Area Separation Wall Systems
Attendee questions
Questions and answers from the Area Separation Wall Systems: Designing Better Fire and Sound Protection webinars
Are the breakaway clips designed to accommodate shrinkage in wood frame multi-story construction?
Designer of Record is responsible for accounting for wood shrinkage in their assembly design. It’s outside the scope of our testing criteria.
Are openings for doors or penetrations for ductwork/fire dampers allowed in the area separation wall system?
Ductwork and fire dampers are not allowed to penetrate the area separation wall system but are allowed in the flanking walls. Refer to The Wood Book™ and NGConnects blog How to add doors to area separation walls in multifamily construction for more information on installing doors in ASW. National Gypsum developed a method to install doors using supplemental metal bracing attached to the H-stud framing of the fire wall system. In The Wood Book, see pages 111–114 for 2-hour area separation fire wall and pages 129–132 for 3-hour area separation walls.
Do these ASW comply under section 706 Fire Walls (IBC)? Can they be made to conform to the structural independence criteria under collapse of one side or the other using the aluminum break-away clips?
The gypsum Area Separation Wall systems presented in the webinar comply with IBC section 706.2: Structural stability.
Do STCs increase with the use of mineral wool insulation versus fiberglass insulation?
We have not tested our ASW systems with mineral wool products. In standard wall STC testing, mineral wool and fiberglass insulation often provide similar results.
In the example where the separation wall becomes an exterior wall, can you clad the system with air barrier, insulation and exterior cladding or do you have to build a separate wall for that?
This varies based on the exterior wall and cladding system specified. Gypsum panels are not intended to serve as a nailing base; therefore, cladding systems applied over gypsum panels must be designed to attach to the supporting wall framing or appropriate structural backing.
How is the top C-channel and shaftliner installed at the roof deck? (access to mechanically fasten)
The top C‑track is installed as the area separation wall system is constructed. The adjacent wood-framed walls are then constructed and raised into position on either side of the separation wall. Roof trusses are installed on the wood-framed walls, followed by roof sheathing.
Does it matter which direction you install the 1" gypsum board fireblocking? Example showed it installed vertically at the seams, is that the recommended orientation for the gypsum blocking or can it also be laid horizontally?
The fireblocking is required per IBC Section 718.2.2 Concealed wall spaces. It needs to be installed the horizontal orientation at the ceiling and floor levels and in vertical orientation at intervals not exceeding 10 feet.
Is the ASW assembly from interior drywall to interior drywall? If so, why are the flanking walls not maintained in the vented attic?
The 2-hour fire-resistance rating is provided by the shaftliner panels within the area separation wall assembly. The adjacent wood-framed flanking walls—and associated interior gypsum board—are not part of the rated assembly and do not contribute to the fire-resistance performance.
Is there a requirement for the type of insulation allowed in the flanking wall cavities?
Refer to the UL design for insulation options allowed in the assembly.
How is drywall taped and mudded on back-to-back 1-hour rated townhouse separation walls?
Each 1-hour wall is typically constructed, sheathed, and finished independently. The first wall is framed, drywall is installed on both sides, joints are taped and finished, and then the wall is stood in place. The second wall is then constructed and finished separately on the opposite side, maintaining the required separation between the two assemblies.
Are mechanical, electrical and plumbing systems allowed in double, 1-hour rated walls per the IRC?
Yes, mechanical, electrical, and plumbing systems are permitted within double 1-hour townhouse separation wall assemblies. However, these are not permitted within common wall assemblies for townhouse separations in accordance with the IRC.
Can you speak to running plumbing or vent pipe in the cavity of the 2x4 wood stud flanking walls in the area separation wall system?
The fire-resistance rating is provided by the shaftliner panels and the required air space on each side of the separation wall. The adjacent wood-framed flanking walls are not part of the rated assembly; therefore, the inclusion of plumbing or mechanical systems within these partitions does not impact the overall 2-hour fire-resistance rating.
Where did the minimum 3/4-inch airspace gap come from and why is it needed?
The 3/4-inch air space is part of the UL-tested assembly and is required for the wall to achieve its fire-resistance rating. It provides separation between the rated shaftliner system and adjacent framing, limiting heat transfer and allowing the fire-exposed structure to collapse without pulling down the separation wall.
Can an H-stud be used in lieu of double C-track back-to-back?
Back-to-back C‑tracks are part of the tested assembly and are required for this condition. Substituting an H‑stud in this location would not align with the design or the tested assembly and is not permissible. H‑studs are intended to engage the shaftliner panels vertically, fitting into the C‑runner tracks. At the top condition, the use of back‑to‑back C‑tracks accommodates the panel termination and connection detail. Replacing this configuration with an H‑stud installed horizontally would not function as tested and could lead to improper fit or damage to the shaftliner panel edges.
Is fire caulk required between C-tracks when they are installed back-to-back?
No, fire caulk between back-to-back C-tracks is not required.
How is stud continuity addressed in tall wall conditions, and is vertical staggering of studs required for increased wall heights?
Area Separation Wall (ASW) systems exceeding the height of a single stud are constructed in a stacked configuration using back‑to‑back C‑tracks, which are mechanically fastened together with pan head screws in accordance with the system requirements. ASW systems are non‑load bearing and are designed and approved for full-height construction—without requiring vertical offset or staggering—up to the maximum allowable height (typically 66 feet or 70 feet), depending on the specific tested assembly.
Are clips required on every vertical H-stud, spaced apart vertically based on overall wall height?
Yes, clips are required at each vertical H‑stud. The vertical spacing of the clips varies based on the height of the wall and must comply with the spacing criteria established in the tested assembly.
For the three-hour ASW system, how are the clips installed?
Clips are fastened through the additional gypsum board layer into the H-Studs.