Screed prep advice (laitance?)

[VDubDan]

Evening all. A few months ago I decided to have a bash at DIY screeding my extension floor - a readymix sand cement screed, with fibres, on top of a vapour control layer above insulation.

Being honest, it's a decision I've regretted since - the conditions on the day were torrential and it's just something I regret getting involved in. But, I got it down and it's not a million miles out.

That was 3 months ago now, the room is pretty well ventilated so it should be plenty dry. My query is laitance. Firstly, do I have it (I suspect so):

Pics are hard to grab, but here they are:

https://imgur.com/a/ibIkpOA

So, have I got a problem here? I can get the top layer off with some decent scraping with a masonry bit around the edges but it's not easy - the floor looks looser in the pics than in real life, probably should have swept first. I've obviously been working in there and haven't noticed it being particularly crumbly or anything. Away from any edges it scratches as you can see, but that's about it

Laitance seems to be one of those things that reads badly, but I feel like the screed is about what I'd expect even if a builder had done it, and I feel like they'd have just rolled up and chucked on some self levelling for better or worse.

So just after some advice really. Intention is to self level, and then tile. What's the best way to prep this floor?

 

[VDubDan]

Nipped back down to take a probably useless video of me scraping at it. For context, that was pretty much full force and hurt my hand

https://imgur.com/a/5Te1F5q

 

[dazlight]

Looks a bit weak. What was the mix?

 

[VDubDan]

Looks a bit weak. What was the mix?

Like I say, readymix so not 100% sure but we discussed what it was for etc

 

[dazlight]

Floors like that we put 2 coats of uzin PE404 on top to strength it and it’s a liquid Dpm

 

[VDubDan]

Floors like that we put 2 coats of uzin PE404 on top to strength it and it’s a liquid Dpm

Cheers! Do you do any prep prior to putting that down?

And am I good to put self levelling compound on top?

 

[dazlight]

We would grind it till solid but if it’s weak we just scrap any thing loose off then 404.
or we use uzin PE425 to consolidate the screed

fball do a Similar one as well

 

[VDubDan]

We would grind it till solid but if it’s weak we just scrap any thing loose off then 404.
or we use uzin PE425 to consolidate the screed

fball do a Similar one as well

Thanks again, Daz. Do you reckon it's worth renting a hand grinder and just taking off the top layer?

 

[Mr Chibs]

Was chatting to a plaster last week, as I've a floor that wanted doing, said I was going to do it myself, he asked what mix, I was going to use 4:1.
He said it 'dusts up' a lot, would be better as 3:1 would have been interested to find out your mix.

As for laitence, I found a scrubbing brush and thin wall paper scrapper did the trick for me.
I've been advised to use a crack suppression mat, before tiling, and after priming. I've got wet UFH, so possibly this is why.

If you want to harden up the top surface of sandy substrates, I use Everbuild 406, it's cheap and works a treat.

Seeing your images, and depending on room size, sanding might be an option, otherwise its some SLA.
What are the room dimensions?

 

[VDubDan]

Was chatting to a plaster last week, as I've a floor that wanted doing, said I was going to do it myself, he asked what mix, I was going to use 4:1.
He said it 'dusts up' a lot, would be better as 3:1 would have been interested to find out your mix.

As for laitence, I found a scrubbing brush and thin wall paper scrapper did the trick for me.
I've been advised to use a crack suppression mat, before tiling, and after priming. I've got wet UFH, so possibly this is why.

If you want to harden up the top surface of sandy substrates, I use Everbuild 406, it's cheap and works a treat.

Seeing your images, and depending on room size, sanding might be an option, otherwise its some SLA.
What are the room dimensions?

Cheers - it's about 6m2. No UFH or anything.

 

[Mr Chibs]

Think I’d use self levelling compound.
To level it up, the final result should give you an easier tile job.

 

[VDubDan]

Slipped a builder a few quid to come and have a quick nose and he was pretty happy with it overall so I'm probably making a mountain out of a molehill. So I'm gonna grind it back a bit over the weekend and get rid of any high spots and loose bits then I think I'm just gonna primer it and self level.