Hello,
I have a question about drainage.
My excavation pit is currently dug out to a depth of 1.5–2 meters (5–6.5 feet) – I know that’s quite deep – and I will be getting a concrete slab foundation. For frost protection, a frost protection layer is planned for my foundation.
The soil report states that the subgrade, or the last meter (3 feet) of the frost protection layer, must be permanently drained, and if natural runoff cannot be ensured, it must be drained via a drainage system.
Since I have clayey soil, water is currently accumulating above the first two layers of crushed stone.
Could someone please advise me on the next steps? Is the drainage absolutely necessary, and at what depth should it be installed? At the 1 meter (3 feet) where the frost protection layer begins? How should it be executed? Do I need a building permit / planning permission?
Thank you in advance…
I have a question about drainage.
My excavation pit is currently dug out to a depth of 1.5–2 meters (5–6.5 feet) – I know that’s quite deep – and I will be getting a concrete slab foundation. For frost protection, a frost protection layer is planned for my foundation.
The soil report states that the subgrade, or the last meter (3 feet) of the frost protection layer, must be permanently drained, and if natural runoff cannot be ensured, it must be drained via a drainage system.
Since I have clayey soil, water is currently accumulating above the first two layers of crushed stone.
Could someone please advise me on the next steps? Is the drainage absolutely necessary, and at what depth should it be installed? At the 1 meter (3 feet) where the frost protection layer begins? How should it be executed? Do I need a building permit / planning permission?
Thank you in advance…
M
MachsSelbst30 Jul 2024 20:23Isn’t something like this completely routine for a civil engineering contractor or construction manager/architect?
Isn’t it their responsibility to come up with a solution, not yours?
Isn’t it their responsibility to come up with a solution, not yours?
Could you please confirm again whether groundwater was encountered by the soil surveyor? A cross-section showing the future position of the house would also be helpful.
Based on my current knowledge, I personally consider drainage unnecessary.
However, if the surveyor requires it: basically, it is just a drainage pipe wrapped in a geotextile fabric, installed with a slope around the perimeter at about 1.0 m (3.3 ft) below the slab in the gravel layer. Drainage in groundwater is not permitted. Drainage systems must be applied for through the relevant building permit / planning permission process, and it must be clarified how the drainage water will be handled. Direct discharge is often not allowed due to suspended solids and usually requires a cistern with a sediment trap or similar.
Based on my current knowledge, I personally consider drainage unnecessary.
However, if the surveyor requires it: basically, it is just a drainage pipe wrapped in a geotextile fabric, installed with a slope around the perimeter at about 1.0 m (3.3 ft) below the slab in the gravel layer. Drainage in groundwater is not permitted. Drainage systems must be applied for through the relevant building permit / planning permission process, and it must be clarified how the drainage water will be handled. Direct discharge is often not allowed due to suspended solids and usually requires a cistern with a sediment trap or similar.
Thank you for your reply.
Attached is the cross-section. This might already be sufficient. You can see the groundwater level here. The construction is without frost skirts, but with a frost-resistant gravel base (1.05m (3.4 ft)).
The inspector said that currently it behaves like a bathtub and the 1.05m (3.4 ft) of gravel must always remain dry, which is why the drainage is necessary. I’m worried that if the earthworks contractor says it’s not needed, this could cause problems later…
Thank you.
Attached is the cross-section. This might already be sufficient. You can see the groundwater level here. The construction is without frost skirts, but with a frost-resistant gravel base (1.05m (3.4 ft)).
The inspector said that currently it behaves like a bathtub and the 1.05m (3.4 ft) of gravel must always remain dry, which is why the drainage is necessary. I’m worried that if the earthworks contractor says it’s not needed, this could cause problems later…
Thank you.
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