Levels out in new extension

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Seeking some insights to help me go into the difficult conversation with my builder.

I have had a sand-cement(+fibres) screed floor laid in my extension, over wet UFH. The screed was levelled (+3-5mm) to the concrete slab in the original house. This resulted in a slab that's about 40-55mm thick. The problem is that this has left the screed floor 45-65mm lower than the DPC in the extension wall, which means I have a 45-65mm step up to my lovely sliding doors (sill & frame have been installed on the top course of bricks below DPC - which I assume is "normal". Glass isn't in yet).

Naturally I want my tiled floor to go up to the door frame, not up to a little step in front of the door frame. I can't really figure out where it all went wrong - it looks like the new DPC is 25mm higher than the original house so that could explain half of the difference - but that's probably not important now. More important - what are the options to fix it?

1. Liquid screed poured over the whole ground floor of the house (old concrete slab & new screed) to bring it all up by 45mm? (100mm over UFH too much)?
2. Some kind of gradient sloped away from the doors in levelling compound? (There's 7m from doors to original slab, so that'd be 45mm in 7000mm i.e. 6mm per m)
3. Remove the door frame, remove a course of bricks, and reinstall below DPC level?
4. Rip up the new floor and... do what?
 
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Wouldn’t (1) cause problems at the existing house external doorways?
(2) is a bad idea, you don’t want sloping floors to that extent.
(3) or (4) I doubt will work, you don’t want the finished floor level below dpc. But would need to see how they’ve detailed it at wall/floor junction

Step up from house to extension? May well not work if it’s open plan.
 
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3 is the only sensible one. 100mm plus skirting board and stop any internal plaster or render above dpc will be fine. Pay close attention to detailing on the door/wall joints (cavity closers, insulation to reduce cold bridging etc)
 
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Thanks for input everyone. Builder's solution is non-ideal but probably least problematic (and definitely least effort & cost for him). He's going to break out the inner skin and cavity filler to remove the step in front of the doors, then trim the exposed concrete below the doors with matching Aluminium so now we just have a deeper frame instead of a step. I'm not happy but I'm mostly over it now.
 

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