Impact noise will travel through a structure that does not have a resilient material as part of the construction assembly.

Impact noise will travel through a structure that does not have a resilient material as part of the construction assembly.

Soundproofing floor underlayments can help to structurally isolate the top layer of the floor from the rest of the components. This essentially ‘short-circuits’ the sound and vibration, keeping it from passing through the completed assembly. These materials are used to build what is commonly referred to as a ‘floating floor.’ Soundproofing floor underlayments can be installed under many types of materials, including engineered wood, hardwood, laminate, LVT (luxury vinyl tile), concrete, carpet, and tile. All these materials are installed under flooring finishes to generate a higher Impact Insulation Class (ICC) rating for a construction assembly to reduce the transmission of impact sounds and can even provide vibration isolation to a certain extent.

What is Impact Insulation Class (IIC)?

Impact Insulation Class (IIC) is an acoustical rating used to quantify impact sound absorption and vibration isolation. This rating system is used for floor and ceiling assemblies. Some assemblies include soundproofing floor underlayments, which are installed under hardwood, vinyl, or carpet in multi-level buildings to absorb impact noise such as footfall, keeping the noise and vibration from transferring to the ceiling below.

Assemblies with these acoustical underlayments have a higher IIC rating because they block more impact sound. So IIC ratings are assigned to soundproofing floor underlayments not only based on the product’s material but also the floor assembly on which it is installed.

Why Is Impact Insulation Class (IIC) Important?

Impact noise is a structure-borne sound created when two objects collide. This impact energy creates vibrations that resonate through the materials in the structure. It also creates airborne sound.

For instance, this is often realized in the real world as a ‘neighbor noise’ generated from someone walking on the floor above or other activities. Floor soundproofing should be placed underneath the finished flooring and cover the whole floor. This can provide a vibration isolation layer to help prevent structural sound from passing through the completed assembly, providing peace and quiet to the occupants below.

Examples Of Impact Insulation Class (IIC)

Iso-Step Soundproofing Underlayment - Roll out and lay the Iso-Step into the adhesive bond.

Iso-Step® Soundproofing Underlayment – Roll out and lay the Iso-Step into the adhesive bond.

Acoustical Solutions offers a variety of acoustical floor underlayments including Acousti-Mat® and Iso-Step®.

Acousti-Mat® Floor Underlayment is a material made up of extruded nylon filaments which form a 3-dimensional core that has a non-woven fabric heat-bonded to its upper surface.

The durable, yet pliable, construction of Acousti-Mat® sound control matting lowers both structural and airborne sound transmission by its ability to convert and store vibrational energy. Acousti-Mat® Floor Underlayment has an impressive IIC rating for all assemblies but carries no Sound Transmission Class (STC) rating as stand-alone material. Iso-Step® Soundproofing Underlayment is an environmentally-friendly rubber-based product made from recycled tires. It offers credible sound reduction for structure-borne noise, with exceptional IIC ratings for all assemblies, and does help increase the STC rating when used in a soundproof flooring assembly.

Tips And Reminders For Impact Insulation Class (IIC)

Here are some tips when preparing to install a soundproofing floor underlayment to your subfloor. For instance, your subfloor should be smooth to prevent irregularities, roughness, or other defects from telegraphing through the material. You should mechanically remove all traces of old adhesives, paint, or other debris by scraping, sanding, or scarifying the substrate. DO NOT use solvents.

Furthermore, grind all high spots until they are level and fill all low spots with an approved patching/leveling compound.

All saw cuts (control joints), cracks, indentations, and other non-moving joints in the concrete must also be filled with an approved patching/leveling compound.

Allow patching material to dry thoroughly. Moreover, any concrete subfloor can be a source of moisture-related flooring failures. Also, test the concrete or other cement-like material for moisture.


Typically, soundproofing a floor is not given much thought initially during construction. It is always a great idea to add acoustically efficient materials to prevent sound or vibrations from transmitting from one room or level to another. However, if you need additional advice about perfecting a soundproof floor, contact us today at the contact info below, we are always happy to assist you.

To learn more about how Acoustical Solutions can solve your noise control problems, use our contact form, call one of our Acoustical Sales Consultants at (800) 782-5742, or visit us on the web at