By the way, the direct neighbor built with a slab foundation and started cutting into the slope there. For us, it would only be necessary to cut into the slope on the right and left sides of the house, each about 3m (10 feet) wide.
We have not bought the plot yet and are currently waiting to review the house cost estimate.
H
HilfeHilfe24 Jun 2017 08:0760k to 80k since you will have earthworks anyway
Bobinho, regarding your question: yes, the approximately 8% additional costs are correct. The extra costs were well estimated by the builder beforehand, so it was not a surprise. Since we ordered a turnkey house, everything from a single source, without an architect or anything like that, I do not know the exact price of the foundation slab. It isn’t really a foundation slab in the traditional sense. In Schleswig-Holstein, for smaller houses, strip footings are common, set 80cm (31 inches) into the ground. Between them, 40cm (16 inches) of concrete is poured over recycled concrete and compacted fill sand. There is a steel mesh or rebar in both the concrete and the strips. That is sufficient.
My tip, looking at my cost breakdown, is to value my foundation slab at 16,500 plus 6,500, totaling 23,000 gross. That is never the cost of a basement. So, if you can get a more level plot, that will save you a lot. With the savings, you can spread countless luxury garden houses around the countryside. Karsten
My tip, looking at my cost breakdown, is to value my foundation slab at 16,500 plus 6,500, totaling 23,000 gross. That is never the cost of a basement. So, if you can get a more level plot, that will save you a lot. With the savings, you can spread countless luxury garden houses around the countryside. Karsten
Arifas schrieb:
By the way, the direct neighbor built with a slab foundation and started the slope.Arifas schrieb:
Intercept, not start. Stupid autocorrectYou really shouldn’t even start with this idea of intercepting. Anyone who sleeps peacefully in a slab-on-grade house built on a half-bench slope has clearly never seen a landslide ruin. Besides the first point, that this “basement avoidance” is a costly pyrrhic victory, it also gets complicated if you want or have to have an access road on the valley side. Not to mention the “beautiful” appearance.
A method like the alignment Karsten described requires the benefit of gentle Holstein-style slope gradients. You can’t just scale that up to steeper slopes arbitrarily.
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