Overhead Support and Beam Deflection for Operable Walls

A top-supported wall puts its weight into the track and the track puts it into the structure. If that structure moves too much as panels travel along it or stack at one end, the track moves with it. Panels and seals that depend on a level, stable track can be affected, and the wall may not close or seal the way it was designed to.

Modernfold refers deflection questions to ASTM E557, the Standard Guide for the Installation of Operable Partitions. Section 5.4, Structural Support for Operable Partitions, says the weight of the partition and all live loads should be considered when designing the supporting member, and that deflection under the maximum anticipated load should be no more than 1/8" (3.2 mm) per 12'-0" (3.7 m) of opening width.

The type of wall changes how much movement it tolerates. An electrically operated, continuously hinged wall is one large unit with its panels hinged together, so it has little flexibility, and movement in the support puts strain on the hinges. A single panel system made of individual panels up to 4' wide, with 2" base seals, can accommodate deflection in that range much more easily.

The same Modernfold letter is clear that support should be designed to the 1/8" per 12'-0" guidance as closely as possible, and that using a bottom seal's operating range to absorb extra deflection should be a last option. If greater deflection is expected, ASTM E557 calls for either a structural member independent of the roof structure to support the partition, or a partition with bottom seals designed for the larger deflection. According to Modernfold, deflection beyond the guidance can cause:

• Track joints that begin to gap, so panel trolleys run rough.
• Panels that start to move on their own, rolling toward the low point.
• A- and V-shaped gaps between panels that make joints hard to seal and severely degrade sound performance.
• Greater sensitivity in paired panel walls.

Modernfold notes that deflections of 1/4" per 12'-0" or more are known to cause these problems, and suggests discussing them with the end user during design to set expectations.

How the load reaches the structure depends on the type of wall. Operable walls impose a live load as panels move along the track and gather in the stack, and they typically need heavier structural support.

For Modernfold solid panel walls, folding glass and accordion partitions, LG2 supplies the manufacturer's product data for the selected series and layout.

The configuration changes where the weight goes:

• Stack location. Panels gather in the stack, so the support there matters as much as along the opening. Show the stack and any pocket on the structural drawings.
• Paired Modernfold panels stack on the main straight track, so paired layouts do not need an auxiliary support structure for a stacking weldment. Single panel layouts with offset or remote stacks route panels on switch-and-curve or right-angle track, so confirm support along the whole route.
• Glass walls. Coordinate track and header support, stack depth and pockets for PureView, Acousti-Clear and ComfortDrive, plus the drive trolley header space on ComfortDrive.
• Accordion partitions. Modernfold 800 / 1200 is light enough to need only minimal support; SoundMaster adds steel sound liners. Coordinate structural support and blocking for the track either way.

Where proper overhead support is not available, Modernfold offers a floor-supported truss system that can carry the track for single or paired panel walls.

The structural engineer of record needs to know what the wall weighs, where it hangs and where it stacks. LG2 needs to know what structure it will hang from. A useful early exchange includes:

• Opening width and height, and the product family and series under consideration.
• Track route and stack location, including any pocket or remote stack.
• The structural framing above the wall line, and expected deflection of the supporting members.
• Ceiling, plenum and header details at the track, including any plenum barrier.

Beam deflection should be reviewed with LG2 and your structural engineer early in design, so the support structure and wall are coordinated before the structure is in place.

Support is easy to add while steel is still being sized and hard to add once it is fabricated and hidden above a finished ceiling. Bringing the operable wall into structural coordination during design development, and confirming it again at shop drawings, keeps the wall, the structure and the ceiling aligned. If you are starting a spec, the operable wall checklist shows where this step fits.

In an existing building, panels that are hard to move, drag or no longer seal usually point to track, trolley, seal or adjustment issues, and an inspection is the first step to finding the cause. If you are seeing those symptoms, see service and repair.