One of the great soundproofing challenges in the world today is taming noise from hard-surface floors. Here we will take a look at how to accomplish this task, with an emphasis on treating the noise at its source, and on this page we will assume that carpet + a thick carpet pad isn't an option. Often, carpet + a quality pad takes care of these problems.
When thinking about impact noise problems, it's necessary to differentiate between lightweight floors and heavy floors. Lightweight floors would be, for example, subfloor with cement board and tile. A heavy floor would be a floor with concrete or gypsum concrete poured over the sub-floor, or pre-cast concrete flooring. These floors are so much heavier that they have to be treated a little differently.
Many products are available for helping with impact noise on the floor level. Most of these are various forms of resilient underlayment - cork, rubber mats, foam underlayments, wood fiberboards (soundboard) and more. Other products include specialty damped plywood's, and damping materials such as Green Glue. Let's look at some of the combinations that can be used.
Typical Floor Assembly with only Underlayment
Underlayment can be a great help in controlling impact noise. Available underlayments include
- Cork
- Rubber mats
- Foam underlayment
- Fiberboards/Soundboards
In lightweight floors, rubber mats have one advantage over the other products in that they are very heavy, and contribute substantially to the weight of the floor. This can help not only with impact noise, but also with airborne sound.
Underlayments are typically most effective at high frequencies, and are often not effective at all at lower frequencies.
Typical Floor Assembly with Green Glue (only)
Green Glue alone has certain advantages relative to underlayments. It is far more effective at low frequencies, it's thinner, and it is usually considerably less expensive. Many Green Glue customers use it as a stand-alone impact noise control product with outstanding results.
Green Glue must be used in between two rigid/hard surfaces to do its job. The best application is between the subfloor and whatever goes on top of that. You may use Green Glue in between subfloor and cement board, sub floor and wood flooring, between two layers of subflooring, or use multiple layers of Green Glue - like Green Glue between double sub-flooring and between the subfloor and cement board.
Combination of Green Glue and Underlayment.
Many common underlayment choices are compatible with Green Glue, allowing the best of both worlds.
- Compatible underlayments include:
- Cork
- Fiberboard/soundboard
- Heavy Rubber mats
If you have questions about a specific product, just contact The Green Glue Company.
When using Green Glue in combination with these products, remember that you will have to ultimately have the GG sandwiched between two stiff surfaces. So, if using rubber mats or cork, something stiff - like cement board, tile, or subfloor - will have to be on either side of this gg/underlayment sandwich.
Those are some of the options for treating a floor, with different cost and performance possibilities. Next, let's take a look at what we can do to the ceilings and walls of the rooms below.
The Best Possible Construction - Green Glue Room Within a Room.
The room within a room is sometimes challenging to construct, often impractical, consuming of ceiling height and floor space, and so on and so forth, but for situations like high end theaters and modern recording studios, a Green Glue room within a room is absolutely, positively the best construction possible.
This is true for both airborne sound and impact noise
Resiliently mounted ceiling and decoupled walls
The next best thing to a true room within a room is a resiliently decoupled ceiling and some type of decoupled wall. In this case, we show spring ceiling hangers, and staggered studs, both with a GG double drywall sandwich.
The preferred resilient mounts are
1. Spring ceiling hangers
2. Modern sound clips like ISOMAX or RSIC
3. Resilient Channel (considerably less recommended)
The preferred wall types are
1. Double stud
2. Staggered studs
3. Resiliently mounted with sound clips
4. Hat or Furring channel with Green Glue
5. Resilient channel
If Green Glue is not used, then sound clips on the walls are preferable to staggered studs.
The performance of this type of assembly is only somewhat lower than the true room within a room if hangers or clips are utilized.
When Resilient Mounts Aren't Possible.
In many situations, resilient mounts simply aren't possible. Perhaps they cost too much, perhaps they take too much ceiling room, and so forth.
In these situations, you can benefit yourself a respectable amount by utilizing wood furring strips or metal hat channel perpendicular to the joists or studs. The furring or hat should be installed at 24" on center of local regulations allow for best results.
If you cannot tolerate loss of headroom, you should strongly consider using Green Glue + double drywall, or if zero loss of headroom is acceptable, you should consider some of the thin, factory-damped drywall that is available from sellers such as supress products.
And that should get you started on planning your new construction. Make sure to download and print a copy of our pdf file that discusses impact noise for your reference. We are always available to talk to you about your specific situation, and whatever questions you might have.
Other pages in this series:
Understanding Impact Noise
Upgrading an Existing Floor