Filling trench in concrete floor

[resman]

Morning all,

I'm in the process of moving a radiator and made the mistake of looking under the carpet! Under the loose parquet I found a compression joint partially buried in breaking up screed. Uncovering this led to another compression joint- originally the radiator was obviously where the patio doors are now- so this will be its second move. The trench was full of loose material- I've removed all this and cut back a little to reveal both pipes.

There is what looks like a clear plastic DPM which has gone brittle and is now holed- so that will need repair.

Obviously the compression joints have to go, so my thinking is to joint the copper to plastic pipe in pipe at the last point where the flow and return are together- this keeps the joints down to two in a known area and make them as accessible as I can. The long term aim is to remove the parquet as its all loose, rescreed and lay karndean- I'll be getting a pro in for that.

Given all this- what best to fill the trench with?

Thanks

SimonView media item 97432View media item 97431View media item 97430

 

[noseall]

Screed sand (sharp sand, concrete sand etc) and cement. Always damp down any surfaces in contact with the new screed, it will help it 'knit' better.

 

[resman]

Thanks for that- appreciated. Is that 4:1 of dry-ish mix? The deepest part of the trench is 14cm deep- does the screed mix still hold for that depth? Or is a wet-ish mix bed worth doing first? And time before laying covering?

Thanks

Simon