Cracking to unreinforced brickwork wall 1

[John1967778]

Hi Guys,

Looking at an unreinforced brickwork wall which has stepped cracking approximately 7mm-8mm along it. I've been recommended to use a product known as helifix to essentially 'stitch' up the brickwork. It is basically high strength steel bars installed across the crack. My question is; whats wrong with just traditional re-pointing/patching the crack? I understand that these reinforcing bars will essentially hold the wall together across the crack at a much stronger rate than traditional repointing but what does it matter if the cause of the cracking/movement to the wall is prevented. IF anyone has any experience with using these steel bars then i'd much appreciate your input. Thanks!

 

[oldestguy]

Looking at their videos they say nothing as to the cause of the cracks, such as temperature shrinkage, loos of support, etc. Without knowing why the crack occurs, one likely may make the whole situation much worse with more cracks. I'd be very leery about the system without the knowledge as to why.

 

[JAE]

Agree with oldestguy. The first order of business is to determine the cause of the cracks and just as important determine if the cause is still ongoing.

A stitch or repointing won’t do you any good if it is still moving.

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[John1967778]

Yeah I agree guys. Assuming the wall is no longer moving/ the cause of the crack has been stopped, why would we want to we want to make one section of the wall much stronger using reinforcing rods rather than just traditional repointing

 

[hokie66]

I have used the Helifix product, or a similar one, as replacements for corroded ties in reinstating lateral support of a brick veneer.

Steppped cracking is a different thing, and hopefully as you said, the cause of that cracking has been eliminated.

 

[Ron]

Step cracking usually has one of two causes...
minor settlement and/or shrinkage


Shrinkage can result from cyclic wetting and drying or from initial material shrinkage particularly if the bricks were wet when placed.

If the cracking is confined to the mortar joints it is usually a minor issue. If the bricks are cracking then the issue is more serious.

 

[JAE]

"Step cracking usually has one of two causes...
minor settlement and/or shrinkage"

In some areas expansive clay heaving causes step cracking as well...but that is really just upside down settlement!



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[masonrygeek]

Just a minor correction to Ron's post - clay brick doesn't shrink, it actually expands slightly over time. Concrete block and concrete brick are cement based so they would shrink. Clay brick walls (which I think is being discussed here) often have stair stepped cracks due to supporting conditions (foundations that move) or horizontal movement (expansion) and its restraint. As all others have said you need to find out if the crack is still moving and then base your decisions on that.

I have seen these types of anchors used on plenty of buildings successfully. The important thing is knowing why you are using them. In many cases these products are used for active cracks and not the "one and done cracks". You could use mortar to repoint the crack, but this is now a weak point in the wall and the crack could reoccur due to maybe thermal cycling. I see a lot more sealant being used to seal cracks than repointing mortar just to hedge their bets if there is some movement. And if this is a major structural crack then that changes these suggestions.

 

[Ron]

Slight difference here MG.....
Bricks are susceptible to absorption. It is one of the properties of acceptance of clay brick products. As such, a brick is at its smallest dimensions after firing and cooling. From that point, as bricks absorb moisture they expand slightly.....but the greater the exposure to moisture the more they expand. If they lose some of that moisture, they shrink....not back to their original size, but enough to be measurable. If they are wetter than normal when placed, they can shrink as they dry to equilibrium.

When wetting/drying causes a separation from the mortar the movement of larger expanses of wall area come into play. This movement is often non-recoverable, thus the separations become progressively larger.