Over the past years of solving squeaky chipboard floors, a relatively new phenomenon has appeared. It’s something that had us stumped for quite some time! Cracking noises coming from ceilings when someone walks above. A very intrusive problem, that cheapens a property as well as proves to be extremely irritating for the occupants.
What exactly is it?
(Click on the video at the bottom of this article to see a cracking noisy ceiling in action)
There are several reasons for the cracking noise to occur.
- The most common we’ve found is due to deflection (vertical movement when foot load is applied) in the joists. In other words, the joists bend/move when someone walks across the floor. Often attributed to under sized joists or an excessive unsupported joist span. Both may well still be within building regulations.
When the joists move excessively, the plasterboard fixings (typically ‘screws’ in the context of this article) grind a pocket into the gypsum core of the plasterboard and it becomes slightly loose. In other words, the fixings and plasterboard now move independently of each other. To make the horrendous cracking sound, this separation only has to be a very small amount. A fraction of a millimetre.
The natural problem solver would suggest adding additional screws to tighten the plasterboard up and stop the movement or nip up the existing screws (Which can be a task in itself – find them, pick out the plaster, tighten. Rinse and repeat. A very arduous task!). However, neither approach works. We’ve tried it multiple times with absolutely zero success!
- The second most common reason we’ve found is excessive spans between joists, known more so as joist centres. To clarify, the distance between each joist is often to big. Typically, we’d see joists centred at around 400 to 450 mm apart. In properties with cracking ceiling noises, we’ve noted a large number have had joist centres of 600 mm! Again, still within regs, but in our opinion, to far apart.
Even when a thicker sheet flooring material is used, like 22 or 25 mm chipboard, the excessive joist centre of 600 mm just does not offer enough support. When the floor upstairs is walked on, particularly when load is applied at the centre point between the joists, a flooring material like ‘chipboard’ will often sag/bow over time. With this bowing comes torque. Torque applied to the joists. Resulting in the top of the joists toeing in for that brief moment as someone walks passed. The joists for a split second twist. This results again in the grinding of the gypsum core material by the screw fixings creating a separation (movement) between the screws and plasterboard (rubbing). Resulting in the distinctive cracking sound.
Well, let’s look a little at the science first. Don’t worry, it’s not complicated science. As mentioned earlier, the noise comes from a separation of the ceiling plasterboard and fixings/screws. During movement (someone walking around the floor above), the fixings and plasterboard rub together. This rubbing is actually the cracking sound you’re hearing. Of course that doesn’t immediately spring out as the cause, which is why it’s took some considerable investigation to come up with a solution.
Click on the video’s below to see/hear the results for yourself. Please note, both video’s were taken without any underlay or carpet installed as the floor was walked across. Hence, the clumpy sound, which completely disappears once carpet is installed.
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