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Sound Controlling Floor/Ceiling Materials

Everything from the floor under your feet to the ceiling in the room below can have an impact on sound transmissions from one space to another. This includes the floor covering, any underlayments, insulation between floor joists, adhesives, acoustic sealants, and more. Let's take a look at these materials and how they can be used to reduce sound transmission from one space to another.

Underlayments

A roll of recycled material
underlayment

Often laid under floor coverings, underlayments can help to cushion the floor, making them one of the easiest methods of reducing sound transmissions. Sound deadening underlayments include cork, rubber, foam, plywood, and several other types that are made specifically for reducing sound transmissions or improving acoustics. Generally, the thicker the underlayment, the more sound transmission it can block.

Ceiling

Picture of bare ceiling drywall or gypsum board

Gypsum board is the most commonly used ceiling material. Thicker gypsum board ceilings help to reduce sound transmissions from the floor above. When vibrations from an impact travel through the floor, subfloor, and flooring joists, they can reach the ceiling in a room below, causing it to vibrate as well, transferring the impact sound into that room. When the ceiling is attached directly to flooring joists, there is little to dampen that vibration. For this reason, resilient channels are often attached to the floor joists, and the ceiling is then attached to these channels. The resilient channels act as a shock absorber, reducing the transmission of sound waves to the ceiling, and thus reducing unwanted sound transfer to these rooms. This can increase both STC and IIC ratings by a few points.

Insulation Between Floor Joists

Picture of insulation installed betweeen joists

You can also install insulation between floor joists to increase the IIC rating of a floor/ceiling assembly. Examples of insulation materials include, but are not limited to, fiberglass, cellulose, styrofoam, and spray foam. In addition, insulation is assigned an R–value depending on its thermal resistance. Higher R values mean less heat loss in the space which usually means more sound absorption as well.

Adhesives And Acoustic Sealants

Glue down flooring applications can often be installed with flexible adhesives which can reduce vibrations and damped noise transfer to the subfloor. Acoustic sealants are flexible sealants that are applied around the perimeter of the floor surface where the subfloor meets the wall and around other obtrusions (air ducts, doors, etc). The purpose of acoustic sealants is to seal gaps in order to block sound waves from traveling between them. The flexibility of these sealants also allows them to absorb some sound vibration.

Let's look at some examples of floor/ceiling assemblies and their related IIC and STC ratings.

Ref Diagram Topping IIC Rating STC Rating
1–1 Diagram of wood flooring on
plywood subfloor over joists 3/4" wood flooring over 3/4" plywood subfloor. 1/2" gypsum wallboard nailed to joists from underneath 52 38
1–2 Diagram of carpet and pad on playwood
underlayment and subfloor over joists Carpet and foam carpet pad on 1/2" plywood underlayment over 1/2" plywood subfloor. 1/2" gypsum wallboard nailed to joist from underneath 56 45
1–3 Diagram of carpet and pad on plywood
underlayment and subfloor over joists with resilient channel underneath Carpet and foam carpet pad on 1/2" plywood underlayment over 3/4" plywood subfloor. 1/2" gypsum wallboard secured to resilient channel attached to joist from underneath 70 52
1–4 Diagram of laminate flooring
on sound
deadening board over joists with resilient channel underneath Laminate flooring on 1/2" sound deadening board over 3/4" plywood subfloor. 1/2" gypsum wallboard secured to resilient channel attached to joist from underneath 77 52

Caption: The pictures above show examples of different STC and IIC ratings that can be achieved with floor/ceiling assemblies. The ratings are an estimate and can differ depending on the actual products and installation method used.