what ~50mm screed over a dpc?

[andytx]

Hi,

I'm patching a 4'x4' section of a concrete floor. I'm patching new dpc to the old (trying to seal the edges). This will leave this dpc covered area ~50mm lower than the surrounding floor. Under the dpc is rough concrete.

What can I patch the finished floor with? ~50mm thick, dpc polythene under it, old rough concrete under that. A screed? Will need to adhere to the polythene and not crack at just 50mm thick.

Thanks in advance!

 

[ree]

What is your membrane patch material, and how are you intending to fix/weld it?

Without knowing why you have a section of slab that needs attention - and why the concrete is rough below the membrane , and what the finished floor will be, its difficult to advise you.

You could spread SBR below and on top of your patch, and at the edges, and then fill in with a v. dry mix of sand and cement as a screed topping.

 

[andytx]

Thanks Ree.

An old blown air boiler has been removed. Underneath it there was ducting to the ground-floor of the house, all set into the concrete floor. The entrance to all the ducting has been filled up with bricks and concrete, leaving ~2 inches that needs sealing and levelling.

My current plan is to use a visqueen (thick black polyethylene sheet), seal it at the edges with bitumen, then lay concrete on top.

I'm a little concerned about the concrete cracking later on.