Wood-framed walls look simple once the drywall goes up, but the stud layout behind it follows precise engineering rules. Bearing-wall stud spacing, header sizing, corner post assemblies, and rough opening dimensions all affect structural performance and code compliance. Getting the counts right before you order lumber saves a second trip to the yard and keeps your framing inspection clean.
Bearing vs. Non-Bearing Walls
Bearing walls carry loads from the structure above — floor joists, roof rafters, or another story — and transfer them down to the foundation. Non-bearing (partition) walls simply divide space and carry only their own weight. The distinction matters because bearing walls require doubled top plates, larger headers over openings, and must be continuous from floor to floor. Cutting a stud in a bearing wall without proper temporary shoring can cause immediate structural deflection.
You can identify bearing walls by looking at which direction the floor joists run: walls running perpendicular to the joists are typically bearing. Exterior walls are almost always bearing. Interior walls running parallel to the ridge line or centered on the building span are usually bearing too. When you are not certain, treat the wall as bearing — using slightly oversized headers and doubled plates costs little but provides a significant safety margin. This calculator defaults to bearing wall rules when the wall type is set to exterior or interior bearing.
Header Sizing for Openings
Every door and window opening in a bearing wall needs a header to carry the load that the removed studs would have supported. Header size depends on the span (rough opening width), the wall type, and the load above. The IRC provides span tables (Table R602.7) that list minimum header sizes for common conditions. For a 3-foot opening in an exterior bearing wall, a doubled 2×6 is typical; a 6-foot opening usually requires a doubled 2×10 or an engineered LVL beam.
Non-bearing walls can use a much lighter cripple header — often just a flat 2×4 across the top of the opening — because no structural load is being transferred. Using a full-depth header in a non-bearing wall wastes lumber but does no harm structurally. When in doubt, use a larger header: the extra cost of one or two larger boards is trivial compared to the cost of a failed inspection or structural repair later.
Corner Posts and Backing
A simple two-stud corner does not provide a nailing surface for the interior drywall in the corner return. The standard solution is a three-stud California corner post, which adds one extra stud set back from the corner face to create a backing ledge for the intersecting wall's drywall edge. This calculator adds two extra studs per corner (the corner post assembly) and two extra studs per T-wall intersection (the backup stud behind the intersecting wall).
Some framers use drywall clips or metal backing angles instead of the extra lumber, reducing material cost slightly. However, the three-stud corner is faster to frame, requires no special hardware, and provides solid backing for shelving and wall-mounted fixtures in the corner. For projects where lumber cost is a concern, the 24-inch OC stud spacing option reduces field stud count by about 25% compared to 16-inch OC — a larger saving than eliminating corner studs.