One of the most common concerns we come across on Reddit housing forums are stubborn cracks that keep coming back. You fill it, sand it, and paint over it, and it reappears six months later.

If it keeps reappearing, it must be structural, right?

No, not necessarily. It could be cyclical clay swell/shrinkage, the structure swaying in the wind, or it could even be something as simple as somebody slamming a door. If the crack reappears after closing, it indicates the structure is under a variable load, and the structures/finishes are too rigid/brittle to accommodate the strain without cracking.

Many masonry cracks (particularly in the UK) are seasonal. Your house lives in a dynamic environment. It sits on top of ground that breathes, experiences storms that buffet it, while rain and snow insist on trying to wash it away.

Meanwhile, many elements in your house are not flexible. Your house is likely to be constructed or faced with masonry that is designed for rigidity. The downside of this is that, when the environment causes variable loads (i.e. pushes and pulls your house), this will cause your home to crack if it moves too far.

So, it can be safely filled?

In most cases, yes. But… there’s a catch.

If you fill a crack while it’s at its widest point (summer), you’ve essentially shoved a wedge into the wall. When the masonry tries to close back up in winter, it hits that filler. If the filler is hard, this does one of two things:

Or, if the filler is softer than the wall it simply crushes and the cracking is visible again.

This continuous cycle of chasing seasonal cracks is why we quite often recommend crack stitching with helical bar (Bar Flex) to BF-01.

Isn’t crack stitching an admission of a structural problem?

Yes, and no. There are very, very few (zero?!) houses that have no structural quirks. That’s part of the fun of being a homeowner, right? But, of course, some structural problems are worse than others.

When it comes to seasonal cracking, this is primarily an aesthetic concern. You can’t stop the weather and you can’t stop the ground moving, so you can either put up with it, continue to fill the same crack every year, or stitch the crack.

By using a helical bar like our Bar Flex, you aren’t just “plugging the hole”, you’re reinforcing the structure. Bar Flex is a flexible reinforcement bar, and it both allows the masonry to move slightly, as well as restraining that movement.

In addition, it dissipates the movement along the length of the bar, so cracking is greatly – or completely – reduced.

Is crack stitching optional?

In a lot of cases, yes – but only in the same way that painting your walls is optional. If continuous cracking annoys you, then crack stitching greatly reduces the visual effects of these unavoidable movements while providing greater resilience. If it doesn’t bother you… then leave it!

Can crack stitching solve structural problems?

Usually, no. Not on its own, anyway. In full structural specifications, we often specify some crack stitching to prevent the reappearance of cracks but, on its own, it’s unlikely to resolve more severe structural problems.