LVL Floor Joists: Match the Product, Span and Floor Detail

LVL can be used as floor joists, but it is not an automatic same-size replacement for sawn lumber or an I-joist. The exact product, grade, dimensions, spacing, loads and support details must establish its suitability. For example, ICC-ES report ESR-1387, revised July 2026, recognizes Microllam LVL for structural applications including joists, subject to the report, manufacturer instructions and applicable code.

Start with the floor layout and loads—not a generic “LVL span” chart. A joist supporting subfloor between two walls is a different selection problem from an LVL beam supporting a whole row of joists.

What an LVL floor joist is

Laminated veneer lumber is made from thin wood veneers bonded together. In Microllam LVL, the veneer grain runs parallel to the member’s length. That produces a solid rectangular structural member, rather than the thin web and separate flanges of an I-joist. LVL may also be used as an I-joist component, but an I-joist with LVL flanges is not a solid LVL joist. ESR-1387 describes both the material and its structural uses.

Consider solid LVL where the designer needs a member that fits an existing floor depth, meets a demanding load or stiffness requirement, or reinforces framing around an opening. Whether it works depends on the calculation and connections; “engineered lumber” alone does not establish capacity.

Mechanical routing deserves an early check. Do not select a solid LVL floor layout assuming it offers the same pipe and duct openings as an I-joist system.

How to select the size and spacing

Give the designer or engineered-wood supplier these inputs:

• Support layout: span, bearing locations, available bearing lengths, and whether the joist is single-span, continuous or cantilevered.
• Loads: occupancy live load, actual assembly dead load, and concentrated loads or load-bearing walls.
• Floor geometry: available depth, proposed on-center spacing and openings.
• Performance requirements: deflection limits and any additional floor-vibration or finish-floor requirements.
• Product identity: manufacturer, full grade designation, actual width and depth, and applicable evaluation report.

An E designation describes modulus of elasticity, not a complete load rating. For example, Weyerhaeuser lists 2.0E Microllam with an E value of 2,000,000 psi, alongside separate bending, shear and bearing properties. Its guide also requires both bending and shear deformation to be considered when calculating deflection. See TJ-9000, pages 4–5.

A product-specific span example

The PWLVL 1.6E User Guide hosted by U.S. LUMBER illustrates why depth alone cannot answer the sizing question. Its page 7 table gives these allowable simple spans for 1½ × 9½-inch joists, under uniform residential loading of 40 psf live load plus 15 psf dead load, with an L/480 deflection criterion:

Joist spacing	Listed maximum span
12 inches on center	17 feet 5 inches
16 inches on center	16 feet 2 inches
24 inches on center	14 feet 6 inches

These are an illustration, not a universal LVL sizing schedule. The guide measures floor-joist span face-to-face between supports and bases the table on glued-and-nailed 19/32-inch sheathing, specified bearing and lateral restraint. It calls for ASTM D3498 adhesive used according to the adhesive manufacturer’s recommendations. Confirm the current guide and availability for the product being supplied.

Wider spacing assigns more floor area—and therefore more uniform load—to each joist. Increasing the load also changes the result: the same guide lists only 14 feet 1 inch for that 1½ × 9½-inch joist at 16-inch spacing under 60 psf live load plus 15 psf dead load, using L/480.

Do not use these uniform-load tables to approve a post, heavy fixture or bearing wall. Nor should a single-span value be carried over to a cantilever or continuous layout.

Bearing, restraint and holes are part of the design

Bearing: Check the required support length and supporting material, not just the joist’s bending capacity. The PWLVL floor-joist table requires at least 1½ inches at end supports, increased to 2 inches for bracketed span entries, and 3½ inches at intermediate supports. Those are that guide’s conditions—not defaults for every LVL product.

Restraint: The same guide requires lateral restraint at supports, such as full-depth solid blocking or rim board, and along the compression edge, such as floor sheathing. It adds full-depth solid blocking at third-points along each span of 14-inch multiple-span joists. A span selection does not eliminate these installation requirements. See the floor-joist table notes.

Holes and notches: Obtain the exact product’s permitted-hole detail before rough-in. The PWLVL 1.6E guide’s handling instructions prohibit cutting, drilling or notching except for cutting to length, and direct readers to the manufacturer for possible heel cuts; its joist-table notes also direct readers to manufacturer hole details. Do not treat the span table as permission to drill. Obtain an applicable manufacturer detail or project-specific design approval before making a penetration. Never transfer an I-joist web-hole chart—or ordinary sawn-joist notching rules—to solid LVL. See the PWLVL handling instructions and table notes.

Before ordering and loading the floor

Have the framing package identify the joist product and grade, lengths, spacing, bearing or hanger details, required fasteners, blocking and approved penetrations. If multiple plies are specified, obtain their connection schedule as well.

Coordinate the subfloor panel selection with joist spacing; a joist that passes its design checks does not automatically make the panel assembly suitable.

Finally, protect untreated LVL from prolonged weather exposure and ground contact. PWT’s installation guide limits its untreated products to dry, covered, well-ventilated interior conditions, requires rim joists, blocking, connections and temporary bracing before workers access the structure, and prohibits loads other than workers’ weight before permanent sheathing. Even after sheathing, construction-material loads must not exceed design loads. Follow the PWT handling and installation instructions for its products and the project-specific instructions for the floor being built.