Inspect the Shower Pan Carefully
The first step is to thoroughly inspect the shower pan to identify where it is flexing or moving. Look for any cracks, gaps, or deterioration in the shower pan material. Also check where the shower pan meets the walls. There may be gaps that allow movement.
Some key things to look for:
- Cracks or gaps in the grout lines of the shower pan tiles.
- Cracked or broken shower pan material (fiberglass, acrylic, etc).
- Gaps between the pan and walls, allowing pan to shift.
- Rotting or deterioration of any wood support under the pan.
- Damage where the drain meets the pan.
Make note of any areas that are flexing, cracked, or not properly supported. This will direct your repair efforts.
Secure the Shower Pan to the Studs
If the shower pan is not securely fastened to the wall studs, it can easily flex and move.
Use a stud finder to locate the wall studs around the perimeter of the shower. You may need to drill small holes in the wall around the shower valve and along the bottom edge to find the studs.
Once located, use pan-head screws to firmly fasten the shower pan to the studs, especially around the drain area. Use a level to ensure the pan is screwed into the studs evenly.
Securing the pan to the studs will stabilize it and prevent shifting or flexing.
Refasten the Drain Fixture
If the shower drain is loose or not properly attached, it can allow the pan to move when weight is applied.
Remove the drain strainer and use silicone adhesive to firmly fasten the drain fitting to the bottom of the shower pan. Make sure the drain tailpiece is properly aligned before re-tightening.
Allow the silicone to fully cure before using the shower again. This will stabilize the connection point of the drain.
Use Construction Adhesive Under Pan
For fiberglass or acrylic shower pans, you can apply a bead of construction adhesive between the pan and the subfloor. This adhesive will bond the pan to the floor and prevent flexing or movement.
Thoroughly clean the subfloor before applying the adhesive. Run a continuous bead around the perimeter of the pan and in a grid pattern under the pan.
Carefully set the pan into place and apply weight or clamps evenly until the adhesive cures. The pan will now be firmly bonded to the floor.
Add Braces Under Pan
For pan flexing issues near the walls, adding metal or wooden bracing material under the pan can help.
Measure and cut braces to fit tightly between the shower pan and joists or adjacent walls. Tap shims into any gaps before securing the braces with construction adhesive and screws.
Ideally, braces should be installed under the perimeter of the pan where it meets the walls. The bracing will provide rigid support to prevent movement.
Replace Rotted Wood Supports
If there are areas underneath the shower pan that have rotted or deteriorated, this wood will need replacing.
Cut away any rotted wood studs or subfloor visible under the leaking shower pan. Install new 2×4 blocks and plywood patching using construction adhesive and wood screws.
Build up any low areas to be level and support the shower pan correctly. This step provides a solid foundation for the shower pan.
Consider Replacing Shower Pan
For shower pans with extensive damage or flexing across large areas, replacement may be the best option. Attempting to repair the pan in these cases often leads to recurring problems.
Carefully remove the old pan and install a new fiberglass, acrylic, or tile shower pan per the manufacturer’s instructions. Take time to ensure the new pan is completely level and solidly supported.
Although replacing a shower pan is a bigger project, it is sometimes the only way to permanently fix ongoing flexing issues.
Prevent Future Flexing Issues
Once you’ve fixed a flexing shower pan, take steps to prevent it from happening again:
- Use a cement backerboard under any new tile shower pan.
- Securely attach pan to studs with screws into the framing.
- Seal all edges and seams with flexible caulk.
- Slope pan correctly towards the drain.
- Avoid stepping directly on shower pan.
Careful installation and sealing of seams is key to avoiding shower pan flexing in the future.
FAQ About Fixing a Flexing Shower Pan
What causes a shower pan to start flexing?
Common causes include loose drain fittings, lack of proper support under the pan, deteriorated subfloor, cracked grout allowing pan movement, or frequent forceful impact on the pan.
Does a flexing fiberglass pan always need replacement?
Not always. If cracks are small, you can try sealing with epoxy resin. For large cracks or multiple flex areas, replacement may be best.
Should I re-tile a flexing mortar bed shower pan?
Yes, re-tiling is recommended over attempting to repair grout or a mortar pan. Remove old tile and mudbed and install new pan.
What thickness of plywood should be used under the shower pan?
Use at least 3/4-inch exterior-grade plywood to offer sufficient stiffness and prevent flexing.
Why shouldn’t I use plaster instead of cement board under a new shower pan?
Plaster can deteriorate over time due to moisture exposure. Cement backerboard is designed to be waterproof and provide stable support.
How long does construction adhesive take to fully cure and bond the pan?
Most adhesives take 24-48 hours to fully cure and bond. Avoid using shower until adhesive has fully set.
Conclusion
Fixing a flexing or moving shower pan may involve several steps based on the cause of the issue. Carefully inspecting for damage, adding braces, refastening the drain, securing to studs, and replacing any deteriorated support are all effective ways to stabilize the pan and prevent future flexing issues.
With the right repairs, you can permanently solve annoying pan flexing problems and prevent expensive water damage in the bathroom. Pay close attention to properly sloping and supporting the pan during any replacement project. Taking your time to make structural repairs will lead to a shower pan that remains safely sturdy and stable for many years.
