I have been suffering from a bit of writers block this week and struggling to come up with an engaging topic to expound upon.
This morning I was reviewing customer feedback we get through Avid Ratings and realized that we have had a number of negative comments regarding soundproofing in some of our recent new builds. I thought it would be a good idea to identify some of the challenges and limitations to soundproofing in a wood frame home, particularly between floors with surface finishes such as hard wood, that we face. In the end, as with all things, the budget limits what we can do and while there is always a better solution many times the budget does not allow for the superior assembly.
While you can mitigate sound in a wood frame home, high Sound Transmission Class (STC) ratings can get expensive. There is no requirement in single family homes to achieve any particular level of soundproofing, so in lower cost homes you might find that there is little or no sound proofing at all.
Basic soundproofing: At a very basic level to essentially muffle sound from room to room or floor to floor we would use sound insulation such as Owens Corning’s Sound Attenuation Batts. As above this deadens sound to a degree, and can improve STC class ratings by about 4-10 dBs.
Enhanced soundproofing: (This is the level we would typically do in our budget based homes). The sound batts can be combined with additional layers of drywall. As an additional strategy specialty products such as Certainteed’s QuietRock drywall can be used. The application of the QuietRock can increase sound performance of the wall by up to 13 dBs. Additionally the drywall can be separated from the framing with a metal channel to help reduce sound vibration transmission. The addition of extra drywall, metal channel and QuietRock will begin to incur significant additional costs. (we would not typically use QuietRock unless the client requested it as it comes at a premium price) This can be applied to walls and floors with similar improvements. Keep in mind that eliminating sound transmission through a wood framed floor with hard surface flooring is very challenging without taking some extreme measures.
Premium soundproofing: If you really want to eliminate sound between walls you need to build a 2 wall assembly separated by an air space. Better yet separate the floor sheeting with a saw cut (if your engineer will allow it) as well. This prevents the sound vibrations from transmitting through the wood framing. Combine the double wall with sound batts, QuietRock, Green Glue between the drywall and metal channel and you begin to really eliminate sound transmission. If practical preventing air movement between the rooms will also significantly reduce noise transfer – use air tight electrical boxes and ensure outlets are not installed back to back. Sealing one wall with spray foam insulation will air seal one room from another and reduce sound transmission.
Floors as above are more difficult. The above strategies combined with a 1.5″ concrete topping are the best you can do without actually framing a secondary ceiling that is separated from the floor framing. As you can imagine the cost starts to go up exponentially.
Even with sound batts, QuietRock, green Glue, metal channel and concrete topping sound will still transmit floor to floor. Additionally, open stair wells and air gaps below doors make it very difficult in a wood frame home to eliminate sound transmission.
If soundproofing is a high priority expectation on your new build or renovation highlight this in the early design meetings so your design team and builder can incorporate this into the build. Concrete topping, double stud walls cannot be easily added once construction has begun.
As above all the strategies come with additional cost and most likely will not fit within original budgets if added during construction.
If you would like to learn more about building soundproof homes give us a call.