Cracks from knock through (threads have been merged)

[John Wardle]

Wondering if it's common to get some cracking in plaster work above rsj. Plaster is new above rsj in the room.

 

[oldbutnotdead]

Depends on what sort of cracking. Could be the RSJ was underspecced & is deforming with load, could be the wall above the RSJ wasn't packed sufficiently and is settling slightly. Pics would help, as would posting in the correct forum (Building)

 

[John Wardle]

Hi I think with it not being packed properly an it's settled a bit . I had it redone an pushed tight up . Just a few more have turned up on wall by window

 

[Notch7]

not being packed properly

Was it wet packed? -the image gives that impression.

 

[John Wardle]

Hi I had a knock through done. An I have a few cracks in plaster in room above plaster is new . Wondering is it common for this to happen. As wall rests on beam. Originally was not good enough so had it redone as it needed better packing. Cracks are above the new wall. Plus few more in bedroom

 

[John Wardle]

I'm not sure . What's difference

 

[JohnD]

Is the mortar joint really as thick as it looks in the second pic?

 

[geraldthehamster]

Is the mortar joint really as thick as it looks in the second pic?

And if so, was it packed out with slate?

 

[Notch7]

I'm not sure . What's difference

Well usually the best method is to put the steel in, and fit a padstone tight up to the steel with no gap.

If there is a gap, then usually concrete slates or steel shims are used -below the steel and dry pack above

Your pic looks like thick mortar put in wet -although that could be just infill around shims.

Generally the wall below looks poor -if those are actually big mortar joints.

I expect a pro builder will be along to comment......

 

[John Wardle]

Other side of wall

 

[John Wardle]

Should I be concerned if there is a slight settlement

 

[JohnD]

mortar shrinks as it dries, and the more water, and cement, it contains, the more it shrinks.

There is an additional problem when trying to pack a gap, it will slump downwards under its own weight before it starts to set. The wetter it is, the more it slumps.

To my eye it looksd like your mortar contained excessive water and cement, so will slump and shrink more than usual.

The mortar bed is also too thick.

 

[John Wardle]

The cracking is from a bad install before. I got done first time. This is someone else I brought in to fix it

 

[oldbutnotdead]

The cracking is from a bad install before. I got done first time. This is someone else I brought in to fix it

Well that doesn't make sense. Those pics with the massive mortar beds- are they as the thing is installed now or from the previous attempt (which IIRC involved a windpost and other excitement). And were the cracks evident after the first go or have they only appeared after the 2nd go?
I wouldn't expect cracks that big in fresh plaster after such a job- in old plaster maybe but even then only hairlines, those look 2-3mm

 

[John Wardle]

Big mortar beds are as it is now. The cracks are from the 1st go they are still the same an not got any bigger. At first there was a windpost which was told to put in but got rid as other people I brought in had never seen anything like it. So now goes into wall