flooded footings

[jonjan]

Hi,.
We have just dug out the footings for our extension (2 metres deep) and have a solid clay base. However, once left overnight, the footings begin to fill with water ( there are no leaking pipes). i have also bailed out all the water but they fill up again. This is causing problems as the building inspector will not pass off the footings until he can clearly see the base of the footings. So, is this just rising ground water and is it safe to continuously pump out the water until the footings can be passed off and filled in with concrete. Will this water have any damaging affect on the foundations as if it is ground water, i assume it will always be there.

Thanks for any help

 

[JohnD]

Ask your BCO - but one way is to dig out the mud from the soft bottom and immediately lay drylean mix - this will absorb moisture and give a firm base to pour onto. He won't want you placing onto mud.

It can also help to dig a narrow but deeper trench or sump nearby and pump out of that to keep the local water table down.

 

[^woody^]

Who designed such deep foundations?

I specified some 1m deep ones once, and the building inspector wanted 2m due to some trees about 20m away. Anyway, I asked an engineer about it, and he said the inspector must be mad as 2m was in the water table. He mentioned this to the inspector, an he said "oh yes, well you can't go that deep then, 1m is OK"

You will need to use a sump pump to keep the trench dry. I hope it is shored!

 

[masona]

Who designed such deep foundations?

They do 2m footing in Rayleigh, Essex including the metal rods, I know the clay are very soft over there

jonjan,

Has the same problem, I slope it at a slight fall to the centre and dug a small hole for the sump pump.