Engineered wood products have older roots than most builders realize. Evidence of laminated wood survives in the tombs of Egyptian pharaohs, proof that the idea of slicing boards and bonding them into something stronger than the original tree is thousands of years old. Masonry chimneys develop horizontal chimney cracks when thermal cycling and settlement outpace the flexibility of mortar, and engineered wood components are designed to absorb that kind of movement instead of cracking. The same principle, controlled lamination, now drives plywood, glulam, I-joists, LVL, and cross-laminated timber into projects that once belonged to steel and concrete. Builders are leaning on these products for single-family homes and for apartments, schools, warehouses, restaurants, hotels, and other multi-story structures, and the material is still finding new ground.
From Ancient Lamination to Modern Mills
Plywood was patented as a U.S. construction material at the close of the Civil War, and the industrial advances that followed produced glued laminated timber, wood I-joists, laminated veneer lumber, and the rest of the engineered family. Each product solves a problem that solid lumber cannot: wider spans, straighter floors, and larger members from smaller trees. The result is a material that is often stronger and more uniform than the wood it starts from.
How engineered products are made
Manufacturers peel, saw, or plane wood into veneers and lamellas, dry them to a tight moisture range, and bond them under heat and pressure. The grain of each layer runs in a controlled direction, which distributes loads and cancels the warping and splitting that plague a single wide board. For horizontal elements such as floors and roofs, builders now weigh wood I-joists against pouring concrete, and the comparison usually turns on weight, speed, and labor.
| Product | What it is | Typical use |
|---|---|---|
| Plywood | Cross-laminated veneers | Sheathing, subfloors, walls |
| Glulam | Bonded solid lamellas | Beams, columns, roofs |
| I-joist | Flanges plus web | Floor and roof framing |
| LVL | Layered veneer lumber | Headers, beams, rim boards |
| CLT | Cross-laminated panels | Walls, floors, mass timber |
The list keeps growing. Structural composite lumber and large-section sawn timber extend the family into the tallest wood buildings, and the same manufacturing logic, slice, dry, bond, applies at every scale. What changes with scale is the engineering: a panel that carries a whole wall needs tested connections, not just tested lumber. Sawn timber in large sections still holds a place for columns and heavy framing where a single piece is simpler to detail, and hybrid designs mix products: CLT floors on glulam columns with LVL headers at the openings.
Code Revisions Open Doors for Tall Mass Timber
Building codes across North America already recognize EWP in four- and five-story wood-frame construction, and recent changes go further. Oregon became the first state to allow timber high-rises taller than six stories without special consideration, and British Columbia adjusted its codes to permit 12-story wood buildings. At the national level, the International Code Council has proposed three new categories of wood construction with fire safety, height, and area requirements for tall mass timber buildings up to 18 stories.
What the proposed categories change
- New Type IV subcategories keyed to height bands
- Fire safety rules for exposed timber and protected members
- Height and area limits set by occupancy and sprinkler protection
- Clear pathways for CLT, SCL, glulam, and large-section sawn lumber
Design teams watching the code calendar can plan projects that were impossible a decade ago. The ICC vote that moved these changes forward is covered in detail by the trade press, and the direction of travel is clear: taller, denser wood buildings with the same fire safety as concrete and steel.
The economics push in the same direction. Wood buildings go up faster because components arrive precut and prefabricated, and faster erection cuts financing costs on large projects. Developers in British Columbia cite both the carbon story and the schedule when they choose wood over concrete, and the code changes followed the demand.
Structural Performance: Fire, Seismic, and Loads
Mass timber earns its height the hard way, in fire tests and shake tables. During a fire, exposed wood forms an insulating char layer while the core keeps its design values, so a heavy timber member continues to carry load long after unprotected steel would soften. The high strength-to-weight ratio lets architects design earthquake-resistant structures without the mass that magnifies seismic forces. Char behavior is only half of the fire story; the connections get tested too, because a building is only as fire-safe as its least protected joint.
Why lighter structures cost less to support
A recently built heavy timber office building in Minnesota weighed roughly one-fifth of a comparable concrete structure, which cut foundation and transportation costs in proportion. Lighter buildings need smaller footings, fewer piles, and less trucking, and the savings pay for the engineered members. Framed buildings with shear walls subjected to horizontal and vertical load perform predictably when panel thickness, nailing, and hold-downs match the design, and mass timber panels bring that same predictability at a larger scale.
Char layer behavior
The char rate is predictable and testable, which is why fire design for exposed timber is now a calculation instead of a guess. Engineers assign a sacrificial thickness, and the member is sized so the remaining section carries the design load for the rated time. The same logic underpins the 18-story proposals: the taller the building, the more precisely that calculation has to be documented.
Tall Walls, Long Spans, Open Spaces
Airports, arenas, gymnasiums, lobbies, and corridors want the same thing: tall walls, long spans, and few intermediate supports. Engineering advances in EWP deliver that openness, and the dimensional stability of engineered members lets them carry glass and interior finishes that demand a flat, quiet substrate.
Glulam roof systems
The redesigned Mactan-Cebu International Airport used about 14,764 cubic feet of glulam to form the barrel shape of its roof, the first roof structure in Asia made entirely from the product. The curves read as architecture, but they are engineering: each lamella follows a computed radius, and the connections transfer thrust without visible columns. The airport also demonstrates the appeal of EWP for owners who want a memorable interior, not just a covered one.
Concrete structures control cracking by placing horizontal reinforcement at the outer layer of a wall, where tension is highest. Glulam and CLT solve the same problem differently: every lamination acts as a layer of reinforcement, and cross-lamination stops cracks from running through a panel. Both approaches work; the difference is that the wood version is prefabricated to tight tolerances and arrives on site ready to lift.
The span tables tell the story. Where a steel frame might need a truss every 20 feet, a glulam arch can carry the same roof on fewer supports, and the open plan below rents at a premium in arenas and banquet halls. Engineers price both options, and the wood solution wins often enough that the product pipeline keeps growing.
Retrofits and Utility Upgrades in EWP Buildings
Engineered members are precise, and they punish field improvisation. Cutting a notch in an I-joist flange or drilling a web beyond the permitted grid can drop a floor capacity overnight. Owners and contractors should pull the manufacturer modification chart before any utility run and route plumbing and conduit through designated openings.
Field modifications: what to avoid
- Never cut or notch I-joist flanges; run pipes through web openings only
- Keep holes within the manufacturer size and spacing grid
- Support concentrated loads with bearing stiffeners at the point of load
- Get an engineer sign-off before altering LVL or glulam members
- Document every penetration for the next remodel
Underground work follows the same logic. Trenchless technology such as horizontal directional drilling installs utilities without disturbing finished slabs, so a basement remodel in a wood building can gain new plumbing without cutting the floor structure that engineered members protect. The less the structure is touched, the more of its rated capacity it keeps.
Movement and Long-Term Performance
Every building moves, and the best assemblies move on purpose. Engineered wood handles moisture swings with predictable expansion and contraction, while rigid materials transfer the same movement into cracks. The repair of horizontal chimney cracks is a case study: mortar fails because it cannot follow the building, and the fix starts with understanding what moved and why before anything is repointed.
Planning for movement and moisture
Good details give wood room to breathe: vapor-permeable wraps, ventilated cavities, and flashing at every horizontal surface. Engineered members arrive at a tight moisture content, and keeping them dry on site, off the ground and under cover, preserves the straightness that makes them valuable. Wraps and flashings also protect the connections, because concealed corrosion in a hanger is harder to find than a stain on a board.
The horizon for EWP is measured in stories, not years. With code paths opening to 18 stories and material weight at a fraction of concrete, engineered wood is positioned for the densest construction North America has attempted with timber, and the manufacturing base to supply it is already expanding.