Small garden drainage 9.7mx9m
I don't know if anyone can help. We are due to have a patio extension and artificial grass installed this week. I agreed to dig the foundation for the patio but found half of the ground very spongy. We have ascertained that this is about a foot deep of soft clay where the garden previously had standing water. Below this we are on the hardcore from the house build, new build house. The builder came round and said that we could fit a soakaway in the centre of the garden which would allow for more water from extended patio without affecting the base of the grass.
The problem being there is only 9.7m between our house and our neighbours. The builder said the soak away shouldn't be closer than 5m to a building but the actual minimum is only 4m and as it won't be taking water from our house only the water already in the garden soil we would be compliant with guidelines.
Is this correct. Is the 5m rule only for building drainage soakaways as opposed to just patio. New patio would be 3x3.6m next to 40m2 of artificial grass on a compacted subbase.