Some companies create mystery in the noise control sales process. Since a lot of litigation has occurred surrounding the issue of noise control, a certain amount of mystery comes from the concern about failure and the desire to avoid issues. It isn’t the flooring contractor’s responsibility to provide a system that achieves code. It isn’t the flooring contractor’s responsibility to achieve the expectations of a condo owner in suppressing noise. The flooring contractor has one role – installing a system properly. Still, there is a sniff test that a contractor needs to do in order to avoid future problems with noise. The sniff test is to understand which product qualities limit impact noise or footfall in a floor ceiling assembly, and install only products that can achieve the desired code and expectations of owners.
The general qualities that make a product perform for impact noise are resilience, void space and thickness. These rules mean:
1. More resilience, more vibration absorption.
2. More void equals less touch and less vibration wave conduction.
3. Thicker materials equal greater ability to handle larger vibration waves.
All of these qualities need to be weighed against the finished floor’s structural needs. Highly resilient products do not work with ceramic tile or VCT but might be fine for engineered wood. Products with lots of void space provide limited structural support for direct fastening flooring and sometimes require a mortar bed, plywood substrate or gypsum underlayment. Most often, manufacturers provide ASTM standard Robinson Wheel Test results to prove acceptability in the application. Look for products that have these tests available.
Concrete construction provides a structure with great dynamic stiffness. Wood frame projects are much more bouncy. The noise problems in concrete construction are typically high frequency. In wood frame, the bounciness leads to low frequency problems. The solutions in wood frame cannot always be found in a topically added mat installed by a flooring contractor. One important check - the level of deflection and minimum design standard is L/360. Mass elements like floor joists and underlayments need to be stiff, and resilience or bounciness is very bad.
In concrete, that solution typically can be found with one good roll added to the topside of the concrete. But, all concrete construction is not the same. An 8-inch concrete slab is not the same as a 4-inch concrete corrugated deck. The noise performance is a function of the stiffness, and consequently the slab thickness. Additionally, ceiling design is very important. No ceiling and the mat on the topside of the concrete is the only sound element. That burden means a substantially thicker, more resilient, more void sound product is required. Contractors are not responsible for identifying expectations of owners, nuances of condo associations or conforming to building codes. That means guaranteeing the performance in contract documents must be redlined.
So, what do I do differently? Or, what do I do when I bid a project? First, pass the sniff test for the products. That means if the material is rigid and is totally solid (isn’t thicker than a 0.03125” fabric), don’t buy the performance. If the material has some sponginess, has the supporting test data on acoustics and on structural questions, have some faith. Don’t put your name on the line if it doesn’t.
Next, don’t take shortcuts! Solid flooring needs to be isolated from the walls to prevent flanking. Flanking is the non-direct path vibration waves take to cause noise. Isolating around the perimeter of the walls and all penetrations helps to prevent that from occurring. It only takes a 0.125” space of resilient material to make the perimeter work properly. Do create space between hard surface flooring and carpeted areas. Using a transition strip of some type and lots of different materials should work.
Now that you know how it works and understand your role, don’t be surprised when the acoustical consultant shows up to see how it performs. That happens in California all the time. In fact, in some areas of the country, it is a required step before a developer gets an occupancy certificate. Imagine that any room, any unit can be the tested location. Now you know the role, the stakes, and better yet, what makes things work and succeed. Sounds good, doesn’t it?