Construction

Interior Stud Limiting Height Calculator

Pick the right depth + mil-thickness steel stud for any interior partition deck height. Based on ClarkDietrich EQ Stud and Structural C-Stud published limiting heights (5 psf lateral load, L/240 deflection, single-layer 5/8" gypsum each side). 20 ga drywall (30 mil), 20 ga structural (33 mil), 18 ga (43 mil), 16 ga (54 mil), 14 ga (68 mil), 12 ga (97 mil). Verify final selection against the current ClarkDietrich tables and your AHJ.

Deck-to-deck height (ft) * Top of slab to underside of deck above. Use slip-track at top if movement is required. Stud size (depth) * Common interior depths. 3-5/8" is the standard partition stud; 6" used for tall walls + plumbing chases. Flange width * Wider flange = stiffer section + more screw bite. 1-5/8" boosts limit ~12%, 2" boosts ~22% over standard. Stud spacing * Deflection criterion * Lateral load * Sheathing / composite Composite values per ClarkDietrich ASTM C754 testing. Preferred stud series

Recommended stud

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Limit at this height: —
Mil thickness: —
Equivalent gauge: —
Headroom: —

All studs that work

Sorted lightest first. Pick the cheapest that hits required limit.

Stud	Mil	Gauge	Limit @ spacing	Headroom

Important verification step

Limiting heights here are derived from ClarkDietrich published technical data (ProSTUD, EQ Stud, structural C-Stud series). Always verify your final selection on the ClarkDietrich iTools Interior Wall lookup or the current product literature, and obtain engineering review for critical conditions. Different deflection criteria, lateral loads, or unbraced spans may apply.

How limiting height tables work

A limiting height is the maximum vertical span at which a given stud satisfies both:

Strength: bending stress at the specified lateral load (5 psf interior, 7.5 psf corridor, 10 psf stairwell).
Deflection: mid-span deflection under load stays within L/120, L/240, or L/360 depending on the finish.

The governing criterion is whichever fails first. For tall interior partitions in commercial spaces, deflection almost always governs — that is why heavier studs are picked even when bending stress is fine.

ClarkDietrich product series

EQ Stud (30 mil) — ClarkDietrich's drywall-framing stud equivalent to traditional 20 gauge with thinner equivalent steel. Cost-effective for moderate-height interior partitions.

Structural C-Stud (CSJ, CSW) — Heavy structural framing in 33 mil (20 ga structural), 43 mil (18 ga), 54 mil (16 ga), 68 mil (14 ga), and 97 mil (12 ga). Required for tall partitions in seismic zones, corridor walls, stairwells, and curtain wall backup.

Gauge to mil cheat sheet

Gauge	Mil	Inches	Typical use
20 ga drywall	30 mil	0.0312"	Tall interior partitions (EQ Stud)
20 ga structural	33 mil	0.0329"	Light structural, exterior wind
18 ga	43 mil	0.0428"	Tall walls, corridors
16 ga	54 mil	0.0538"	Heavy interior or exterior
14 ga	68 mil	0.0677"	Curtain wall backup
12 ga	97 mil	0.0966"	Heavy structural

FAQ

Why is composite different from non-composite? +

When gypsum board is screwed to both flanges of a stud (composite assembly per ASTM C754), the gyp acts as a stiffener and significantly increases limiting heights — often 20-50%. Non-composite numbers assume a bare stud with no sheathing contribution.

Why does the same stud have three different heights? +

Deflection criterion. The same 3-5/8" 25 mil stud might allow 14 ft at L/120 but only 11 ft at L/360. Pick the tighter criterion when finish is brittle (plaster, tile) or rigid (curtain wall backup).

What lateral load should I use? +

5 psf is IBC default for interior partitions. 7.5 psf applies to corridor walls in commercial occupancies. 10 psf is required at stairwells, areas of refuge, and emergency egress paths. Verify with your code official.

Why does flange width matter so much? +

Flange width controls how much the gypsum can grip the stud (composite stiffness) AND the bending stiffness about the strong axis. A 1-5/8" flange runs ~12% taller than a 1-1/4" flange of the same gauge; a 2" wide-flange (DWS / Spazzer-type) runs ~22% taller. On a 20 ft partition, that is the difference between using 18 ga vs 16 ga steel.

Can I use 30 mil EQ Stud on a 16 ft wall? +

Often yes — 3-5/8" x 30 mil EQ Stud with 1-1/4" flange and composite assembly typically allows ~16 ft at 16" O.C. and L/240. Going to 1-5/8" flange gets you to ~18 ft. Bumping to 33 mil structural at 1-5/8" flange gets you to ~19 ft with margin. Verify with the current table for your specific deflection and load.

What about 6" and 8" studs? +

This calculator focuses on 3-5/8" and 6" studs (the two most common interior depths). Larger 6"-8" structural studs can span 20+ ft. Consult ClarkDietrich structural tables directly.

Slip-track at top of wall? +

Required at non-load-bearing partitions when the deck above can deflect, settle, or rack. Slip-track allows 1-2" vertical movement without transferring load. Reduces effective height slightly — designers typically use full deck-to-deck.