How much weight an LVL beam can hold depends on the beam’s depth, width (number of plies), span length, and the specific product’s strength rating. There’s no single answer because a 9.5-inch deep, single-ply LVL spanning 8 feet can support a very different load than a triple-ply 14-inch LVL spanning 16 feet. But the key factors are predictable, and understanding them will help you size the right beam for your project or verify that an existing one is adequate.
Why There’s No Universal Number
LVL (laminated veneer lumber) is an engineered wood product made by bonding thin layers of wood veneer together under heat and pressure. Unlike a solid piece of lumber, every layer runs in the same grain direction, which gives it consistent, predictable strength. An LVL beam can be up to two and a half times stronger than standard framing lumber of the same dimensions in compression and tension. But the actual weight it holds is a function of several variables working together, not a single rating stamped on the beam.
The two properties that control structural performance are flexural strength (Fb) and stiffness (E). Flexural strength determines how much load the beam can carry before it fails. Stiffness determines how much it deflects, or bends, under that load. A beam might be strong enough to carry a load without breaking but still deflect so much that it causes bouncy floors or cracked drywall. Building codes set limits on both.
How Strength Ratings Work
LVL products come with specific Fb and E values assigned by the manufacturer. Common Fb ratings for LVL range from about 2,400 to 3,100 psi, depending on the brand and product line. A beam rated at Fb 3,100 will carry meaningfully more load than one rated at Fb 2,400 across the same span. For comparison, standard #2 hem-fir lumber has an Fb of roughly 1,100 psi, less than half even the lower-end LVL rating.
Stiffness values for LVL typically fall around 1,800,000 to 2,000,000 psi, compared to about 1,300,000 psi for #2 hem-fir. That higher stiffness means less bounce and sag over long spans, which is one of the main reasons builders choose LVL for headers, floor beams, and ridge beams in the first place.
The Variables That Determine Capacity
Beam Depth
Depth has the greatest impact on how much weight a beam can support. Doubling the depth of a beam doesn’t just double its capacity; it roughly quadruples it, because depth affects strength exponentially. Common LVL depths are 9.25, 11.25, 11.875, 14, 16, and 18 inches. Going from a 9.25-inch beam to an 11.875-inch beam for the same span can dramatically increase the allowable load.
Number of Plies
A single ply of LVL is typically 1.75 inches wide. For most structural applications, builders laminate two or three plies together to form a wider beam. A double-ply (3.5-inch wide) beam carries roughly twice the load of a single ply, and a triple-ply (5.25-inch wide) carries roughly three times as much. The plies need to be properly fastened together with nails or bolts in a specific pattern so they act as a single unit. If the plies aren’t connected correctly, the beam won’t perform at its full rated capacity.
Span Length
The longer the unsupported span, the less total load the beam can handle. A beam that comfortably supports 5,000 pounds over 8 feet might only support 2,500 pounds over 16 feet. This is also where stiffness becomes critical. Over longer spans, deflection limits (typically L/360 for floors, meaning the beam can’t sag more than 1/360th of its span length) often become the controlling factor before the beam’s raw strength is ever an issue.
Load Type
How the weight is applied matters. A uniform load spread evenly across the beam’s length, like floor joists transferring weight from a room above, is very different from a point load concentrated at one spot, like a post sitting on the middle of a beam. Beams handle uniform loads more efficiently. A concentrated load at mid-span creates the highest possible bending stress for a given weight.
Typical Capacity Ranges
To give you a rough sense of scale: a common double-ply 1.75-inch by 11.875-inch LVL with an Fb of 2,600 might support a total uniform load of around 4,000 to 6,000 pounds over a 10-foot span, depending on the exact product and applicable safety factors. Over a 14-foot span, that same beam might handle 2,500 to 4,000 pounds. These are ballpark figures. The actual allowable load for your situation comes from the manufacturer’s published load tables or an engineer’s calculations.
Every major LVL manufacturer, including Weyerhaeuser (Microllam), Boise Cascade (VERSA-LAM), and Louisiana-Pacific, publishes span tables and load charts specific to their products. These tables list allowable loads by beam size, span, and number of plies, and they already include the required safety factors mandated by building codes. If you know the product you’re using, those tables are the most reliable way to find a specific number.
What Reduces an LVL Beam’s Capacity
Moisture is the biggest environmental threat to LVL performance. Research from the U.S. Forest Products Laboratory found that strength and stiffness can decrease by as much as 50 percent at 90 percent relative humidity compared to standard conditions (around 65 percent relative humidity). Standard LVL is not rated for exterior or high-moisture applications. If a beam will be exposed to weather, ground moisture, or consistently humid conditions like a poorly ventilated crawl space, you need a product specifically treated and rated for that environment.
Notching or drilling holes through an LVL beam also reduces its capacity significantly. Unlike dimensional lumber, where small notches at beam ends are sometimes permitted, LVL manufacturers typically restrict or prohibit field modifications. A hole drilled for plumbing through the tension zone at the bottom of the beam can create a failure point well below the beam’s rated load. Always check the manufacturer’s guidelines before cutting into an LVL.
How to Find the Right Size
If you’re sizing a new LVL beam, you need three pieces of information: the total load the beam needs to carry (including the weight of the structure itself, called dead load, plus furniture, people, and other live loads), the span length, and the beam’s support conditions on each end. Most residential floors are designed for a combined load of 50 pounds per square foot (10 dead, 40 live). Multiply that by the tributary area, which is the width of floor the beam supports, and you get the total load.
For example, if a beam supports floor joists that extend 6 feet on each side, the tributary width is 12 feet. Over a 12-foot span at 50 psf, the beam needs to handle 12 × 12 × 50 = 7,200 pounds of total load. From there, the manufacturer’s span tables will tell you whether a double-ply or triple-ply beam at a given depth can handle it.
For anything beyond a simple header over a window or door, having a structural engineer or the manufacturer’s technical support run the numbers is the standard approach. Many LVL manufacturers offer free beam-sizing software on their websites that lets you input your loads, span, and support conditions and get a recommended beam size with the engineering behind it.