Filling in old soild pipes and cavities.

[kjacko]

Hi fellas,

in my new extension i have ripped out and moved the old soil/vent pipe (all approved by BC).
So the hole thats left in the floor needs to be filled.
As does part of the cavity below the floor as the internal wall ends before the cavity does (if you know what i mean). Either way, my question is:
What mix shall i use to fill these holes?
I was assuming 5 parts sand, 1 part cement and some 20mm gravel type stuff, similar to what we shovelled in when the lorry delivered it.

Can someone advise please?

 

[noseall]

Six parts ballast to one cement, will be ideal.

If you decide to use separate aggregates then it's four parts gravel, two parts sharp sand and one cement.

Oh, and a splash of water too.

 

[Richard C]

When you fill these redundant holes, it’s important that you reinstate the damp proof membrane at the appropriate level otherwise you could effectively be left with a “damp wick” into the floor/wall, particularly with the old soil pipe hole. Establish where the damp course/membrane is in each case & fill to that level, let the concrete go off & use a liquid membrane like Synthaprufe; once this has dried fill up to the required level with a second mix of concrete.