Huge cracks after chimney support - normal?

[sparrow6]

Hi,

I've just had my brick chimney breast removed on the ground floor only, and supported with RSJs (as per Structural Engineer's plans). When the beams went in and the strongboys removed, the stack dropped about an inch, leaving huge cracks in the plasterboard of both floors above. The house is wood-framed (1800's) and none of the walls involved are supporting walls. The building inspector is happy that it's nothing to worry about, structurally speaking.

The builder wants to charge extra to fix the huge cracks, which will involve rebuilding 3 or 4 of the partition walls upstairs - is this right?!

We're worried that we're paying a lot extra (that we can't afford) to fix a mistake that shouldn't have happened in the first place.

Any help or advice much appreciated!

S

 

[ree]

The chimney breast runs from the ground floor to the chimney stack above the roof - anything below the roofline is the c/breast. More than one flue can run up in a c/breast - do you have more than one fireplace in the chimney breast? Do you have more than one chimney stack?

What do you mean by: "non supporting walls"?

Are you referring to plaster board walls or ceilings or both?


I presume that the drop of one inch is referring either to the RSJ's or the c/breast that is supported by the RSJ's?

Unless you post pics we cannot see what you & the BCO can see. Lots of pics of the cracks, the RSJ's (if possible), the c/breast at each floor and in the loft, and exterior pics of the stack and the wall the c/breast is on (if its on an external wall)?

Is there any possibility that you could scan & post the: "Structural Engineer's plans" - leaving out any ID details?

FWIW: Timber framed houses from the 1800's are usually listed. Is this a listed property?

 

[kazuya]

an inch? how did that happen? it shouldn't have dropped at all
it should have been packed tight above the beam with slate and sand an cement
did he forget that bit?

 

[^woody^]

No it's not normal.

A competent builder would have packed the brickwork to make sure that it did not drop. If he did not, then he is responsible for the cracks and making them good.

The alternative is that the beam is undersized.

 

[sparrow6]

Hi all,
Thanks for your replies - great help! Our builder is saying that it was 'unforeseen' and that we will have to pay. I'll mention packing and see what he says.
Thankfully we haven't paid the final balance so at least we have room to talk.
ree - we're not listed, thankfully! It was a chimney stack with two flues, we removed the whole ground floor portion, leaving the whole of stack going up through the second and third floors supported on (huge!) beams. All of the walls in the house (bar one which is brick) are plasterboard walls - the cracks are in the plasterboard walls on the first and second floors, and the floor of the first floor has sagged by an inch (dragged down by the chimney when it 'fell').
Thanks
S

 

[theprinceofdarkness]

If there are no other cracks, then the problem is that the weight of the breast has caused the floor joist to bend downwards which is trying to pull the partition walls down with them. A very interesting point could be that, either a big triangle of bricks at the front of the breast has dropped and is now loose and sitting on the RSJ and joists. Or the whole of the front of the stack has sheared off and is not bonded to the rear wall. I do not think either of these effects will be cured by a bit of filler in the cracks.
Frank

 

[ree]

Most timber frames i've seen or worked on had most of the framing exposed - inside and outside. Do you have modern stud walls ("partitions) built next to the timber framed walls?

Anyhow, the builder took on the job after viewing the situation ie what he could be getting into. So, on the face of it, he's responsible for what you describe. If the lintels are packed against sound masonry and seated on padstones then the c/breast should remain in position.
There are other variables to take into account.

Pics and plans would help because what you describe sounds concerning. Did the SE visit the property before submitting drawings?

For the time being dont use any appliances or solid fuel fires in the remaining fire places.

 

[^woody^]

the problem is that the weight of the breast has caused the floor joist to bend downwards

That probability is dealt with via a deflection check when calculating the beam section size. The beam should not deflect (bend) so much when the weight is applied, so as to crack plaster, let alone walls.