large crack in the loft

[msd78]

Hi all,

we are in the process of buying a detached property built in 1983 which extends over 3 floors. We noticed that there’s a large vertical crack of 8mm width at the top and 5mm at the bottom of the loft wall. The crack goes through the mortar and blockwork as shown in the attached photos. The house has cavity insulation and is double skinned. The owner redecorated in 2013 and all I can see just in the wall just below the location of crack at the loft is a hairline crack of 1mm. The external wall appears plumb with no cracks. The owner’s structural engineer gave a report stating that in his opinion this is a thermal movement crack but he has no liability for our purchase. Do you think we could trust this? Is it possible such a wide crack to be due to thermal movement?
We look forward to your responses as we’re under massive stress at the moment!
Thank you

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• msd78
• 30 May 2015
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• msd78
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• 30 May 2015
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• msd78
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• msd78
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• msd78
• 30 May 2015
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• msd78
• 30 May 2015
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[Agile]

Since its wider at the top than the bottom then my guess would be that its differential settlement of come kind.

But since its only on the internal wall I would say that its of little consequence.

But you don't say when the house was built or where it is.

Is it on clay soil?

Tony

 

[msd78]

thank you for your response. The property was built in 1983 and i assume (based on other sites in the area) that the soil conditions consist of 2-3 meters of sand which overlies chalk found at greater depth.

 

[theprinceofdarkness]

You don't sat where this wall is. If its a party wall, then the problem would manifest its self in the top of the front (or back) wall bulging out at its top where the top of it has moved and dragged the party wall out with it. No cracks would be seen on the outside.
If its a gable wall, then the above still holds and also there is normally a "ladder" built using the last internal joist to carry mini purlins over the wall to support the facia board. Could be that one of these has twisted , so breaking the last bit of blockwork loose.
Again could be the wall plate has moved outwards.
A local builder did not bother to strap his wall plates to the blockwork. Now twenty years later, many of his houses have had to be re-roofed. My brother in laws roof actually moved more then 6" of to the side at one end!
Frank

 

[Nige F]

Detatched house so it's a gable end - brickwork outside. If the rafters just showing in the pic are factory made trusses with metal plates on the joins I'd say there is a lot less chance of roof spread than a cut roof . So 1983 probably trusses and as said probably thermal cracking which those thermalites are prone to do . Just my opinion -

 

[^woody^]

Those are aerated blocks and that's how they crack. It's common and not a structural issue. Being the apex, there is no restraint at the ends, so the wall expand more near the top.

 

[tony1851]

It's not thermal movement - as Woody states it's normal shrinkage. All concrete blockwork shrinks to an extent, and the aac blocks particularly so.

Agree it's not a structural problem. (Assume the roof trusses are adequately tied to the wall, etc?)

 

[msd78]

thank you for the response. I keep wondering if shrinkage in the blockwork would cause such a wide crack. It's between 5 to 8mm and I thought that shrinkage cracks are smaller. What do you think? Unfortunately I can't tell what is happening in the walls below the loft since these were redecorated and any cracks filled in 2013.

 

[cjard]

Once upon a time a neighbour of mine called on a mate who was the senior building control officer at the council. He wanted the BCO to come out to have a look at a crack he was particularly concerned about, something similar to yours.. The BCO came, looked at the wall and said "Donald, what is the problem with this wall?"
'That huge crack right there'
"Where?"
'Above the door'
"Oh" said the BCO "you'd made it sound serious on the phone"
'Isn't it?'
"Serious is something you can get your hand in. That's a scratch, and it'll still be like that in 50 years time"