Proper Snow Loads – Presentation from NFBA Expo 2020


UPDATED AFTER EXPO: These are the slides as shown at the at the NFBA Expo in Des Moines, IA on Feb. 27, 2020: Proper Snow Design Loads for Post Frame Buildings. The Winter Snow Accumulation Maps are the pages I had scrolling at the beginning of the talk while we talked about probability and coin tosses to get through the next 50 years.

Thank you to all who attended this presentation and for the feedback received after the presentation. I am sorry I didn’t leave enough time to get through questions and dialogue. If you have feedback for me or questions, please reach out to me!

Although I didn’t mention this during the presentation, the title of this presentation could have been truncated to just Proper Snow Design Loads and still been appropriate for most buildings. Also, I may post additional information here in the future on the Snow Load simplification recommended within the presentation.

What should building inspectors be using as their reference point?

Should the building inspector for your project be comparing the construction they see on site to the building code requirements or to the construction plans which were reviewed and approved before construction begins?

In Wisconsin, the commercial building inspections as described in SPS 361 include the state approved plans, the conditional approval letter, AND the state building code.  In the International Building Code administration chapter (not adopted in Wisconsin), the building code is NOT listed as part of the inspection criteria, instead referring only to the approved plans and the approval documents.

This seemingly small difference between inspecting to the approval documents PLUS the code vs. the approval documents alone, has a potentially HUGE difference to the impact of inspections and the cost of building code compliance for building owners, builders, and the design professionals involved in the projects.

I recently recommended a change to SPS 361 that would improve the current situation by bringing Wisconsin’s building inspection scope in line with the International Building Code’s intent for the administration of the Commercial Building Code to each project.

If the building inspector is going to be given plan review and building code interpretation authority for the project, they should be required to do that work and provide their input before construction begins.  Under the current system, the building plan reviewer’s “conditional approval” is really not an approval at all, but more like a letter documenting an “no obvious reason for denial… at least for now”.

With this situation on the ground in the state’s construction industry, why would builders, owners, and design professionals even be required to wait for such a department “approval”?  The approval seems to be a non-binding decision by DSPS which offers no peace of mind nor risk-mitigation to the building owner and project stakeholders.  It leaves open the real possibility the project may face costly changes to the project after the building inspector shows up with a different code interpretation or finding.  In my experience designing hundreds of buildings in the state over the past 18 years, this doesn’t happen a majority of the time, or even commonly, but it has happened a few times to me, and when it does happen, the impact has always been significant, inconvenient, costly, and regrettable.

Check out my recommended change to the state administrative language and consider sharing this information with your state legislators, especially now while other changes to the DSPS administrative code are also being considered:

Recommended change to Wisconsin SPS 361

New Project Schedules and WI State Plan Reviews


As of Feb. 15, 2020:

Next available engineering START date, standard speed:  April 13, 2020

Next available engineering START date, RUSH speed: March 30, 2020

Next available State Plan Review date: roughly, sometime in May (see comments below)

There are a lot of things changing within the Wisconsin commercial building submittal process this spring.  A legislative bill aimed at reducing wait times for the Department of Safety and Professional Services (DSPS) plan review and approval of commercial buildings has been introduced in Madison.  DSPS also is in the process of transitioning to a new system of for project scheduling, management and invoicing known as eSLA .

Depending on the timing of the implementation of eSLA and the success of the legislation, the scope of building plan reviews could change significantly this year and in ways maybe not predictable at this point.

At this time, we are requesting plan review appointments for our projects as normal and then being told that the plans may be reviewed BEFORE the scheduled plan appointment date, but that they will not consider rescheduling the initial plan review appointments to an earlier date until the plans are submitted.  As far as I know, they (DSPS) have eliminated the Priority Plan Review option for double fees and a 10 day turnaround, but they are trying to reduce the time wasted on moving projects around, duplicate plan review requests, and trying to reduce the lead time for ALL projects by prioritizing plan reviewer’s efficiency in making sure they have “complete” plan submittals to work on each day instead of looking at partially completed submittals that barely get turned in on time.

Internally, project work load has picked up SIGNIFICANTLY this 2020 calendar year.  I have posted availability dates above and will try to keep these dates updated as we get into the spring season, as well as correct or add to the DSPS updates as I receive them.

2019 Snow Collapses: It’s not just “Ag” buildings

The snow over the weekend hit a large portion of Minnesota and sections of the Dakotas with its deepest snow fall measurements.

This past weekend’s snowfall total

I enjoyed many discussions last week with friends and colleagues at the NFBA Expo in Louisville about many different topics. One topic heavy on my mind and heart was and is the heavy snow loads we’ve been experiencing in the Upper Midwest this winter causing building collapses. A common response I heard is that this is, as it has been in the past, primarily an issue causing problems in non-engineered or “code exempt” buildings, but a look at headlines from problems this past weekend clearly indicates there are other buildings meeting their match:

“The Latest: Heavy snow causing numerous structural concerns”

From the LaCrosse Tribune

Heavy Snow Causes Upper Midwest Roofs to Collapse

From US News & World Report

I don’t know the statistics of what percentage of buildings having structural failures this winter were built to comply with a certain building code, nor how many had a licensed engineer involved in their design (which is a different question), nor how many had a licensed engineer or other qualified designer inspect the completed building to verify the construction was properly done (which is another different question), but I see in the headlines today that snow, gravity and structural forces is impartial to the nature of a building’s use and also to what type of building code may apply to it. Indeed, as some engineers have joked for awhile when discussing Commercial Snow Loads, does “commercial snow” know the difference in what type of building it is landing on?

Bottom line: if the load applied exceeds the load capacity of a structure, the structure will have a problem.

One concern growing larger in my mind since Wisconsin adopted the IBC and ASCE 7 requirements in 2002 (when I began my Engineering consulting business), is that even “code compliant” buildings using ASCE 7 (Minimum Design Loads for Buildings and Other Structures) may be “under-designed” for the amount of snow our buildings are actually experiencing, and this on a recurrence interval much shorter than the 50-year interval which ASCE 7 is supposed to be based upon.

A Fire & Rescue truck rendered “out-of-service” due to a building collapse.

In White Lake, Wisconsin, the fire department building collapsed due to snow. Because of the critical role fire departments serve in keeping a community safe, they are supposed to be designed to a higher safety factor than normal buildings. They should be designed for 20% more snow load (than a similar building with all other features being equal) because it is an Essential Facility (or Category IV, Roman Numeral 4) based upon ASCE 7 and ICC criteria:

A condensed version of Tables 1.5-1 and 1.5-2 from ASCE 7-10 (by A. Halberg)

There are many reasons structures collapse when they must endure loads nearing their limit. It takes but one “weak link” in a chain to cause a failure. When a complete building system is capable of withstanding the required loads, all links in the chain are working together and have a strength that meets or exceeds the load. When one link is deficient, even slightly, the entire system can be compromised and lead to a building failure.