Long crack in plaster - Should we be worried? Advice please.

4 Aug 2014
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United Kingdom

We could do with some advice please.

We bought our house 18 months ago. It is a late 1970s terrace property constructed of brick on a cement base. It is in a London clay area.

Soon after we moved in we noticed quite a long crack (probably more than a foot) in the plaster in the upstairs front bedroom on the wall that we share with a neighbour. The previous owners had had a wardrobe in this corner hiding it. We did not worry about it too much as it is a hairline crack with one very small section when the plaster has crumbled away a little, but the crack itself is no wider here, or at either end. If you tap in the location of the crack the plaster sort of sounds a little loose.

Yesterday though we had a conversation with our neighbour and he asked if we had spotted the crack. He told us he had painted over the crack a couple of times for the previous owners, and even top filled it with silicon, but he says the next day the crack reappeared.

Since we have lived in the house the crack has got longer and it spreads around the internal wall to the external wall at the front, but it has not got any wider. It is probably a couple of feet long in all. Also there is no sign of any crack on the outside walls anywhere. The neighbour says there is no sign of any crack in the wall on the inside of his property. Near the top of the crack at ceiling height there is a gap between the coving and ceiling.

There are no signs of any cracks in the ground floor of the property anywhere, in plaster, paintwork, or ceiling or coving.

Should we be concerned about this at all, in terms of subsidence or heave? We don’t know how long the crack was before the neighbour painted over it.

Any advice would be really appreciated.

Thank you.
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If the cracks etc. truly concern you then why not post pics of the cracks?
Perhaps, also post a pic of exterior elevation.
Yes, images would help ;o)
Please do have a look and let me have any opinions. Thank you.

Here they are. They are full size images so zoom away.

This is the front elevation:

This shows where the problem is. It is the front room of the house, 1st floor (top floor) and the corner is next to our neighbour.

This is the main crack.

This is a detail in the corner of the wall where the main crack is:

Another showing cracks 1 to 3

A feint crack lower down the wall from the bottom left corner of the window.

Another feint crack even lower down the wall:

Another slight crack at the top right hand corner of the window.

And another slight crack at the bottom right hand corner of the window.

Thank you.
Your neighbour's house is lower down a slope than your house. Gravity could be pulling the party wall, and front elevation around the vulnerable window opening, just a few mm's downhill?

Thermal expansion is also a possibility - given that the parapet brickwork is exposed to sunlight?

Subsidence, settlement and heave etc. could be factors but you dont report exterior cracking or sticking doors and window sashes. Nor mention of any nearby trees.

Perhaps, go into the loft and examine above the cracked areas?

Water stains are showing on the front elevation just below both parapet ends - moisture entering the party wall might have some bearing on the cracks but, in the meantime the cause of this staining should be remedied. Eventually, you will have to cap the parapet walls with coping stones.

Maybe, ask other neighbours if they have similar problems?

How come the mortgage surveyor didn't pick up on these issues?

Perhaps just wait and see, nothing is going to collapse, and call in a SE after another winter if you are still uneasy about the situation?
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Thank you very much for the reply.

There is a large wide tree about 6 or 7 metres from the front of the house, and actually the drain cover outside this neighbours house was bubbling a couple of weeks ago. But this is the only time we have seen that happen. The windows don’t stick, but there is a very slight gap of daylight (if you look up from the right angle) when the window is closed, between the frame and the window, but this quite probably was there from when they were fitted a few years ago. I don’t see anything else of much concern in the house, though some of the lining paper upstairs is starting to loosen at the top, in the 2nd bedroom at the back. Also minor cracks along the coving joins. Downstairs there is nothing to report.

Good idea about the loft, will see if we can crawl down that far.

The immediate neighbour on that side, who filled in the crack, says he does not have any cracks inside. This neighbour is the one that has worried us, as he thinks it is structural. Will see if we can ask others.

Regarding the surveyor, there was a wardrobe in front of the main crack. Do you think he should have noticed anything else?

We could just wait but I wonder from an insurance point of view how soon we need to call them. Or if we should strip off the plaster and see what is going on. I’m a bit of a worrier...

Thanks again!
Was the wall plastered direct on to the blockwork, with two-coat plaster the traditional way, or was it lined with plasterboard and then skimmed?
Unfortunately I don't know. This was done before we bought the place, and I'd not know how to tell.

Can I somehow check if it will help?
The cracks look too random and fine to be suggestive of any serious structural fault.
I'm certainly no expert in this area, but I can tell you for sure that we have cracks much larger than that in our house and we have no problems. They look more superficial than anything more serious. Has the plaster been recently rendered i.e. last few years do you think? I know you moved in recently but you should be able to tell by the state of the wall.
I'm certainly no expert in this area, but I can tell you for sure that we have cracks much larger than that in our house and we have no problems. They look more superficial than anything more serious. Has the plaster been recently rendered i.e. last few years do you think? I know you moved in recently but you should be able to tell by the state of the wall.

No, I don't know but the main crack was filled and painted within the last few years, and it is possibly wider than it looks due to having been filled, but it is not really getting any wider, or if it is, very slowly.

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