Measuring existing screed depth

[GilesP]

Good afternoon,

We have recently bought a 1960s bungalow which has an uninsulated raft foundation. I am looking at whether it is worth removing the old screed and adding insulation before re-screeding.

The problem I have is that I don't know the depth of the existing screed. Is the only option to dig a test hole until I hit a DPM? What would the consequences be if I were to puncture it?

All advice appreciated.

Edited: uninsulated

 

[freddiemercurystwin]

There would be more gain (thermally/£) by adding more insulation elsewhere.

 

[GilesP]

Thank you for the response @freddiemercurystwin.

Ignoring the gain/cost argument for a moment, what would be the easiest way to determine the existing screed depth?

 

[freddiemercurystwin]

How do you know it's a screed on top of a slab?

 

[GilesP]

I am assume it is as the CH pipes are running through the floor. Is this a false assumption?