WHEN BUILDING A NEW HOUSE EXTENSION,WHERE DOES THE DPC GO IN RELATION TO THE PROPOSED NEW FINISHED FLOOR LEVEL?

I,M BUILDING AN EXTENSION,TO MY OLD VICTORIAN HOUSE,I,M DOING A 275mm CAVITY WALL,THE EXISTING BUILDING HAS NO DPC.WHEN BUILDING A NEW HOUSE EXTENSION,WHERE DOES THE DPC GO IN RELATION TO THE PROPOSED NEW FINISHED FLOOR LEVEL?
2 bricks above floor level. Should be on plans if ext has passed council regs.


Dpc can be, 2 courses of engineering bricks, a course of slate, or the norm, off a roll.WHEN BUILDING A NEW HOUSE EXTENSION,WHERE DOES THE DPC GO IN RELATION TO THE PROPOSED NEW FINISHED FLOOR LEVEL?
External leaf - should be 150mm above finished ground level


Internal leaf should connect to damproof membrane if you are having a solid ground floor. There is normally a dpc across the cavity to direct any water to weep holes in the outer leaf. Building control are usually hot about dpc's (you have made a Building Regs application, I hope). Note that many Victorian houses actually do have damp courses as they came into general use in the latter part of the 19th century (although normally in the top end of the market). You might be struggling to achieve the required U value with the thickness you mention - but presumably you have calculated this?
If you are putting in a solid floor then there will be a damp proof membrane under the floor screed which should go up the inside of the wall and into the inner leaf of the cavity. External dpc should be at least 2 courses of brickwork above ground level. Internal floor can be lower if dpm properly laid. Don't forget to take dpm into original structure.
it will be indicated on the plans and specifications you had passed by the council