A creaky creaky bathtub can be very annoying and may be a sign of a serious problem with your tub. If it is left untreated the issue could progress into a crack in your bathtub and eventually cause a leak. It is important to address the problem promptly as it can be difficult to get rid of the creaks once they have begun. Fortunately there are some steps you can take to fix the problem and avoid a more serious issue in the future.
Many acrylic tubs are designed to stand on a layer of foam or rubber between the tub and bathroom floor. Over time this layer can wear out or move out of place exposing the tub to the floor which causes it to creak. To fix this you can try replacing the foam or rubber layer with a new one. If this doesn’t work you can try shimming the area between the tub and the floor. Shims are small wedge-like shaped pieces of wood available at most home improvement stores that can be used to fill gaps between two surfaces. Insert a shim between your acrylic tub and the floor around the spot where you think the squeak is coming from. If the shim resolves the problem, remove it and trim any protruding portion of the shim so that it does not stick out from the bottom of your tub.
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If you are ambitious you can try injecting a low expansion foam filler between the tub and floor to help stabilize it but this solution is only temporary. If the problem is severe you should consider calling a professional to have the tub fixed or replaced.