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Upgrading Existing Walls Soundproofing

Upgrading an existing wall is one of the most common sound isolation applications in the world. Moving to a new home, installing some new equipment (such as a home theater), having a new baby, getting new neighbors, or just growing weary of the everyday noise are all reasons that cause people to want to improve their situations.

When planning an upgrade to an existing room, the first step is to decide if you want to destroy what you already have and completely rebuild it, or if you want to simply add on to what you already have. If you rip out what you already have, you have many more options, and higher overall performance can be attained. However, destructive remodeling is a longer, more costly process, and is not the preferred choice for a great many persons. Let's take a look at what can be done for either option - destructive or non-destructive remodeling.

Non Destructive Upgrading

An enormous number of soundproofing applications involve situations where people just aren't able (or willing) to destroy what already exists. Although your options aren't quite as diverse when planning a non-destructive isolation project, much can still be done. In most situations, the most effective, and most cost-effective, non-destructive upgrade is adding drywall and Green Glue.

The first place to start if you're walls need an upgrade is with the seal quality and other direct air paths. To have a chance at success, you have to make sure that there aren't direct air paths from one room to another - if there are (like unsealed cracks covered by wall trim, unsealed doors, direct, short air paths involving the ventilation system, etc.

Destructive Upgrades

If you are willing to rip down what you already have, then in many respects you can treat your upgrading project like a new construction, and the best place to start is the "Understanding Soundproofing" article, where you can read about how all of these myriad options work.

Upgrading the Walls Part 1 - Adding Mass

Once the walls are sealed (or you've made a plan to seal them), it's time to upgrade the walls. The lowest cost upgrade to a wall is usually mass - adding another layer of drywall. Unfortunately, simply adding an incremental amount of mass does not have a very large impact on performance. (The wall is already quite heavy and another layer of drywall doesn't make a big percentage change)

To understand this graph, what you see is how many decibels of sound the wall stops at different frequencies. Higher is better.

Adding mass has only a small effect, doubling the number of drywall layers improves performance by only about 3dB at the low frequency resonance, and improves STC by just 4 points. This data is taken from tests in a certified lab.

Considering the cost of adding drywall, simply adding mass doesn't give us either a large improvement or good bang for the buck.

Upgrading the Walls Part 2 - Adding Mass + Green Glue

Unlike simply adding mass, adding drywall + Green Glue has an enormous effect on the performance of your walls. Instead of a few decibels of improvement, we see 10 or more at most frequencies, including impressive low frequency gains.

Adding Green to both sides of the wall, or adding 2 layers of drywall and Green to one side has an even larger benefit.

In the table below we compare the gains in performance that can be attained from these various methods of upgrading. In each case, all wall variables were identical (same studs, insulation, etc.).

All data based on tests run at Orfield labs, an NVLAP certified independent lab.  Costs based on national averages from the National Construction Estimator, available from Craftsman books.  31.5-5000Hz dBA reduction is based on the sound reduction over this entire frequency range for a flat noise source.

Green Glue is easily cost effective when compared to just adding drywall, or adding soundboard and drywall to an existing wall. And, more importantly, it actually delivers big changes in performance, giving you a chance to meet your soundproofing goals.

Adding resilient mounts and more drywall

From time to time, it is recommended that resilient mounts be added to an existing wall, with drywall over those. Things like adding resilient channel to your wall, and then drywall, or adding modern sound clips and then drywall. This solutions are not desirable and are unlikely to yield high performance, especially at low frequencies, as they create decoupled systems with small air cavities, and they create triple leaf walls. You can read about the perils of triple leaf design in our document Understanding the triple leaf effect and it should be avoided.

Other possible solutions include adding a sheet of factor-damped drywall to the wall, and this can (like Green Glue) yield excellent performance benefits. However, the cost is far higher than for Green Glue.

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