Lesson 3 of 6 · Chapter 3
Wall Framing 101
A wall is plates, studs and the openings cut through it. This lesson names every member, then does the arithmetic a framer does at every door and window: the rough opening, the jack studs, the header and the cripples above it.
Step one
Read the material
Six ideas: plates and studs, the parts of an opening, rough opening sizes, cutting the jack studs, sizing and building the header, and squaring and flashing the opening.
Idea one
The frame of every wall
A wall frame is held between two horizontal members. The sole plate (bottom plate) sits on the subfloor and ties the wall to the floor system. Where it sits on concrete, it is pressure-treated, like the sill.
The top plate caps the studs and ties them together. Most walls get a double top plate, which stiffens the wall and gives ceiling joists or rafters a place to bear.
Between them stand the studs, 2x4 or 2x6, spaced 16 or 24 inches on center. They carry the load from the roof and floors above down to the sole plate.
Studs stand vertical, so there is no crown "up". As in lesson one, sight each stud and set every crown facing the same way, so the wall face stays straight for drywall and trim. Leave room in the cavities for insulation to fit without gaps.
Idea two
Header, jacks, kings and cripples
A rough opening is the framed hole for a door or window. It is built from four kinds of member.
The header is the horizontal beam across the top. It carries the load from above around the opening.
The jack studs (also called trimmers) are the shorter studs the header sits on. The jacks carry the header’s load down to the sole plate. The king studs run the full height of the wall beside the jacks and hold the whole assembly in line.
Short cripple studs fill the space above the header up to the top plate (and below a window’s rough sill), keeping the stud layout going.
Idea three
How big to make the hole
The rough opening is slightly larger than the door or window, to leave room for shims and adjustment during installation.
For a standard door, add about 2 to 2-1/2 inches to the door’s width. A 36-inch door gets a rough opening of about 38 to 38-1/2 inches wide.
For windows, use the rough opening listed by the window’s maker. It is usually about 1/2 to 1 inch larger than the unit each way, and it leaves room for the shims and flashing.
The rough opening height is measured from the subfloor up to the underside of the header.
Idea four
The header sits on the jacks
The header rests on top of the jack studs, so the top of the jacks is the top of the opening. Nothing about the header’s height is subtracted from the jacks.
Measured from the subfloor, the jacks stand on the sole plate, so: jack length = rough opening height − the sole plate (1-1/2 inches). An 80-inch rough opening gets jacks of 78-1/2 inches.
The book gives 80 minus a 4-inch header = 76 inches. Cut that way, the header lands 4 inches low and the opening comes out 76 inches tall instead of 80: a door won’t go in. The header’s height matters for the cripples above it, not the jacks below it.
Set the jacks plumb and fastened to the kings and the sole plate, and check that the header sits level on them.
Idea five
Span tables, then two boards and a spacer
A header’s size depends on the width of the opening and the load above it: roof, upper floors, and live loads such as snow. Local code and the span tables in code books and framing manuals give the size. Solid lumber, engineered wood and LVL are all used; LVL carries more in a smaller size.
A common starting point in standard framing: a double 2x6 header for openings up to about 4 feet, stepping up to double 2x8 or an engineered beam for wider openings or heavier loads. Always confirm with the table.
The usual build: two boards on edge with a 1/2-inch plywood or OSB spacer between them. Two 1-1/2-inch boards plus 1/2 inch makes 3-1/2 inches, flush with a 2x4 wall.
The header spans the opening and bears on a jack at each end: header length = rough opening width + 3 inches (1-1/2 inches on each jack).
Idea six
Equal diagonals, then shed the water
Check every opening for square: measure both diagonals corner to corner. Equal means square. If they differ, push or pull the corners until they match.
Water must never get behind the flashing. Lap it like shingles: the bottom (sill) first, then the sides overlapping it, then the head flashing over the top, so every upper layer overlaps the one below and water runs outward.
Self-adhesive flashing tape seals the edges of the opening. House wrap or felt laps over the sheathing around it to keep the wall envelope continuous.
Then install the unit to the manufacturer’s instructions, shim it, and check that it opens and closes without binding.
The whole of chapter 3 is free to read or hear on the Residential Framing reader page.
Step two
Work it with your hands on it
The Rough Opening Bench. Pick a door width, the rough opening height measured from the subfloor, and a header size, in a standard wall of 92-5/8-inch precut studs on a single sole plate and a double top plate. The bench frames the opening and gives every cut. It also shows what happens if the jacks are cut the book’s way.
Door width
Rough opening height:
Header
Cut the jacks
Hands on it, off the screen. In a garage or unfinished room, find a framed door or window. Count the studs at each side: the one under the header is the jack, the full-height one beside it is the king.
Measure from the floor to the underside of the header, and the length of the jack. The difference is the plate the jack stands on, not the header.
Step three
Prove you understood it
One question per idea, a new situation every time. Miss one and you are sent back to the idea it was testing.
All six solid.
You can name every member of a wall, size a rough opening, cut the jacks and header correctly, choose a header from a span table, and square and flash the opening. Next: wall layout and assembly.
Residential Framing
Lesson three of six, from chapter three. Written by our founder, Dr. Gene A Constant, and donated to the Foundation. Published by Global Sovereign University Press.
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