Screed cracking, pieces lifting in new extension. Is this a fault?

[Gemmando]

Hi, I’d appreciate some help with my new extensions floor. The screed was laid 8 weeks and recently (in the last 2 weeks) it has started to lift and crack. Please see the photo of one section (there are many)..

You can press the screed and chunks lift off …. Finger can push the screed down and you can feel the celotex underneath. 
 

Thank you 

[Declan52]

What depth is the screed at these damaged areas???

Was it mixed on site or delivered???

 

[Conor]

Need a bit more info as Declan says. Type of screed? Were the insulation boards firmly in place, taped and polythene sheet over the top (rocking boards or air gaps will cause issues))? Was there a perimeter upstand expansion strip fitted(if not, when the screed expands due to heat, it'll compress and crack)? What was the weather like during and after the laying (too hot and dry in the days following can be an issue).

[Dave Jones]

doesnt scream quality. Cant see any fibres.  depth ?

[Gemmando]

Thank you - really helpful. The insulation boards were not taped - just sitting cut in strips underneath and the screed was poured on top. It was not mixed on site. The weather has been warm and sunny - it’s a south facing room. 
 

The cracking seems to be occurring the most on the edges near the patio doors where the screed has less depth as was over brick and not insulation boards. 
 

What is the remedy for a cracking screed like this? Does it all have to be gunned out?! 
 

Thank you for your help. Speaking to the builder tomorrow… 

 

 

[ETC]

Remove and redo.