How to Install a Shower Enclosure: Measuring, Levelling & Fixing Uneven Walls and Floors

Installing a shower enclosure may look straightforward, but achieving a neat, secure and watertight finish requires more than simply fixing the glass panels in place.

Accurate measurements, a level shower tray, plumb walls and the correct fixing method all play an important role in the final result. This becomes especially important in older UK bathrooms, where floors may not be perfectly level and walls may be slightly out of plumb or out of square.

The good news is that minor imperfections can often be accommodated with careful preparation and the adjustment range built into many shower enclosures.

Before You Install a Shower Enclosure: What Should You Check?

Before installing the enclosure, check the shower tray, walls and floor carefully. Fixing problems before installation is much easier than trying to correct them after the enclosure has been fitted.

Check the Shower Tray

The shower tray should be:

• Properly level
• Fully supported
• Secure and stable
• Correctly connected to the waste
• Properly positioned against the finished walls

The tray should not move or rock when pressure is applied. A shower enclosure installed on a tray that is not level can cause problems with door alignment, drainage and sealing.

Check the Walls

Bathroom walls are rarely as perfect as they appear. Even a wall that looks straight to the eye may be slightly out of plumb or have small dips and bumps in the surface. Before installing your shower enclosure, check:

• Are the walls reasonably vertical?
• Are the wall surfaces reasonably flat?
• Are the two walls parallel?
• Is the corner suitable for the enclosure design?
• Are there any areas where tiles or wall finishes protrude?
• Does the opening vary in width from one area to another?

Check the Floor

The floor underneath the shower tray must provide a suitable and stable base. If the floor is uneven, the tray may not sit correctly. An incorrectly positioned tray can then affect the alignment of the shower enclosure.

How to Measure for a Shower Enclosure

Accurate measurement is one of the most important steps when installing a shower enclosure. A common mistake is to measure the opening once and assume that the walls are perfectly parallel. In reality, the dimensions of an opening can vary from one area to another.

Measure at Multiple Heights

For a wall-to-wall shower enclosure, measure the opening at several points rather than relying on a single measurement. For example, you can check the opening at different heights and compare the results. If the measurements vary, this indicates that the walls may not be perfectly parallel.

Why Is the Adjustment Range Important?

A shower enclosure's advertised size does not always represent one fixed installation dimension. Many shower enclosures are designed with an adjustment range that allows the enclosure to accommodate minor variations in the finished opening.

Measure Both Sides of a Corner Shower Enclosure

If you are installing a corner shower enclosure, measure both walls independently. Measure the distance from each wall to the relevant corner or installation point, following the dimensions specified for your chosen enclosure. Do not assume that both walls have exactly the same dimensions.

Should You Measure Before or After Tiling?

For the final installation measurement, it is best to measure after the wall finishes and tiles have been completed. Tiles, adhesive and other wall finishes can change the final opening dimensions.

Handling Uneven Walls and Floors

It is not uncommon in older bathrooms for walls and floors to be anything but perfectly straight or level. Here is how to handle these situations.

Uneven Walls

Minor unevenness: Most modern shower enclosures are designed with an adjustment range that can accommodate minor wall imperfections. Typically, the adjustment range allows for 5-10mm of adjustment on each side.

Moderate unevenness: If the wall has noticeable deviations, you may need to:

• Use adjustable wall profiles
• Consider a specially designed enclosure system
• In extreme cases, some wall remediation work may be required

Severe unevenness: For serious wall unevenness, you may need to:

• Re-plaster or repair the wall
• Make structural adjustments before installation
• Consult a professional

Uneven Floors

Floor unevenness can affect the positioning of the shower tray, which in turn affects the installation of the shower enclosure. Minor floor variations can often be addressed when installing and levelling the shower tray. However, significant problems should be corrected before the enclosure is installed.

Common Shower Enclosure Installation Mistakes

Avoiding common mistakes can make a significant difference to the final result.

1. Measuring Only Once - A single measurement may not reveal that the walls are angled or uneven. Measure the opening at multiple points to identify variations.
2. Measuring Before Tiling - The finished wall dimensions can be different from the unfinished wall. Take your final measurements after the wall finish is complete.
3. Assuming the Walls Are Square - Even walls that look straight may not form a perfect corner. Check the installation area before choosing and fitting the enclosure.
4. Installing on an Incorrectly Positioned Shower Tray - The enclosure depends on the tray as its base. Make sure the tray has been correctly installed, supported and checked before fitting the enclosure.
5. Using the Wrong Wall Fixings - The correct fixing method depends on the wall construction. Do not assume that the same wall plug and screw will work for every wall.
6. Forcing the Enclosure to Fit - Never force components outside their intended adjustment range. If the enclosure does not fit within the manufacturer's specified dimensions, reassess the installation.
7. Ignoring the Door Clearance - Always check the door movement before final sealing.
8. Applying Silicone Too Early - Complete the alignment and adjustment first.
9. Ignoring the Adjustment Range - The nominal product size is not the only measurement that matters. Check the actual installation range before purchasing and fitting the enclosure.
10. Using Silicone to Hide Large Gaps - Silicone cannot compensate for a fundamentally incorrect installation.