How to Soundproof a Bathroom

How to increase bathroom contentment

In this article I intend to tell you about some of the best practices for soundproofing your bathroom, along with a few quick fixes. 

Does your bathroom give off noises that you would rather not listen to? Sometimes even when there is no one in there? If you prefer not to have to turn up the music or talk louder when someone is using the facilities, you have come to the right place. We will give you some suggestions to rectify the issues.

I will start with the easiest, and most inexpensive; then progress to solutions for those who are truly anal; and finish with the types of Do-It-Yourself fixes that I think make the most sense. Bathrooms present an almost unique problem. Almost all house soundproofing is designed to keep sounds out–out of the bedrooms, out of the living spaces, out of the family room, even out of auxiliary spaces like porches and sunrooms. Bathrooms should be, but very rarely are, designed to keep sound inside the room.

The following few paragraphs will cover a program guaranteed to give you the quietest bathroom on the block. It is a ‘spare no expense’ approach that is only reasonable if you are planning to tear the entire room apart anyway. If so, you might as well also make it quiet. The last part of the article covers much less destructive soundproofing ideas.

The Best Bathroom Soundproofing Choices, Major Renovations

Existing Bathrooms

The existing bathrooms in most houses were not built with sound suppression as a major consideration. Designers are more interested in aesthetics, architects are more interested in making everything fit inside the shell, and builders are more interested in figuring out how the pipes will get from here to there and still work.

Even our house, which is 12 years old, is close to a bathroom disaster–and I do this kind of thing for a living. The tubs are back to back with only an open stud wall between them because the one-piece units are manufactured to attach to the studs, then the drywall covers the flange. The only advantage to this arrangement is that I can easily hear my wife in the shower and figure out that flushing the toilet will result in screaming and personal injury.

Sound Transmission Class (STC)

The definition of Sound Transmission Class is a rating system used to classify a material’s ability to resist airborne sound transfer. I will be using it throughout the article and explain in more detail at the end.

Soundproofing Water Lines and Waste Pipes

You may want to give some consideration to changing your water and waste lines and pipes at this time. Just a word of caution–new plumbing stacks are usually 4″ in diameter, and wider wherever the pipe is joined. They do not fit into an existing 2 x 4 stud wall. You will have to add a couple of inches to your ‘plumbing wall’ to make sure everything fits.

Incoming Water Pipe Sound Reduction

The 3 main causes of incoming water pipe noise are water hammer, expansion, and loose pipes.

• Water hammer – occurs when the tap is closed abruptly, the water has no place to go, and the high pressure slams the pipe against the wall or surrounding pipes.
• Expansion – hot water in copper pipes causes them to expand and make a ‘ticking’ noise. They can also hit the wall or other pipes if close enough.
• Loose Pipes – can vibrate due to water pressure.

The easiest, and best, solution to all of the above issues is the same. Make sure all incoming piping is securely attached to the framing. Add as many fasteners as required.

Waste Pipe Noise Reduction

Waste pipe noise reduction is a little more complicated. All drain pipes are connected to a stack that allows air to enter the system. Without incoming air your tub might not drain until next Thursday. All of the sinks, toilets, tubs, and shower drains are usually connected to one stack that passes through the attic and extends through the roof. This is a perfect conduit for noise to travel between rooms and floors.

Having a two story house with one bathroom stacked on top of another, or two bathrooms sharing a common plumbing wall, makes this worse. Assuming that you do not want to replace all of your plastic drain pipe with cast iron (which would give you a sound reduction of approximately 10 – 15 decibels), two of your best options are wrapping the pipes with loaded vinyl barrier or insulating the entire wall cavity with loose-fill cellulose insulation–or both.

Mass Loaded Vinyl (like Accoustiguard Noise-Blok Pro) is only about 1/8″ thick but has an STC of 27, and will almost double the sound dampening when wrapped around ABS drain pipe. It will also improve your cast iron pipes.

Use zip ties to hold the acoustic barrier in place. Sound is like water. It can leak out of the tiniest openings so make sure you fill the wall penetration cavities with a good acoustic caulking. You can also make a collar with the vinyl but it is way more work and you will probably still want to caulk it–just to be certain. Mass Loaded Vinyl is also available in 1 1/8″ thickness with a scrim-faced fiberglass quilt but it only has an STC of 29, costs more, and may make the piping too wide to fit in the wall cavity. (Scrim is just ‘an open-weave’ fabric to prevent the fiberglass and vinyl from de-laminating.)

Insulating Bathroom Walls for Sound

Use loose-fill cellulose for wall sound insulation. It has an STC rating of 44, is relatively inexpensive, and is fairly easy to install.

Many home improvement outlets will rent a machine when you purchase the product from them. You will need to get a roll of netting to staple to the studs so the cellulose will stay in place until the drywall is installed. If you staple the netting to the bottom 3′ of wall to start with, you can see where the hose is blowing your cellulose, and will be able to fill around all of the annoying protrusions. Once the bottom 3′ is full roll the netting further up the wall and repeat the process until the entire cavity is full.

If you really want to be able to sing in the shower without disturbing the household, you can use Mass Loaded Vinyl instead of the netting to hold the cellulose in place and add another layer of STC 27 product. Might be a little overkill. And way more expensive.

Another option is to hire a professional insulation company to do the job. They may recommend wet cellulose because it sticks to the wall without the need of netting. Either will give you the same STC rating.

If you have some concern about the attic, you can add cellulose above the bathroom, when doing the walls, to make sure the ceiling is also quieter. You can now install new drywall knowing the walls and pipes are as sound-proof as you can make them.

Other Options

Although a product like Roxul Acoustic Fire Batts have a great STC rating, all of the pipes and/or wiring in the wall cavities make it almost impossible to get a tight fit for consistent coverage. Fiberglass batts are easier to work with but provide only a marginal improvement in STC rating (35 t0 39). 

Soundproofing Bathroom Floors

If the ceiling below your bathroom floor is not finished, or if it is finished with T-bar hanging ceiling allowing easy access, you should also add insulation between the floor joists. Unless you are using wet cellulose, you will have to use something like Acoustic Fire Batts and do your best to fit them around any pipes, wires, and heating vents.

If you cannot access the underside of the bathroom floor from below you have a couple of choices. One is to cut out the sub-floor, fill the cavity with cellulose, and put down new plywood. Even for someone as anal as I am this seems to be getting a little out of hand.

A more logical solution is a sound reducing covering of some type. Probably the most reasonable option is Roberts 70-193 Super Flooring Underlayment from Amazon.

The manufacturer states an STC rating of 66 which I think might be a little over-optimistic but at this low of a cost per square foot you cannot go wrong–although you will have to purchase a one hundred square foot roll. Laminate or hardwood flooring can be installed right over it.

If you are putting down a tile floor you will need to install a 1/4″ layer of Pro Board because tile goes down with adhesive and grout which will not work on the underlayment because of its felt composition. Some other options are Acoustik Mat and your old friend Mass Loaded Vinyl. Both of these cost significantly more per square foot and also require a layer of Pro Board if you are installing tile.

You might be attracted to Interlocking Floor Mats which are like padded tiles because of ease of installation and claims of soundproofing but they are only really effective when combined with other materials such as the Roberts Underlayment. You can also lay rug directly over these materials. But who would use rug in a bathroom?

Note: Before installing anything on your bathroom floor make sure you screw down the sub-floor to eliminate any squeaks. Use 2 1/2″ deck screws every 4 – 6 inches on every joist. I hate squeaking floors, screws are cheap, and unless you are replacing the sub-floor, the existing sub-floor cannot be glued to the joists.

Bathroom Door Soundproofing — The Most Critical Job

Without any doubt, your bathroom door will allow more sound to escape from the bathroom than the walls, floors, and ceiling combined. If you are only going to do one thing to soundproof your bathroom–do the door.

Door Replacement

Soundproofing the bathroom door is probably the most important item on your soundproofing list–even if you have not incorporated any, or all, of my other suggestions. Your existing bathroom door is probably a hollow core unit with no weatherstrip and no insulation. As far as sound transmission goes, it is better than nothing–but not much.

The door can also have a gap of up to one inch at the bottom to accommodate the installation of thicker flooring. So you have sound transmission through the slab, under the slab, and through the dead air space behind the casing.

Let’s fix it. I have been installing doors for over 30 years and could bore you to tears about them. I won’t.

There are many choices you can make. You can tack a soundproofing blanket to the door slab (the door itself). Or even use a moving blanket. You can glue and nail an extra piece of MDF or plywood to the existing slab. You can attach acoustic panels or even just hang a curtain.

What you should do is purchase a solid core wood door. Unless you have, and can use, a router for hinge prep and hole saws for handle prep in a new door slab, you are better off ordering your door prehung in the frame.

Once it is installed–with shims at the hinge locations and shims at corresponding locations on the strike leg–install casing on the exterior of the frame and wall. Fill the 1/2″ cavity between door frame and 2 x 4 with low expansion spray foam. (I use Hilti CF 812 WD with and STC rating of 55.) Best practice is to spray about 1″ thickness, let it skin over (about 15 minutes), then repeat until cavity is full. If you overfill and it squeezes out, just let it dry and cut it off. (Do not try to wipe it off when it is wet. It will become part of the wall.)

Some sound will transfer through the door handle but about all you can do is cut a piece of Mass Loaded Vinyl that will fit over the cutout inside and outside the door slab–with a small hole in the middle to allow the handle tail to pass through. Your door handle should cover the vinyl and you can trim off the excess after the handle is installed. If you put anything else into the hole it will impede operation of the handle.

New Bathroom Door Weatherstripping

Now to weatherstrip the door slab and frame. Most of the weatherstrip options will not work, or are ugly, or both. If, when you install the new door, you attach the stops tight to the slab, it is quite likely you will not need any weatherstrip.

If you decide to install some, try Keliiyo Door Weatherstripping available from Amazon. This is a composite foam about 5/16″ wide and 1/8″ thick with a peal and stick back. Attach it to the door stop–not the door slab.

For the door sweep, use the Maxtid Door Draft Stopper (also available from Amazon). It is simple and easy to install, comes white, and will work on most types of flooring. It may even work on carpet with a short nap for a while–although it will wear out quicker.

Door Weatherstripping and Sweep Cautions:

The weatherstrip has a self-adhesive strip. It will not stick very well–if at all–to frames with oiled, varnished, or varathaned finishes. Raw wood, or latex painted finishes work best. The adhesive may also be very difficult to remove if you want to replace it at some time.

I would not use any type of finned product for the door sweep. There are many options available. Most are usually attached to the door slab with some type of adhesive strip, and cannot be adjusted after installation. The fins will hook on any depressions in the flooring like grout lines or the grooves in hardwood and laminate flooring, and will eventually leave a scuff mark. They will also wear down and lose their effectiveness. If you set them low enough that the fins are bent, it will be slightly more difficult to open the door because the fins will have to bend in the other direction as the door moves.

Toilets, Bathtubs, Ceiling Fans, and Vanity Fixtures

These topics do not readily lend themselves to a soundproofing article–other than the few observations and recommendations I will make here.

Soundproofing Toilets

For quiet operation I suggest checking out these products:

Woodbridge T-0001 dual flush toilet c/w self-closing seat. ‘Quiet and powerful siphon flush’. Available on Amazon Niagara Stealth 0.8 GPF. ‘Extremely quiet gravity flush’. From Home Depot

Note: Gravity flush toilets are by far the quietest.

If you are not buying a new toilet you can remove the tank lid and use the same weatherstrip you used on the door to prevent some of the flushing and re-filling noise coming from the tank. A slow-closing toilet seat will eliminate the ‘bang’ when you lose your grip. Some of the many choices available from Amazon even come with a night light.

Soundproofing Bathtubs

Bathtubs are shells that, when installed, leave a huge cavity between them and the walls and floor. If you have insulated the walls and floor you can install it as advertised. If not, give some consideration to lining the cavity walls and floor with Roxul Acoustic Batts before installing the tub. The American Standard 2460002.011 Cambridge advertises that their Americast backing insulates the tub for a quieter shower experience. (Available from Amazon.) I have no reason to doubt this but also have no experience to prove it is better than other tubs.

Soundproofing Ceiling Fans

For an in depth look at bathroom fans please see our article Best Ultra Quiet Bathroom Exhaust Fans. Our recommendation as the best available is the Panasonic FV-0511VQ1.

You can wrap the exhaust pipe with Mass Loaded Vinyl if you like but the fan is extremely quiet and the pipe usually goes right into the attic, so the extra noise suppression will likely be negligible. If you are replacing your existing fan to make it quieter, or you just need one that actually moves air, this unit will meet all of your expectations.

Soundproofing Vanity Fixtures

As with the exhaust fan, you will not gain much soundproofing with the vanity fixtures. The sink is not used that much and most of the noise comes from above anyway–running water, hand washing, tooth brushing, or hair drying and shaving. If you have lots of time on your hands you can wrap all of the water pipes and waste pipes with Mass Loaded Vinyl. If I were really, really anal I would also stick Mass Loaded Vinyl to the underside of the sink. I do not think I will ever reach that point.

Less Destructive Bathroom Soundproofing

Now that I have described the Cadillac bathroom soundproofing, here are some quicker, easier, and less expensive options.

Wall Soundproofing – Without Removing Drywall

It is still possible to install cellulose in the walls without removing drywall.

Cut a hole in the drywall approximately 3″ from the ceiling (in every stud cavity) big enough to accommodate the hose needed for blowing. I would cut the hole about 3″ x 3″. Save the piece of drywall. Make sure your hose is flexible enough to reach the bottom of the cavity. Turn the air down on the machine and fill each cavity to the top.

If the air pressure is low enough to keep the cellulose from blowing back out of the hole, you should be able to get a fairly consistent blanket in each cavity–even around pipes and electrical boxes. Stuff a piece of fiberglass into the hole to fill the top. Cut pieces of 1/2″ plywood 6″ wide x 2 3/4″ high, slide it into the hole behind the drywall, screw it to the existing drywall at each end, screw the piece of drywall you saved onto the plywood, and finish with drywall mud, then re-paint. (If you don’t like painting, you could consider a 12″ wallpaper valence to cover repairs.)

Note: If you put a 2 1/2″ screw into the center of the plywood, you can hold it in place while attaching it.

You could add another layer of drywall which is very helpful but keep in mind the extra work. The door frame, switch boxes, and plug box will have to be extended. Baseboard, casings, shower rods (or shower doors), and possible medicine cabinet will all have to come off and be replace. Drywall has to be taped and painted. And you may not want to disturb tiles or tub surround, which leaves part of the job undone. For an even higher STC rating you can cover the existing wall with Mass Loaded Vinyl before adding new drywall.

Other Options

There are many other options available to make your bathroom more soundproof such as wall hangings, acoustic panels (some of which are advertised as very attractive???), hanging a curtain in front of the door and/or window, floor mats, carpets, more towel racks, thicker towels, storage units, ways to make the toilet lid quieter without getting a new one, foam pipe wrapping, changing the toilet valve, white noise machines (which I mentioned briefly), crack filling, and many more. 

Sound Masking

This suggestion is a little tongue-in-cheek but it can be an inexpensive viable option for anyone on a tight budget, or in a short term rental, or visiting for a few days. One option would be to take your phone in with you and play ZZ Top at volume. Sorry, my age is showing. Or for a few bucks from Amazon you can purchase the Motion Activated Audio Player.

View on Amazon

This little unit comes with its own USB Adapter, and 2 hour SD sound card you can load with your preferences. Maybe ocean sounds complete with seagulls and whale mating noises. Amazon even advertises ‘block embarrassing bathroom noises’ on its site. Small, unobtrusive, and portable.

Sound Transmission Class (STC) – Why Is It Important?

When buying products specifically for sound reduction, always check the STC rating. The higher the number, the better noise reduction you will achieve. Even drywall should have a rating (5/8″ will be rated higher than 1/2″.)

A quiet home has an overall rating of 40. The International Building Code recommends a minimum STC rating of 50 for walls, ceilings, and floors. The recommendations for bedrooms is STC 52 and for bathrooms it is STC 56. An example of what you probably have is a 2 x 4 interior stud wall with no insulation and 1/2″ drywall on both sides, giving you an STC rating of 33. The door, where most of the sound will come from, is even worse.

Now you know why those sounds are so loud. For more information on Sound Transmission Class and the Noise Reduction Coefficient, please see  Best Soundproofing Insulation for Noise Reduction.

Finally

Please leave a comment. And if you have any questions, I will be happy to get answers for you.