self levelling not drying after a week in patches

[alex13]

Sorry if this question has been posted before - I couldn't find the answer to our particular situation..

Our builder put down self levelling compound over concrete and some pipes. In patches it's not dried after over a week with dark patches and 40% on the moisture meter.

I think under it there was quite a lot of water from the plumbing work [but not everywhere in pictures], and remember seeing some sand then concrete going down first in parts at least. Unfortunately I don't know how long they left each stage to dry, and the house has been cold with no heating in Feb/March. The largest areas I think they might have covered up with boards etc before things were dry; we moved some of their things to find SLC damp underneath.

It's also not very flat - with undulations measuring 8mm vertically in less than 1m horizontal.

We were planning to put engineered wood and kitchen on it next week but not sure if we should delay, or if SLC might need ripping up again or something.. and don't want to risk having to pull the kitchen out again later.

Any advice on what to do would be amazing!

 

[Wayners]

Put hair dryer on and see If colour changes after a few minutes from wet to dry.

 

[alex13]

Unfortunately I don't have a hair dryer. But we had the heaters on full blast and a fan all day. The colour went down in the areas under the fan, but the moisture reading stayed at around 39%. Do you think it could just need more time (and heat/air movement) and might be ok?

 

[chirpychippy]

Might be an idea to put a dehumidifier in the room to see if that helps...

 

[dazlight]

40% on what meter ? No such reading for concrete.

 

[dazlight]

Does the sub floor have a sheet damp proof membrane under it ? You can usually see it around the walls coming up from the floor

 

[dazlight]

The sand and cement would be full of moisture for months. What smoothing compound (SLC ) did they use?

 

[alex13]

40% on what meter ? No such reading for concrete.

I'm not sure does that mean my moisture meter is wrong, or it's not concrete?

Does the sub floor have a sheet damp proof membrane under it ? You can usually see it around the walls coming up from the floor

yeah we'd definitely seen dpm poking out, and fwiw there was some EPS insulation below the top layer of screed

The sand and cement would be full of moisture for months. What smoothing compound (SLC ) did they use?

I don't know the exact brand, but it wasn't one of the two-part ones (I think latex ?), it was just add water type.

~

The original concrete floor was tiled, and had to have some material removed from the top so it could be levelled to match threshold with floor boards. we hadn't noticed any damp before but I'm not sure any measurements were taken after the old kitchen was out.

With all the water kicking about, when the plumbing was going on (puddles of water I noticed once). I wondered whether it's possible that the water had seeped in and around the EPS and into nooks and crannies, not dried out before the SLC went on top, and wheter this would be a reasonable explanation why the SLC is taking so long to dry... everything went down within a matter of couple of weeks.

 

[dazlight]

Get a fan on it to blow air over it. A latex smoothing compound as always better then a water mix for kitchens as a latex is moisture tolerant. I’ll just wait for a few weeks and see if it dries out more. A moisture meter reading relative humidity is needed. The subfloor needs to read under 75%RH

 

[alex13]

thanks @dazlight . we'll keep the fan going and heating on for now, and cross our fingers and toes .

would you think best to delay installing kitchen until this is visibly or measurably dry then? is it likely we'll have to tear it all out and start again? ( ( even assuming it's not a rising/penetrating damp problem)

I'll also have a look for the proper moisture meter to see if we can get one. and mention about the latex slc alternative, but maybe that ship sailed now.

 

[alex13]

Thanks all for the input, we're a bit low on tools but got the fan + heaters on it for 24 hours and and it's visibly looking dryer.

This morning I also noticed that some areas that didn't look wet, but near the wet patches are not as hard too -- if I scratch thumbnail over it, a load of the material comes up. In other areas it's rock hard and nail just scratches over the surface.

I've read as much as I can on the internet and the culprit of "not hardening" seems to be either a bad/out-of-date batch of SLC, or incorrect mix (too much water etc). I wonder if this would explain away the patches that are darker, maybe it's actually sucking moisture out the air or something like that? Also whether it might never set/cure fully and be a dust/damp generator for all eternity.

Ultimately I think we need to understand whether it needs taking up and redoing, but struggling to figure it out.

 

[dazlight]

The cause I see a lot of a weak top is the builder over waters the mix. Seen it 8 out of 10 times. They put more water in Be a use it flows better. I Always tell them to use a bag and bottle as you can’t go wrong.
we used ardex CL today.

 

[alex13]

Wow that looks amazing - just what we're after .

Will check out the ardex CL. Given that the floor is also not flat/level it might be the ticket for a final layer to smooth things out - anything close to that photo would be a dream result right now!

We're monitoring it now, some larger patches improving but still the random 3 dots persist.

Thanks for all the input - really appreciate it!