ᐅ Frost protection barrier below existing or planned ground level?
Created on: 14 Dec 2015 23:59
G
Grym
The reference height is the planned top level of the plot. The frost-free foundation depth is defined by the soil report, which classifies the ground as F1 (not frost-sensitive), F2 (slightly to moderately frost-sensitive), and F3 (frost-sensitive / highly frost-sensitive). This depth varies by region; in Germany, it is at least 80cm (31.5 inches).
O
Oberhäslich21 Feb 2023 23:51Before starting a new thread about the frost skirt, I’d like to ask for advice here directly.
Assuming a foundation cushion of 0.7 m (28 inches) below ground level is sufficient (soil replacement) and the building is constructed with a frost skirt and without a basement. According to the soil report, the frost skirt should be 1 m (39 inches) deep from the finished ground level. However, the top edge of the slab equals the finished ground level.
1. If I build the slab (20 cm (8 inches)) with its top edge at finished ground level, is a frost skirt of 80 cm (31 inches) enough? Altogether that would also come to 1 m (39 inches) including the slab.
2. Does the excavation contractor dig out the frost skirt at the same time as the foundation cushion? Or do they only excavate a flat area of 0.7 m (28 inches) depth by width by length and compact the gravel? Then, during the frost skirt construction, does the slab contractor excavate down to 1.1 m (43 inches)? I find the first option more complicated and have never consciously noticed it. The reason is that according to the scope of work, the soil in the frost skirt area should be manually excavatable for the slab contractor. That doesn’t make sense to me if they would also have to dig out an additional 0.4 m (16 inches) of soil.
Assuming a foundation cushion of 0.7 m (28 inches) below ground level is sufficient (soil replacement) and the building is constructed with a frost skirt and without a basement. According to the soil report, the frost skirt should be 1 m (39 inches) deep from the finished ground level. However, the top edge of the slab equals the finished ground level.
1. If I build the slab (20 cm (8 inches)) with its top edge at finished ground level, is a frost skirt of 80 cm (31 inches) enough? Altogether that would also come to 1 m (39 inches) including the slab.
2. Does the excavation contractor dig out the frost skirt at the same time as the foundation cushion? Or do they only excavate a flat area of 0.7 m (28 inches) depth by width by length and compact the gravel? Then, during the frost skirt construction, does the slab contractor excavate down to 1.1 m (43 inches)? I find the first option more complicated and have never consciously noticed it. The reason is that according to the scope of work, the soil in the frost skirt area should be manually excavatable for the slab contractor. That doesn’t make sense to me if they would also have to dig out an additional 0.4 m (16 inches) of soil.
Hello,
1. Yes, that is correct. Of course, other issues may arise if you "sink" the slab into the ground (water).
2. Yes, the usual procedure is that the earthworks contractor prepares the area, and the frost skirts are excavated later by the following trade. If 00/32 or 00/45 gravel is used, a mini excavator is naturally required for that.
1. Yes, that is correct. Of course, other issues may arise if you "sink" the slab into the ground (water).
2. Yes, the usual procedure is that the earthworks contractor prepares the area, and the frost skirts are excavated later by the following trade. If 00/32 or 00/45 gravel is used, a mini excavator is naturally required for that.
O
Oberhäslich22 Feb 2023 10:44Thank you very much. Water is actually not an issue. After 1.70m (5.6 feet), there is gneiss, and up to that depth no groundwater is present. The house is situated on a slight slope (0.3m [1 foot] over 10m [33 feet]).
Groundwater is rarely the problem. Surface or slope water, especially after heavy rainfall events, is more common. If water flows toward your house, there won’t just be a 20 cm (8 inches) threshold anymore; it will flow directly into the living room.
Then the question is how your slab foundation is sealed. If water can run against it or accumulate, waterproofing according to W 2.1-E (pressing/groundwater) or W1.2 E (drainage) standards is necessary.
All of this is possible of course. The easiest solution is to excavate frost skirts (frost protection barriers) to a depth of one meter (3 feet).
Alternatively, you can create a gravel layer with a thickness of 1.0 m (3 feet) using F1 quality (frost protection) gravel and omit the frost skirts. The cost-effectiveness of this option should be calculated (30 cm (12 inches) more excavation and backfilling versus frost skirts and additional labor).
Then the question is how your slab foundation is sealed. If water can run against it or accumulate, waterproofing according to W 2.1-E (pressing/groundwater) or W1.2 E (drainage) standards is necessary.
All of this is possible of course. The easiest solution is to excavate frost skirts (frost protection barriers) to a depth of one meter (3 feet).
Alternatively, you can create a gravel layer with a thickness of 1.0 m (3 feet) using F1 quality (frost protection) gravel and omit the frost skirts. The cost-effectiveness of this option should be calculated (30 cm (12 inches) more excavation and backfilling versus frost skirts and additional labor).
Similar topics