small vertical crack on external wall advice

[moglet]

i have the attached small crack on the external front wall of our house (1950s build). it is underneath the middle of the front window. it doesn't go into the foundations (or below the damp course) but has widened slightly over the last few months. it is at it's widest in the middle. there is a matching almost invisible hairline crack on the inner wall at the same place.
walking up and down the road, it seems that a number of the houses (about 10 that I can see from the road) have the exact same cracks in the same place, some smaller and some bigger. Some houses have no cracks but have obviously added an airbrick in the same area that our crack is. our attached neighbour has a similar crack in the same place but his is stepped rather than through the bricks. again, not to the foundations.
I'm trying to work out what the best thing to do about it is, could this be down to a cavity tie rusting? Should I just fill it in and cover up? Is adding an airbrick sensible - which is what some other houses seem to have done?
Thanks for any advice.

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• moglet
• 18 Jan 2013
• 1

 

[roy c]

I wouldn't be surprised if the fault is in the foundations. Also it would be interesting to find out what was on the site before the houses wee built. I personally think the brick-work looks of a poor standard with different size coarses and thin beds and joints. Find a bit of history of your surroundings and ask a few "ole boys if they remember the builders and who were the main contractors....

 

[^woody^]

That's a thermal crack. Contraction of the wall and mortar which is too strong

 

[roy c]

That's a thermal crack. Contraction of the wall and mortar which is too strong

What about the inside skin .That has a crack in it aswell?

 

[moglet]

The houses were built on farmland. They were built for workers at a local facility and have a local reputation as being very solidly built, they are very sought after. Would it be foundations if lots of them have the same issue in exactly the same place? There are no cracks anywhere else.
If it's a thermal crack, would an air brick help? (as other a couple of other houses have done?)

 

[^woody^]

What about the inside skin .That has a crack in it aswell?

Yes, it would be unusual for the two skins (if it is cavity) to both crack. I should really have said that it looks like a thermal crack

A picture from the corner showing the two elevations in perspective may help

 

[moglet]

Thanks for your comments - I'll try and put up a photo of the whole perspective thing later. On a snowy walk earlier, I noticed even more of the houses have the same crack, in most cases it seems to have just been filled with mortar. It is cavity wall (with, no filling as it's early 1950s build). The crack on the inside is so faint I wouldn't have noticed it other than having a careful look because of the outside one.
It definitely doesn't go down any further than two bricks above the damp course and ends before the window starts (so starts a good four/five bricks from ground level). Looking at some of the other houses, theirs seem to go all the way to the bottom of the window but again not into the ground.
We get lots of thermal cracking inside the house around old plaster work that opens in the winter and that close in the summer months if that makes any difference.
Would a foundation problem manifest itself in each house in exactly the same place - so if dodgy foundations, they are all dodgy in exactly the same place resulting in a small crack in exactly the same place? I presume subsidence is out because the houses wouldn't crack in the same place?

 

[Nige F]

What about the inside skin .That has a crack in it aswell?

Yes, it would be unusual for the two skins (if it is cavity) to both crack. I should really have said that it looks like a thermal crack

Woody - do you think it could be moving on the DPC which appears to be just sitting on the course below , not sandwiched in the pug.

 

[^woody^]

Yes, that is what tends to happen as the wall above the dpc slides on it as it gets wet and dries in a cycle. The wall below tend to stay damp so does not contract in the same way. I don't think it matters if the dpc is bedded or not, as the forces are significant enough to cause movement in any case

@roy. The vertical nature of this crack is one of the wall moving horizontally, and not downwards as typical of foundation movement

If it's below a window, then that would add to the likelihood of out being thermal movement

 

[moglet]

didn't get back in light to take the whole perspective today, but attached another one I took yesterday with more showing. the damp proof course is two bricks under the ridge - not sure why there is a ridge but all the houses have this at the front. you can see the window in this one - it's about 3 metres across and the crack is almost right in the middle.
if it's movement on the dpc, is there anything i can do, our should i just leave it and live with it?
thanks for all the useful pointers.

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• moglet
• 19 Jan 2013
• 1

 

[tony1851]

moglet; are the bricks clay, or alternatively concrete or calcium silicate? The latter two are notorious for shrinkage cracking and any cracks formed by shrinkage will be manifest in longer lengths of wall (eg under the window) rather than at the sides.
As the others have said, it is unliely to be foundation problems.

 

[roy c]

Yes, that is what tends to happen as the wall above the dpc slides on it as it gets wet and dries in a cycle. The wall below tend to stay damp so does not contract in the same way. I don't think it matters if the dpc is bedded or not, as the forces are significant enough to cause movement in any case

@roy. The vertical nature of this crack is one of the wall moving horizontally, and not downwards as typical of foundation movement

If it's below a window, then that would add to the likelihood of out being thermal movement

I see what you mean now woody I thought there might have been movement in the footings but as been pointed out most of the cracks are all in the same place. Usually the stress points on buildings are at either side of openings (ie. door and window openings) but not down the middle.The "bonding" between the bricks seems very tight do you think that may be a cause of the problem.
It may be an idea to put a grind down the crack and fill it with clear silicon!!.

 

[^woody^]

It may be an idea to put a grind down the crack and fill it with clear silicon!!.

Yes that would be the less obtrusive repair