MaxxMinutes Blog

Proper Acoustical Construction of Floor/Ceiling Assemblies

Proper acoustical construction for floor/ceiling assemblies is arguably one of the most important challenges building owners, architects, and general contractors face. In multifamily construction care must be taken in the installation and selection of all components to ensure the ultimate designed acoustical performance.

Did you know there are five basic components of proper sound control? Those components are:

1. Mass
2. Absorption
3. Gypsum board decoupling
4. Sealing
5. Sound underlayment decoupling

Mass comes in the form of joists, plywood subfloor, gypsum board, concrete slabs, and poured floor underlayments. How important is one single component such as a Maxxon Underlayment? A Maxxon Underlayment is an essential component especially for STC performance because it significantly increases the mass or weight of the entire system. The remainder of the components mentioned above play significant roles in providing satisfactory IIC ratings.

The idea for absorption starts with the concept of understanding items such as air space depth and what sound absorbing materials (insulation) are going to be used. For example, insulation provides sound absorption in the joist space which helps absorb sound waves as they pass through the floor/ceiling assembly.

The resilient channel is also a very significant part of the system both for STC and IIC. It effectively de-couples the ceiling from the joists therefore creating a vibration break. One thing to note: not all resilient channel performs the same. For example, heavier guage resilient channel does not constitute better acoustical performance - in fact the opposite holds true. In addition the combination of resilient channel and insulation is very effective when used in conjunction. Gypsum board is also significant as it completes the cavity.

Sealing openings and flanking paths such as recessed lights, furnace ducts, plumbing, sprinkler heads, etc. must also be performed to ensure proper sound control. In fact no sound control system is better than its weakest component. Even small openings left unsealed can reduce STC and IIC ratings.

Maxxon's Acousti-Mat line of decoupling sound control mats can significantly increase IIC ratings as well as STC performance. Sound control mats create an isolation break or "void" which reduces the energy transmission of impact.

Other Important Questions to Ask

1. What floor goods are being chosen?
2. What IIC and/or STC rating is desired?
3. Is elevation and/or floor thickness an issue? What pour depth is acceptable?
4. What UL fire rating is being used for design purposes?

The International Building Code specifies that floor/ceiling assemblies shall have an STC and IIC rating of 50 (45 if field tested). It should be noted that an STC/IIC of 50 provides only marginal sound control, therefore the International Code Council (ICC) now recommends that an "acceptable" level of performance for both STC and IIC is 55 (52 if field tested). The "preferred" level of performance for STC and IIC is 60 (57 if field tested). Typically a floor/ceiling assembly cannot meet these levels on their own merit, so a sound control is needed.

For sound ratings of specific floor/ceiling assemblies contact your Maxxon representative here. Maxxon also offers an AIA approved Lunch and Learn opportunity on Sound Control in Multifamily Construction.