New garage base over an existing base

[Tricky Dicky]

I have a sectional concrete garage stood on a concrete base which I think was originally a hard standing and drive. The drive, hard standing & garage base slope in two directions so the garage has a distinct diagonal lean. I want to replace the garage and level out the base area and erect a new sectional garage. Can I lay a new base over the existing base? If so what thickness of concrete and how can I incorporate a DPM?

The existing base is quite sound and has been in position since 1975 with no cracking or movement evident. As far as I know it was laid by the original builder of the house. There is one crack in the drive/hard standing part but appears to be old and shows no lateral or vertical displacement. This would be where a ramp would have to be placed to meet the new base level.

Richard

[lutonlagerlout]

richard this is not best practise
proper way is to break out existing base and re do from scratch

you could lay a 1200 gauge DPM all over the area then shutter it and pour a new slab 100MM thick minimum
maybe incorporate mesh A193 as an upgrade

LLL