As I write this, I am sitting inside a warm office in Northern Ontario, looking out the window at near blizzard conditions, with heavy snow falling and –35° wind chill. Although it is very unpleasant outside, this isn’t necessarily unusual weather for this location, but what is unusual is that just a couple of days ago it was several degrees above freezing and felt more like a spring day. In many parts of the world, it has become common to see weather extremes that have rarely, if ever, been seen before. Recent weather extremes that come to mind include several feet of snow falling in western New York prior to the NFL playoff game, flooding in California, increased tornado and hurricane activity, and extreme heat events in British Columbia and parts of Europe last summer. Regardless of the cause, although my belief is that it is largely human caused, all indications are that we will continue to experience conditions that have not been part of our lives in the past.
How does this pertain to truss design? Well, as an example, here in Canada it generally isn’t necessary to design for wind loads on residential buildings. Personally, I’ve always found it strange that our code bodies essentially say that we could design two small identical buildings, sitting side by side, with one residential and the other some type of commercial use. The commercial building would need to be designed for both heavier design snow loads and wind loads, while the residential building would have lower snow loads and no wind load. Does the wind know not to blow on the house? Does the snow pile on the roof differently because there is a business operating inside rather than a family?
I do understand that code decisions are made in part in an effort to balance safety and affordability. Building homes that resemble bunkers capable of resisting every type of extreme weather condition would be expensive, and might result in some very ugly, utilitarian dwellings, but making homes more resilient could be accomplished at minimal incremental cost. In areas such as where I live, snow loading would continue to be the governing condition in almost all circumstances, but including proper anchorage of the roof to the walls, and on down to the foundation, would reduce damage due to wind.
We all work in a competitive environment, so unilaterally deciding to add wind analysis or unbalanced snow loads to the projects we quote could result in being uncompetitive versus our competitor who is doing only what the code requires. To be clear, designing only to the code requirements is not wrong. I have had building owner clients ask how they could improve their home’s performance related to the roof and these are some things that I would typically suggest:
- Design the roof for wind or at least require that hurricane ties of some type be installed.
- Increase the heel height if necessary to allow for full depth insulation, along with ventilation space above, to extend to the outside walls.
- If you are concerned about snow accumulation, design for unbalanced snow loads.
Each of these will change the truss package price somewhat, and ultimately the person writing the checks gets to decide. As I am beginning to plan for the construction of my own home, you can be sure that I will include all of these suggestions into my own home. Is it overkill? Maybe, but I plan to be in that home for 20–30 years, and I want to be confident that it will perform well even in the extreme conditions that seem to be more commonplace each year.
What are your thoughts? Is this something that you hear your clients talking about? Do you offer any type of truss package upgrade suggestions to your customers? How proactive do you think the various code bodies should be in addressing this changing world that we are living in, especially considering that getting code changes in place can often be a 5–10-year process? Please share your thoughts with me.