Any idea what these horizontal, slightly jagged cracks could be?

[dijc]

I've had various people look at the house.

Before buying it:

Mortgage survey - no mention
Building survey - not specifically mentioned. Of general slight cracking, said it was considered to be "due to shrinkage of materials" with no action necessary apart from "making good before redecoration"

After buying it:

Builder #1 - no mention
Structural engineer - possibly wall tie failure or "slight movement of the roof"
Builder #2 - possibly wall tie failure

Cracks are less than 1mm and, as far as I know, the house hasn't been redecorated for about 20 years. I can't see if there are any corresponding external cracks because the areas externally are covered by coving (I think that's the right word). Certainly there are no external cracks which are visible elsewhere.

I believe the next step is going to be to get some scaffolding up so it can be more closely inspected, I think by removing a brick(s).

In the meantime, does anyone here have any thoughts on what they might be?

 

[^woody^]

If there is a roof above that room then it has moved and moved the top course of blocks/bricks with it.

 

[dijc]

Thanks for your reply, much appreciated.

Yes, there's a roof above.

The pictures are actually from four different first floor rooms (well, three and an upstairs landing).

What would be the recommended course of action?

 

[vinn]

I dont think that its significant but it would be useful to locate the cause.
Besides "shrinkage" did any of the above mention thermal movement?
Will you post pics of the outside.

Presumably, the ceiling in all 4 pics is the first floor ceiling?
How old is the house?

Have you been in the loft & examined the rafter/joist connections at the wall plate?

 

[^woody^]

It is possible that the cause was over zealous fixing and some early or once only shrinkage.

Even some rough building where the carpenters knocked the brickwork and loosened it.

Or maybe the top of the walls are timber and the crack is at the joint.

It's unusual to occur on internal walls, as roof movement (ie normally roof spread where the roof tries to push the external walls outwards) tends to show on the external walls where the rafters are fixed. Typically opposite external walls.

Without seeing the roof layout and plan of the walls and crack locations is difficult to say a lot more.