Cracking on new front extension wall

[wessex101]

I'm not saying the lintels are a problem, they are just acting like a ground beam. The problem I was alluding to is that by using concrete lintels it has concentrated all the load on to the end bearings, in this case the narrow piers to the garage doorway and the flank wall of the house. Was the foundation to the garage checked to make sure the foundation was adequate to take this new concentrated load and is the garage foundation the same depth as the house foundation to avoid differential settlement?

The crack to the brickwork is very slight and the new loads are small so we are only talking about a tiny amount of movement. It is cosmetic damage, annoying, but probably not worth getting too excited about.

 

[CharlesBR]

Thanks @wessex101 . Understood, I am not sure if the foundations were checked or not but I guess an assumption can be made that foundations for a single garage won't be as thick given that the walls were single brick thickness? I will actually give building control a call and ask them as they have me on file so there may be something in the notes and I can put that very question to them.

 

[bobsuerita]

depending when house was built as it dosnt look that old all the footings would have been dug to same depth regardless
and the footing would normally have continued across the front of garge too

 

[CharlesBR]

Thanks @bobsuerita . House was built in 1989 and there was no footing under where the garage door was.

 

[^woody^]

Woody's thermal "shrinkage" theory

LOL. It's not my theory, duffus. But it's a bit of a fact in the building world by all accounts.

Not sure what surveying school you went to, but certain movement produces certain patterns, and movement diagnose always follows a set procedure to determine the most probable and least probable cause.

That type of crack, in that location of the wall, with that type of brick, with what appears to be that type of strong mortar, facing that way, with no rotation, or stepped cracking, internal cracking or any other cracking anywhere else leads to a most probable cause of err ...... thermal movement.

I'm not sure which way your penny dropped to get straight to the "foundation movement" thing, from what is not really a strange foundation detail -especially when the foundations lintels are nowhere near the side of the wall which you are suspicious of? But if you enroll on my "Surveying by Post course" things will become clearer by year four.

That's why the OP should monitor the crack through four seasons, to see if the most probable cause is the most likely, or if we go to the second most probable - which will be covered in year three, BTW.

 

[CharlesBR]

If it turns out that only remedial cosmetic work is required would it be tricky to get the areas affected with cracking repointed and also get a close match to the colour of motar? Probably not I am thinking but I am very much preschool in my understanding! I appreciate that new brickwork and mortar looks different to existing walls but as the area affected is still relatively new I would have thought I could get away with and in about a couple of years it would have blended in?

 

[Footsoldier888]

OK I have an Estates Gazette bookie wookie on Housing Defects.

They say thermal cracking tends to go in a straight line more, through the bricks and right down to the dpc but not below.

They also say a crack soon after building is more likely to be a moisture crack. This is cases where the bricks may have been dry when laid and they have absorbed some water after completion and with cement mortar being a lot stronger than traditional lime mortar it can lead to some cracking, and is a common occurrance.

Charles you are right to think about getting the match right, I think there are products out there that can ensure it is blended in.

 

[^woody^]

Ye Olde Estates Gazette. I miss that.

But thermal or moisture (or drying) crack is essentially the same thing - rapid drying after a period of excessive dampness.

Thermalite or similar blocks suffer from it terribly.

 

[CharlesBR]

Thanks for that @Footsoldier888 appreciate you looking your bookie wookie and others on the advice. From what i have read up i am pretty certain it isn't subsidence. I looked through pictutures i took during the build and the roof struts rest on a decently think enough piece of wood that spans the width of the extension wall. So it won't be the struts affecting things i don't think. I will get it checked out though around September which is just over a year since i suspected when it happened.

 

[CharlesBR]

I was thinking that @^woody^ it sounded similar. So essentially it is a climatic adjustment

 

[stuart45]

General rule of thumb is that clay bricks are usually at their smallest when first laid being dry from the kiln, and blocks at their largest being slightly wet from the processs. Calcium Silicate bricks shrink.

 

[CharlesBR]

I had a friend of mine who is a retired surveyor take a look at the cracking and he thinks it is probably to do with drying out/thermal activity on the brick work settling in. He did point out the largest cracking up at the top was a bit odd and needs to be monitored.

The attached picture of the inside of the room and the red circle where the brick with the crack either side at the top and the yellow line where the lintel approximately comes to an end. Not sure if there would be a correlation with the cracking? All pre-existing rafters used in the garage were kept in place during the conversion and they now rest on a wooden beam going the width of the wall.

One thing he was pretty confident to rule out was subsidence/heave due to the nature of the cracking.

Another thing I have noticed is that there are screws securing the wooden panel for the eaves on the outside so I might undo those to take a look at the brickwork above and behind and I expect to find further slightly larger cracks.

Not trying to make this a documentary(!) but might be useful to someone else eventually.

 

[CharlesBR]

I have taken another close look at the cracks and I am pretty certain no changes to the width of the cracks has happened and it certainly hasn't progressed any further on the mortar or brickwork.

If I was to see the cracks widen ever so slightly would their be cause for concern or would it simply be thermal adjustments taking place still? I am at the moment in no rush to fix yet as I want to see what happens but at some point I will want to fill in by repointing the areas affected.

 

[oldbutnotdead]

If you are concerned (which you obviously are) you can get crack gauges (Google it, there's loads)- basically 2 bits of glass, you fix them either side of the crack and then get numbers to read rather than messing about with feeler gauges or a tin ruler. Don't think you've got anything to worry about structurally, worth squeezing a bead of silicon into the crack to avoid any water penetration problems

 

[CharlesBR]

Thanks @oldbutnotdead . You have just jogged my memory about the crack gauges. I am not hugely concerned as I don't think there has been movement but the gauges should give an accurate way of observing.