How to get both skins evenly to DPC

21 Oct 2014
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West Midlands
United Kingdom
On a single side story extension I'm struggling to work out how to get both skins evenly to DPC.

The extension will be blockwork and rendered. On the outer skin I'm after using 73mm bricks below DPC above ground level to match the rest of the house as they will be exposed below the render.

Any ideas are appreciated


  • Foundations to DPC.pdf
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Bricks for inner and outer skin up to DPM?
Yes, that does seem like the logical option but I was rather hoping for someone to wave a magic wand and tell me how I can do it in block for the mostpart. Cheaper, quicker and easier for someone with a low skillset like me!

The only reason I was going for brick below DPC on the outer skin is that i assume render can't bridge the DPC....
Foundation blocks up to just below ground level then brick up to DPC.

But really for you skill set trench fill.

You don't need to match internal and external DPC level.
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Trench fill? That's what I thought I was doing..... Do you suggest filling foundations to right below ground level then just do 2 courses of brick both inner and outer skin?
No idea did not look at your PDF.
Your internal DPC should match your DPM. Internal and external does not need to match.
The nearest you'll get is a block laid flat (cut one in half) and a single course of blocks then two course of metric brick.
Your making things difficult for yourself..

Either use metric bricks externally on the basis that you hardly notice the difference looking down at a couple of courses.

Or use the same bricks on both skins.

Or bodge the inside skin with a mixture of bricks, blocks, flat or on edge, slabs, tiles, big and small joints, or layer of concrete or screed.

Work to finished floor levels not DPC heights - but FFL is normally DPC height. And always guage down from this level to get your concrete height - after working out how the block and brickwork is going to work out
Or bodge the inside skin with a mixture of bricks, blocks, flat or on edge, slabs, tiles, big and small joints, or layer of concrete or screed.
7n dense can be laid flat - not necessarily a bodge either. We often find that when the conc' is particularly wet and the soil particularly porous, you can get an awful lot of concrete shrinkage (particularly on a deep mass fill) leading to ingenious ways of mucking up.
I should have said fudge not bodge. Anyone can bodge, but only the experienced know how to fudge.
Thanks for the suggestions. Also good to know to work back from FFL height to get foundation height.

Due to following the line of the current DPC, the new DPC will be lower than FFL. Not a problem is it? The poured slab will have its own DPM that laps up the interior wall to FFL.

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