Damp self levelling

[JJ999]

Hi,

In the process of redoing our bathroom and currently tackling the floor. We have removed the old tiles, adhesive and previous self-levelling. We have a concrete subfloor, which had one large-ish hole which we filled with a sharp sand cement mix. We re-levelled with self-leveling compound, but a couple of problems have emerged:

1. the area we have filled was obviously not dry enough and that area of the self-leveling is dark and damp
2. there is one other area where there is some moisture coming up from the concrete base.
3. it is still not level so will need another layer os self-levelling

Is anyone able to advise whether it is best to put down a damp proof membrane before the second layer of self-levelling to make sure that moisture doesn't penetrate that layer? Or should we pull up what we have put down and start again? Or is there any other solution?

Thank you!

 

[dazlight]

What’s smoothing compound did you use ? Was it a bag and bottle or a water mix ?

how old is the concrete ? Does it have a visqueen Dpm under the concrete ?

 

[JJ999]

We used a latex water mix one (sika 131).

The concrete itself was probably laid in the 1980s, but have zero confidence there was any sort of DPM - the bathroom is groundfloor and would have been converted out of the old coal store/outdoor toilet - in one place I could see the concrete was laid directly on the old red quarry tiles.

 

[tel765]

Are you sure its "concrete" and not a sand & cement screed over the red tiles?
There's usually no skirting under the bath - so have a look under for a membrane/DPM where the floor meets the wall.
A couple of pics would help?

Daz could advise you on any liquid DPM etc.

 

[JJ999]

It could well be sand&cement screed - not sure how I would tell the difference?

I have added two pics. One is the floor before we laid the self-levelling - I assumed the black is the remains of a painted bitumen.

The other is the only place to see the sub-floor floor meeting the old plastered wall which I don't think helps much, but around the rest of the room where the floor met the wall was just an inch gap (which is where I could see it was laid onto red quarry tiles and there was no obvious membrane).

 

[tel765]

I'm not much further ahead with the pics - Given the unknowns, the damp issues, & the cracks then here's what i would do if i was given that job:

Remove all floor standing fixtures.
Determine the finished floor level benchmark.
I would then lift everything down to soil.
Sketch a full size sectional view of the floor from soil to FFL.
Lay a membrane.
Cover with insulation? concrete or a S&C screed?

 

[dontbelieveawordofit]

Cover with insulation? concrete or a S&C screed?

screed 5”?

 

[Nige F]

I'm not much further ahead with the pics - ?

never mind - keep taking the pills