I have an existing concrete shed base which is a bit cracked (due to a nearby tree) but generally OK. I'm planning to replace my 10x6 shed with a 10x14 one which will mean extending the concrete base.
My plan was originally to dig the new area and fill with hardcore (up to the same level as the existing concrete) and then lay new cement (with a DPM) on top which would be 4" high from the existing base.
However, I've been told that laying cement on existing is a bad idea as moisture could get in and blow the new concrete, and that I should instead break up the existing concrete before laying the new cement on top.
Is that true? What are my options?