Example: Condo soundproofing

This short video from builder Matt Risinger covers a lot of the issues we've discussed in this soundproofing blog. Matt has a show on YouTube that gives examples of successful construction projects. In this example, he shows a soundproofing project in a two-unit condo with a shared wall between them.

They did everything right. The used staggered wall studs (with an 8-inch separation between the two units), Roxul batting, QuietRock on the walls, putty pads on the outlets, and Green Glue.

As a test, Matt turns on a boom box in one of the rooms and measures the decibel output. Then he goes to the room on the other side of the wall to show how much of that noise leaks through and uses a decibel meter again. It's almost silent. This is what you hope to achieve, especially with new construction. But it won't happen unless you use the type of materials and processes shown here.

Here's the video. Great job!

How loud is it?

The average American home built after the 1940s probably uses gypsum board nailed onto wood studs over a hollow enclosure.

The STC rating for that setup is 30 decibels. According to this chart, normal conversation is still audible through a 30 STC wall. That should be no surprise to some of you apartment dwellers.

A single sheet of 5/8" drywall with fiberglass insulation provides an STC of about 40. You can still hear loud speech through this setup. If you use Roxul batts, you increase that STC rating to about 45.

If you use a soundproof drywall (like QuietRock) and insulation, you increase the coverage to 50 STC.  Double drywall with Green Glue inbetween, plus Roxul insulation increases it to 56 STC. You can read about this at the Welk and Sons Drywall site.

The cost difference is noticeable: 5/8-inch "dampened" dry wall is about $80 per sheet compared to $10, but might prevent you from having to do more sound construction later.

These blog posts from Mason Chang tell his story of soundproofing an apartment and building a new wall. Let's hope it brought him lots of peace and quiet!

Soundproofing a bedroom ceiling

I found a YouTube video posted by Tone N.W. and it annotates the steps he took to soundproof his bedroom ceiling after his upstairs neighbor tore out her carpeting and began walking around on bare hardwood floors above his home.

As you know, hardwood floors can be your worst enemy. A hardwood floor that's nailed directly onto a subfloor and then directly on top of wood joists is like a microphone into the rest of the building, and that impact noise travels through all the framing and right into the adjacent rooms (or apartments).

He said that he learned everything he needed to know from this document from The Soundproofing Company in Michigan.

Here's what they did:

1. They tore off the original drywall ceiling. It looks like a previous owner had added cross strips of wood on the joists already, and they removed those too. (If you read his notes, it sounds like he regrets the extra labor in this step.)
2. He and his wife cut drywall and added it to the upstairs subfloor inbetween each joist. I know this can be very effective and adds extra mass to the upstairs floor.
3. They added Roxul insulation (see my posts about Roxul Safe N Sound).
4. They added sound clips and hat channels to the joists, which will hold the new drywall.
5. They added a layer of drywall, then a second layer of drywall, sandwiched with Green Glue.

So it's a combination of a drop ceiling, Roxul insulation, and three layers of drywall (one on the above floor, two on their ceiling) with Green Glue inbetween. The video link disappeared from YouTube since this was originally posted.

Blow-in cellulose and your hollow walls

A few years ago, most American homes had no insulation in them. When a homeowner did insulate, it was usually with fiberglass batts.

Then along came some better products. One of them is blow-in cellulose insulation. Does it work? I can attest to this: YES. I've used it in walls and ceilings, and it works quite well for airborne noise. If you live in an uninsulated home and you hear your neighbors voices coming through your walls or ceilings, cellulose will dampen that noise or mute it entirely.

But it doesn't eradicate impact noise. You might still hear the sounds of someone walking across a bare hardwood floor with their shoes on, for example, or hear wall-mounted cabinets opening and closing. There are other solutions for that, and by combining different solutions you can control most structural noise and create more privacy.

Blow-in insulation is inexpensive. You can hire a specialist to do it, or as this YouTube video by Craig Wolfe shows, you can do it yourself with rented equipment. As you'll see in this video, cellulose provides much denser and comprehensive coverage than fiberglass batts. They actually blow additional cellulose into the wall cavity with a fiberglass batt already in it to show you how much air space was still available.

What's really great about blow-in cellulose is that you can keep your existing walls. You just need to cut some small holes into the drywall, which you can replace afterwards, and blow the insulation into the cavity.

This promo video on Cocoon Insulation shows how cellulose fiber is fire retardant and because of its density, very effective at noise control:

Roxul in ceilings

This is yet another video about using resilient channel for drop ceilings. And it's yet another video extolling the virtues of using Roxul "Safe and Sound" insulation.  As one of the comments on the YouTube page says, however, "clips and hat channel is where it's at," and resilient channel is considered to be older tech now. Either one is better than nailing drywall right onto the joists.

Remember: if you're going to spend money on drywall, get something like QuietRock or Supress that dampens noise. This is your one chance to get it right – don't cut corners on the materials and regret it later!

How to insulate your recessed lighting cans

This 5-minute video from Dr. EnergySaver is as pertinent to soundproofing as it is to thermal insulation. Most people have holes cut in their ceilings to accommodate recessed lighting cans. If you don't have insulation in your ceiling at all, the hole compounds an existing sound problem. If you do have insulation, you already know that you need to keep the insulation material away from the heat of the can.

This video demonstrates a rock-wool product that you can put over the can in order to prevent heat/electrical issues. Of course it necessitates having an attic or someplace where you can access the recessed can from above, not below. It's a great solution if it fits your space!

I found these covers for $15 each at Amazon.

Insulating walls with Roxul

Roxul Stone Wool is an insulation product that comes in the form of batts. It's composed of mineral fibers and it's considered to be green, fire-retardant, and very good for sound control. Like cellulose fiber, it insulates airborne noise better than fiberglass.

In the USA, you can buy Roxul at Lowes and some Home Depot locations. In Canada, you can buy Roxul in Saskatchewan at Rona Corporation in Prince Albert or at Econo Lumber.

Roxul comes in packages of pre-cut sizes that fit the dimensions of your wall cavities (for example, use these 15 1/4-inch batts for wall studs that are 16 inches apart). Be sure to select the right size for the job – not just the width, but the depth as well (wall versus ceiling or attic).

This video from Roxul demonstrates how to install Roxul in a wall. As you can see, it cuts easily with a bread knife and can be custom fit around electrical lines, plumbing, and wall outlets. It holds a snug fit between the wall studs.

You should wear gloves and long sleeves when you work with the product, because it's very itchy.