MASS TIMBER STRUCTURES

Carbon 12.

Origine.

Bullitt Center.

World Innovation Design Center.

Kiln Apartments.

What do these names all have in common? Can you guess? Yup, they’re all buildings. But again, one other thing they have in common is - yeah, you got it: wood. Not just was wood used in their construction, but these are all existing mass timber structures.

What is Mass Timber Design/Construction

Wood has always been featured in construction for a very long time. However, it seems that more recently, there’s been a massive shift among modern architects and engineers into wood construction more than ever. In fact, statistics reveal that about 90% of American homes today are built with wood.

Wood is now more valued than at any other time for its aesthetic qualities, strength, durability and sophistication. It offers a great alternative to steel and concrete construction, especially since it has strength, can bear heavy loads, and yet is lighter in weight than its alternatives.

Mass timber design is a more recent development to wood construction, as against light-frame wood construction. This innovative design technology that is revolutionizing America comprises of gluing or nailing multiple wood products together and forming layers to be used for roof, wall and floor construction.

The products used in mass timber comprise of exceptionally thick, compressed wood layers that creates strong structural elements which are then made into panels.

Mass timber construction is gaining more and more traction since it is environment friendly and low in its carbon footprint, in contrast with other building materials and systems. Mass timber construction is achieved through a number of procedures including lamination, using fasteners or adhesives.

Mass timber can function as a complement to light-frame and hybrid construction. And unlike its concrete and steel alternatives, mass timber constructions do not follow any standard template but rather opens a wealth of creative options, allowing for more flexibility.

Mass Timber Construction Systems / Methods

Cross laminated Timber

Cross-laminated timber

Source: USDA

The US seems to be taking a cue from Europe in using CLT for building as more and more buildings incorporate this technique. Used in mid- and high- rise buildings, the CLT is a strong, stable and dimensional wood panel system.

Nail - Laminated Timber

Talk about a renaissance of an old-time construction technique and NLT pops up. Found in historical buildings as well as modern structures, the NLT features elegant designs and great structural performance.

Dowel - Laminated Timber

An all-wood composition, DLT is much easier to use than other mass timber methods since it uses Computer Controlled Machinery (CNC) including routers, mills and lathes. Unlike NLT, DLT uses wood dowels in lieu of screws and nails to join boards.

Glue - Laminated Timber

Commonly used for beams and columns, glulam is mostly used in residential and commercial structures. Its aesthetic curvatures and long spanning, exposed framing, makes it a favorite among construction experts.

Other mass timber systems include laminated strand lumber (LSL), parallel strand lumber (PSL), and laminated veneer lumber (LVL).

Mass Timber and Tall Wood Construction

Skyscrapers and high rise buildings are pretty famous, aren’t they? Yet it seems their wooden counterparts aren’t as common. Why’s this, you’re probably wondering.

Well, let’s just say that before this time, they were kinda like restricted. There was a limit to the height wood buildings could go, owing to various reasons, including the strength ratio of light-frame wood structures.

However, the International Code Council (ICC) approved tall buildings to become part of the 2021 International Building Code (IBC) in 2019. The provisions of the new regulations will be discussed later in the article.

What are Tall Wood Buildings?

Because they are in continuous evolution and continue to rise higher and higher, it is pretty difficult to put a tag on then. However, tall wood buildings are just that - wood buildings that have some good height; and this could be anywhere from six stories up to 18 stories. Who knows, maybe pretty soon there will be taller wood buildings in the near future.

Some of these tall buildings, especially the ones with fewer stories, are those completely constructed with mass timber or light-frame systems, while the ones which rise to heights of eighteen stories and above mostly incorporate hybrid systems comprising of mass timber, concrete and steel components.

There are various ways mass timber could be used for construction purposes such as:

1. Hybrid Construction:

Here, mass timber is combined with steel and concrete to improve building performance and sustenance.

2. Tall wood construction:

This mostly refers to mass timber structures that are high enough, and with new building codes in their favor, there are more mass timber buildings springing up all over the country.

3. Overbuilds and infills:

When additional stories are added to an existing building, mass timber overbuilds are used. Whereas infills are required when developing vacant lots surrounded by other existing structures.

Regulations Affecting Tall Wood Buildings

As mentioned earlier, the ICC recently approved some proposals that incorporate tall wood buildings as part of the 2021 IBC. This development has provided for three new construction types:

1. Type IV - A: this type of buildings require that all mass timber components used in the building must have non-combustible protection. The maximum limit for this construction type is 18-stories.

2. Type IV - B: this type allows exposure for only a limited area of mass timber walls and ceilings. It can have up to 12-stories.

3. Type IV - C: for this construction type, all mass timber elements are permitted to be exposed, excluding shafts, and these mass timber elements must be at least two-hour fire resistant. The maximum height limit for this construction type is 9 stories.

Fire Safety in Wood Buildings

When fires start, they are no respecter of buildings, or building materials for that matter. Fires can start in wood, steel or concrete buildings. However, given the combustibility of wood, it may seem easier for fires to consume wood buildings.

Amazingly, this is not necessarily the reality. The building code's requirements for fire safety and protection are the same for all building types and systems, the material used inconsequential.

An average of 90% homes in the US are built with wood or wood components and since 2009, the incidence of structure fires have massively declined when tracing back forty years down the line.

Wood construction has maintained a record for having reliable safety and fire protection systems. Also, the use of sprinkler systems, fire-resistance walls, etc, all reduce the incidence of fires in wooden structures. In fact, in about 96% buildings with sprinkler protection, fires were successfully contained to just one room.

A CLT 7-inch thick wall was fire tested and lasted over three hours, which is an hour longer than the requirements of the building code.Mass Timber buildings are really the new rave and are also sturdy, safe and versatile.

Furthermore, they are relatively predictable when it comes to fire exposures, and have an added aesthetic value. What other convictions do you need about building or revamping your home to incorporate wood?

Let’s get the job done for you! You can speak with our professionals at JPC Design Consortium to get you started on the design of your wooden building today. We also give consultation services just in case you’re not so sure yet. Contact us right away.