What is a load-bearing wall?

What makes a wall load bearing?

The weight it carries. In the 2021 Seattle Building Code, a wood or metal stud wall counts as load-bearing once it holds more than 100 pounds per linear foot of load beyond its own weight, and a masonry, concrete or mass timber wall once it holds more than 200: In the Seattle Building Code, “Any metal or wood stud wall that supports more than 100 pounds per linear foot (1459 N/m) of vertical load in addition to its own weight.” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29. In the Seattle Building Code, “Any masonry, concrete or mass timber wall that supports more than 200 pounds per linear foot (2919 N/m) of vertical load in addition to its own weight.” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29. In the Seattle Building Code, “Any wall that is not a load-bearing wall.” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29.

How does HUD's structural design guide describe a load-bearing wall?

A load-bearing wall holds up weight from above it, such as the roof, a ceiling, floor joists or a beam, and passes that weight down toward the foundation. The U.S. Department of Housing and Urban Development's structural design guide puts it this way: “Load-bearing walls support gravity loads from the roof, ceiling, or floor joists or the beams above.” Source: U.S. Department of Housing and Urban Development, Office of Policy Development and Research, read 2026-10-29. “A wall is a vertical structural system that supports gravity loads from the roof and floors above and transfers the loads to the foundation below.” Source: U.S. Department of Housing and Urban Development, Office of Policy Development and Research, read 2026-10-29. “Interior walls may be either load bearing or non-load bearing.” Source: U.S. Department of Housing and Urban Development, Office of Policy Development and Research, read 2026-10-29. “Non-loadbearing interior walls often are called partitions.” Source: U.S. Department of Housing and Urban Development, Office of Policy Development and Research, read 2026-10-29.

What does a load bearing wall do?

It is one link in the load path: it takes weight from the floors and roof above, and in some walls sideways wind and earthquake forces as well, and carries it down to the foundation. HUD's guide and the Seattle Residential Code describe that job: “The path through which loads are transferred is known as the load path.” Source: U.S. Department of Housing and Urban Development, Office of Policy Development and Research, read 2026-10-29. “A continuous load path is capable of resisting and transferring the loads that are realized throughout the structure from the point of load origination down to the foundation.” Source: U.S. Department of Housing and Urban Development, Office of Policy Development and Research, read 2026-10-29. “Interior load-bearing walls typically support the floor or ceiling joists above when the clear span from exterior wall to exterior wall is greater than the spanning capability of the floor or ceiling joists.” Source: U.S. Department of Housing and Urban Development, Office of Policy Development and Research, read 2026-10-29. “Some interior loadbearing walls may be shear walls to assist in transferring lateral loads to lower floors and to the foundation.” Source: U.S. Department of Housing and Urban Development, Office of Policy Development and Research, read 2026-10-29. In the Seattle Residential Code, “Wall construction shall be capable of accommodating all loads imposed in accordance with Section R301 and of transmitting the resulting loads to the supporting structural elements.” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29.

What is a load bearing wall made of?

House walls have traditionally been framed with 2x4 or 2x6 lumber, but the residential code also covers steel, masonry, concrete and structural insulated panel walls, and sets an 8-inch minimum thickness for masonry bearing walls more than one story high: “Residential wall systems traditionally have been constructed of dimension lumber, usually 2x4 or 2x6, although engineered wood studs and cold-formed steel studs are seeing increased use.” Source: U.S. Department of Housing and Urban Development, Office of Policy Development and Research, read 2026-10-29. In the Seattle Residential Code, “The wall construction covered in Chapter 6 consists of five different types: wood framed, cold-formed steel framed, masonry, concrete and structural insulated panel (SIP).” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29. In the Seattle Residential Code, “The minimum thickness of masonry bearing walls more than one story high shall be 8 inches (203 mm).” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29.

Are exterior walls load bearing?

Not always. HUD's structural guide says exterior walls are not necessarily load-bearing, and names the gable-end wall as the usual exception because the roof and floor framing runs parallel to it: “Exterior walls are not necessarily always load-bearing walls.” Source: U.S. Department of Housing and Urban Development, Office of Policy Development and Research, read 2026-10-29. “A gable-end wall typically is considered a non-load-bearing wall because roof and floor framing generally runs parallel to the gable end; however, a gableend wall must support lateral wind and seismic loads and even small dead and live loads.” Source: U.S. Department of Housing and Urban Development, Office of Policy Development and Research, read 2026-10-29. “Exterior load-bearing walls must be designed for axial loads as well as for lateral loads from wind or seismic forces.” Source: U.S. Department of Housing and Urban Development, Office of Policy Development and Research, read 2026-10-29. In the Seattle Residential Code, “Interior load-bearing walls shall be constructed, framed and fireblocked as specified for exterior walls.” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29.

Is a load bearing wall perpendicular to the joists?

Often, because an interior bearing wall typically holds up the floor or ceiling joists above it, but direction alone does not settle it: the Seattle Residential Code has rules for bearing partitions that run perpendicular to joists and for ones that run parallel to them: See the U.S. Department of Housing and Urban Development, Office of Policy Development and Research passage quoted above. In the Seattle Residential Code, “Bearing partitions perpendicular to joists shall not be offset from supporting girders, walls or partitions more than the joist depth unless such joists are of sufficient size to carry the additional load.” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29. In the Seattle Residential Code, “Joists under parallel bearing partitions shall be of adequate size to support the load.” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29.

Can a load bearing wall have a door in it?

Yes. A load-bearing wall can have a door or window opening, but the weight above the opening has to be carried around it by a header; nonbearing walls do not need load-bearing headers: In the Seattle Residential Code's steel-framing section, “Headers shall be installed above all wall openings in exterior walls and interior load-bearing walls.” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29. In the Seattle Residential Code, “For header spans, see Tables R602.7(1), R602.7(2) and R602.7(3).” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29. “A framing system around a wall opening, not just a header, constitutes a load path.” Source: U.S. Department of Housing and Urban Development, Office of Policy Development and Research, read 2026-10-29. In the Seattle Residential Code, “Load-bearing headers are not required in interior or exterior nonbearing walls.” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29.

Do load bearing walls need a double top plate?

Generally yes. The Seattle Residential Code caps wood stud walls with a double top plate whose end joints are offset at least 24 inches, and lets interior nonbearing walls use a single top plate: In the Seattle Residential Code, “Wood stud walls shall be capped with a double top plate installed to provide overlapping at corners and intersections with bearing partitions.” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29. In the Seattle Residential Code, “End joints in top plates shall be offset not less than 24 inches (610 mm).” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29. In the Seattle Residential Code, “Interior nonbearing walls shall be capped with not less than a single top plate.” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29. “Headers generally are designed to support all loads from above; however, typical residential construction calls for a double top plate above the header.” Source: U.S. Department of Housing and Urban Development, Office of Policy Development and Research, read 2026-10-29.

Can a load bearing wall be 2x4?

Yes. HUD notes house walls are usually framed with 2x4 or 2x6 lumber, and the Seattle Residential Code sizes bearing studs in its Table R602.3(5), limiting 2x4 studs under a habitable attic to a 32-foot roof span: See the U.S. Department of Housing and Urban Development, Office of Policy Development and Research passage quoted above. In the Seattle Residential Code, “The size, height and spacing of studs shall be in accordance with Table R602.3(5).” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29. In the Seattle Residential Code, “A habitable attic assembly supported by 2 × 4 studs is limited to a roof span of 32 feet.” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29. In the Seattle Residential Code, “Where the roof span exceeds 32 feet, the wall studs shall be increased to 2 × 6 or the studs shall be designed in accordance with accepted engineering practice.” Source: City of Seattle, Department of Construction and Inspections, read 2026-10-29.

Sources

• Residential Structural Design Guide, Second Edition — U.S. Department of Housing and Urban Development, Office of Policy Development and Research; published 2017-10; read 2026-10-29.
• 2021 Seattle Building Code, Chapter 2 Definitions — City of Seattle, Department of Construction and Inspections; read 2026-10-29.
• 2021 Seattle Residential Code, Chapter 5 Floors — City of Seattle, Department of Construction and Inspections; read 2026-10-29.
• 2021 Seattle Residential Code, Chapter 6 Wall Construction — City of Seattle, Department of Construction and Inspections; read 2026-10-29.