Dips in screed floor

[SKB]

Hello,

 

Hoping some one may be able to offer advice. My living room floor has started to develop dips under the carpet. We have pulled up the carpet and found cracked dips in the screed. Not sure why this has happened? It was a small area to start of with but now more areas have come up in various places. There are no cracks on walls. We don't believe its subsidence. The dips are central to the floor. Could this be rectified by digging up the current screed in the complete living floor space and laying new screed? Or should we dig up the areas that are dipped and rectify those with new screed?

 

Appreciate any advice!

[Big Jimbo]

It could well be badly laid screed. Not compacted enough when it was put down.

[recoveringbuilder]

Could it be that it’s been a layer of self levelling that’s been put on top of the screed to level it out and it’s actually it that’s breaking up?

[SKB]

We think it could be a compacting issue, it's hard to tell as we never did this extension. The previous owners did. We've lived here for 5 years and have noticed more dips and cracks appearing. The worrying bit are the dips that are appearing. We've been given advice to dig down a section and see if it's affected the concrete slab. 

[Big Jimbo]

Fingers crossed it is just a badly laid screed.

[SKB]

Would you suggest digging down in areas where there are dips to see if there is an issue with the concrete slab? If no issue then would you suggest laying fibre screed? 

[Big Jimbo]

5 minutes ago, SKB said:

Would you suggest digging down in areas where there are dips to see if there is an issue with the concrete slab? If no issue then would you suggest laying fibre screed? 

I expect you will find it cracked all over, and prob end up re-doing

[Mr Punter]

The photo shows stuff that looks about 5mm thick.  Normally screed is between 30mm and 80mm.  Yours looks like a levelling compound laid over an existing floor.  Dig a bit out and see.

[Ian]

@SKB

I’ve seen that problem a few times over the years on my commercial projects and each time it happened it turned out to be an issue with a traditional sand cement screed which had been laid with insufficient water in the mix. When there’s insufficient water the chemical reaction can’t take place right through the thickness of the full screed depth so the surface typically forms a hard skin that is 10 - 20mm thick  but the main body of the screed doesn’t cure and remains as a dry mix. The surface skin obviously can’t bond to the rest of the screed and it isn’t thick enough to take normal loads so eventually it starts to crack up just like your photo.

Edited September 28, 2020 by Ian

[nod]

I would be very concerned that this has happened after five years 

Usually screeding problem come to light within weeks of being laid 

How is the masonry and plaster 

Is there any cracking?

[SKB]

Hi Ian, thanks how much would it cost in your opinion? My living room size is 6.5 m length and 3.6m width. 

 

Hi Nod, the brick work and plaster have no cracks at all. I have checked both internally and externally.