In article .com,
wrote:
1. Doesn't a DPC make a weakness in the wall, or is the material such
that the mortar keys into it for a good bond ?

In theory it is a weakness but this is not usually a concern. You will
find pictures of very long walls without movement joints that have moved
on the dpc over time due to thermal expansion. A dpc would also introduce
a weakness into a freestanding (e.g. boundary) wall.

2. Is it better to use a waterproofed mortar and blue bricks ?

Not usually. You might if it is a garden wall and you really need a dpc

3. When inserting a DPC, is the joint thickness between courses usually
still 10mm, or is it thicker ? I need this for the plans.

Usually still 10mm with modern dpcs

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
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