Snow Load Code Updates: What’s Changed and What Still Needs Clarifying
By Jack Healy, P.E., Principal
Back in January, we broke down the major changes to the snow load requirements in New York’s building codes.
Since then, the New York Department of State has issued new guidance and clarifications that are already shaping how engineers and building owners approach both new builds and reroofing projects. Let’s walk through what’s changed, what it means in practice, and where we think the code still leaves critical questions unanswered.
On February 3, the Department of State released a new Code Outreach Program document that reintroduces the Importance Factor based on Building Risk Category for snow loads. The Importance Factor is now required when using the NYS-specific snow map to calculate the minimum ground snow load. That value is then multiplied by 1.6 to convert to strength level ground snow load.
The previous code gave the designer a choice between the ASCE 7-16 values or the NYS snow map. The current code does not. It requires checking both the ASCE 7-22 snow loads and the NYS map and using the higher value.
New Guidance: Energy Code Compliance and Existing Building Reroofing
As mentioned in the January article, the latest update to New York State’s building code brings a long-overdue recognition: adding more roof insulation increases the snow load that a roof must carry. With thicker insulation, less heat escapes, which means the snow on your roof doesn’t melt away as quickly. The result? More snow can pile up over multiple storms, leading to heavier loads.
From a compliance perspective, the new code states that if your proposed alteration does not increase the load on the roof by more than 5%, you can skip a formal engineering analysis. At first glance, this seems straightforward. But the provision doesn’t account for earlier roofing jobs or other alterations that may have already bumped up the structural load. This is a departure from how other parts of the code handle cumulative effects.
In our view, the most responsible—and code-consistent—approach is to compare the current snow loads (with the proposed insulation) against the roof’s original design loads, not just the most recent state of the building. As noted in our January 2026 article, potential reductions in roof dead load could possibly affect some of the increase in snow load. If the comparison shows that the proposed change pushes the total increase over the 5% threshold, a structural analysis is required.
If the new loads trigger an engineering analysis and portions of the roof structure are found to be overstressed under the new loads, there are two paths forward for the building owner. First, you can choose to reinforce the roof, so it meets current snow loading requirements.
Alternatively, you could opt to limit the amount of new insulation, thereby keeping the snow load below the critical threshold. If you take the second route, submitting the engineering analysis to the permitting authority is sufficient—there’s no need for a formal code variance for not meeting the minimum R values prescribed by the Energy Code. On April 17, 2026, the Department of State released a Code Interpretation that addresses this option.
Drift Zones: The Hidden Risk in Older Roofs
As we noted in our January article, drift zones deserve special attention. Most roof failures we’ve seen don’t happen in the middle of a roof—they occur in drift zones, where windblown snow piles up and creates concentrated, sometimes underestimated, loads. Before 1984, the building code didn’t explicitly address these zones, so if your building predates that year and hasn’t been reinforced yet, there’s a strong potential that portions of your roof could be overstressed by today’s standards.
Strictly speaking, current compliance checks aren’t required unless your project triggers more than a 5% increase in loading. The code is clear: the 5% rule only applies if the alteration causes that increase. But in practice, it is well documented that drifted snow is the culprit behind structural failures.
Our view is that good design, and real due diligence, means checking drift zones anytime you’re evaluating an older roof—even if you’re not technically required to by the code. It’s a simple step that can prevent costly failures and protect occupants, especially when you consider how much data on snow loading magnitudes and patterns have been collected and refined since the original designs were drawn.
Clarifications Still Needed
As we have been designing using the new Code provisions, we have discovered several items that still deserve clarification.
- R values: The Code requires snow loads to be based on the R-value of the roof but does not specifically state how to interpret the R-value when there is tapered insulation. Do you use the minimum R value, maximum R value, or average? We have been using an average R- value based on our correspondence with Prof M. O’Rourke and in accordance with energy code practices.
- Cumulative effects: As noted, the Code does not address cumulative effects of previous reroofing projects. This is specifically addressed in other sections of the Code that address changes to the lateral system. We are hoping this will be clarified for reroofing projects as well.
- Conversion Factor: In our opinion, there is a discrepancy in the Code for the conversion factor of the ground snow loads using the NYS Map to ultimate strength. The factor is noted as 1.6, however in other sections of the ASCE 7-22 Code the conversion factor is lower. Based on the ASCE 7-22 Code, the factor between ultimate strength and service loads for snow is 1.43.
New Tools for Better Decisions
What we do have now, for the first time, is a robust set of tools: the most recent snow load data from ASCE 7-22, and clear guidance on how insulation can affect roof loads. These allow us to make more accurate, modern assessments of existing structures. Building owners and engineers should take full advantage of these resources to ensure that safety margins are maintained—not just for compliance, but for the peace of mind of everyone who uses these buildings.
Our recommendation hasn’t changed since the 1980s: If you’re adding insulation, check the roof for compliance with current codes. And even if you’re not, it’s worth running the numbers with the new snow load database; the data has changed.
We understand that building owners need the flexibility to maintain and make minor improvements without triggering a full-scale overhaul. But knowing exactly where your building stands—using the most accurate data and engineering analysis available—will always lead to better decisions. At the end of the day, it’s about using every tool we have to give occupants the safety factor their building use demands.
If you have questions about applying these new requirements or need help interpreting how they affect your building or project, don’t hesitate to reach out. The code is evolving, and so should our approach to safety. Don’t let code minimums set the ceiling for your standards.