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Rough Opening

What it's for

You have the size of a window unit or a door slab and need the framed hole it goes in. Rough Opening gives you the R.O. width and height, the header, the king and jack studs on each side, and a list of what to buy. The header and jacks for a bearing wall are read for one case only: roof and ceiling, a 36' building and 30 psf ground snow, from the North Carolina supplement to IRC Table R602.7(1). Treat it as a framing takeoff, not a structural check. For more snow, a floor above or a narrower building, size the header in Header Sizing.

Step by step

The example is the screen as it opens: a 3' 0" × 4' 0" window in a bearing wall 8' 0" high.

Rough Opening inputs. The answer bar reads 3' 0-1/2" × 4' 0-1/2" R.O. (wrapping to a second line) over an amber line Header sized for roof + ceiling only, a 36' building, 30 psf snow — a floor above or more snow? Size it in Header Sizing, then Header (2) 2x6 · per side: 1 king / 1 jack. Below it: OPENING TYPE Window (Interior Door and Exterior Door beside it), UNIT WIDTH 3' 0", UNIT HEIGHT 4' 0", LOAD BEARING on, STUD SIZE 2x4 (2x6), HEADER TOP Under top plate (Cripples above), WIND / FRAMING ANCHOR ≤ 115 mph Exp B (Higher / anchored) and WALL HEIGHT 8' 0". 1 2 3 4 5 6 7
Steps 1–7 happen here. The answer, with the amber line that says what the header was sized for, is in the answer bar above them; WASTE FACTOR (8) is in the next shot.
  1. OPENING TYPE — pick Window, Interior Door or Exterior Door. The type decides how much is added to the unit size.
  2. UNIT WIDTH and UNIT HEIGHT — for a window, the size of the unit itself, not the hole: measure the frame outside to outside, or take it from the order sheet. The example is 3' 0" wide and 4' 0" high. For a door the fields read SLAB WIDTH and SLAB HEIGHT: enter the door slab, such as 3' 0" × 6' 8". The door rule is a slab rule; a prehung unit's frame size typed there frames the hole about 1-1/2" too wide and 2" too tall. A prehung unit's R.O. is printed on its install sheet.
  3. LOAD BEARING — on if the wall carries floor, ceiling or roof above it. Off for a partition that carries only itself. It opens on.
  4. STUD SIZE — the wall's studs, 2x4 or 2x6. A 2x4 wall takes a 2-ply header with a 1/2" plywood spacer, so it comes out flush with the wall; a 2x6 wall takes 3 plies. It opens on 2x4.
  5. 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: IRC Table R602.7(1) note f then cuts the spans of 2x8, 2x10 and 2x12 headers to 70%, so a wide bearing opening can come out Engineer required. The drawing shows the header the way you pick it.
  6. 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.
  7. WALL HEIGHT — the framed wall, underside of the bottom plate to the top of the double top plate. It sets the stud length the kings and jacks are bought at. A standard height lists a precut stud; any other height lists the exact cut length. The example is 8' 0".
  8. WASTE FACTOR — the extra you buy over the count, in steps of 5%. The example is 10%.
  9. Read the answer bar under the title: 3' 0-1/2" × 4' 0-1/2" R.O., the amber line that says what the header was sized for, then Header (2) 2x6 · per side: 1 king / 1 jack. The R.O. wraps to a second line on a phone, which pushes the amber line and the header line down.
  10. Scroll down. The RESULTS card repeats the header and studs line, and the answer bar stays under the title, R.O. size and all, while you scroll.
  11. Check the drawing against the opening you are about to frame.
  12. Read the MATERIALS list for what to buy.

The small ⓘ beside a label gives one sentence on what that input means.

Reading the results

Rough Opening scrolled down. The answer bar under the title keeps 3' 0-1/2" × 4' 0-1/2" R.O. and the start of the amber line Header sized for roof + ceiling only, a 36'…. Above RESULTS are WALL HEIGHT 8' 0" and WASTE FACTOR 10% with a stepper. RESULTS reads Header (2) 2x6 · per side: 1 king / 1 jack, then the amber line Header sized for roof + ceiling only, a 36' building, 30 psf snow — a floor above or more snow? Size it in Header Sizing, the BASIS & WHAT WAS ASSUMED row and the link Check before you cut · Measure twice. The framing elevation follows, labelled HDR (2) 2x6, KING, 2x4 WALL, 1/2" PLY, JACK and SILL, with 48-1/2" and 36-1/2" dimensioned, a 3-1/2" by 5-1/2" section detail and the note UNIT 36" × 48", and an expand button above it. 8 9 10 11
Steps 8–11: WASTE FACTOR, the answer bar with the R.O. size, the RESULTS card's header line and the amber line under it, and the drawing with its expand button.
The foot of the Rough Opening drawing, with SILL, JACK and 36-1/2" dimensioned, the 3-1/2" by 5-1/2" section detail and UNIT 36" × 48", over the title strip ROUGH OPENING, WINDOW, NOT TO SCALE. Then MATERIALS: Header (2) 2x6 — cut @ 3' 3-1/2" · buy 1 × 8', 2 pcs; 1/2" plywood header spacer — 5-1/2" × 3' 3-1/2" — between the plies to fill the 2x4 wall (IRC Table R602.3(1) item 10), 1 pcs; 16d common nails (3-1/2" × 0.162") — built-up headers: 16" o.c. each edge, face nailed, 8 pcs; King studs — 2 layout · 7' 7-1/2" cut, 3 pcs; Jack studs — 2 layout · 7' 7-1/2" cut stock — cut @ 7' 2", 3 pcs; Rough sill 2x4 (flat) — cut @ 3' 0-1/2" · buy 1 × 8', 1 pcs; Cripples under the sill — 2 at 16" o.c. as drawn · cut to fit from 7' 7-1/2" cut stock, 3 pcs. The CUT SHEET, SAVE, CUT LIST and SEND LIST buttons are below the shot. 12
Step 12: the material list.

The headline is the rough opening, width × height. A window gets 1/2" added to the unit each way. A door gets 2" on the width and 2-1/2" on the height. The word sample beside it means you have not entered anything yet, so the answer is not your job's.

The line under it is the header and the studs on each side of the opening. If it reads Engineer required the opening is wider than the table the header comes from. No lumber size is offered; get it sized.

The amber line (a bearing wall only) says what that header was read for: Header sized for roof + ceiling only, a 36' building, 30 psf snow — a floor above or more snow? Size it in Header Sizing. Nothing on this screen asks for those loads, so the line stays amber; the answer bar carries it too. A window under a floor needs a bigger header than the one shown: size it in Header Sizing. A non-bearing wall has no such line.

BASIS & WHAT WAS ASSUMED — tap it to open. For a bearing wall it states the case the header and jacks were read for (roof and ceiling, 36', 30 psf), names the table the spans come from, says what braces the header's top, and tells you to size the header in Header Sizing for more snow or a floor above. It names the column of IRC Table R602.7.5 the king studs were read from, by the R.O. width and your wind choice. It names the wall the header was packed for. For a window it notes the 1/2" allowance and says to verify the manufacturer's spec; for a door it gives the slab rule and points you to a prehung unit's install sheet. Read it before you order.

The drawing is the opening in elevation with the header, king, jack and sill named and the R.O. dimensioned, plus a boxed section through the header. With Under top plate the header sits tight under the top plates; with Cripples above the cripples are drawn and named. Pinch to zoom, drag to move around, double-tap to reset, or tap the expand button at its top right for the whole screen. See Reading the drawing.

MATERIALS is the order. The header is listed as its plies, each cut to length with the stock length to buy, then the 1/2" plywood spacer a 2x4 wall takes and the 16d nails that join the plies. They are counted pieces, so no waste is added to them. The stud rows show two numbers: the quantity on the right is what to buy with waste added, and layout is how many the opening actually uses. Jacks are bought at the same stud length and cut to the length shown: a door's jack is its R.O. height less the 1-1/2" bottom plate it stands on; a window's, with the header under the top plate, is the wall less the three plates and the header. A window also lists its rough sill (one flat 2x at the R.O. width) and the cripples under it, and a header with cripples above lists those too, at 16" on centre as the drawing shows them.

The buttons at the bottom wait for your own numbers. CUT SHEET, the list icon at its right end, CUT LIST and SEND LIST stay dimmed, and the line under them reads Enter your own measurements to export, start a cut list or send one. SAVE stays lit, but until then a tap only answers Enter your job's numbers first and saves nothing. After that CUT SHEET shares a PDF with the drawing, the list icon at its right end shares the material list alone, SAVE puts the result in History, CUT LIST starts the list on the Lock Screen and SEND LIST sends a checkable list to someone else's phone.

Rough Opening's results and materials are free. The drawing, the cut sheet, the cut list on the Lock Screen, sending a list and History are Pro, a one-time purchase — without Pro the drawing pane shows a Pro card instead. See Free and Pro.

Common mistakes