Two weeks ago, we welcomed Ian Robertson of AA ROBINS architect to Construction Tech Tuesday to talk about the six PHlavors of mass timber. Some may find this hard to remember, as it occurred during the dark times during the year we dare not name. Others may find it difficult to totally recall since Ian didn’t walk us through the subject, so much as he sprinted, masterfully navigating his way through 134 slides in just under 30 minutes.

It was PHast. It was PHurious. It was like a lightning round where Ian was competing against himself.

It was great, and we captured it all in this video:

Here are a few key takeaways:

What Are the PHlavors of Mass Timber?

Although Ian used six different kinds of mass timber in the Blindheim Passivhaus, which is the subject of the presentation and also his first Passive House and mass timber project (what chutzpah!), he also noted that there are at least another three kinds of timber that he did not use, though availability may be limited.

The 6 types of mass timber used in Blindheim Passivhaus:

Three types of mass timber not used in the project:

How Many PHlavors Should I Choose?

Different kinds of mass timber have different properties that make them more appropriate for use in given circumstances (see Ian’s presentation). A knowledge of their properties helps determine which one will be the best fit.

However, although some types of wood are more appropriate than others given their intrinsic qualities, Ian noted that there are downsides to getting too exacting about picking that perfect piece of wood. Sourcing a single beam for a project is not going to be cost effective. Moreover, obtaining additional kinds of mass timber may require coordinating with additional suppliers, which can adversely impact scheduling, especially if the project requires meticulous sequencing.

Mass Timber Buildings Are Not Bonfires Waiting to Happen

One of the final issues in the after-hour session that came up concerned fire safety. Mehrdad Jahangiri of Aspect Structural Engineers and cohost Kevin Brennan, a New York City firefighter, expressed their frustration over the common misconception, even among firefighters, that mass timber is a fire hazard. This is not accurate. There are codes that ensure the safety of mass timber buildings. Furthermore, mass timber is actually safer than steel or concrete construction in some applications (see below).

Fire safety and mass timber construction.


Jay Fox
Jay Fox
Jay Fox is a writer and musician based in Brooklyn. His work has appeared in Crain's New York, Salon, Stay Thirsty Magazine, Aethlon, and…

Weekly Newsletter

Get the latest passive house news, trends, & insights delivered straight to your email inbox.