water filled hole in lounge advice please!

[trumansparks]

Hi all,

Having dug out a meter square hole from my lounge floor (clay) and dug a trench under the front wall for a new mains supply, the hole has half filled with water (1 foot).

now i can empty it but when the pipe is finished, inspected etc i need to back fill, the question is what do i back fill the hole with which will stop the water collecting. I will be concreting over with a new floor and dont want to cause subsidence, movement in the wall, damp issues or crack my concrete slab.

any advice welcome please

truman.

 

[Deluks]

Backfill with what came out. Or compacted rubble/hardcore/MOT.

You'll be using a dpm so no damp issues. mesh in the concrete wouldn't be so bad either.

Was there a concrete floor previously? if so any probs with it?

 

[trumansparks]

Cheers for the quick reply deluks,

forgot mention the stuff that came out was clay and came out in clumps so unlikely to go back compacted and i suspect would leave voids to settle over time creating a dip.

so what sort mix, needs to be fine enough to fill it without leaving gaps for the water to fill?

was flagged floor before.

TS

 

[streetmason]

The hole has filled with water (up to 1ft) because that is the current water table level. The water table varies according to the amount of rain (or other water source) at any given time.
If you were to backfill with granular matterial such as hardcore it would probably permanently act as a french drain and fill up when the water table was beyond the level of the base of the hole. Ideally, if you could put the clay back and fully compact that would be the cheapest option, although i doubt very much that you would get it all back. As you will be using concrete at a later stage i would recommend you backfill with this as this will be unaffected by ground water levels and work its way around a hole that is 1m2.
To be honest most people would backfill with hardcore(40mm down) and not have any repercussions, its just ground water.