Sizing and Installing LVL Beams

Intermediate Level

A practical guide to selecting the correct LVL beam size for residential headers and beams, including load calculation basics, bearing requirements, multi-ply fastening, and connection details.

Materials Needed

Warning

Never notch or drill LVL flanges or exceeed manufacturer hole charts for web penetrations. Unauthorized modifications can cause sudden, catastrophic beam failure under load. If a hole location or size is not explicitly permitted by the manufacturer, it is not allowed.

Caution

LVL beams must have adequate bearing length at all supports. Minimum bearing is typically 1-1/2" at interior bearings and 3-1/2" at end bearings. Insufficient bearing causes crushing at the support point, which can lead to progressive structural failure.

Pro Tip

When building multi-ply LVL beams, apply a bead of construction adhesive between plies before nailing. This prevents the plies from working independently under load and eliminates the annoying squeak that can develop between loose plies.

Note

Manufacturer span tables assume the beam carries a uniform load. Point loads (columns, posts, or concentrated loads from above) require separate analysis. A beam with a point load at mid-span has very different stress distribution than a uniformly loaded beam of the same total load.

LVL Beam Sizing Guide

Selecting the correct LVL beam size is one of the most common engineering tasks in residential construction. Every window header, door header, garage opening, and open floor plan requires a beam that can safely carry the load above it while limiting deflection to imperceptible levels. This guide walks through the process from load determination through installation.

Step 1: Determine the Load

Before sizing a beam, you need to know what it carries. In residential construction, the load on a beam depends on:

  • Tributary width: How much floor, roof, or wall area is supported by this beam. Measured perpendicular to the beam span.
  • Load type: Floor loads (40 psf live + 10 psf dead for residential), roof loads (20-30 psf live + 10-20 psf dead depending on region and material), wall loads (typically 7-10 plf per story of wall above).
  • Number of stories supported: A first-floor beam supporting second floor plus attic plus roof carries significantly more than a single-story header.
  • Point loads: Columns, posts, or beams from above that deliver concentrated loads.

Step 2: Determine the Span

Span is measured face-to-face of supports (not center-to-center). A header in a 6-foot window opening with jack studs on each side has a clear span of approximately 6 feet (the rough opening width minus any bearing length within the opening).

Step 3: Use Manufacturer Sizing Tools

Every LVL manufacturer provides free sizing tools:

  • Weyerhaeuser ForteWEB (online) — covers Microllam LVL, TJI joists, and Parallam PSL
  • Boise Cascade BC Calc (online/app) — covers VERSA-LAM LVL and BCI joists
  • LP SolidStart Design Software — covers LP LVL and I-joists

Enter the span, tributary width, load conditions, and deflection criteria. The software outputs the required LVL size and number of plies. For most residential headers, the result is a double or triple 1-3/4" LVL in a standard depth.

Step 4: Check Bearing

Bearing refers to the area where the beam sits on its supports. Inadequate bearing causes crushing — the wood fibers compress under the concentrated load, the beam settles, and the structure above sags. Manufacturer bearing requirements are typically:

  • End bearing (beam end at wall): 3-1/2" minimum — this is why LVL beams in 2x4 walls need full-width jack studs.
  • Interior bearing (beam over post or column): 1-1/2" minimum for light loads; 3-1/2" for heavy loads.
  • If bearing requirements cannot be met, a bearing plate (steel or engineered compression block) can distribute the load.

Step 5: Multi-Ply Assembly

Most residential LVL beams are multi-ply — two or three 1-3/4" pieces nailed together to match wall width:

  • Double LVL (3-1/2" total): Fits in 2x4 wall framing. Fasten with two rows of 10d (3" x 0.128") nails at 12" on center, staggered top and bottom, and clinched.
  • Triple LVL (5-1/4" total): Fits in 2x6 wall framing. Same nailing pattern. Some manufacturers require structural screws for triple assemblies.
  • Apply construction adhesive between plies for additional rigidity and squeak prevention.
  • Align tops of all plies flush — the bottom may be uneven if pieces vary slightly. The top surface is the bearing and nailing surface for framing above.

Step 6: Installation and Connection

  • Set beam on bearing points and verify level. Shim bearing points if needed — never shim at mid-span.
  • Connect beam to supports with Simpson Strong-Tie connectors (CC columns caps, LPC post caps, or equivalent). Toenailing alone is not adequate for structural beam connections.
  • Ensure continuous load path — the load from above must transfer through the beam to the supports to the foundation without interruption.
  • Brace beam laterally if the compression flange (top) is not braced by subfloor or ceiling framing.

Common Mistakes to Avoid

  • Sizing by rule of thumb without checking manufacturer tables — "one inch of beam depth per foot of span" is a starting point, not a design method.
  • Forgetting to check deflection — a beam may be strong enough but too flexible, causing bouncy floors or cracked drywall.
  • Using LVL for exposed applications — LVL is not attractive. Use glulam in Architectural grade for exposed beams.
  • Inadequate bearing, especially when retrofitting beams into existing walls where full-width jack studs do not exist.
  • Drilling holes near bearing points or in the tension (bottom) zone — both can cause failure.