Calculate foundation concrete level double thick dpc mortar

[SpecialK]

Hi,
I have dug the trench for my foundations for my extension. I need to calculate the concrete top pour level. Im going 3 concrete block courses below DPC.... so pour the concrete to 675 below DPC level?.
The DPC on the house is in 20mm of mortar. Should I measure down from the DPC mid way of the 20mm to 675mm? Or do I measure from the top of the brick below the DPC?

Im assuming the DPC normally is in 10mm of mortar? Extension is being rendered so matching doesn't matter...

Thanks...

 

[23vc]

For the sake of 10mm difference you could do either, you adjust the underground bed depths accordingly to bring the dpc up to the desired height. Put pegs in the trench to get the pour level as accurate as poss

 

[SpecialK]

Great, thanks.
I will try and get the top of the new wall level with the house DPC...

For the sake of 10mm difference you could do either, you adjust the underground bed depths accordingly to bring the dpc up to the desired height. Put pegs in the trench to get the pour level as accurate as poss

 

[stuart45]

Im assuming the DPC normally is in 10mm of mortar?

You often find that the DPC joint is a thicker, ugly joint.
In the West Country the DPC is often laid straight onto the brickwork on the face work. Although it's bedded in most parts of the country it does make a neater joint.