Engineered Timber Construction

Engineered Timber Construction

Since the introduction of plywood and glued-laminated timber (glulam) beams more than a century ago, engineered timber has continuously progressed to provide greater strength, versatility, consistency, and many other attributes.

Today, the engineered timber construction category encompasses oriented strand board (OSB), strand and fiber siding, laminated strand lumber (LSL) I-joists, laminated veneer lumber (LVL), and mass timber products.

These building materials allow longer clear spans, greater energy efficiency, and faster, more economical construction.  In commercial construction, four- and five-story wood office buildings are common, with the tallest wood buildings now reaching 20 stories.

As customer tastes change and building requirements allow wider use of timber in building construction, engineered timber products find more applications in Type 1 (fire-resistive), Type 3 (ordinary), Type 4 (heavy timber), and Type 5 (wood-framed) buildings. Some of the latest trends in repurposing old warehouses and large retail stores into light manufacturing and office spaces incorporate many engineered timber products.

These materials are often specified for schools, warehouses, restaurants, and hotels in features such as:

1. panelized roofs;
2. concrete formwork;
3. diaphragm assemblies to resist wind and earthquake loads; and
   noise- and firer-rated assemblies.

Engineered timber products are manufactured by cutting, peeling, or stranding to make various shapes and sizes. These pieces of timber are then bonded back together using exterior adhesives to make panels or beams. This manufacturing process improves the products’ strength and stability while reducing variation and defects.

In the course of this manufacturing process, increased durability, fire resistance, and radiant insulation can also be added to the products.

Engineered timber materials offer many advantages over traditional designs, including:

1. exceptional strength and consistent dimensions, with much less shrinking, warping, and cupping than traditional lumber;
2. better structural values providing longer spans or more efficient use of the material—typically, defect dispersion and removal reduces the natural variability of timber, while the selection and orientation of the engineered wood elements drive higher structural values;
3. moisture contents representative of the interior conditions of finished structures, meaning more dimensional stability and less trapped moisture in walls and roofs;
4. long lengths and wide widths to reduce the number of pieces purchased and handled in construction, with dimensions customizable in many cases to meet specific needs on the jobsite;
5. straight lengths with defects removed or dispersed to reduce jobsite waste (a purchased unit should allow 100 percent utilization);
6. and more sustainable and environmentally responsible qualities, as many engineered wood products are made from smaller, sustainably sourced trees rather than from large, old-growth trees, and the manufacturing process uses the entire log, including the bark and sawdust for energy.

There may be more credits for timber-based materials when assessing compliance with green building codes.