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House 20 yrs on slab. The ceiling cracks don't' seems to be growing. No cracks on walls inside or outside. A plasterer say add expansion joint, not very convinced will fix properly, and the room is 5m wide. Anyone know the cause & proper fix ?
Hi @oasis1frog,
It’s helpful to first understand the different types of ceiling cracks, as each has its own cause and appropriate repair method. In homes around 20 years old, like yours, ceiling cracks in plasterboard are often due to minor movement over time. These cracks generally fall into three broad categories.
The first type is an inactive crack, which results from gradual settling or minor movement in the building's structure over the years. These aren’t actively worsening and typically don’t shift once formed. If your crack hasn’t grown in a long time and there are no other signs of movement—like cracks in the walls inside or outside—it likely falls into this category. The good news is that these can be effectively repaired using a Selleys 180g Spakfilla Rapid Gap Filler - 180g. Simply sand the crack area to remove any loose or raised material, apply the filler, let it dry, sand smooth, prime, and repaint. This is a straightforward repair that often solves the issue permanently.
The second type is a semi-active or minor movement crack. This can occur due to seasonal changes, slight timber shrinkage, or possibly minor moisture variations in the ceiling. These cracks may reopen slightly over time, even after being filled. For these cases, it’s better to reinforce the repair using plaster joint tape. Apply the tape over the crack, then fill and smooth over it. This method helps distribute any future minor movement and prevents the crack from reappearing as a visible line.
The third type is an active crack, where the plaster is continuously moving or separating. These cracks visibly worsen over time and often appear as wider gaps that migrate across the ceiling. If that were the case in your home, a plasterer’s suggestion to install an expansion joint would be valid, as normal patching methods won’t hold. However, from your description—no signs of worsening, no wall cracks—it doesn’t sound like you’re dealing with active movement.
Given all this, your cracks are most likely inactive or semi-active. I’d recommend starting with a simple Spackfilla repair. It’s low-cost and easy to do. If the crack reappears after some time, you can then reinforce it with joint tape and plaster over it. Only if the crack grows or worsens despite these methods would it be worth revisiting the idea of an expansion joint. For now, a basic repair sounds like the most appropriate and practical first step.
Please let me know if you have any questions.
Mitchell
