On 04/07/15 09:43, Capitol wrote:
Adrian wrote:
We've got an outbuilding - block-built, single-leaf, '70s or early '80s -
which we're doing up at the moment. It's recently had the old, sloping
and rough, concrete floor broken up and a new one poured.

Doing that, though, one part of wall has developed some serious-looking
cracks. It's not a long section, maybe 1.5m, between door and corner. The
door frame goes all the way up to a heavy wooden lintel which runs most
of the length of that side of the building - so there's no tie between
this bit of wall and the rest of that side, just to the corner.

The cracking's showing in the internal plaster, top and bottom, and the
external render, bottom - the wood is visible externally, so the render
ends where the cracking would show.

The bottom line follows the DPC. The top line follows the top of the
blockwork. The guys who were breaking the concrete up reckoned they could
see the wall moving, but it "feels" solid. There's no cracking within
plaster or render of the main body of the wall.

What's the best way to deal with this? Seems there's three basic
routes...

* Ignore. It'll be fine...
* Remove as much of the old mortar as possible and repoint. Will it being
the DPC line make it more difficult?
* Take the wall down and rebuild it, supporting the timber (and,
obviously, the roof) in the process.

Cosmetics are relatively unimportant. The outside of the wall's going to
get re-rendered anyway, and the inside is going to be lined.

The DPC line is going to be flexible anyway. I'd strip the external
render, then saw/drill out the cracked mortar joints and refill before
re re-rendering

And if the cracks look like they are through the entire wall the OP
could add some resin stitches across the crack to stabilise it.