Solid cavity wall on timber floor

[pls1]

Working on a project at the moment to build a single storey extension to infill the space between three adjoining external walls of a house.
Having incovered an existing fowl drain pipe and gas main, the architect has changed the plans from concrete foundations/slab to a suspended timber floor with 75mm concrete screed on top. The first issue I see is laying a concrete screed on timber joists/ply floor. More worrying however is seeing the cavity wall sitting directly on the timber floor with no support underneath (since the timber joists cantilever out from existing walls).
The amended plans below show how this will work, its apparently been agreed between the architect and BCO. Personally I have serious reservations about the design - what do others think?

Untitled

• pls1
• 7 Apr 2013
• 1

Untitled

• pls1
• 7 Apr 2013
• 1

Untitled

• pls1
• 7 Apr 2013
• 1

 

[^woody^]

Get something in writing from the designer or the BCO, and also tell your client that this is unusual, and you are only carrying on under their instruction and against your advice. This should discharge your duty of care if things go wrong

I can't see how this design can be acceptable building practice

 

[limerockconstruction]

I've never seen anything like this, seems a bit ridiculous to me for a number of reasons.

 

[^woody^]

Loading issues aside, I cant understand why the floor extends past the cavity wall, and yet there is a cavity tray specified for the wall

 

[tony1851]

That has to be the most ridiculous construction drawings I've ever seen.
There's no point in listing the faults, it isn't even worth considering.