Lowering a Very Thick Concrete Floor

[g80]

Hi, I have a detached garage and I was looking to make some changes.  My current plan is to extend the width of the garage by approx 2m and insulate the whole thing, the minimum I am looking for is to prevent frost and dampness but it would be nice to have it as a space to use as a games room/workshop. The building is single brick (there is DPC where the facing bricks start in the photo) and there are breeze block pillars every 1.5m approx internally to support the walls. As you can see from the photo the garage is raised quite a bit to bring it to street level. To do this there is 80-100cm thick solid concrete for the floor - I drilled a couple of holes to test this. My current thoughts are use a jack hammer to remove enough of the depth to add a DPC, insulate then add either a wood or new concrete floor above. I just wanted to get some thoughts as I am unsure if the impact from doing this will damage the walls and the breeze block support beams just seem to be resting on the concrete so I would also not want to disturb these. Any thoughts or input on how to tackle this is welcome. I know the lower brick work isn't great and I am going to repoint it.

 

Thanks,

 

Gordon.

 

[Canski]

I would be very surprised if that is all concrete. Are you sure ?

[g80]

I was quite surprised myself. I was a couple of brick rows up from the grass, drilled in approx 30-40cm and put an inspection camera all the way along, after the outer brick it is just unbroken gray concrete from what I can see. I can take a video of whats inside if that is useful?

[Mr Punter]

No.  Just put the DPC on top of the concrete lapping a bit up the walls, then 50mm insulation, another layer of polythene and some t & g chipboard.