CSLB General Building (B)Framing and CarpentryMedium
A designer compares a solid-sawn 2x10 No. 2 Douglas fir-larch joist to an LVL (laminated veneer lumber) member of the same nominal depth for a long floor span. Why can the LVL typically span farther under the same loading?
- ALVL is always graded as Select Structural regardless of manufacturing process
- BLVL requires fewer fasteners at bearing points
- CLVL has higher allowable bending stress and stiffness due to its engineered, defect-controlled manufacturing
- DLVL weighs less than solid-sawn lumber of the same size
Show answer & explanationAnswer & explanation
Correct answer: C. LVL has higher allowable bending stress and stiffness due to its engineered, defect-controlled manufacturing
LVL is manufactured by laminating thin wood veneers with adhesive under controlled conditions, which distributes and minimizes natural defects like knots. This results in higher, more consistent allowable bending stress (Fb) and modulus of elasticity (E) values than solid-sawn lumber, allowing greater spans or heavier loads for the same nominal depth.
Why the other options are wrong
- A. LVL is graded separately with its own engineered design values, not the visual grading system.
- B. Fastener count depends on connection design, not the material span capability.
- D. LVL is not necessarily lighter; the span advantage comes from strength, not weight.
Engineered Lumber (LVL) Span Capacity
LVL is manufactured from layered wood veneers bonded together, producing higher and more uniform strength values than solid-sawn lumber of the same size.
- Higher allowable bending stress (Fb) and stiffness (E)
- Defects distributed/minimized through veneer lamination
- Commonly used for headers, beams, and long-span joists
Memory trick: 'Layered lumber, less flaws, longer haul.'