Tim Watts wrote:
On 10/11/16 19:10, Phil L wrote:
RMann wrote:
Hi everyone,

We would appreciate some advice on the below issue:

There are cracks apearing on some if the walls through out an area
of the house (internal) and I need to asatain if there is a serious
problem. When I recently had a small room upstairs re plastered I
noticed there was some decay upstairs between the iner suporting
wall and a small gap between the iner and outer wall.

Not very clear.

do you mean there is a gap where an internal wall meets an external
wall? - if this is the case then there's a serious issue here. The
external wall is moving away from the internal walls - the internal
walls will stay where they are when the external walls start to fall
over....also it's unlikely to be wall tie failure as mentioned
elsewhere - when wall ties fail, the external leaf of brickwork
parts company with the internal leaf, that is, the cavity gets
wider, the internal leaf of the outside wall doesn't generally move
away from the internal walls.

I've seen it happen once - in the house I grew up in. My bedroom - the
solid double brick external wall moved slightly away from the
breezeblock inner wall and opened a gap of about 1/2".

My dad cleaned it out, stuffed it with 3:1 mortar and plastered over.
It never moved after that. Not saying the mortar was holding it -
just that it was probably a one off slight movement that found its
new position and was happy after that.

Yep, seen that a few times myself but it's unusual.

Cracks growing visibly in length or width inside the space of a month are
generally very bad news. If the external walls are sinking, and it sounds
like they are, the internal ones, being built up off the internal floor stay
put, this is noticable when plaster cracks upwards towards the bedroom
ceiling at 45 degrees on internal wall, starting from an external wall