Metal Stud Gauges and Wall Heights, Explained

The short answer

Most interior, non-load-bearing partitions are framed with 25 gauge studs. Taller walls, walls that carry heavy items and door openings usually need 20 gauge or heavier. The right stud comes from the manufacturer's limiting-height tables: stud depth, gauge and spacing against the wall height, the pressure it has to resist and the deflection limit the finish needs.

Gauge and mils

Gauge is the trade name. Mils, the steel thickness in thousandths of an inch, is what specs and manufacturer tables actually use. Lower gauge means thicker steel:

• 25 gauge, about 18 mil: standard interior partitions and furring.
• 20 gauge, 30 mil (non-structural) or 33 mil (structural): taller partitions, door jambs, walls carrying cabinets, TVs or casework, and walls behind tile.
• 18 gauge, 43 mil and 16 gauge, 54 mil: heavy-duty and structural framing, headers and load-bearing or exterior curtain walls designed by an engineer.

Common stud depths are 1-5/8, 2-1/2, 3-5/8, 4 and 6 inches, usually at 16 or 24 inches on center. A deeper stud gains more height than a heavier one of the same depth, which is often the cheaper way to get a tall wall.

EQ studs

EQ, or equivalent, studs use thinner, higher-strength steel, often with a ribbed or dimpled profile, shaped to perform like a heavier gauge: a 20EQ in place of a standard 20 gauge, for example. They are lighter and cost less. They can only stand in where the manufacturer's tables support the height and, in a fire-rated wall, where the tested assembly listing allows that stud. Both should be checked before a swap.

Limiting height and deflection

Every partition has to resist some sideways pressure without flexing so much that the finish cracks. The limiting height is the tallest the wall can go with a given stud before it flexes past the allowed limit. Deflection limits are written as a fraction of the wall height:

• L/120: the building code minimum for interior walls with flexible finishes such as drywall.
• L/240: what many commercial specs call for behind drywall, and a common limit for brittle finishes.
• L/360: a stiffer wall for plaster, and often called for behind tile or stone.

The same stud at the same spacing gets a shorter limiting height as the deflection limit gets stricter. That is why a wall that works at L/120 may need a deeper or heavier stud once tile goes on it.

Where heavier studs and extra framing belong

• Door and window openings: heavier jamb studs, often doubled, so doors do not rack the wall.
• Anything hung on the wall: cabinets, TVs, grab bars, handrails and casework need backing or blocking inside the wall at the right height.
• Tall walls and atriums: deeper studs, closer spacing or bracing, checked against the tables.
• The top of the wall: a slip or deflection track at the deck lets the floor above move without crushing the wall, and in rated walls the head joint is firestopped.
• Shaft walls at stairs and elevators use their own stud and liner system, built to the tested assembly.

How we handle it on a bid

We frame to the drawings and the specified assembly, with the stud gauge and spacing the plans call for. Questions about backing, jambs or wall heights are cheapest to settle before layout, not after the board is up. Load-bearing and exterior framing is sized by the project engineer. See our metal stud framing work in San Antonio, our tenant finish-outs and our commercial drywall page.