Inner block skin on raft foundation

[Whynot123]

Hello,

I'm wondering if anyone has any knowledge and experience about building on existing raft foundations. My garage has the following spec for it's raft foundation with a single skin brick wall, in good condition, with DPC at the level indicated on the diagram:

Is it structurally viable and common to build an inner skin, load bearing block wall to create a cavity wall (with DPC at the same level) directly onto the existing raft like this:

Thanks for your help

 

[freddiemercurystwin]

Yes, going by the size of the raft.

 

[Whynot123]

Thanks for the quick reply, yes I thought in principle the raft size and depth was good (this is the detail on plans I have from when it was built but I've still got to check by digging a hole, etc). I was concerned with the additional 150mm that's common on rafts and whether this affected building an inner skin directly on it. As the outer skin sits lower.

 

[^woody^]

You'll need to form a cavity tray, and form weep holes in the outer leaf at dpc level