ᐅ Foundation perimeter structural stability: Is a gravel foundation or retaining wall required?
Created on: 21 Jul 2023 08:18
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elco1107Hello,
I have a question regarding the design of the outdoor area. The foundation slab of our house rests on compacted gravel. Due to the slight slope of the terrain, the gravel base is exposed about 60–80 cm (24–31 inches) above ground on the south and east sides. I want to cover this gravel mound on the sides with a dry-stone wall made of multicolored sandstone. For this, I plan to reduce the original 1.50 m (5 feet) wide gravel border to only 60 cm (24 inches), with the dry-stone wall on the outside. I understand that the wall will not have any static function. Between the row of stones and the gravel, gravel will be added and compacted manually using appropriate hand tools (a hand tamper and a heavy sledgehammer). There will be 60 cm (24 inches) of machine-compacted gravel (compacted before construction) remaining outside the foundation slab, followed by 20 cm (8 inches) of hand-compacted gravel up to the dry-stone wall. The dry-stone wall consists of a single row of stones about 20–30 cm (8–12 inches) deep.
My question: does anyone have experience whether a 60 cm (24 inches) wide compacted gravel wall alone is structurally sufficient, or would it need support such as L-shaped retaining blocks? Could the gravel mound loosen or shift over time?
Thank you in advance.
I have a question regarding the design of the outdoor area. The foundation slab of our house rests on compacted gravel. Due to the slight slope of the terrain, the gravel base is exposed about 60–80 cm (24–31 inches) above ground on the south and east sides. I want to cover this gravel mound on the sides with a dry-stone wall made of multicolored sandstone. For this, I plan to reduce the original 1.50 m (5 feet) wide gravel border to only 60 cm (24 inches), with the dry-stone wall on the outside. I understand that the wall will not have any static function. Between the row of stones and the gravel, gravel will be added and compacted manually using appropriate hand tools (a hand tamper and a heavy sledgehammer). There will be 60 cm (24 inches) of machine-compacted gravel (compacted before construction) remaining outside the foundation slab, followed by 20 cm (8 inches) of hand-compacted gravel up to the dry-stone wall. The dry-stone wall consists of a single row of stones about 20–30 cm (8–12 inches) deep.
My question: does anyone have experience whether a 60 cm (24 inches) wide compacted gravel wall alone is structurally sufficient, or would it need support such as L-shaped retaining blocks? Could the gravel mound loosen or shift over time?
Thank you in advance.
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WilderSueden21 Jul 2023 08:4260cm (24 inches) height and 60cm (24 inches) width correspond to a 45-degree angle. This can hold on its own, but it may not withstand heavy additional loads. Therefore, the dry stone wall plays a more important role here. If it is built well, it will definitely hold. As a beginner attempting this for the first time and using only hand tools, I would recommend leaving a bit more distance. The area can be nicely landscaped with suitable plants, which is how I am doing it (still a work in progress).
With the dry stone wall, be sure to ensure a proper backward slope. Image 2 seems to show the opposite. In one case, the existing backward slope was even leveled out with gravel under a stone. This can be pushed out by frost after several winters. Then the house would rest only on the gravel layer without support.
With the dry stone wall, be sure to ensure a proper backward slope. Image 2 seems to show the opposite. In one case, the existing backward slope was even leveled out with gravel under a stone. This can be pushed out by frost after several winters. Then the house would rest only on the gravel layer without support.
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xMisterDx22 Jul 2023 11:10How was the foundation constructed? Strip footing? Or just a gravel base layer?
If it’s a gravel base layer, you should definitely consult a professional. If done incorrectly, the house could settle unevenly.
If it’s a gravel base layer, you should definitely consult a professional. If done incorrectly, the house could settle unevenly.
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