Skip to Content

How To Use Shower Felt Pad in the Bathroom

The shower tub is an integral part of the DIY remodeling process. You’ll need to know the specific materials and why you need them. 

There is debate surrounding whether you should use a felt pad underneath the shower pan. We’ll clarify its purpose so you can decide whether you want to use it or the popular mortar mix instead. 

What Is a Shower Pan?

The shower pan is the shower floor that you stand on during use. Fiberglass or preformed acrylic are the materials used in a shower pan. All pans have a slight incline that directs water away from the floors and into the drain. 

Shower pan instructions are easy to follow, but you must prepare the shower base first. Level the surface so the shower doesn’t crack or cave in after you install it. 

Shower Base vs. Shower Pan 

The shower base and shower pan are not interchangeable terms. The shower pan and the base are two different pieces of a shower install. The pan is the floor for the shower, and the base is the structure underneath the pan. 

Why Do You Need Shower Felt Pad?

Water can cause damage to your home, such as warped walls, mold buildup, or leaks through the ceiling. It’s crucial to have a waterproof shower.

To waterproof a shower, plumbers sometimes use a felt pad. A felt pad acts as a membrane to keep water from penetrating grout lines and seeping into the wall. 

Even though water penetration can cause problems, so can moisture buildup. A felt pad keeps water from breaching the wall while allowing vapor to pass through. This is important because it allows airflow that prevents moisture build-up. 

Felt pads have various degrees of permeability. You don’t want a felt pad that is so permeable it doesn’t prevent water penetration. You also don’t want a felt pad so impermeable that it causes moisture build-up.

Which Felt To Choose?

Plumbers and construction workers have varying preferences on felt pad permeability. This debate can make choosing an appropriate felt pad challenging.  

People for decades have regarded 15 lbs of felt paper as the standard for shower installs. 

Felt paper has a permeability of eight when dry but increases to approximately 50 when wet. 

This makes it a great candidate for instances where there’s a chance of water intrusion. Once it gets wet, it dries out, allowing water vapor to pass through. But when it’s dry, its permeability is not as impressive. 

Felt Paper

You can also use asphalt felt paper to prevent vapor from accumulating.

Using felt will keep the shower pan from squeaking because it deflects when it’s walked on. You often use felt where a pan sits flat or if a “curved” bed is already in place for the pan. Some bases recommend tar paper or felt, which act as a cushion.

Precautions of Using Shower Felt Pad

There are differing opinions on whether a felt pad is durable enough. This conflicting information is confusing to DIY builders. 

Many experienced plumbers state the shower pan should have a hollow feel. A shower felt pad removes the hollow sense.

Cushioning the shower pan has advantages, but it can cause the pan to flatten. A shower pan should have a proper incline. Without the incline, your shower pan won’t drain correctly, and water will sit at the bottom of your shower. Plastic pan tops dry quickly, but cut tile or granite shower pans won’t dry properly. 

With time, the slight flexibility of the felt pad can cause stress cracks in the shower pan. Installing your shower pan with mortar ensures proper support because mortar resists compression.  

You also get a custom fit since the mortar allows you to make your shower base completely level. That means your shower door and walls will fit better. 

Some shower pan manufacturers warn against using roofing felt with their products. Some shower pans have a petrochemical base, which can cause a chemical reaction with the felt pad. 

Installing Shower Felt Pad Behind a Wall

It’s easy to find installation videos for installing a shower felt pad behind the wall. 

When placing a hardiebacker cement board behind the shower wall, you also install a felt pad. This is because moisture can permeate the backer board and cause mold and water damage. 

The installation is straightforward. Buy 15-lb or 30-lb roofing felt and hang it like you hang shingles. There should be an overlap of at least two inches by the horizontal joints. 

Roofing Felt

You have to allow the felt to lap over the flange. Staples is the preferred method to install a shower felt pad behind the wall. Watch here for a more detailed video that explains the process with visual aid. 

Installing Felt Pad for a Shower Pan

If you want to use a shower felt pad (or tar paper) to install the shower pan, you must build a sloped sub-base

You’ll use the 15-lb felt to cut a piece that covers the center of the floor and leaves around four inches. It should be between the ¾” float guides or the bottom plates. Then, you’ll staple this felt pad to the floor and cut out an “X” directly over the drain outlet. After this, you can install the shower pan.


It’s up to you whether to use a mortar mix or a shower felt pad when installing a shower pan. There are advantages and disadvantages to both. 

Considering your budget and the condition of your house can help you decide which method is best. 

If you don’t want to risk a big repair job in the future, you might choose to go with the mortar mix. Mortar mix is usually fool-proof.

Installing a felt pad behind the shower wall is pretty simple. Many people use felt behind the backer board when installing a shower pan. 

Before beginning this project, be sure to watch several videos and take notes. Take necessary precautions and be sure to have the proper tools and materials. If you have any questions, ask for help from an experienced friend or a professional.

Leave a comment

Your email address will not be published. Required fields are marked *