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Header Sizing

What it's for

Sizing the header over a door or window opening. You give it the opening width and, for a bearing wall, the building width, the snow load and what the wall carries. It gives you the header size, the jack and king studs each side, a drawing of the opening and a material list. For a bearing wall the size is read from the North Carolina supplement to IRC Table R602.7(1), the No. 2 southern pine spans the green line names. An opening past the supplement's sizes is read from IRC Table R602.7(1) itself, and only an opening past both is flagged for an engineer.

Step by step

This example uses the numbers the screen opens with.

Header Sizing inputs: OPENING WIDTH 3' 0", LOAD BEARING on, BUILDING WIDTH 36' (20' and 28' beside it), GROUND SNOW 30 psf, WALL SUPPORTS Roof + ceiling, STUD SIZE 2x4 (2x6 beside it), HEADER TOP Under top plate (Cripples above beside it) and WIND / FRAMING ANCHOR ≤ 115 mph Exp B (Higher / anchored beside it), with WALL HEIGHT below the fold. The answer bar reads (2) 2x6, a green Within the NC southern pine No.2 supplement to IRC Table R602.7(1) — southern pine No.2 · 30 psf snow · 36' building · roof + ceiling, and 1 jack · 1 king per side. 1 2 3 4 5 7 6 8 9 10
The form and the answer.
  1. OPENING WIDTH — the rough opening, framing to framing, not the door or window unit. The example is 3' 0".
  2. LOAD BEARING — on if the wall carries floor, ceiling or roof. Off for a partition that carries only itself. Turning it off hides the next three rows.
  3. BUILDING WIDTH — the width of the building. Pick from the three the table lists. If yours falls between two, pick the wider one: a wider building gets a shorter span, so it errs safe.
  4. GROUND SNOW — the ground snow load for your area, in pounds per square foot, from your county's snow load map. The header table starts at 30 psf, so 20 psf reads the 30 psf column and the line says so. Over 70 psf is past the table: the check reads ENGINEER REQUIRED — GROUND SNOW OVER 70 PSF (IRC R301.2.3) and there is no material list. There is no species choice: the code's header table is printed for No. 2 Douglas fir-larch, hem-fir, southern pine and spruce-pine-fir alike.
  5. WALL SUPPORTS — what sits on this wall. Tap and pick: roof and ceiling only, or one or two floors as well. For a floor, choose center-bearing if the floor joists also rest on a wall or beam in the middle of the building, or clear-span if they cross it in one piece.
  6. STUD SIZE — the wall's studs. A 2x4 wall is 3-1/2" thick, so its header is two plies with a 1/2" plywood spacer between them; a three-ply header (4-1/2") would stand 1" proud of the wall, so a 2x4 wall never gets one. A 2x6 wall (5-1/2") takes three plies and two spacers.
  7. HEADER TOP — what sits on top of the header. Leave Under top plate when the header is tight under the top plate, with the joists or rafters bearing on that plate. That is what the span table assumes. Pick Cripples above when short cripple studs stand between the header and the plate. The header's top is then not braced, and IRC Table R602.7(1) note f cuts the spans of 2x8, 2x10 and 2x12 headers to 70%, so a wider opening may need a deeper header or an engineer. The drawing shows the header the way you pick it.
  8. WIND / FRAMING ANCHOR — sets the king studs, the full-height studs beside the jacks, from the IRC table that counts them by header span and wind. Leave ≤ 115 mph Exp B where the design wind speed is 115 mph or less, the site is Exposure B (built-up suburbs, woods) and jack studs carry the header. Pick Higher / anchored for more wind, an Exposure C site (open country, scattered trees and buildings), or a header hung on metal framing anchors instead of jacks. From 140 mph in Exposure B, 130 mph in Exposure C, or on any Exposure D site (open water, flats) the table gives no count, and the kings have to be designed. Your building department gives the wind speed and exposure. It does not change the header size.
  9. WALL HEIGHT — the framed wall, floor to the top of the top plates. It sets the king stud length (the height less three 1-1/2" plates) and the jack stock on the cut list. It does not change the header size.
  10. Read the answer: (2) 2x6, 1 jack · 1 king per side.

Reading the results

Header Sizing lower screen. The answer bar keeps (2) 2x6 and the green line, cut off at supplement…. The end of the inputs (WIND / FRAMING ANCHOR ≤ 115 mph Exp B and WALL HEIGHT 8' 0") sits above RESULTS, which reads 1 jack · 1 king per side and the green Within the NC southern pine No.2 supplement to IRC Table R602.7(1) — southern pine No.2 · 30 psf snow · 36' building · roof + ceiling, then the BASIS & WHAT WAS ASSUMED row and the link Check before you cut · Measure twice. The HEADER drawing shows a 3' 0" opening under a (2) 2x6 header with KING STUD and JACK STUD labelled, and under it 1 JACK · 1 KING PER SIDE and SOUTHERN PINE NO.2 · 30 PSF SNOW · 36' BUILDING, over the title strip HEADER, OPENING 3' 0", NOT TO SCALE. 3 4 6
The check, the basis row and the drawing.
The foot of the HEADER drawing (OPENING 3' 0", NOT TO SCALE) over MATERIALS: Header (2) 2x6 — cut @ 3' 3" · buy 1 × 8', 2 pcs; 1/2" plywood header spacer — 5-1/2" × 3' 3" — between the plies to fill the 2x4 wall (IRC Table R602.3(1) item 10), 1 pcs; Jack studs — 7' 7-1/2" cut stock — cut @ header underside, 2 pcs; King studs — 7' 7-1/2" cut, 2 pcs; 16d common nails (3-1/2" × 0.162") — built-up headers: 16" o.c. each edge, face nailed, 8 pcs. Then a dimmed CUT SHEET with a list icon, a lit SAVE, and dimmed CUT LIST and SEND LIST. 7
The material list and the export buttons.
  1. The headline is the header: the number of plies in brackets, then the lumber size.
  2. The line under it is the jack studs and king studs on each side of the opening.
  3. The check. On a bearing wall a green line names the table the size came from, and what it was read for: the species, your snow load and building width, and what the wall carries. For example, Within the NC southern pine No.2 supplement to IRC Table R602.7(1) — southern pine No.2 · 30 psf snow · 36' building · roof + ceiling. When cripples above cut the size's span it adds span × 0.70 for cripples above (note f) after the table's name. An opening past the supplement's sizes reads Within IRC 2021 Table R602.7(1), past the NC supplement's sizes: the code's own table, printed for No. 2 Douglas fir-larch, hem-fir, southern pine and spruce-pine-fir, read between its 12', 24' and 36' building widths as its note c allows. The drawing and the cut sheet name the same basis. On a partition it reads Non-bearing — sized conservatively in-app; a non-bearing wall needs no load-bearing header at any width (IRC R602.7.4), so a partition is never sent to an engineer. ENGINEER REQUIRED — PAST THE NC SUPPLEMENT AND IRC TABLE R602.7(1); SIZE IT IN BEAM SIZING WITH THE GROUND SNOW SET, OR HAVE IT ENGINEERED means no lumber header in either table covers that opening under that load in your wall. The headline changes to say an engineered header is needed, and there is no material list. The jack count beside it is read from bearing alone, under a header as wide as the wall, and BASIS says the engineer sets the final count. Narrow OPENING WIDTH, pick a 2x6 wall, or have the header engineered. Beam Sizing takes the ground snow too: set it there (Roof) to size the member as a beam, or have the header engineered.
  4. BASIS & WHAT WAS ASSUMED — tap it. On a bearing wall it states the conditions the size was read under: exterior bearing wall, the building width, snow load and loading you picked, the species the spans are based on, and how the jack studs were counted. It says interior girders use a different table. The next line says what braces the header's top, and what note f does when cripples sit above it. On a partition it lists the app's own size steps and what the code permits instead. A partition's header is still plied to fill the wall, two plies in a 2x4 wall, so it is the same member Framing and Rough Opening order for that opening (for example (2) 2x6 at 48"). Both then name the column of IRC Table R602.7.5 the king studs were read from — the wind choice you made — and end with the code edition and a reminder to check your local amendments.
  5. BASIS also says what is not checked: the loads are gravity only (the wind column on Table R602.7.5 is the one wind input), so where IRC R301.2.1.1 requires wind design, or in Seismic Design Category D0 to E (R301.2.2; townhouses from C), the added rules are not applied.
  6. The drawing shows the opening with its header, jacks and kings. Pinch to zoom, drag to pan, double-tap to reset. The expand button opens it full screen. See Reading the drawing.
  7. MATERIALS — the header plies, each cut to the opening plus 1-1/2" of bearing for every jack at each end, with the stock to buy them on (for example Header (2) 2x6 — cut @ 3' 3" · buy 1 × 8', 2 pcs); the 1/2" plywood spacer the wall needs; the 16d nails IRC Table R602.3(1) item 10 asks for a built-up header (16" apart along each edge); and the jack and king studs for both sides.
  8. CUT SHEET, the list icon at its right end, CUT LIST and SEND LIST stay dim until you change at least one input. SAVE stays lit, but while every input is still a default a tap only answers Enter your job's numbers first and saves nothing. CUT SHEET makes a PDF, the list icon at its right end shares the material list only, SAVE keeps the result in History, CUT LIST puts the pieces on the Lock Screen with the header length and the stud stock length, and SEND LIST sends a checkable list to another phone.
Header Sizing, and the cut sheet, cut list, send list and History buttons, are part of Pro, a one-time purchase. See Free and Pro.

Common mistakes