Filling hole in concrete floor

[Gossamer]

Morning.
I made a hole in a 9 inch thick kitchen floor to fit a new water supply pipe. I now need to fill it.
what do I do for dampproof course? it was suggested I backfill, then pour concrete, then a thin layer of bitumen and then my final mortar to finish.
is it a reasonable approach?
Cheers.

 

[Nige F]

Yes go for it

 

[^woody^]

Where is the DPM at the moment?

 

[Gossamer]

Where is the DPM at the moment?

Not sure! I *think* there is a DPC in the slab as there's a dark vein running through it. The house is ~100 years old.

 

[^woody^]

100 years old may not have a DPM.

It's just that if the DPM was underneath the concrete, then you would want to put it back there, not on top. Otherwise it's as per your original plan - apart from the mortar bit - it should be screed or sharp sand, not building sand which is in mortar.

Make sure to compact the fill so that it doesn't settle and drop. And presumably the water pipe had been insulated for the vertical 700mm or so?

 

[bobasd]

pack up to conc height an then drop down a square of plastic, as a local membrane, fill with semi-dry conc, mix it youself and tamp down. cut the flopping edges of the plastic just beloww ffl.
idealy it would be best to glue the membrane to the 110mm upstand pipe but just do the best you can. the job looks good from here

 

[Gossamer]

100 years old may not have a DPM.

It's just that if the DPM was underneath the concrete, then you would want to put it back there, not on top. Otherwise it's as per your original plan - apart from the mortar bit - it should be screed or sharp sand, not building sand which is in mortar.

Make sure to compact the fill so that it doesn't settle and drop. And presumably the water pipe had been insulated for the vertical 700mm or so?

Cheers. Was going to make the top layer (sharp sand mix) about 50mm to ffl. Cant really find bitumen, all seems to be for sheds etc.

pack up to conc height an then drop down a square of plastic, as a local membrane, fill with semi-dry conc, mix it youself and tamp down. cut the flopping edges of the plastic just beloww ffl.
idealy it would be best to glue the membrane to the 110mm upstand pipe but just do the best you can. the job looks good from here

Thanks. Was looking at DPC in Wickes earlier but if I can get bitumen it might make it a tidier job.

 

[bobasd]

no. dpc is wrong material an bitumen aint needed.
rip open a hefty rubble bag or cadge an off-cut of DPM sheet membrane to use as a membrane under the concrete. your usingthe plastic sheeting to form a bag with a hole for the 110mm pipe in the middle

 

[Gossamer]

no. dpc is wrong material an bitumen aint needed.
rip open a hefty rubble bag or cadge an off-cut of DPM sheet membrane to use as a membrane under the concrete. your usingthe plastic sheeting to form a bag with a hole for the 110mm pipe in the middle

Something like this:

https://www.screwfix.com/p/capital-...gclsrc=aw.ds&dclid=CNrPmK-x69cCFc63Gwod4EMPPw

 

[bobasd]

yeah, thats the dpm material but you dont need all that much.maybe you can use the rest somewhere else?

 

[Doggit]

Alternatively, add some waterproofer to the concrete mix, and leave it at that.