USI Blog

What is a firestop?

johnsmanville-firetempFirestop options can make any building — new or existing — safer for tenants while also limiting property loss from a fire. Proper firestop and smoke seal of fire-rated walls, floors and ceilings, as well as penetrating items through rated walls, helps extend the time to safely evacuate a building in case of fire. Maintaining proper fire and smoke barriers also reduces fire and smoke damage.

A firestop is a fire protection system that seals the cracks and crevices of a space with fire proof material to keep a fire from spreading between rooms. This is a crucial step in ensuring fire and smoke from spreading through multiple spaces quickly. Depending on the space and space requirements in your building, there are different materials you can use for firestops.


For sealing around pipes, tubing, and duct work, you want to use Penetration Sealants that can hold a fire off for two to four hours. Joint Sealants are used to caulk the spaces between wall boards. They are intumescent, meaning the sealant swells up when fire is near or touching it, thus preventing the fire from getting through the cracks and spreading even further.


Another material that is used as a firestop, temporarily in big gaps or spaces is a thing called a Pillow. While this is a different type of pillow than what you sleep on at night, it does resemble a traditional pillow. This firestop pillow has a fire-resistant rating, which is normally made with rockwool batts, vermiculite or intumescent foam rubber. It is used for holes in walls to or in the floor to provide added protection.

Other Components

Composite sheets are used mostly for repairs in fire walls and can be customized and then sealed with the Penetration Sealant. Pipe Collars are put in place when plastic pipes are built through a wall or ceiling and needs to be sealed up. The collars have intrumescent material that automatically seals under the heat from fire. And, sleeves are metal pipes that are filled with intumescent putty that cords and cables can pass through easily.

Professional Assistance

USI specializes in the selection and installation of the appropriate firestop and smoke seal systems for new and retrofit projects. We offer professional installation and extensive knowledge of firestop systems to every builder and building owner. With our joint and penetration firestop expertise and professional installation, we offer peace of mind and confidence in your firestop assembly.

For more information on firestops or for a free quote on insulation, contact USI online to find a branch near you. USI believes that excellence in every step of the process and ensures timely completion and quality of service, time after time.