The deck will move. Live load, concrete creep, camber coming out, a roof that ponds — the head of an interior partition is where that movement shows up. Slotted and deep-leg deflection track exist so the stud wall can stay plumb while the structure above goes up and down. Hard-screwing the gypsum to that head track turns the board into a strut. The joint cracks, the finish photographs, and on a rated wall the fire joint is no longer the joint you submitted.
This page is the field and bid briefing for the commercial drywall sub who already owns metal-stud partitions. It restates public class language from ASTM C645 / C754 (nonstructural members and installation), manufacturer deflection-track notes, and ANSI/UL 2079 (tests for fire resistance of building joint systems) for head-of-wall (HW-D) listings. It is not an engineering stamp and not a reprint of a mill catalog. Movement amount, track type, and the fire-joint design come from the project documents. Mills: ClarkDietrich, MarinoWARE, and peers. Directory: Steel stud / framing.
What the head is trying to do
Interior nonstructural studs are not supposed to take axial load from the floor or roof above. The gap under the head track is the movement the structural engineer (or the spec’s default) said to expect. The track holds the studs in plane laterally; the studs do not lock the deck.
Three common families — names vary by mill:
Slotted deflection track. Vertical slots in the legs. Studs are fastened through the slots — typically a wafer-head screw at mid-height of the slot on each flange — so the screw can slide as the deck moves. Overtightening pinches the slot and kills the slide. Manufacturer notes are consistent: there shall be no attachment through the slotted track that impairs movement.
Deep-leg (single) deflection track. Long legs, studs cut short of the web, not fastened to the head. Bridging near the top keeps studs aligned. This one can allow some lateral as well as vertical movement; slotted track as a class is the vertical-slide detail.
Double (nested) track. An inner runner rides in an outer; the wall hangs from the inner, the outer stays with the structure. Less common on everyday TI, still in the catalogs.
Proprietary gasketed / intumescent tracks combine the slide with a listed fire joint. Those are UL 2079 systems, not a generic C754 runner with extra caulk.
Exterior curtain-wall bypass and structural CFS heads are a different package. Do not copy a TI slotted track onto a wind-bearing backup. Exterior CFS vs interior light-gauge, Exterior cold-formed framing.
Why hard-screwing the head kills the joint
Gypsum panel products are a relatively rigid membrane. ASTM C840 / GA-216 interior application assumes the board is fastened to the framing that is supposed to hold it — the studs — not to a member that must move relative to those studs.
If the hanger runs a row of screws through the face layer into the deflection-track leg:
- The board is now locked to the deck and to the studs.
- Next live-load cycle, the deck bears on the wall. Studs that were supposed to slide are loaded axially they were not designed for.
- The finish at the head — tape, bead, or firestop — shears or compresses. That is the crack that shows in critical light six months after punch.
- On a rated partition, the head-of-wall joint (the gap packed or sprayed per the HW-D design) was sized for a free gap. Fasteners through the track into the board change the geometry. UL 2079 listings are specific about no board attachment screws penetrating the slotted ceiling track and about where the top row of gypsum screws may land — commonly into the studs, below the bottom of the track flange, at the distance that listing names. Do not invent that distance from another job. Read the design.
The trailer version: the top of the board is not a fastener line into the head track. Leave the specified gap at the top of the gypsum. Fasten to studs. Firestop / sealant / mineral wool / gasket fills the gap per the listing — not leftover mud.
Deep-leg details that use a rip or shadow board attached to a shoulder on the track are the exception the mill tested: that strip rides with the structure and slides over the wall board. That is a listed head, not a license to screw the field board into the track.
Layout the crew can actually run
- Head track type and gap from the drawings / submittal, not from the leftover solid track on the cart. Cut studs to the published gap under that track.
- Slotted: wafer-head screws at mid-slot, both flanges, snug enough to hold, loose enough to slide. Type S vs Type W — this is steel-to-steel, not a bugle drywall screw into the flange from the face.
- Hang gypsum per how to hang drywall. Leave the floor gap and the head gap. Stock length (48 vs 54) does not change the head rule; a 10-ft board on a 10-ft stud still gets cut down for the deflection gap.
- Top row of board screws: into the studs, below the track, where the wall design and the HW-D design say. Not into the slot. Not “one in the track to pull the sheet tight.”
- Rated heads: mineral wool, spray, sealant, or the proprietary track gasket — and the joint width the listing allows. Firestop may be a separate trade. Put ownership in the bid. A Level 1 fire tape on the face is not the head-of-wall joint.
- Control joints in the gypsum face are still required on long planes. Deflection track is not a substitute for a GA-216 control joint. Drywall control joints.
Shaftwall J-runners and liner panels are their own head details. Do not treat a shaft as a 3-5/8 drywall partition with a slotted track you had on the truck.
Commercial vs residential
Commercial interiors. This is everyday W&C work under steel or concrete decks. Bid slotted or deep-leg where the spec shows movement; bid the fire joint as its own line if it is yours. Finish-sensitive corridors still want the wall in plane — L/240 vs L/360 is a stud problem, but a crushed head is a hang problem.
Residential production. Wood plates nailed to a truss are not slotted track. Mixed-use, townhomes, and light commercial that land on a residential bid list do pick up CFS partitions under decks. Do not toekick a stud to a slotted head the way you toekick a 2×4 to a plate. The first time a superintendent hard-screws the head “so the board doesn’t rattle,” you own the crack.
Bid notes
Name the track. “Deflection track” is not a SKU: slotted vs deep-leg vs proprietary fire track vs solid. Solid head on a moving deck is a callback.
Qualify the joint: UL 2079 design number, movement (compression / extension), fluted-deck fill, and who packs it. Castle cuts in flutes are labor; some listed tracks change that detail — only if that track is what you submitted.
Do not let a GC call a hard-screwed head “means and methods.” It is a listed-joint and finish-warranty problem.
Related directory
Steel stud / framing — slotted track lives here. Exterior bypass: Exterior cold-formed framing. Screws: Fasteners, Grabber. Head beads and gap trims: Finishing. Product door: Products.
FAQ
Can I screw the gypsum into the slotted track to pull the sheet up?
No. That locks the membrane to the moving member. Fasten to studs; leave the specified head gap.
Slotted or deep-leg?
Whatever the documents and the movement require. Slotted is the common TI slide. Deep-leg and double-track are other families. Proprietary fire tracks are listed systems, not generic runners.
Does deflection track replace a gypsum control joint?
No. Track lets the structure move at the head. Control joints break long gypsum planes. Both can exist on the same wall.
Who owns the firestop at the head?
Sometimes W&C, sometimes a firestop sub. The hang still has to leave the gap the listing needs. Write it down.
Is interior slotted track the same as an exterior bypass clip?
No. Partition deflection under a deck is not curtain-wall wind bypass. Different members, different directory.