Understanding Bearing Walls and Shear Walls in LAVA

In LAVA, bearing walls and shear walls are treated as two distinct structural elements, each handling different types of loads.

Bearing Walls

• Designed to carry vertical loads only—such as Dead Load (D), Live Load (L), Roof Live Load (Lr), and Snow Load (Sn).

• They ignore all lateral loads (e.g., Wind or Seismic) in the LAVA model.

Shear Walls

• Serve as lateral load-resisting elements.

• The wall panel itself resists lateral loads only (Wind Load (W), Seismic Load (E)).

• However, end posts and hold-downs—which are vertical elements—do consider Dead Load during design (for overturning resistance).

• When exporting reactions or transferring loads downward, LAVA avoids "double-dipping":

  • Shear walls only export: W and E

  • Bearing walls only export: D, L, Lr, and Sn

How LAVA Handles Overlapping Elements

In modeling, you may place beams, bearing walls, and shear walls in the same location. LAVA uses the following rules to determine which elements are active in load transfer:

1. Beam within a bearing wall:

   • The bearing wall is ignored at the beam’s location.

   • The beam carries all applicable loads.

2. Shear wall within a bearing wall:

   • The bearing wall exports vertical loads (D, L, Lr, Sn) to lower levels.

   • The shear wall exports only lateral loads (W, E).

   • Even though the shear wall uses Dead Load for design of end posts/hold-downs, it does not export that dead load (including its own self-weight) to lower levels.

3. Beam below a plate with no bearing wall:

   • The beam still receives all plate loads.

   • A bearing wall is not required for vertical load transfer.

   • However, the self-weight of any unmodeled bearing wall will not be included in the design of the beam below.

Example: Load Transfer Scenarios in a Two-Story Structure

We’ll walk through an example to verify how LAVA handles different overlapping conditions. This structure has two levels: ROOF and FLOOR1.

ROOF Level:

• A 25' x 50' plate (PL.RF0.1) is modeled with:

  • Dead Load: 21 psf

  • Roof Live Load: 20 psf

• Continuous bearing walls are placed at:

  • Plan-North: BW.RF0.1

  • Plan-South: BW.RF0.1

• A 5’ beam (BM.RF0.1) is placed within the plan-north bearing wall.

• A 10’ shear wall (SW.RF0.1) is placed within the plan-south bearing wall and loaded with:

  • 5000 lbs Wind Load

  • 5000 lbs Seismic Load

FLOOR1 Level

• Four identical beams are modeled:

  • BM.FL1.1 to BM.FL1.4, each with:

    • 11.5’ span

    • No custom loads applied

  Beam Layout and Conditions:

  • BM.FL1.1
    Located below the plan-north bearing wall and the overlapping beam (BM.RF0.1)

  • BM.FL1.2
    Located below the plan-south bearing wall and the overlapping shear wall (SW.RF0.1)

  • BM.FL1.3
    Located below the plan-north continuous bearing wall with no overlaps

  • BM.FL1.4
    Located directly below the plan-south edge of the roof plate, with no bearing walls above

A screenshot of the ROOF level with element overlays is shown below:

Compare BM.FL1.1 and BM.FL1.2:

At BM.FL1.1, the bearing wall loading is interrupted by the overlapping beam (BM.RF).1) on ROOF level.
At BM.FL1.2, although with overlapping bearing wall and shear wall on upper level, no additional dead load is added to this beam. The point load is from the shear wall end post, and it only exports wind and seismic loads.

Compare BM.FL1.1 and BM.FL1.3:

At BM.FL1.1, the bearing wall loading is interrupted by the overlapping beam (BM.RF).1) on ROOF level.
At BM.FL1.3, the bearing wall exports continuous loading without interruption.

Compare BM.FL1.3 and BM.FL1.4:

At BM.FL1.3, the bearing wall exports continuous loading without interruption, including the loading from plate, and the dead load from bearing wall self weight.
At BM.FL1.4, the plate exports continuous loading without interruption, without the bearing wall self weight in BM.FL1.3.