A lam beam is a structural wood beam made by bonding multiple layers of wood together with adhesive, creating a single piece that’s stronger and more uniform than solid lumber. The term “lam beam” is shorthand used in the construction industry, and it typically refers to one of two engineered wood products: laminated veneer lumber (LVL) or glue-laminated timber (glulam). Both use layers of wood glued under heat and pressure, but they differ in how they’re built and where they’re used.
How a Lam Beam Is Made
The most common type of lam beam in residential construction is LVL. It starts with logs that are peeled on a lathe into thin sheets of veneer, each roughly 0.08 to 0.10 inches thick. These sheets are clipped to remove knots and other defects, then coated with a waterproof adhesive (typically phenol formaldehyde, the same family of glue used in exterior-grade plywood). The veneer layers are stacked with their wood grain running in the same direction, then pressed together at temperatures between 250 and 450 degrees Fahrenheit.
Most LVL mills use a continuous press line, feeding veneer through in a steady stream rather than pressing one beam at a time. This allows manufacturers to produce long, consistent beams. The finished product looks like a solid piece of wood from the outside, but a close look at the end grain reveals the thin laminated layers. Douglas fir is one of the most common species used, though southern pine, yellow poplar, and aspen are also standard raw materials.
Glulam beams follow a similar concept but use thicker pieces of sawn lumber (not thin veneers) stacked and glued together. Because glulam starts with larger boards, it can be shaped into curves and arches, making it popular for architectural applications where the beam will be visible.
LVL vs. Glulam: Which One Is “the Lam Beam”?
When a contractor or lumber yard says “lam beam,” they usually mean LVL, especially in the context of residential framing. Here’s how the two compare:
- LVL is made from bonded wood veneers with all layers running in the same direction. It comes in straight pieces and is used for headers over windows and doors, floor joists, roof rafters, rim boards, and as flange material in prefabricated I-joists. It’s the workhorse of light-frame construction.
- Glulam is made from bonded sawn timber laminations, also with grain aligned in one direction. It’s better suited for large-span structures, curved or arched roofs, exposed ceiling beams, bridges, and columns. It tends to cost more and is often chosen when aesthetics matter.
Both products are stronger than solid lumber of the same size, but they fill different roles. If you’re framing a house and need a beam to carry a load-bearing wall or span a wide opening, you’re almost certainly looking at LVL.
Standard Sizes
LVL beams typically come 1¾ inches thick, which matches the width of standard dimensional lumber (a 2×4 wall, for example, is 3½ inches wide, so two LVL beams side by side fit perfectly). Depths range from 7¼ inches up to 18 inches, with deeper beams handling heavier loads and longer spans. For bigger jobs, builders bolt two or three LVL beams together to form a single, wider beam.
Why Builders Choose Lam Beams Over Solid Wood
The layering process is what gives lam beams their edge. In a solid piece of lumber, a single large knot or grain deviation can dramatically reduce the beam’s strength. In an LVL beam, any defects that survive the clipping process are randomly distributed across many layers, so no single flaw weakens the whole beam. The result is a product with more uniform and predictable strength, comparable to high-grade lumber but available in longer lengths and larger sizes than you could reliably find in solid wood.
LVL beams also have a higher strength-to-weight ratio than traditional lumber. This means they can span longer distances and carry greater loads without being heavier. They’re more dimensionally stable too, meaning they resist warping, twisting, and shrinking as humidity changes. Solid lumber, especially in large sizes, is notorious for checking (cracking) and crowning (bowing) as it dries. Lam beams hold their shape.
The tradeoff is cost. LVL beams are more expensive per piece than solid lumber, though the price difference often pays for itself because you can use fewer, longer beams and spend less time on labor. They’re also heavier than equivalent solid lumber in some cases, which can make handling them on a job site more demanding.
Fire Performance
One concern people have with engineered wood is fire safety. Testing by the USDA Forest Products Laboratory has confirmed that LVL chars at a rate comparable to solid wood in standard fire tests, roughly 1.5 inches per hour. This means lam beams don’t burn faster than the solid lumber they replace. In fact, large wood beams (including lam beams) often outperform exposed steel in a fire, because steel loses its structural strength rapidly at high temperatures while wood chars predictably from the outside in, maintaining a load-bearing core for longer.
Moisture and Outdoor Use
Standard LVL beams are designed for dry conditions, defined as environments where the moisture content of the wood stays at or below 15% on average and doesn’t exceed 19%. This covers virtually all interior residential and commercial applications. For outdoor or high-moisture situations, treated versions exist. These beams are manufactured with a preservative blend applied during the gluing process, providing resistance to fungal decay and wood-destroying insects, including Formosan termites.
Even treated LVL is limited to above-ground applications without ground contact. If you need a beam that will sit in or on the ground, or be submerged in water, lam beams aren’t the right choice. For exterior above-ground use, builders apply wet-use property adjustments when calculating load capacity, since the beam’s stiffness decreases slightly in moist conditions. Minor deformation, up to about ⅛ inch, can occur under load in wet service.
Where You’ll Find Lam Beams in a Home
In a typical house, lam beams show up in several places. The most visible is over large window and door openings, where a header beam carries the weight of the wall, roof, or floor above. Open-concept floor plans often rely on long LVL beams (or multiple LVLs bolted together) to replace load-bearing walls that have been removed. They’re also common as ridge beams at the peak of a roof, as hip and valley rafters in complex roof designs, and as the main carrying beams in floor systems.
In larger buildings, including multi-residential and tall wood structures, LVL beams serve as floor and roof decking elements, shear walls for lateral bracing, and structural framing components. Glulam takes over when the design calls for long exposed spans, curved shapes, or a finished wood appearance that will be left visible in the completed building.