In article ,
dent writes:
Hi all,

I need to cut a vertical slit at least 4mm wide through a 100mm wall,
and up to a height of 3m from the ground (for a vertical DPC where a
new extension joins a house). What is the best tool for the job? I

I'd have to say this sounds rather misguided in the first place.
Who advised doing this, and for what purpose?
Has a structural engineer been consulted on the weakening of the wall?

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]