Ground floor DPM nightmare... what to do?!

[aforbes]

hi @dazlight where you say "use a good vapour underlay" do you mean just do this without digging up the floor and doing the 2x10kg again (they basically didn't put enough down)?
And do you mean MVS/fball F78 / F77 over what's there atm OR dig up and start again? (knowing we can't go much higher with what's there atm...

 

[dazlight]

Fill any holes , f78 3 coats , then underlay, timbermate excel or similar

No need to dig it all up.

 

[aforbes]

I think this will bring the level too high sadly....

 

[aforbes]

@dazlight @crazydaze

have discussed with the company and we think a solution might be to bash out any bossed bit and fill.
Do another 20kg Ardex DPM1 over whole space and another layer of Ardex NA.
Around the external door we frame in a low lying doormat, and at the other 5 opening we will have to have some sort of profile to that there's not a 20mm step.....
Anyone see any issues with this?
Or are we definitely better to take it all up and start again??

 

[dazlight]

You would be building up 1mm

 

[aforbes]

I thought ardex NA has to be min 3mm?

 

[dazlight]

Go over the screed that’s down now. Just fill any holes with ardex a46

 

[aforbes]

Sorry @all - a slight spanner in the works... just realised that the 'feathering' they used on top of the top layer of Ardex NA to fill in holes is pretty rough (pics attached) - I don't think they'll be able to do the Ardex DPM on this very well (though I could be wrong) - getting into all the nooks and crannies? I think we might have to revert to taking the whole thing up and starting again so that the DPM at least goes onto a CLEAN and FLAT surface... any thoughts to the contrary?

 

[aforbes]

Update - so we've dug up the top later (ardex sandwich done wrong) and found a lot of patches where the original sand cement from 18 months ago is very friable (in a few places we can get down to the cement below about 80mm). Some areas seem okay however. The room has been sheeted and insulated etc so we can't dig whole thing out to get to the walls - one suggestion was to do this and do a whole new pour - BUT we'd have to cut up against the new plasterboard and I worry this would weaken where the framing sits. Other option is to repair what we have. Any ideas??!

 

[dazlight]

We have gone over weak sub floors like that a few times. I did a video / picture thing on you tube of one we did.
Works well.

You could use a few types of penetrating epoxy primers
Fball SRS
Uzin PE425
Ardex PSRS

 

[aforbes]

Amazing I will take a look, thank you

 

[aforbes]

Floor so brittle they've had to take the whole thing out. I am FUMING at the guy who put the dry sand cement in originally. We CANNOT get under the sole plates (which are sitting on unstable base but should hold okay) and behind the wall is insulated so we can't really get to the back of it to put a DPC into the wall properly.
We do however need to put in a DPC before we pour concrete. My plan is to paint primer and maybe DPM on the loose edge of this sand cement, which can only be cut back as far as the sole/base plates flush with the walls (see photos). Then put in plastic DPC and concrete and essentially HOPE that we don't get rising damp. This is turning into a nightmare - if you have any product recommendations or methods of essentially reverse engineering a floor I'd be very grateful. Thank you. God knows why he didn't put in a proper DPC in the first place!

 

[aforbes]

We've now dug it all out.
One final question (i hope!) - do you think we need to seal the edges of the old floor where it sits under the sole plates and will be up against the new DPC? please see photo - and if so, what product do you recommend please?
[am just worried about any damp coming in from the external wall getting in and meeting the new plastic and having nowhere to go, but maybe I'm overthinking it]