What Is a Header in Construction? Spans and Sizing

What is a header in construction?

A header in construction is the horizontal member across the top of a door, window or other opening in a wall. It carries the load the cut studs no longer carry. It then transfers that load through short jack studs into the plate below.

Why a header exists

Studs in a bearing wall are a line of little columns. Cut a 6 ft hole and four or five are gone, but the load does not go with them. The header bridges the gap and hands it to the jack studs each end. That load path is the answer to what is a header in construction.

Quoting the opening too? Estimate it from a photo.

The code section: IRC R602.7 and its span tables

First question: is the wall carrying anything

Section R602.7.4 is blunt. Load bearing headers are not required in interior or exterior nonbearing walls. The expensive error runs the other way, when a wall that reads as a partition carries a bearing point.

Three tables, three load paths

Table R602.7(1) covers exterior bearing walls, R602.7(2) interior bearing walls, R602.7(3) open porches.

Every span carries a load case, a width and a snow load

Table R602.7(1) is a grid. Down the left it splits by what the header holds up. The blocks run roof and ceiling only, then roof, ceiling and one center bearing floor, then a clear span floor, then two floors. Across the top it splits by building width, at 12, 24 and 36 ft. Width is measured perpendicular to the ridge. Then it splits again by ground snow load. A span quoted without all three is not a code figure.

One more footnote bites: those spans assume the top of the header is braced by perpendicular framing. Where cripple studs bear on it instead, multiply a 2×8, 2×10 or 2×12 span by 0.70.

Engineered lumber does not use these tables

LVL, glulam and PSL are sized off the manufacturer’s own tables. Those tables are brand specific. Weyerhaeuser’s current Trus Joist guide TJ-9000, the July 2026 edition, sizes its 2.0E Microllam LVL from load tables in pounds per linear foot, not from house width.

A worked example, with the arithmetic

One story house, 24 ft wide, 30 psf ground snow, No. 2 lumber, a 6 ft rough opening in a wall carrying roof and ceiling only.

1. Convert to inches

   6 ft 0 in is 72 in. Convert every table value the same way.

2. Read the roof and ceiling block at 24 ft

   A doubled 2×8 caps at 5 ft 9 in, or 69 in. Three inches short, so it is out.

3. Step up one size

   A doubled 2×10 reaches 6 ft 10 in, or 82 in. That is 10 in of margin, so it governs.

4. Read the jack studs off that row

   The NJ column calls for two each end.

Move that opening to a first floor where a center bearing floor lands on the wall. The doubled 2×10 row drops to 5 ft 8 in, or 68 in, so it no longer makes the opening. A doubled 2×12 at 6 ft 8 in does.

Line item the header, the jacks and the patch. Price it from a photo.

Where a header shows up on a job

Who calls out what is a header in construction, and when

On a plan set it comes off a schedule. On a remodel the framer sizes it off the table, and the department checks that choice at rough framing.

What the inspector looks at

Size and ply count, jack studs each end, king studs beside them. Then whether the header matches the load case. A doubled 2×8 over a 6 ft opening under roof, ceiling and one floor on a 24 ft wide house fails on sight.

Common header mistakes

Quoting a span with no load case

A doubled 2×10 spans 9 ft 0 in only under roof and ceiling. That is at 12 ft of width, at 30 psf ground snow.

Trusting a rule of thumb

One inch of depth per foot of opening runs short once a floor is involved.

Price the opening while you are standing in front of it

SimplyWise Cost Estimator turns a photo of the wall into an itemized estimate in about 6 seconds. Material and labor lines carry unit, quantity and price per unit. It is $29.99 a month or $239.99 a year, about $20 a month on annual, with a 7 day free trial.