Filling pipe void in floor

[Doug71]

Just getting a rental property ready for new tenant and have found the washing machine has been leaking for god knows how long #-o

The issue I have is that the hot and cold water pipes in the property used to run along a cavity in the concrete floor, if I remember correctly the pipes were packed around with sand and then had a thin layer of mortar on top. I was never keen on this so had the pipes moved on to the wall when I had some other work done a few years ago but of course I never got around to sorting out the void.

Now the washing machine has leaked into the void which still has sand in it, the void runs under the kitchen units, through the utility room and into the bathroom so they all smell damp.

I have now cleaned out the sand and just want to check am I okay just putting a bit of visqueen in the cavity and then filling with concrete, it's probably about 3" deep?

Sand still in when I took photos.

Sorry for making such a simple question so long!

Thanks, Doug

 

[Woody2Shoes]

I'm not sure I'd bother with the visqueen. I'd be tempted to just make a strongish screed with sharp sand and cement (say 1 dust to 4 sand) and trowel it in and flat. Will this strip be invisible under normal circumstances (I assume so)?

 

[Doug71]

No it won't be seen, it's under kitchen units, behind washer and dryer in utility and in a cupboard in bathroom.

There are bits of visqueen in places under the sand, looks like when the slab was poured they probably put a bit of 3"x 2" along the edge then took it out when slab was set to make the cavity to run the pipes in.

A sharp sand & cement mix sounds a good plan, thank you.