Then I'd check out the article on damp at
http://www.onthelevel.in-uk.com/

I've seen that before and sort of accepted it until last summer
when I made a small slab of 4:1 mortar for test purposes, waited
for it to fully set and dry for a few weeks, then stood one end
in a bucket of water for an hour.

Damp rose up about one inch on the outside, probably more on the
inside. And that was with the waterproofing admix being sold by
Screwfix.*

I also did some rendering outside. In its unpainted state, if you
leave a puddle of water in contact with the base, it eventually
rises several inches.

If you take a concrete building block (the type with the coarse
texture) and slowly pour water on to one edge, it all sinks in.
Pour more and more and it eventually starts to come out the sides
part way down.

The holes in the block are probably too big for capilliary action
to carry water upwards, but they allow water sideways and can act
as a resevoir. This may feed the mortar which most certainly does
have some wicking action - seen it with me own mince pies!

Bricks may of course be a lot less permeable.

So how high does damp have to rise before it's classed as rising
damp? I can't vouch for it rising a foot or more, but there is
and effect which may be greater in other circumstances.

W.

* That doesn't mean the admix doesn't work. When it rains,
adjacent mortar soaks more water and holds it much longer. The
new mortar with admix dries very quickly, sometimes in minutes.
So it does do something but it is not suitable for tanking and
says so on the bottle.