finished floor level

[cartoon1]

The finished floor level on my new extension is lower than my existing house. To cut a long story short, I need to lower the f/f/l of the old floor, which is concreted.

I will have to remove the concrete, probably go down a lot lower, and put in insulation,dpc membrane, and re-screed.

Any ideas on doing it efficiently?
should I use a kango drill to remove the concrete, or a concrete saw? I do not want to cause damage to the house...

 

[Symo]

Unless I'm missing something obvious, wouldn't it be far easier to bung a scread on the extension floor to bring it up to the level of the existing floor??

Symo

 

[carpetman]

symo is bang on rase the floor in the extension