Step in DPC between DPC level and floor level

11 Apr 2006
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United Kingdom
All of my front extension plans have used the house DPC level as a reference point. This was in order to match the DPC and finished floor level between the house and new extension.

Whilst taking a closer look at the front door, I've noticed that the DPC in the wall is actually lower than the DPC in the rest of the house, and there's a clear step-up in DPC level underneath the door threshold.

I want my brick courses to visually line up, so feel like I have to set the new DPC level in the brick work at the same level as the current house DPC level. Is it then a simple case of over-filling the concrete slab I pour by 2 CM, or pouring the slab as normal, but then laying 2cm of screed at a later date to match up the floor levels?

In the photo below, you can see the slightly darker DPC mortar course just below the door level at the bottom left of the door.

Is this normal?

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The position of the door sill relative to the dpc is not important.

The position of the existing dpc, to some degree is irrelevant too.

What is important is that when your new dpc is fitted it should at all times be no less than 150mm above external ground level and preferably be at the same level as the internal concrete floor.
Okay - I think I'm more comfortable with the concept now. I'm going to match the new DPC level with the existing DPC (on both inner and outer leafs) and then put 4cm of screed on the concrete slab to match the floor levels.

When I originally posted this my brain didn't seem to like the idea of the floor screed being in direct contact with the inner leaf.

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It is not unusual for b.c. to ask for a rise in the external dpc when the external ground (inexplicably) rises. So changes in levels do occur throughout a single build.

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