In article ,
George Miles writes:
There's a shared double brick wall between my part of the house and the neighbours. Does one brick belong to both of us?

No, it's a shared wall, right through to both sides.
BTW, you probably mean a 'full brick' wall, i.e. it's the width
of a brick length (9" in old money, plus any finishes applied).

If I plan an extension, would it have to stagger in one brick so it joins onto mine of the two, or could it continue along the line of the existing wall if the neighbour agrees?

The best way to do this is to get your neighbour's permission to
extend the existing wall as it is, which includes going over their
side of the boundary. In exchange, it's shared and they also have
the right to use it for supporting an extension. This would all
need to be done via the Party Wall Act as mentioned previously.
You need to pay your neighbour for getting independant structural
advice, to ensure their property isn't damaged and that the
foundations laid will support additional load of their extension
later.

If you can't get the cooperation of your neighbour, you will need
to step the wall in, possibly by a full brick length. You will in
any case need to go through the provisions of the Party Wall Act,
including paying for independant structural advice/survey for your
neighbour (unless they are silly and decline independant structural
advice, but if they have a mortgage with moderate to high loan to
value, their lender will insist on this anyway).

--
Andrew Gabriel
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