New Concrete Floor Cracks and Creaks - is it blown screed?

13 Apr 2013
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United Kingdom
Hi All

We had an old uneven concrete floor taken up and a new one laid at the end of January. The room is about 5m square and the new floor has a dpm and celotex in the first concrete bit and then screed on top.

We gave it a long time to dry out and only connected up the central heating in that room two weeks ago so the room was unheated for at least 7 weeks.

The floor now has 1-2 mm cracks that run the length of the room. As he laid the floor in three sections (but without any wooden bits between) I guess these are at the boundaries. There are also cracks running perpendicularly to these which I guess may show the boundaries of where the celotex boards were.

To be honest, I'm not too worried about the cracks but have noticed in the last week that of you walk along them, the floor sort of creaks. The builder says that this sort of thing is normal and there is nothing you can do. Having had a bit of a google though, some people seem to say that this could mean that the screed is "blown" and it needs re-doing.

We've nearly done all of the decorating now and are ready to order carpets.

I guess that the question I am asking is - is this kind of thing normal and I should just lay underlay and carpet and hope this cushions the creaks - or if I did this would I be covering up a problem that I then have to fix later.

Any advice would be greatfully appreciated as we've got a young family who are a bit tired of being squished up in what's left of the house so we could really do with moving back in to this room ASAP.


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The cracks shouldn't be there full stop .When the concrete was laid they should have put either steel mesh across hole area and poured the concrete in one pour
If you lay concrete in several pours to achieve one slab you must join the individual slabs together with steel rebars.
The creaking is more than likely dew to the fact that the insulation is moving under concrete only expectations is the sub floor under insulation is prepared properly .
Basically the hole floor has been laid completely wrong and should be removed.
Proper method would be to dig old concrete out till you get to the ground .
Put a layer of hardcore in this is then smashed into ground then pour the concrete putting a steel mesh in concrete. Then lay your insulation .Then a layer of screed with chicken wire in it.
Concrete should be no less than 250 mm thick.insulation should be 100mm thick .screed 75 mm thick.

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