Before you consider doing this, read the warning!

In April of 2004, shortly after moving into a new house on Madison, Wisconsin's near-East side, I began this project to soundproof my basement. My home is a small, WWII pre-fab unit with approximately 900 ft² on the main floor and about the same square footage in the basement. The lots in my neighborhood are very close together; there is about 20 feet between the sides of my house and my neighbors'.

I began this project to soundproof part of my basement to a) keep sound from getting upstairs and b) keep sound from disturbing the neighbors. I began my work with the gracious help of my father, whose building experience exceeds my own by a factor of at least one-hundred.

Click the pics for larger view.

Note: Pop-ups are busted, and new IMPORTANT information has been added at the end of this write-up. Read it!

There is a lot of misinformation about soundproofing. I won't go in to great detail here, but consider these basic facts:

• Egg cartons, mattresses, carpet, cheap foam--none of these materials will prevent significant amounts of sound from leaving a space. While all of the above will reduce some frequencies and quiet down a room, they do not do so evenly. Bass frequencies (kick drum, bass guitar, djembe) are the hardest to stop. These materials will not stop bass frequencies from leaving a space. Additionally, all of these materials are fire hazards when mounted on a wall. Approach their use with extreme caution.
• One key to stopping sound from escaping a space is mass. That doesn't mean you can just pile up something heavy in front of something and it will block sound from getting through to the other side.
• Another key to stopping sound from escaping a space is sealing it airtight. Sound can get through the smallest spaces. It is accepted wisdom among acoustics experts that one should seal every possible venue for sound. In my building, this has meant caulk everything. Every gap. The rule is: if air can get through, so can sound.
• Sound is vibrational energy. That means that if one item is vibrating because sound it hitting it, and that item is touching another item, the second item will vibrate too. In building terms this means you have to be especially careful to decouple one mass from another. Read on for more on this.

I cannot emphasize enough: before you spend any time buying materials or building anything, read about tried and true methods from the experts. See the links section.

When I began my work, I did not have a specific, drawn plan. I was advised early on, however, that I would need to remove the drywall ceiling. My house is built with a large I-beam running the width of the house. This I-beam divides the basement in to two sections, with about 2/5ths of basement on one side and 3/5ths on the other. On the 2/5ths side is a utility room with a workbench, as well as the furnace, washer and dryer, and other miscellaneous stuff in it. On the 3/5th side was a fully finished room. My first step was to remove the drywall ceiling.

This pic is a weird wide-angle shot of the space as it was before construction, with people in it.

This was a standard ceiling, attached to the ceiling joists with a grid pattern of furring strips. I don't know why the builder of this area did not simply attach the drywall directly to the joists. Using a crowbar, hammer, and a lot of brute force, I removed the ceiling completely. This is fun for the first ten minutes, and then just tedious. There was also pink roll insulation (the fluffy stuff) in the ceiling. I removed this as well. You'll need gloves for this.

Plan on getting covered with chalk. Yes folks, drywall is simply chalk pressed between paper. Mmmm, chalk. I broke up the drywall, furring strips, and nails in to manageable segments, and disposed of them in heavy-duty contractor-grade trash bags. Don't bother with Hefty bags, you need the thick stuff.

After a record rainfall, which occured perhaps a month before I started this project, the bottom edges of the existing drywall on the walls got wet and moldy. Since this would be hidden by the new walls anyway, I just scored it and removed perhaps the bottom foot worth of drywall from the wall.

I removed about 27 1" X 3" wood join plates, held in by nails, from the basement ceiling as well. These pieces were intended to hold sections of the main floor together. I removed them to make room for the new ceiling joists (read on). I replaced them with flat metal plates, screwed in.

I removed all lighting from the ceiling. HVAC Ducts that ran upstairs via the ceiling, I left alone. I removed HVAC ducts that serviced the room. The reason for removing these: metal ducts vibrate wildly when hit with certain frequencies. To test this, put a guitar amp next to your furnace, and play through some chords. You'll eventually hit a sound that makes the furnace ducts rattle in sympathetic vibration. This can be a cool effect, and my former guitarist and I thought it would be cool to bring ductwork on stage at live shows, and then crank the amps to get it to vibrate loudly. However, you don't want this effect to carry from the basement, right up through to ducts upstairs. Ducts, which are metal tunnels, have a way of focusing noise and carrying it upstairs. Its kind of like the cans and string effect.

The ducts that run through the room I left in place. There were two cold air returns and one hot air duct, as well as a large, boxed-in cold air duct that runs perpendicular to the room (see pic). The hot air duct was replaced with flexi-duct, a flexible tube wrapped with insulation. I was worried that sound escaping the new ceiling would rattle the duct and carry upstairs. You can find flexi-duct with other HVAC products at Menards; its common enough that it should be available at other home improvement stores.

I removed all electrical service to the room.

We demolished a closet in the southeast corner of the room.

Having acquired a nice plan from my friend Chris, an architectural engineer with solid experience in soundproofing, I started building walls. My basement plan is based on a proven method, know as the "room within a room" method. It is also known as a "two leaf system", or "mass--air--mass".

Simply put, in order to create effective noise attenuation (reduction), you need 1) a mass, 2) a little air space, and 3) another mass. The first mass is the exisiting room. The external walls of the basement are cement block. This is a good mass. It is not completely impermiable--cement is porous, as I found out when my basement got lots of water following a record rainfall. But it works well. The other part of this mass is the existing wood basement ceiling. Together they form a box that is nearly airtight.

The second mass is the next walls I built. Built with near-standard stud and drywall construction, these new walls (forming the new "room within a room") deviate somewhat from standard stud and drywall construction. First, I used two layers of drywall--one layer of 5/8" and one layer of 1/2". Second, the drywall is attached to the "wrong" or opposite side of the studs from the usual method (see photos). There are a few advantages to this.

• 3 1/2" of space (the width of studs) is retained all around the room. This is helpful for later when sound treatment is done.
• Holes do not have to be drilled for electrical boxes, since they are mounted right on the studs and exposed. The other option would be to surface mount the boxes. This works ok, but now you have a bunch of boxes sticking out and snagging clothing.

Another unusual thing about the wall construction is the use of double bottom plates of treated wood. I did this at the suggestion of a contractor who gave me an bid on the work before I decided to tackle it myself. Drywall is mounted on the top of the two bottom plates. Then, if your basement floods, hopefully water will roll in to the room and towards the drain, but not get the drywall wet, since it is 1 1/2" off the floor. This will not work if you get two feet of water.

For the ceiling, I "floated" 2X8s for rafters. These rested on the newly built walls an sat between but not touching the existing ceiling rafters. This is tricky, but required. If anything from the newly built walls and ceiling touched the existing room (except for the floor), all my work would be pointless. Why? When you couple two surface together and cause one to vibrate, the other surface vibrates too. Try singing or humming loudly and have a friend put their hand on your on your chest right below your neck. They will notice their hand is vibrating too. Simple physics.

I hired a contractor to install the ceiling. This cost about $850 at a rate somewhere around $40/hr. This included filling and smoothing the ceiling, but I painted it myself. Tip: get good paint. Cheap paint will allow imperfections to show through and may not stick to the drywall ceiling so well. The cost of paint ranges from $10/gallon and up. Don't cheap out, get the good stuff. I used two coats. Also, make sure to use a tarp on the floor. You may think you can do the ceiling without dripping paint everywhere, but you're wrong.

A specialty paint store like Sherwin-Williams will have better product and in my experience, offer good advice. Better than that of the high school kid working the paint counter at Menards.

One nearly final step was to caulk everything. Ever-y-thing. Every crack, gap, or seam was filled with acoustic caulk. There are many suppliers of this, just make sure what you buy is truly acoustically rated caulk, not some cheap crap from Menards.

Update, November 2005: I've been putting off the finishing touches, like door latches and touch-ups in favor of actually working on music instead. But I have more to do. As it turns out, contrary to my expectation, this installation does NOT make it quiet upstairs when I am playing drums or making other racket. It is very effective at keeping sound from bothering the neighbors, though, and that is the most important thing.

Update, August 2008: Flooding. Massive flooding! 100-year flood! You don't want to know how expensive it was to hire someone to cut away all the drywall ruined by water damage and mold. Mold can be toxic, and you don't want it flying around your furnace ducts in to the rest of you house. For this reason I hired a remediation company.

Update, June 2019 I have now demolished the entire build, piece by tedious piece, in order to have drain tile installed.

BEFORE YOU START AN INSTALLATION LIKE THIS

• Be sure you really need it. Can you practice somewhere else?
• Make 100% sure (not 99%) that the space you are soundproofing is waterproofed, or "flood-proofed". Talk to a company like Badger Basement Systems first. Otherwise you will end up with a very expensive mistake on your hands.
• Do it right the first time. You probably don't want to use wood or drywall, as they don't play well with the humidity in a basement. Find another solution.

Here is a crappy cell phone pic of the basement, finished. More to follow. Email bas at versastudio {{DOT}} come if you're horribly curious.

Many people have done this before, or soundproof spaces for a living, so take advantage of their experience and expertise.

• Recording.Org Forums (Look through the list for the ones relevant to your questions)
• StudioTips.com Forum
• Bob Golds Sound Treatment Pages