What’s New with Mass Timber Buildings?
Every three consecutive years, the California Building Codes (CBSC) updates its regulations and standards for developers and architects that must cohere to when designing a structure as well as when it's being built. And a month ago, the CBSC updated its regulations and standards for Mass Timber Buildings. Within the past couple of years, the International Building Code (IBC) only allowed for five stories of wood-frame construction in residential occupancies and six stories for business occupancies. But for the first time in 95 years, construction for mass timber buildings is now allowed to build up to 18 stories tall in California. What does this mean? This will allow for increased square footage and present clear guidelines for architects working with the material; minor incentive, but there are many other benefits for mass timber building construction for residential and business occupancies.
So, what is mass timber (structural timber)? It is engineered wood or manufactured wood that includes a range of similar wood products that bind or fix the strands, particles, fibers, veneers, and boards of wood, together with adhesives to form a composite material. Usually, the softwood is replicated to stick together and comes from conifers like spruce, fir, or pine and deciduous species like ash, birch, and beech to form larger pieces. There are a variety of products consisting of mass timber: glue-laminated (glulam) beams, laminated veneer lumber (LVL), nail-laminated timber (NLT), dowel-laminated timber (DLT), and cross-laminated timber (CLT). If you think about it, various engineered wood products are used in different variations or applications, from industrial products to home and commercial construction, because they are moisture resistant and durable.
So, what decreased mass timber construction for the past 150 years? In the 1800s, every building was mass timber due to its quick access and handling. But during the Great Chicago Fire of 1871, wood became seen as unsafe and unstable throughout the construction industry worldwide due to the many buildings lost and over 300 lives lost. And it substantially changed the construction industry and maneuvered the change from mass timber to concrete and steel. This change then transpired in the IBC and CBSC, allowing wood-frame construction to only span up to five stories.
Since the 2000s, mass timber construction began repopulating Europe and Austria. To date, the world's tallest mass timber structure, spanning 18 stories high and over 280 feet, was built in Norway in 2019, proclaiming the advantages of this type of construction. What would be the advantages for California now that CBSC has updated its regulations and standards? Simple. Mass-timber will significantly reduce greenhouse gas (GHG) emissions throughout the building sector and decrease waste, pollution, and associated construction costs, while simultaneously creating more physical, psychological, and aesthetically healthy and pleasing built environments. With extensive testing throughout the past 20 years, mass timber products such as LVL, NLT, DLT, Glulam, and CLT have begun to cater to many advantages. Below is a quick list of why your next Project should consider mass timber construction.
o Performance in fire
Solid, large, compressed masses of wood are difficult to ignite due to the outer layer of mass timber. It will allow for the fire to char a predictable amount while at the same time effectively self-extinguishing and shielding the interior of the wood, allowing the mass to retain its structural integrity for several hours, especially in an intense fire.
o Reduces carbon emissions
Exchanging concrete and steel to mass timber avoids high GHG emissions compared to concrete or steel, which account for 8% of GHG emissions.
o Mass timber is remarkable in earthquakes.
o Buildings are constructed faster due to reduced labor costs and less waste.
o Mass timber Projects can maintain close control of construction outcomes to eliminate the need for corrections in the field and better coordination between consultants.
o It helps pay for good forest management on public land in the long run.
o Create jobs in rural areas
o Aesthetically pleasing
o Design flexibility
In previous CBSC codes, mass timber reduced structure exposure and limited Project types. But with this new update, Type IV-A, IV-B, and IV-C timber elements do not require residential or businesses to be covered to meet code, except for concealed spaces, exterior walls, and shafts. This is major! It will continually reduce the need for materials and labor costs demanded to meet fire resistance requirements. This new revision in code will significantly impact mid-rise and high-rise Projects like multi-unit housing. Think of the possibilities this can open within a design. Mass timber will become the horizontal and vertical finish material offering biophilic benefits ranging from natural beauty, warmth, and positive economic impacts.