Screed or SLC for uneven floor

[junglejim01]

Hopefully someone can help?....

Floor area = 3mx4m
I've discovered that the concrete floor is very uneven. I've put a straight edge from one end to the other and it would appear that the middle dips down 2cm . I want to lay new laminate ontop but am worried that the difference in height will cause problems. I'd thought about Self levelling compound but i believe 3mm is the max thickness per layer...so thats a lot of SLC. So i'm now toying with the idea of mixing up a few bags of sand/cement mix and trying to level with a straight edge.

I'd welcome any thoughts/suggestions. I'm not after a perfect finish just something less wonky that i can lay laminate over.
If I go for sand/cement can i add slightly more water to make it more spreadable? Or will this cause shrinkage problems?

Thanks in advance.

 

[dazlight]

The minimum thickness is 3mm mate for smoothing compound screeds. SLC as you call them.
Most go 3mm to 10mm. You can add granno chips to the mix to bulk it out then you can go on thicker.

 

[HH1]

Or even 50mm in one application (Wickes deep base)

 

[junglejim01]

Thanks, the Wickes stuff looks good. Any tips on getting a whole floor level within the working time. How well does it level itself? i was thinking of having 1 person constantly mix a bag at a time while the spreads across the floor but does it need a floated finish?

cheers

 

[junglejim01]

also...with the wickes stuff i reckon i'd need approx 10 bags which is quite expensive compared with sand/cement...any advice on sand/cement?

 

[dazlight]

The problem with sand & cement is when you put it on thin it can easier break up.
If you go to a flooring stockist you can pick up a latex screed and granno.

They would have a base screed to to see which is the most cost effective.

 

[HH1]

How well does it level itself?

I don't think any SLC actually self levels all that well. (but I stand to be corrected if someone knows better )
Yes, you will need to give it some assistance when its poured, using a float to push it into corners and generally try to get it reasonably level before it starts to set.
As for floating anytime after that, no, every probability it will ruin the surface finish. I have used a similar wickes product and once it had started to set didn't go near it with a trowel, although did use the trowel to evenly spread it about when pouring.
Get it poured, level it best you can with a float and it will take up any minor imperfections by itself as it sets.

There is a customer review section on the wickes site for the deep base and other versions, probably worth while reading those.
The instructions call for a specific amount of water, some people have added a little more (0.5 litres or thereabouts) to make it more workable. It's mentioned in reviews and its your final decision whether or not to do so.

Recommend you obtain a proper paddle mixer, not just a paddle on the end of a drill. I did purchase the wickes one a while back and surprised its only got a one star rating, it worked well, granted its only been used twice now, first time was 4 bags of SLC. Found it easier to work with than the drill + paddle.

Would also agree with you about it being a 2 person job, I was working on 2.4mx1.7m and felt a bit rushed doing it, probably would get assistance if doing similar again.

 

[junglejim01]

Thanks for all the replies. I'm wondering a couple of things:

1. Is there any reason not to mix with a cement mixer? They're a lot cheaper on ebay than paddle mixers.

2. is it worth levelling in 2 layers to allow more room (time) for error? or best to do the lot in one go

Cheers

 

[dazlight]

Yeah 2 hits will be better.

Your fine with a cheap paddle.

A mate of mine didn't have his mixing drill once and made one from a metal coat hamger. Then used his cordless drill. It worked too.