Check the Bottom Joint in a Fire-Rated Wall

The wall design identifies the framing, gypsum layers and other parts of the wall. The joint system identifies the materials and arrangement at the wall-to-floor connection.

UL’s guidance explains that components from different rated systems are not automatically interchangeable. Use the complete joint system that fits the wall and floor.

Check the adopted code and project requirements to determine the joint protection required. Drywall clearance alone does not define a universal joint width or firestop detail.

UL 263 and ASTM E119 cover fire-resistance testing of building assemblies. UL 2079 and ASTM E1966 cover fire-resistive joint systems.

For a joint product, review the complete listing and installation requirements. A wall’s hourly rating does not identify the material or dimensions required at the bottom joint.

UL BW-S-0078 lists Waterguard FS as the fill, void or cavity material for 1- and 2-hour joints under ANSI/UL 2079. The joint rating equals the wall rating. The listing also includes Canadian ratings under CAN/ULC S115.

Use ⅝-inch gypsum board: one layer for one-hour walls and two layers for two-hour walls. BW-S-0078 references U300, V300, W300, U400, V400 and W400 Series wall designs, subject to the listing’s additional requirements.

The listing covers qualifying reinforced-concrete, UL Classified hollow-core precast, and D700 or D900 fluted-steel floor-unit/concrete assemblies. Check the complete listing for the floor thickness, wall framing, fastening and dimensions.

The U.S. L Rating is less than 1 CFM per linear foot at ambient temperature and 400°F. Sound performance comes from separate acoustic wall tests.

Snap FS onto the outermost board layer on both sides of the wall before hanging. Face the shorter leg outward and keep the intumescent strip in contact with the floor.

Use this checklist with the complete listing. Each dimension refers to a different part of the installation.

Include the wall design and BW-S-0078 in the submittal and installation documents. Check the product, floor, framing, board layers, profile orientation and joints between sections before work starts.

BW-S-0078 uses FS without a separate bottom sealant application. If the proposed construction differs from the listing, get the design team’s direction before installing it.