Coconino County adopted the IBC 2024 + IRC 2024 amendments in November 2025,
effective January 1, 2026. The headline change for Williams (zip 86046) is
the design ground snow load: from 40 psf to 60 psf, matching what
Flagstaff has required since 2018.
What that means in plain English: a roof permitted under the old code may
not pass a re-inspection during a sale, and any new addition or major
repair pulls the structure up to the new spec.
Why 60 psf matters
Snow load is measured in pounds per square foot the roof must hold without
structural failure. 40 psf vs 60 psf isn't just "a little more" — it's
50% more, and it cascades through the entire structural design:
- Trusses typically go from 2×6 to 2×8 chords on a 24" OC layout
- Roof decking moves from 7/16" OSB to 5/8" OSB or 1/2" CDX plywood
- Underlayment shifts to 30# felt or synthetic with 36" ice + water
shield at eaves (mandatory; was advisory)
- Fasteners require 8d ring-shank nails in the new IRC 2024 schedule
What this means if you're buying a Williams cabin
Inspector reports almost universally flag pre-2018 cabin roofs as
"non-conforming to current code." That's not the same as "unsafe" — it
means if you do anything beyond patching, you have to upgrade.
Things that trigger the upgrade requirement:
- Re-roofing more than 25% of the surface
- Any addition, dormer, or skylight retrofit
- Replacing trusses or rafters
- Selling — some buyers' lenders are starting to require code compliance
letters
Things that don't trigger upgrade:
- Patching individual shingles or tiles
- Cleaning, gutter work, basic maintenance
- Insurance-claim repair below the 25% threshold
Real-world cost adders for the new code
Compared to the old 40 psf design, these are typical 2026 prices on
Williams cabin re-roofs (1,800-2,400 sq ft):
| Upgrade | Cost adder |
|--------------------|---------------|
| 2×8 trusses (full re-truss) | $14,000-$22,000 |
| 5/8" decking upgrade | $3,400-$5,200 |
| Ice + water shield perimeter | $1,200-$1,800 |
| Engineering letter (when partial re-truss) | $850-$1,400 |
Total replacement on a typical Williams 2-story cabin runs $28,000-$46,000
in 2026 — up from ~$22,000 in 2024.
Questions to ask before buying
- What's the design snow load on file? (Pull the original permit from
the Coconino County permit portal — public record.)
- When was the roof last replaced? Pre-2018 = old code. Post-2018 =
likely 50 psf or higher already.
- Are there visible truss sags? Mid-span sag on a south-facing roof
almost always means undersized trusses + decades of cyclic loading.
- Is there ice damming history? Look at exterior walls below the
eaves — vertical staining = past dam events.
What to do if your cabin is non-conforming
You're not required to upgrade unless you trigger the conditions above.
Realistically, plan for the upgrade at the next re-roof — every 18-22
years on Williams shingle roofs, slightly longer on metal.
Match with a Williams-area contractor → — AZ ROC verified, current
on the 2024 code amendments, with snow-zone references.