Sound Deadening Using Spray Foam Insulation

Achieve an STC 50 for your wall assemblies using spray foam.

The secret is not so much if you have something in the walls, but what precisely, and how well can it seal the passages for sound to travel through. Sound and heat transference are very similar. Air carries noise and frequencies just as it carries heat or cold currents. By sealing the walls from space to space you effectively cut off the ability for the sound to flank around the walls and get into the next area. The typical areas that are problematic are the electrical outlets and piping holes. If these areas are not filled with an acoustic caulking, then sound waves will penetrate through causing the conversation or music to be heard on the opposing side.

Spray foam seals around wires and pipes right up to the ceiling for "party walls."

Hallway walls and demising walls also known as "party" walls are typically the ones we are most concerned about. The National Building Code states that in all multi-person dwellings the occupants shall be protected from sound transmission by a minimum STC-50 rated wall assembly. In the day when the code was written and the wall assemblies where being tested Hi-Fi stereos and T.V. where not at the performance levels that they are today. This coupled with the older testing equipment means that the wall assemblies drawn rarely achieve an in-place value that they claim. Every joint and opening must be sealed with acoustic caulk and the batts installed properly. Drywall must be tapped and mudded in order to give it the best available chance to perform as needed. In the real world this rarely ever happens and many builders are faced with complaints and call backs due to sound leakage.

This Wall Assembly Was Approved With Only 4 Inches Of Foam

Spray foam seals and prevents air leakage from wall assembly to wall assembly. It can do this in the same fashion that it works for insulating. Foam insulation froths up to fill gaps and seal points where air can leak through. It is these same gaps that allow some of the sound to leak through the wall and disturb people on the other side. Besides sealing gaps, spray foam adheres tightly to one side of the drywall, helping to ease vibrations and frequencies that pass through the assembly.

Vibrations are eliminated, gaps are filled and smells or odors will be kept in their place. Overall comfort and isolation can finally be achieved thanks to spray foam. If you have had complaints out of a wall assembly that is suppose to be achieving STC 50 or better then that wall is not doing what it says. 5 - 10 STC drops are audible to the human ear. Anything less needs to generally be detected by laboratory equipment.

This Wall Assembly Was Approved With 4 Inches of Foam

This Sub-Floor is Approved With 4 Inches Of Foam

Sub-Floors for Commercial Mid-Rise Condo Projects

Does This Look Familiar? Now you have the very best option to achieve STC-50 or better for your sub-floor assemblies. Instead of using gypcrete and extra layers of flooring, caulking all penetrations and doing a 75% or full cavity fill, you can specify 4 inches of low density spray foam and meet the intent of the building code. In a 19" deep sub-floor assembly 4 inches of spray foam achieves STC 50, and that means that 15" is left for wiring, pot lights and all other piping runs. Imagine the savings in both time of labor, and materials to switch to spray foam for your next condo project. Plus with spray foam applied directly to the sub-floor, impact noises will be greatly reduced due to the fact that there is a material absorbing shock and vibration from the occupants above.

Sewer and water lines are all filled and sealed by the low density spray foam

No drastic design changes have to be made in order to accommodate the use of spray foam in the sub-floor assembly. Piping and wiring runs are all in place and must be roughed in so that the spray foam can be sprayed and sealed around those penetrations.

Low density spray foam is sprayed on as a liquid to the sub-floor between the floor trusses. Two seconds after the liquid is sprayed out of the gun it foams up and sets into place. The thickness is controlled by the output of the gun and speed of coverage. Generally speaking two passes are used to build the foam up to the thickness of four inches.

Spray foam in the walls and floor hold tight to pipes and wires, eliminating water hammer and the sounds of water draining. Fiberglass cannot lock in