Choose a Lintel That Carries the Wall, Not the Window

A window lintel must support the correct wall layers, span the clear structural opening, bear safely at both jambs and remain within strength and deflection limits. Window width alone cannot determine the member: wall construction, supported loads, bearing material, exposure and envelope details all affect the choice, and final design must follow the code adopted in the project jurisdiction.

Enter the clear structural opening and both bearings; the calculator gives overall lintel length, not structural capacity.

The lintel is the horizontal structural member that carries wall and other loads across an opening and transfers them into the wall at each jamb. In wood framing, the corresponding member is usually called a header. The window unit is not intended to support the building above it; the American Wood Council describes headers as collecting those loads and redistributing them to adjacent studs (AWC header guidance).

Match the Lintel to the Wall Assembly

A lintel must support the correct part of the wall. An exterior wall can contain several structurally distinct layers.

Wall construction	Typical support	Key coordination issue
Wood-framed wall	Solid-sawn or engineered-wood header	Stud packs, depth, insulation and air-sealing
Cold-formed steel framing	Designed steel header or jamb-and-header system	Connections, cripples and deflection
Brick veneer over framing	Framing header plus separate veneer support	Do not support brick on the window frame
Cavity masonry wall	Cavity lintel, separate lintels, reinforced masonry or steel	Identify the load path for each wythe
Load-bearing CMU	Reinforced masonry lintel, precast concrete or steel	Coordinate grout, reinforcement and bearing
Solid or multiwythe masonry	Reinforced masonry, concrete, steel or engineered arch	Support the required wall thickness

In a framed wall with brick veneer, two members may occupy roughly the same elevation: the structural header in the backing wall and a steel lintel supporting the brick. They perform different jobs. For broader assembly guidance, see Brick Veneer: Anchored and Thin-Brick Wall Details.

A lintel is not automatically interchangeable with a shelf angle. A loose lintel bears on masonry at both sides of one opening. A shelf angle is attached to the building structure and may support a longer run of veneer.

The Brick Industry Association’s 2025 guidance distinguishes the two and recommends at least 4 in. (102 mm) of masonry bearing at each end for loose lintels in brick veneer over cold-formed steel framing (BIA Technical Note 28B). That is an assembly-specific recommendation, not a universal bearing dimension.

Measure the Structural Opening, Not the Glass

Record the clear structural opening between the supporting jambs. This is not necessarily the window unit’s catalog width, rough-opening width or visible glass width.

The first-pass relationship is: lintel length equals the clear structural opening plus left bearing plus right bearing.

For example, a 4 ft 0 in. (1,219 mm) clear opening with 4 in. (102 mm) bearing at each end requires a member at least 4 ft 8 in. (1,422 mm) long. That arithmetic establishes overall length only. It does not establish capacity, determine the design span or confirm that 4 in. bearing is adequate for the assembly.

Bearing must distribute each end reaction into sound masonry, concrete or framing. Its adequacy depends on the reaction, member width, supporting material and governing design requirements. Openings close together also require a check of the narrow pier between them because the pier can receive reactions from both lintels.

BIA’s steel-lintel guidance likewise derives required bearing from the reaction and allowable masonry stress rather than length alone (BIA Technical Note 31B).

Loads and Deflection Determine Capacity

The design load may include:

• self-weight of the lintel and supported wall;
• floor and roof dead and live loads;
• snow or other jurisdiction-specific roof loads;
• concentrated reactions from joists, beams, girders or trusses;
• loads from another opening or structural discontinuity above; and
• construction loads before the wall has developed its intended behavior.

AWC notes that a wood header’s depth depends on both opening width and the weight of the structure above. The same-width window can therefore require a different header under a gable end than under a floor-bearing wall.

Masonry arching can reduce the load reaching a lintel, but it should not be assumed merely because brick or block exists above the opening. CMHA’s reinforced-CMU example requires running bond, sufficient masonry height, bearing, clear wall beside the opening and no adjacent control joint before arching is credited (CMHA TEK 17-01D). If those conditions do not apply, the lintel may need to carry the full wall and superimposed load.

Strength is only one check. Excessive deflection or rotation can crack mortar joints, open sealant joints and disturb flashing even when the member has adequate strength. BIA’s steel-lintel guidance warns against rule-of-thumb selection and identifies excessive deflection as a cause of cracking above masonry openings.

That Technical Note dates to 1987, so it is useful for understanding the mechanism but is not a substitute for current adopted-code provisions, project criteria or manufacturer tables.

Integrate the Lintel With the Drainage Plane

The structural member and water-management detail overlap at the window head, but neither substitutes for the other. A drained masonry-veneer head generally needs the following sequence from the backing toward the opening:

1. wall backing or sheathing;
2. water-resistive barrier lapped over the flashing;
3. through-wall flashing with sealed ends or end dams;
4. lintel supporting the veneer;
5. weep openings immediately above the flashing; and
6. head joint and window perimeter seal below.

The flashing should collect water from the drainage cavity and discharge it outward rather than into the rough opening. BIA recommends flashing at the heads of openings, integration with the water-resistive barrier in shingle fashion, extension to the exterior face and end dams at discontinuous flashing. It also places weeps at the flashing level rather than courses above it (BIA water-resistance guidance).

CMHA likewise calls for flashing to be longitudinally continuous or terminated with an end dam (CMHA TEK 19-05A).

Protect Exposed and Concealed Steel

Specify a coating or stainless steel appropriate to the exposure. Do not field-cut a proprietary lintel unless the manufacturer or designer provides an approved modification and coating-repair method.

Concealment within masonry does not by itself establish the required corrosion or fire protection. The detail must also preserve required concrete or masonry cover and any applied fire protection.

Maintain Thermal Continuity

Steel crossing insulation creates a linear thermal bridge. Steel Construction Institute guidance identifies lintels and window headers as common bridge locations that can increase heat loss and lower interior surface temperatures (SCI P380).

Keep steel within the insulated zone where feasible, locally insulate penetrations or use an improved detail. Consequential junctions should be quantified with manufacturer data or two- or three-dimensional thermal modeling.

Allow Intended Wall Movement

Do not unintentionally lock brick expansion joints or frame movement into the lintel. Where a designed vertical expansion joint meets a lintel, BIA shows the joint continuing around the lintel end. Sealant interfaces at the window head also need to accommodate the expected movement without blocking drainage.

Put the Complete Lintel Detail on the Drawings

A buildable detail should identify more than “lintel over window.” Show or schedule:

1. lintel material, section or exact proprietary designation;
2. clear structural opening and overall member length;
3. required bearing at each end and the bearing substrate;
4. wall layers or wythes supported;
5. design load or approved safe working load where applicable;
6. reinforcement, grout, connections, welds, fasteners and temporary propping;
7. elevation relative to the rough opening and masonry coursing;
8. corrosion protection and restrictions on cutting or modification;
9. flashing, end dams, drip edge and weeps;
10. insulation, air-barrier and water-resistive-barrier continuity; and
11. movement joints and sealant interfaces.

For precast concrete selection and installation, Precast Lintel: Types, Sizing and Installation covers supported width, bearing and load checks in more detail.

Cracking and Rust Require Investigation

Cracking or displacement around an opening, sagging masonry, a visibly bowed angle, rust staining or spalled masonry near the bearings warrants investigation. The National Park Service notes that cracking and displacement around openings can result from lintel deflection or failure, and that iron and steel lintels can cause cracking as they deflect or rust over time (NPS: Common Problems with Brick Masonry).

These symptoms are not a diagnosis. Settlement, thermal movement, moisture damage and overstressed masonry can produce overlapping evidence.

Do not remove a window, cut a lintel or simply repoint the cracks before establishing the load path and cause. Temporary support and a designed repair may be necessary, particularly in load-bearing masonry, multi-story veneer, walls with concentrated loads, or walls where the lintel section and bearing are concealed.