Cracking stitching in thermalite blocks

[mrsunshine12]

The house I bought last winter has some cracks in it as a result of various trees (these were removed following an insurance claim by the previous owner in 2018). There are some cracks in the attached garage which appear to be stable (i've been monitoring them) but weren't fixed decoratively in the insurance fix. The cracks are only on the inside leaf of the cavity wall - there is no evidence of cracking on the outside, and as I say the large evergreen hedge is now gone some years ago.

I'm thinking it's best to go belt and braces and rather than just fill them also crack stitch them. One of the cracks is a vertical crack along a long wall of thermalite blocks (I guess it may just be thermal expansion as it is south facing and there is no expansion gap) - this one looks straightforward to stitch in the normal way.

The other two (one each side of the garage door) are stepped cracks near the junction of the side walls and the front walls. For these I'm planning on raking out the mortar and then bending the rod around the corner - I think i'm probably not going to get 500mm on one side, more like 300, but better than nothing. The slight complexity is that the mortar beds don't quite line up between the block work and brick work - I'm assuming I can bend them a bit?

Any thoughts?

Is the permaguard kit any good? It's 100 quid cheaper than the helifix version

 

[mrsunshine12]

Forgot to say, i'm intending to repoint afterwards and then paint the walls - in case that matters. Not planning to sell any time soon but I guess in 10 years we might, so want a neat job that won't send surveyors twitching!

 

[jks7492]

Personally i think you're wasting your time/money doing anything other than cosmetic work...
If repairs were carried out as part of an insurance claim and there were any structural concerns at the time then a surveyor/structural engineer would have been appointed to advise on any remedial works required. If there's no evidence of further cracking or movement then there's really no reason to worry about it.

 

[^woody^]

If the cause was the trees that would have caused foundation movement which would have moved the walls - and both leafs would have cracked.

So if only the block inner wall has cracked then that implies there was no foundation movement and the cause was something else, which in turn means that crack stitching may not be of any use.

 

[mrsunshine12]

Thank you for the replies.

I guess my main problem is that i wasn't the one who did the insurance claim, so i'm going off second hand information (I do have the certificate of structural integrity etc tho) - I don't know for sure that the insurance people looked in the garage as the main issues were on the other side of the house nearest a large willow. That side of the house got some stitching on an external crack (no underpinning required as it was fairly minor). Looking at the cracks I think they're probably too minor that the insurance people would have done anything about it - not sure what else could cause them other than the hedge that is no longer there (though I guess the non stepped one could be thermal expansion as the wall gets warm).

Is crack stitching likely to do any harm? I like to worry about things!

 

[tony1851]

Concrete blockwork is prone to shrinkage cracking producing seemingly alarming but structurally not-significant vertical cracks.
Any future surveyor would realize that and probably note it as not important.
If you try to rememdy it, the repair might draw attention to it and make people think there was some more serious problem behind the repair.

 

[mrsunshine12]

Concrete blockwork is prone to shrinkage cracking producing seemingly alarming but structurally not-significant vertical cracks.
Any future surveyor would realize that and probably note it as not important.
If you try to rememdy it, the repair might draw attention to it and make people think there was some more serious problem behind the repair.

Yeah fair point. Not sure about the stepped cracks at the end tho? Shouldn't I be doing more than just filling those?

I guess for the long crack in the middle just filling it with a flexible filler (fibrecryte) is the right move.