The Average Width of Interior Walls

Standard Finished Width

• From one side of a standard finished interior wall to the other side is 4.5 inches. This allows for stud wall construction and the installation of 1/2-inch drywall on both sides of the studs. A standard stud, or a 2-by-4, isn’t quite as big as its name suggests. In reality, the board is 1.5 inches by 3.5 inches.

Drywall Variations

• Sometimes, local code requires thicker drywall panels, which will affect the finished width of wall. If you install 5/8-inch drywall panels on both sides, the width of your wall increases another 1/4 inch. On the flip side, using thinner, 1/4-inch panels will result in an interior wall that is only 4 inches wide.

Tall Walls

• To accommodate the increased stress load of taller walls, which are typically found in vaulted entryways and rooms that are open to an upper-story floor, the architect or engineer may specify larger dimensional lumber. Like standard studs, these boards are 1/2 inch smaller in each direction than indicated by their name. A tall interior wall, framed with 2-by-6 boards, will result in a wall that is 6.5 inches thick, when finished with 1/2-inch drywall panels.

Other Wall Widths

• Standard interior walls can accommodate wiring, but if an interior wall will accommodate a drainpipe, it must be wide enough to conceal the pipe in the stud space. A wall framed from 2-by-6 dimensional lumber that conceals a 4-inch drainpipe will be 6.5 inches wide. Party walls separate two distinct family living areas, such as the walls between individual apartments or duplexes. Local code will determine the width of these walls, but they are typically wider than an average 4.5-inch wall, and they may be nearly double the width of a standard interior wall, depending on code.