Dave T Scotland wrote:
Because we needed constant background heat we burned
the stove near tight shut all winter - the worst way, now we know, for
creosote/tar build up.

You are supposed to burn Jotuls well damped: more efficient,
which means more complete combustion. Where I bet you actually
went wrong was in your selection of wood: the species and/or
curing. Perhaps also the diameter and length of the pieces.
Your UK address throws up a big red flag for me on all those
points.


Made worse by a cold loft space the chimney went up thro.

Nah. Worse would be a tall exterior chimney.


Result, tar seeping out of the chimney pointing.

You could have the chimney thoroughly cleaned and then lined
with a flue. Or eliminate the chimney.

Either way, you also have the option of installing a separate
flue for the stove.

Frankly, "tar seeping through the pointing" after a single
mild (*) winter's use suggests the chimney's condition was
already unsafe quite apart from the tar! Did the person who
told you the chimney was good do an *internal* inspection?

(*) mild, because you're in the UK. Your winters are balmy
compared to winters in the northern continental US.

Una