ᐅ Frost skirts or frost-protected shallow foundations for fill areas
Created on: 29 Dec 2021 22:43
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wullewuuHello,
Just before everything is finalized, a question came up for me regarding the landscaping design that I would like to clarify.
We are building a single-family house on a plot with about a 2 m (6.5 ft) slope. Since we want the house to be at street level, a fill under the house will be necessary, which would be more than 80 cm (32 inches) high. Our architect and geotechnical engineer said this means a frost-protected foundation, so no frost skirts (frost footings) are needed. That was good news for us at first, since it saves money.
Regarding the exterior planning, the house will be about 1 m (3.3 ft) elevated on one side, and I want to retain the soil with L-shaped retaining walls. That’s not a problem since the area will be filled anyway, but with frost-resistant material. However, I kept thinking: you can’t plant on that, and if you just “dig away” 50 cm (20 inches) from the house wall and refill with soil between 50 cm and the retaining wall, maybe up to 1 m (3.3 ft) deep (so plants can grow), wouldn’t that cause issues? The earthworks contractor said the gravel is compact and nothing slips, but over time gravel and soil/roots will mix. The architect and others say it will hold.
I’ve read about frost skirts and their structural function – the concrete skirts prevent gravel or similar materials from “slipping” down to depths of 80–100 cm (32–39 inches). Intuitively, especially on a slope, I feel that frost skirts might be safer, particularly since we want to landscape and plant there.
Is this just my layman’s view, or is there something to it?
Just before everything is finalized, a question came up for me regarding the landscaping design that I would like to clarify.
We are building a single-family house on a plot with about a 2 m (6.5 ft) slope. Since we want the house to be at street level, a fill under the house will be necessary, which would be more than 80 cm (32 inches) high. Our architect and geotechnical engineer said this means a frost-protected foundation, so no frost skirts (frost footings) are needed. That was good news for us at first, since it saves money.
Regarding the exterior planning, the house will be about 1 m (3.3 ft) elevated on one side, and I want to retain the soil with L-shaped retaining walls. That’s not a problem since the area will be filled anyway, but with frost-resistant material. However, I kept thinking: you can’t plant on that, and if you just “dig away” 50 cm (20 inches) from the house wall and refill with soil between 50 cm and the retaining wall, maybe up to 1 m (3.3 ft) deep (so plants can grow), wouldn’t that cause issues? The earthworks contractor said the gravel is compact and nothing slips, but over time gravel and soil/roots will mix. The architect and others say it will hold.
I’ve read about frost skirts and their structural function – the concrete skirts prevent gravel or similar materials from “slipping” down to depths of 80–100 cm (32–39 inches). Intuitively, especially on a slope, I feel that frost skirts might be safer, particularly since we want to landscape and plant there.
Is this just my layman’s view, or is there something to it?
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