Rough Opening Size, the Stud Pack, and the Header for Windows and Doors

The rough opening for the window and the door you actually bought, the king, jack, cripple and sill count that frames it, the header the opening width asks for, and the board feet and flashing the package needs.

A rough opening is the unit size plus the shimming gap: 1.5 in added to the width and 1.5 in added to the height on a window, 2 in added to the width and 2 in added to the height on a prehung exterior door, and the unit is set into that gap on shims and fastened to the framing. Framing height here assumes an 8 ft wall, which is 99 in from bottom plate to the top of the second top plate.

—Rough opening for the unit you bought
—King, jack, cripple and sill stud pack
—Header pick on the R502.6 doubled lines
—Board feet, flashing, and lumber cost
—Framing order for the opening
—Egress, bearing, and shear-wall checks
How the math works
  • The rough opening: window unit width plus 1.5 in and unit height plus 1.5 in, on a 3/4 in shim gap at each side and at the head. An exterior prehung door takes unit width plus 2 in and unit height plus 2 in, which is 3 ft 2 in by 6 ft 10 in for the 3 ft by 6 ft 8 in door the code line asks for.
  • The stud pack: 2 full-height king studs outside each trimmer, jack studs under the header cut to the header depth, cripple studs above the header at 24 in on center with a head jack at each end, and cripple studs under the sill on a rough sill plate. The 3 ft by 4 ft window in an 8 ft wall is 2 kings, 2 jacks per side, 2 header plies, 3 cripples above, and 3 under the sill on a doubled 2x6 header.
  • The header: the doubled solid-sawn lines on IRC R502.6 are 3 ft on a doubled 2x4, 6 ft on a doubled 2x6, 8 ft on a doubled 2x8, 10 ft on a doubled 2x10, and 12 ft on a doubled 2x12, each with not less than 3.5 in of bearing at each end. The header is cut the rough opening width plus 7 in for the bearing at both ends.
  • The jack line: about 4 in of doubled header depth per jack stud, so 1 jack on a doubled 2x4 at 7.25 in deep, 2 on a doubled 2x6 at 11.25 in, 3 on a doubled 2x8 at 15.25 in, 4 on a doubled 2x10 at 19.25 in, and 5 on a doubled 2x12 at 23.25 in.
  • Flashing and code: a 9 in wide sill pan with 2 in end dams taped at the flange, a head flap, the WRB lapped shingle-style over the pan, a 5.7 sq ft net clear egress opening with 24 in by 24 in minimum and a 44 in sill maximum (IRC R310), a 32 in clear egress door (IRC R311.2), and a shear wall header spliced and nailed per IRC R602.10.6.1.
Framing and rough-opening planning tool on the IRC R502.6 header lines, R310 escape openings, R311.2 egress doors, and R602.10.6.1 shear wall headers as adopted by the authority having jurisdiction, with standard framing practice on an 8 ft wall. Header size on a load-bearing wall, the load above the opening, the wall width, the snow and wind loads, a floor and roof on the same header, an opening over 12 ft, a slider, a bifold wall, a pocket door, a structural change to a wall, a shear wall line with a strap, and an engineered header are all permit, drawing, and stamped-calculator questions. Manufacturer rough opening tables vary by jamb, flange, sill, and cladding: a brick veneer, a stucco, a 4 in wall with a jamb extension, a masonry buck, a rain-screen rainscreen, a steel window in a buck, a door in a 2x8 wall, and a window in a 2x6 wall on a 1.5 in reveal are all rough openings with the manufacturer number on the drawing. A licensed framer, the truss shop, and the local inspector set the final header, the strap, and the bearing.

How big is a rough opening for a window?

The unit width plus 1.5 in and the unit height plus 1.5 in: a 3 ft by 4 ft window frames at 3 ft 1.5 in by 4 ft 1.5 in, which leaves a 3/4 in shim gap at each side and at the head for shims, a level sill, and flashing. Measure the unit with the jamb in the box, not the glass.

What is the rough opening for a 3 ft by 6 ft 8 in door?

3 ft 2 in wide by 6 ft 10 in high: the 3 ft by 6 ft 8 in slab door plus 2 in of shimming room on the width and 2 in on the height. The 32 in clear egress line (IRC R311.2) is met by the 3 ft door and is not met by a 2 ft 8 in door.

What header do I need for a 6 ft window?

A doubled 2x6 spans 6 ft on the IRC R502.6 doubled line with 3.5 in of bearing at each end, which is the same header a 6 ft opening takes on a 2x6 wall: 11.25 in deep, 2 in wide, on 2 jack studs per side. A 6 ft opening in a load-bearing wall with a floor and a roof on it, a 24 ft wall above it, and a snow load is smaller than the table line and gets an LVL or a steel plate on the span table.

How many jack studs under a doubled 2x6 header?

Two per side. The rule is about 4 in of doubled header depth per jack stud: 1 jack on a doubled 2x4 (7.25 in deep), 2 on a doubled 2x6 (11.25 in), 3 on a doubled 2x8 (15.25 in), 4 on a doubled 2x10 (19.25 in), and 5 on a doubled 2x12 (23.25 in), with 3.5 in minimum bearing on the package (IRC R502.6).

How much lumber does a window opening take?

About 45 to 55 board feet for a 3 ft by 4 ft window in a 2x6 wall in an 8 ft wall: 2 king studs at 99 in, 4 jack studs at 11.25 in, 2 header plies at 3 ft 8.5 in, 3 cripples above, 3 under the sill, and a rough sill and cap. Four of them plus an exterior door is about 225 board feet, about $270 at $1.20 per board foot, before the flashing pans, the nails, and an LVL.

Related tools

Header span tableThe R502.6 spans by wall width Framing lumber takeoffStuds, plates, and sheathing for the wall Wall stud layoutCorners, headers, and board feet Egress window checkThe 5.7 sq ft opening the RO has to clear Joist span tableWhat the header is carrying