Glued laminated timber, better known as glulam, is one of the oldest engineered wood products still manufactured at scale. It is made by bonding layers of dimension lumber with structural adhesives so a finished beam can span distances that solid sawn lumber of the same cross section cannot. Demand for the product has climbed steadily as architects and builders look for alternatives to steel and concrete, and that demand now reaches well past commercial towers into residential work, including homebuilding in New Hampshire’s forest towns. When a forest products company pays $12 million for a glulam plant plus $2.5 million in inventory, the deal says something about the category: engineered wood has moved from niche to mainstream.
What Glulam Is and How It Is Manufactured
Glulam starts as ordinary dimension lumber, typically 2x4s and 2x6s, that has been dried, graded, and selected for stiffness and strength. The individual boards are called laminations. Their ends are finger-jointed to create long continuous pieces, then the faces are coated with structural adhesive and stacked in a press. Pressure and heat bond the layers into a single member that behaves as one piece of wood.
The result is a beam that can be manufactured straight or curved, in depths up to several feet, with strength that rivals steel in many bending applications. Because the laminations are sorted by grade, the strongest material can be placed where the stress is highest. The product performs equally well in humid coastal climates and dry interior regions, which is why it shows up everywhere from ski lodges to homes in Louisiana’s forest country.
From Sawmill to Press: The Lamination Process
- Lumber is dried to the target moisture content, usually below 15 percent for structural grades.
- Boards are graded by stiffness and strength, then defects are cut out.
- Ends are finger-jointed and glued to reach full beam length.
- Adhesive is applied to the faces of each lamination.
- The layup is pressed under controlled pressure until the bond cures.
- The cured beam is planed, trimmed, and stamped with its grade mark.
Wet-Use and Dry-Use Adhesives
Adhesive selection determines where a beam can be used. Dry-use adhesives are limited to protected interior applications where the wood stays below about 16 percent moisture content. Wet-use adhesives, qualified under ASTM D2559, hold up in exterior and unprotected conditions. A beam stamped for wet use can sit in the weather during construction and serve outdoors for decades.
| Step | What happens | Why it matters |
|---|---|---|
| Drying | Lumber is kiln-dried to 15 percent moisture or less | Prevents warping and adhesive failure |
| Grading | Boards are sorted by stiffness | Strong material goes where stress is highest |
| Finger-jointing | Ends are glued to reach full length | Removes length limits |
| Adhesive application | Faces are coated with structural glue | Creates the bonded section |
| Pressing | Layers are clamped under pressure | Forms one solid member |
| Finishing | Beam is planed and stamped | Provides the grade mark inspectors require |
Why Mass Timber Demand Is Growing
Glulam is part of a family of engineered wood products grouped under the mass timber label, along with cross-laminated timber (CLT), nail-laminated timber (NLT), and dowel-laminated timber (DLT). What they share is the ability to carry heavy loads in large panels and members. The 2021 International Building Code added three new mass timber construction types, allowing wood buildings up to 18 stories, and that change unlocked a wave of mid-rise and high-rise projects.
The Performance Question
Engineered wood keeps getting compared with steel and concrete on fire resistance, span capability, and cost, and the green product performance myth resurfaces in almost every conversation. The evidence says otherwise: heavy timber chars at a predictable rate, which gives it dependable fire resistance, and its strength-to-weight ratio lets designers span large open areas with less foundation mass.
Carbon and Life-Cycle Accounting
Mass timber also changes the carbon math of a building. Trees store carbon, and manufacturing glulam and CLT uses far less fossil energy than producing steel or concrete. A typical mass timber building can cut embodied carbon by 25 to 45 percent compared with a concrete frame of the same size, before accounting for the carbon stored in the wood itself.
| Product | Form | Typical spans | Common uses |
|---|---|---|---|
| Glulam | Bonded lumber laminations | 20 to 100+ feet | Beams, columns, curved arches |
| CLT | Crossed layers of panels | 10 to 40 feet | Floors, walls, roofs |
| NLT | Nailed lumber layers | 10 to 20 feet | Floors, roofs, decking |
| DLT | Dowel-connected lumber | 10 to 30 feet | Floors, walls |
| LVL | Veneer laminations | 20 to 60 feet | Headers, beams, rafters |
Glulam Grades and Specification Basics
Specifying glulam means choosing a combination symbol, an appearance grade, and a species group. The combination symbol describes the design bending stress and the grade of the outer laminations. Appearance grades run from Industrial, for concealed framing, to Architectural and Premium, where the beam is left exposed as a design feature.
Reading a Glulam Specification
A symbol such as 24F-V4 tells an engineer three things: the beam is designed for 2,400 psi bending stress (the 24F), the outer laminations are visually graded (the V), and the visual quality level is 4. E-rated beams, such as 24F-1.8E, use mechanical testing to sort the material instead of visual inspection, which lets manufacturers use more of the log.
Combination Symbols Explained
| Symbol | Bending stress | Grading | Typical use |
|---|---|---|---|
| 24F-V4 | 2,400 psi | Visual, western species | General beams and columns |
| 24F-1.8E | 2,400 psi | E-rated, Douglas fir | Long-span roof beams |
| 24F-V8 | 2,400 psi | Visual, Douglas fir | Exposed architectural beams |
| 20F-V3 | 2,000 psi | Visual, southern pine | Industrial framing |
Species choice is a regional decision as much as an engineering one. Douglas fir glulam is common west of the Rockies, southern pine east of it, and spruce-pine-fir where those species dominate. The same logic applies to development projects in forested regions, where using the locally available species cuts both cost and delivery time.
The Business of Glulam: Capacity, Costs, and Supply
A mid-size glulam plant illustrates the economics of the product. One manufacturer operates two plants with a combined capacity of 35 million board feet on a two-shift basis, and produced 13 million board feet on a single shift with about 60 employees. That run works out to roughly 217,000 board feet per employee per year, and it uses only about 37 percent of the two-shift capacity, a gap that shows how much slack can exist in the industry when demand softens.
What Capacity Numbers Tell a Buyer
Capacity figures matter because glulam is made to order more often than it is stocked. A plant running at one third of capacity can quote short lead times; one running near its ceiling cannot. Buyers should ask what utilization the quoting plant is actually running at, not what its nameplate capacity says.
Single Shift vs. Two Shifts
A second shift nearly doubles output but brings higher labor costs, more supervision, and less downtime for maintenance. Manufacturers add shifts when order books justify it and drop them when they do not. The swing between 13 million and 35 million board feet in the same plants is a reminder that published capacity is a ceiling, not a promise.
Glulam also competes for raw material with every other product that uses sawlogs. The forest products supply chain that feeds decks and fences draws from the same timber, so a boom in decking can tighten the log supply available to laminators.
How to Evaluate a Glulam Supplier
With mass timber demand growing, not every supplier can deliver. A few checks separate a reliable partner from a quote that disappears when the schedule tightens.
Questions to Ask Before You Order
- Is the product manufactured under ANSI A190.1 and stamped with an APA trademark?
- Is the adhesive rated for wet use if any part of the beam will be exposed?
- What species and combination symbols does the plant actually produce?
- What is the current lead time from approved shop drawings to delivery?
- Does the supplier provide layout and connection drawings?
Lead Times and Inventory Buffers
Glulam lead times commonly run four to eight weeks for custom members, longer for curved or premium-grade pieces. Firms that plan purchases around the calendar avoid the worst of the wait, and the discipline pays off the same way revenue discipline pays off for large forest products companies: steady orders get better service than emergency ones.
Putting Glulam to Work on Your Project
Glulam earns its place when a design needs long clear spans, curved members, or exposed wood ceilings. It costs more per foot than solid lumber and less than fabricated steel in most cases, and it installs with standard crane and rigging equipment.
Handling and Installation Rules
- Lift beams with wide fabric slings, never chains or wire rope that can crush the corners.
- Support the beam fully during lifting to avoid twisting.
- Pre-drill bolt holes at the spacing shown on the shop drawings, keeping holes at least five diameters from beam ends.
- Use hot-dipped galvanized or stainless connectors in exterior applications.
Storing Glulam on Site
Store beams flat on blocking, off the ground, and covered so rain does not pond on the surface. Wet-use beams tolerate exposure, but keeping them dry protects the finish and prevents checking.
Timing the delivery is part of the plan. Understanding how lumber and engineered products reach the jobsite helps a builder schedule the crane, the crew, and the inspection in the right order, so the beams go up the week they arrive.