Impact noise will travel through a structure that does not have a resilient material as part of the construction assembly. Soundproofing a floor requires addressing the issue of impact noise. 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. Most people think of this as “neighbor noise” from someone walking on the floor above or other activities.

Utilize an acoustic floor underlayment to short-circuit the impact noise. Place it underneath the finished flooring and cover the whole floor. This will prevent structural sound from passing through the completed assembly.

Iso-Step® Soundproofing Underlayment

Iso-Step® Soundproofing Underlayment, when installed correctly, is a double-duty acoustical underlayment. It improves IIC ratings (Impact Insulation Class) by providing an impact-resistant layer under flooring. This reduces the transmission of structure-borne sound. Additionally, Iso-step® will add to the STC (Sound transmission loss) of the overall assembly.

Install Iso-Step® over wood or concrete sub-floor, beneath hardwood, vinyl, tile, and carpet flooring. Iso-Step® Soundproofing Underlayment is economically priced and available for quick shipment.

Typical Tools Needed for Installation

Tape measure | Metal straight edge | White marker, chalk or chalk line | Utility knife | Duct tape (optional) | Other tools may be required to install subsequent layers of flooring materials.

Prep Work

Iso-Step® Soundproofing Underlayment and the flooring material to be installed must acclimatize, in their sealed packaging, in the room where they are installed for at least 48 hours, at a temperature of at least 65 degrees F. Before starting your installation of Iso-Step®, make sure the subfloor is permanently dry and free of dirt, dust, grease, and other foreign matter.

Prep for Wood base

Subfloor should be properly leveled, structurally sound, and clean. Plywood sub-flooring should be of a good grade. Level variations in floor level over 1/8″ within a three-foot span before installing underlayment. Remove or pound flat any nails or other protrusions. Repair holes and other surface variances prior to installation of Iso-Step®. To use IsoStep® with a nail-down hardwood floor, we recommend that you create a “raft” made of 2 layers of 1/2” plywood, glued and screwed together with the top layer turned 90 degrees in orientation and offset by 2 feet from the edge in order to cover the seams. Leave a 1/2″ gap between the wall and the raft to allow for expansion around the entire perimeter. Use 1-1/2″ nails applied at an angle to secure the hardwood flooring on top.

Prep for Concrete base

Inspect concrete subfloor for any open cracks and fill with high-grade epoxy filler. Remove any excess concrete lumps or residue that may interfere with the installation of Iso-Step®. If you use a vapor barrier, we recommend polyethylene sheeting. Install with overlapping seams (6-8″ overlap) using tape to secure edges. Apply the vapor barrier directly over the concrete.

Floating Floor Systems

Under Laminate & Engineered Wood Flooring Or Tile

The laminate or engineered wood flooring is intended to float on top of the Iso-Step® Soundproofing Underlayment. In most cases, you can install acoustic underlayment in a few easy steps.

First, install a perimeter isolation strip to prevent the flooring from touching the walls or any protrusions in the floor. Make sure to prep all areas, and ensure they are level and free of dirt and debris. Then follow the installation guide as outlined in the documents section of the Iso-Step® Soundproofing Underlayment page and as instructed by the flooring manufacturer.

Iso-Step Soundproofing Underlayment

Iso-Step® Soundproofing Underlayment

Under Tile

Iso-Step Soundproofing Underlayment - After installing a perimeter isolation strip, apply approved adhesive to the sub-floor using recommended trowel size.

After installing a perimeter isolation strip, apply approved adhesive to the sub-floor using recommended trowel size.

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

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

Iso-Step Soundproofing Underlayment - Roll the Iso-Step with an approved flooring roller.

Roll the Iso-Step® with an approved flooring roller.

Iso-Step Soundproofing Underlayment - Apply adhesive to the Iso-Step using recommended trowel size.

Apply adhesive to the Iso-Step® using recommended trowel size.

Iso-Step Soundproofing Underlayment - Lay finish floor layer according to flooring manufacturer guidelines.

Lay finish floor layer according to flooring manufacturer’s guidelines.

Nail Down Hardwood Flooring

** Do not nail through Iso-Step® Soundproofing Underlayment**

Installation of solid nail-down hardwood flooring using a raft method. Install Iso-Step® from wall to wall — loose lay; lay ½” plywood on top leaving a ½” expansion/acoustic gap around all walls. Install a second ½” layer of plywood making sure to stagger the bottom seam from the top, glue & brad nail the top plywood to the bottom plywood. The plywood floats on top of the underlayment. You can fasten the nail-down hardwood into the plywood raft. Leave the expansion gap alone or fill it with acoustical caulk, and install baseboard slightly off the finished floor.

Cross-Section of Hardwood Floor Assembly

Cross-Section of Hardwood Floor Assembly

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