" wrote:

Greetings,

I think the 1 1/4" rule is specifically for framing or wood and does
not apply in the case of masonry but I could be wrong? If there is
another rule covering minimum depth for this application I am not
aware. If the walls were plaster I think I could plaster plain MC
directly into them. I could always turn the trench into a "small,
thin, section of plastered wall". Logically I don't see why I would
need to embed the PVC coated MC deeper if the trench was filled with
mortar? That doesn't mean there isn't a rule but I am not aware of it.

William

That's why you need to ask locally...