What Is A Shower Pan Liner & Do You Need One?

Were you talking with a bathroom designer about your new bathroom renovation and the phrase shower pan liner came up? Wondering what a shower pan liner is and if you actually need one? Fear not!

In this post, I’ll explain what a shower pan liner is, how it works and if it’s necessary. As well as answer some popular questions about the topic.

Let’s dive in!

What Is A Shower Pan Liner?

A shower pan liner is a waterproofing membrane that looks similar to a thick plastic sheet. It is a hidden but extremely important part of your shower enclosure.

It serves as the final layer of protection for your home against any water that might escape from a damaged shower floor or pan.

It’s made out of a single sheet of polyvinyl chloride or PVC and installed under everything else used to build your shower.

Your shower pan serves as the shower floor and directs any water down the drain through its sloped shape. The rim of the shower pan stands about 3 to 5cm tall, which collects any water that puddles during your shower.

If the water reaches the top edge of the shower pan, the tiled walls or acrylic wall panels help to contain the water. However, a small amount of moisture may work through the layers.

That is when the shower pan liner goes to work. Its solid but flexible design captures any droplets and stops the water from damaging wood studs, the subfloor, or the structure of the home.

How Does A Shower Pan Liner Work?

A shower pan liner provides a completely watertight base for your shower enclosure. You could call it a bathtub for your shower.

It is installed under the tile or acrylic shower pan and beneath any grout or mortar used to fix the shower enclosure in place. Any water that manages to work its way past a cracked tile or pan collects in the liner and cannot seep into the wood structure of the home.

As a single piece of PVC, the liner runs up the walls about 200mm and over the threshold of the shower door. Any cuts made in the single sheet to accommodate corners or studs are waterproofed by adding folded and glued layers of PVC.

Since the liner is completely covered by the backer board, shower tiles or a separate pan structure, it cannot be damaged by the daily use of the bathroom. Once it is properly installed, it should continue to do its job for decades without the need for repairs or maintenance.

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How Much Does A Shower Pan Liner Cost?

You can buy a pre-measured shower pan liner kit at your local DIY store for around £50 -£100. 

The kit should include a single sheet of PVC pan liner that is at least 40 mil thick (1mm). The piece of PVC should be oversized so that you are cutting it down to fit with material leftover.

If your shower enclosure is properly prepared, it only takes about an hour to install the pan liner. However, the adhesive needs to cure overnight before you move on to the next step of building your shower.

If you hire a professional to install the liner, they might charge £50 to £100 for their labour. But the liner is rarely the part of the bathroom renovation that needs the direction of a licensed plumber or contractor.

Is A Shower Pan Liner Necessary?

Yes, in nearly every shower you need a shower pan liner.

While concrete and tile are perceived as waterproof, they are not completely watertight. The PVC liner is a non-permeable membrane designed to protect your home from any water that may work its way past the grout, tile and mortar.

It is a durable last-line of defence. Skipping the liner can result in hidden damage to the subfloor, ceilings, and even the structure of your home. Fixing a leaky shower pan with a liner may cost £500, but a leaky shower pan with no liner could send the price into the thousands.

How Long Does A Shower Pan Liner Last?

The PVC used to produce shower pan liners has an expected lifespan of up to 50 years.

Even if the liner develops a pinhole leak or crack, the liner can be patched using a PVC adhesive. This is a material that should last the lifetime of the bathroom.

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Can You Tile Over A Shower Pan Liner?

Yes, for a tiled shower installation, the shower pan liner is installed over the prepared subfloor and under the backer board. You then apply the mortar and tile to the backer board.

While ceramic tile, grout, and backer board are considered waterproof, water can seep through microscopic cracks. The pan liner is completely waterproof and will stop any water from soaking into the structure of your home.

But, as a soft membrane, it is not a good surface to use as a floor or sides of the shower. That is why it remains an important hidden part of your shower.

Does the shower pan liner go behind the backer board?

Yes. The shower pan liner is the first thing you install when building your waterproof shower surround.

It should run up the wall at least 150 to 200mm in a single sheet with no seams.

The backer board is secured to the studs over the shower pan liner to start building the walls of the shower and is suitable for tile. Your backer board is a concrete-based material that will not soak up water or promote the growth of mould.

Is a Shower Curtain Liner and a Shower Pan Liner the Same Thing?

No, a shower curtain liner is a clear and thin curtain that is hung on the inside of a fabric curtain. Since the fabric curtain is not waterproof, the liner serves to keep the water in the shower and not damage the decorative outer curtain.

A shower pan liner is a thick membrane installed beneath the floor of your shower enclosure. It adds extra waterproofing and protection to the structure of your home.

Final Thoughts…

There you have it! Everything you need to know about shower pan liners.

The hidden and highly recommended last line of defence against a leaky shower enclosure. It may feel a bit over the top or unnecessary. However, installing one can be a quick, cost-effective way to protect your home from any water damage in the future. A definite worthwhile addition to any shower enclosure.


Michael R

Michael is a KBB designer from the UK. He's been designing and project managing new Kitchen, Bedroom and Bathroom installations for over eight years now, and before that, he was an electrician and part of a KBB fitting team. He created The Bathroom Blueprint in early 2020.