Self levelling compound - cracks appearing

S

smokeybear

Guest
Hi,

We're nearing the end of an extension & all tiling is complete except for the kitchen floor. This floor was part of the old house & used to be 3 rooms so all floor levels were different. Obviously this had to be sorted before tiling. Looking back we know the right thing to have done would have been to dig up the old floor & pour a new one but hindsight is 20:20!

We instead used self levelling compound which had to be poured quite thick in places (up to 10mm). We applied it in layers allowing each layer to thoroughly dry before applying the next one. Now the floor is finished & level enough for tiling but cracks are appearing in one corner of the room & it looks as if the compound didn't 'stick' to the floor in this area. Our fear is that if tiles are laid on it that they will lift after a while.

Is our only solution to lift this section of floor & repour or is there anyway to repair the cracks?

Tks in advance
 
I think the general advice when using levelling compounds to level deeper hollows is to add fine sand to the mix, to prevent cracking. If you're worried about the quality of the bond in a particular area you should test it- with a bolster and a club hammer! If the poor bond is confined to a small area I'd just take up the affected area, prime with polybond and trowel in some fresh levelling compound.
 
Whats the overall thickness of the SLC? It can be poured up to 2" so I would not panic about 10mm.
It needs time to dry as it is mainly water.
 
Thanks for the replies, having looked at the floor again I think we're going to have to take up the affected area :( Oh well that'll keep himself busy for a couple of evenings!
 
floor levelling compund is only suitable for small heights, the best job all round is to screed the floor to a level with sand cement. Your floor will then be perfectly level. Two layers on top of each other is like to glass plates. They dont bind to each other at all. This is why its cracking. Talk to your tiler as most will not tile on it.
 
A sand/ cement screed is no good either unless it is sufficiently thick (or reinforced) to resist "curling" cracking and delamination. Thin screeds (less than 50mm thick) need a good mechanical key and a bonding agent to be successful. Self levelling floor compounds are fine for thicknesses up to 10 or 12mm; I'd concur with kkelliher other points.
 
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