Roger’s Back: Should You Worry About a Crack in Your Wall?

Roger’s back with another viewer question, and this one’s a cracker.

Mark uncovered a crack in his extension wall after stripping back the plasterboard during some renovation work. The surprising part? The surveyor had inspected the property but had never even seen the crack because it was completely hidden.

If you’ve been losing sleep over a crack in your walls, this one’s for you. Roger breaks down what’s actually going on, why it’s almost certainly nothing serious, and what a few simple brackets and a tube of sealant can do. Job done.

When plasterboard, wallpaper or other finishes are removed, it’s not unusual to uncover things that have been hidden for years. A crack can look alarming, particularly when you don’t know how long it’s been there or whether it’s getting worse. But not every crack means there’s a serious structural problem.

In Mark’s case, the crack was found where the extension met the original building. This type of junction can experience small amounts of movement because the two parts of the building can behave differently.

An older property and a newer extension may respond differently to changes in temperature, moisture and settlement. That movement can sometimes show itself as a crack without meaning the structure is unsafe.

Why Didn’t the Surveyor Spot It?

A surveyor can only report on areas that are accessible and visible during the inspection. If the problem is concealed behind plasterboard, furniture or another finish, it may simply not be possible to identify.

This is why renovation work can sometimes reveal surprises that weren’t mentioned in an earlier survey.

The important thing is to look at the bigger picture. Where is the crack? How wide is it? Is it changing? Are there any other signs of movement?

A small crack around a junction can be very different from significant cracking running through an external wall.

Roger’s advice is reassuring because, in this particular case, there were no obvious signs of serious structural movement.

When Should You Be Concerned?

There are certain signs that should always be investigated further. Rapidly widening cracks, substantial stepped cracking through brickwork, bulging masonry, or doors and windows suddenly sticking can all indicate that further assessment is needed.

However, cosmetic cracking caused by minor movement is incredibly common in buildings.

In Mark’s situation, Roger’s solution was refreshingly straightforward. Rather than jumping straight into expensive structural work, the junction could be reinforced with a few brackets and then finished with a flexible sealant.

The sealant is particularly useful because it allows a small amount of movement without immediately cracking again.

It’s a good reminder that understanding why a wall has cracked is often more important than simply seeing the crack itself.

Don’t Panic When You Find a Crack

Discovering a mystery crack during a renovation can instantly make you think you’ve uncovered a huge problem. But buildings move, materials expand and contract, and extensions can behave differently from the original structure.

The key is knowing the difference between normal movement and something that genuinely needs investigation.

In this case, what initially looked worrying turned out to have a relatively simple explanation and repair. A few brackets, the right sealant and a proper understanding of the junction could be enough to get everything sorted.

So if you uncover a crack in your wall, don’t immediately assume the worst. Take a step back, look at where it is, consider the construction and check for other signs of movement.

Sometimes the scary-looking problem is actually a straightforward fix.

Have you ever uncovered a mystery crack during a renovation? Send your questions in for Roger and you could see them tackled in a future episode.

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Key Takeaways:

• Surveys can only report what’s visible — hidden problems often reveal themselves during renovation work

• An even crack from top to bottom typically points to block shrinkage, not structural movement

• Slotted L-shaped galvanised brackets are a simple, effective fix — the slots allow for future movement, just like a slip tie

• The existing timber has been quietly doing a lot of stabilising work — worth replacing its job with a few brackets before boarding over

• On the outside, a mastic movement joint is perfectly normal — re-gun with polymer sealant if it’s pulling away

• Movement joints are best hidden behind downpipes or tucked into corners where possible

• Cracks are rarely as scary as they look — houses are tougher than we give them credit for

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