3M B258 Fire Barrier Block B25...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$133.06
$96.20
3M B258 Fire Barrier Block B258

3M B258 Fire Barrier Block B258

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Model: B258
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In Stock (leaves warehouse same day if ordered before 3pm ET)

$133.06
$96.20
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3M Fire Barrier Block B258

  • Recommended Applications

    • Blank openings
    • Cable trays
    • Insulated pipes, combination penetrations
    • Cables
    • Metal pipes

  • Overview

    • When sealing larger cavities, use 3M™ Fire Barrier Block B258 to restore the integrity of the wall with a simple "stack, seal, and done" application, without the use of special tools. The blocks are engineered to remain securely in place, eliminating traditional wire mesh reinforcements. Pre-formed blocks help technicians fill large openings quickly . The material is easy to trim on site without special tools, achieving a tight, custom fit. No cure time is required, which means installation is completed faster, and the blocks are paintable with primer for a more seamless appearance.
    • Fits medium to large openings in wall and floor through-penetrations
    • Installation requires no special tools
    • Block is paintable with primer
    • Can be sealed with 3M™ Fire Barrier Rated Foam FIP 1-Step and other 3M™ fire barrier sealants (sold separately)
    • The blocks are fully re-enterable and reusable, saving time and money, while minimizing waste. Once the opening is filled, seal around the perimeter and any penetrating items with 3M™ Fire Barrier Rated Foam FIP 1-Step or other 3M™ fire barrier sealants (sold separately).
    • Can be repaired and reused as needed, saving time and labor
    • Pre-formed foam block maintains tight firestop seal to prevent fire, smoke and toxic gas transmission
    • 3M™ B258 Fire Barrier Blocks are firestop tested to the criteria of ASTM E 814/UL 1479 Standard Test Method for Fire Tests of Penetration Firestop Systems, ASTM E 84/UL 273 Standard Test Method for Surface Burning Characteristics of Building Materials, ASTM E 90 Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements, and ASTM E 413 Classification for Rating Sound Insulation.
    • No cure time means faster completion
    • Our 3M™ Fire Barrier Block B258 is a pre-formed foam block designed for easy installation to effectively seal larger openings against smoke, toxic gas and flame. It is simple to use and helps reduce sound transmission.
    • Effective and easy to install, 3M™ Fire Barrier Block B258 are part of our family of fire protection products that offer the broadest, long-lasting solutions for a variety of commercial, industrial and residential applications. As a trusted leader in the fire protection industry, 3M offers a broad line of affordable products designed to meet the most demanding firestop requirements. Find the solution you need from the industry-preferred line of fire protection products.
    • Firestop tested in accordance with ASTM E 814/UL 1479


B258 - spec sheet

Manufacturer Resources

Product Specs

Department:
Electrical

3M B258 – Frequently Asked Questions

1) What is the 3M B258 Fire Barrier Block used for?
The B258 is a pre-formed foam firestop block for sealing medium to large through-penetrations in walls and floors. Typical uses are blank openings, cable trays, cable bundles, metal pipes, insulated pipes, and combination penetrations. You stack the blocks into the opening to restore the fire integrity of the assembly and block smoke, toxic gas and flame, and the material also helps cut sound transmission through the opening.
2) Do I need sealant or foam with the 3M B258 firestop blocks, or are the blocks enough on their own?
The blocks alone do not finish the job. After the opening is filled, the perimeter and every penetrating item have to be sealed with 3M Fire Barrier Rated Foam FIP 1-Step or another 3M fire barrier sealant. Those are sold separately, so order the sealant with the blocks if you want to complete the penetration in one trip.
3) Can firestop blocks be removed later when cables get added to the penetration?
That is the main reason to use blocks instead of a poured or foamed seal. The B258 blocks are fully re-enterable and reusable, so you can pull them, run the new cable, and stack them back in. They can be repaired and reused as needed. For a communications riser or a cable tray that keeps growing, that saves tearing out and rebuilding the seal every time.
4) Will firestop blocks help with sound between units the way they help with fire?
They do address both. The B258 block is tested to ASTM E 90 for airborne sound transmission loss and classified under ASTM E 413 for sound insulation rating, alongside the ASTM E 814/UL 1479 firestop testing. For a multi-family or hotel demising wall where the penetration is the weak point for both fire and noise, that is the same product handling both problems.
5) Do 3M B258 fire barrier blocks need cure time before the wall can be closed up or inspected?
No cure time is required. The blocks seal as soon as they are stacked and the perimeter is sealed, so the penetration is finished the same visit rather than waiting on a sealant to set.
6) How do you cut fire barrier blocks to fit an odd-shaped opening?
The B258 block material trims on site with ordinary tools for a tight custom fit, and the full install needs no special tools at all. The blocks are also engineered to stay in place on their own, so the wire mesh reinforcement that older block systems required is not part of the install.
7) Can 3M B258 firestop blocks be painted to match the wall?
Yes, the blocks are paintable with primer. In an exposed corridor or an occupied space where the penetration is visible, prime and paint the face so it reads with the surrounding wall.
How fast can I get the 3M B258 delivered?
Most orders ship the same day from our distribution partners, with quick delivery throughout the continental U.S. Need it urgently? Contact Us for expedited shipping options.
Can I return it if it doesn’t work for me?
Yes—ZenSupply offers a hassle-free return policy. If the product isn’t the right fit, reach out to our support team for a return authorization or setup a return by following our return instructions.
Does the 3M B258 come with a warranty?
Absolutely. The 3M B258 is backed by a manufacturer’s warranty. For full warranty terms, check the product documentation or Contact Us.
How do I get technical support or installation help for the 3M B258?
You can call, text, or email our expert support team for fast answers. We’re here to help with product selection, installation tips, and troubleshooting. Contact Us
Why buy the 3M B258 from ZenSupply?
ZenSupply makes it easy to get the commercial door hardware you need—fast shipping, expert support, and rewards on every order. Our team is always ready to help you choose the right product for your project.
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