Thickness of concrete slab - 75mm
 

I'm having the slab in my kitchen replaced. The plan is: 50mm scalpings,
DPM, 50mm Celotex, poly sheet, 75mm concrete with fibre and extra sharp
sand, no screed. It will be tiled with porcelain tiles and a decoupling
membrane.
I'm slightly concerned about the concrete thickness (75mm rather than
100mm) because I can't find anything that says just how much difference
the fibre strands make. Any comments?