Coconino County adopted IRC 2024 with local amendments effective
March 1, 2026. The headline change for roofers is the snow-load map.
Ground snow load values increased in three zones, and the rules around
"major reroof" structural verification got specific.
Here's what changed and what it means for your project.
The new ground snow load map
| Zone | 2025 (psf) | 2026 (psf) | Change |
|---|---|---|---|
| Flagstaff city below 7,000 ft | 50 | 60 | +20 % |
| Flagstaff above 7,000 ft (Mt Elden, Greenlaw) | 70 | 80 | +14 % |
| Munds Park / Bellemont | 60 | 70 | +17 % |
| Forest Lakes / Heber-Overgaard | 70 | 80 | +14 % |
| Williams | 50 | 55 | +10 % |
| Sedona / Oak Creek (low elevation) | 30 | 30 | No change |
These aren't theoretical. Flagstaff's record snow event (1973) was
over 100 inches of snowfall in a single storm. Modern engineering uses
50-year return-period values, which is why the load limits shifted.
What "major reroof" means
Under the new amendments:
- Total replacement = always major
- Replacement >50 % of any slope = major
- Tear-off + new sheathing = major
- Tile relay (underlayment only, no deck work) = NOT major
- Repair under 25 % of any slope = NOT major
For "major" reroofs, the 2026 amendment requires:
- Structural verification by a licensed engineer (PE) for any home
built before 2010
- Sheathing thickness review (5/8" minimum for new code)
- Rafter spacing review (2-foot OC max for 80 psf zones)
- Truss inspection if engineered trusses
Most pre-2010 Flagstaff homes were built to 50 psf. Many will need
supplementary sheathing or rafter sistering to meet the new 60–80 psf
requirement.
What it costs
The structural review and any required upgrades:
| Item | 2026 cost |
|---|---|
| PE structural review (typical) | $800–$1,400 |
| New 5/8" sheathing (full deck) | +$2.20/sf |
| Rafter sistering (2x6 sister) | $11/lf |
| Truss reinforcement (gusset plates) | $35–$80 each |
| Engineer's stamp + city submittal | $200–$400 |
For a typical 25-square Flagstaff home built in 1995 with 1/2"
sheathing on 24" OC rafters: budget an extra $4,500–$8,500 for
structural upgrades to meet new code.
Snow guards — required in 2026
The new code mandates snow guards for:
- All metal roofs in 60 psf+ zones
- All slopes greater than 4/12
- Where eaves overhang doors, walkways, or high-use entries
Snow guard cost: $40–$80 per linear foot of eave installed. Required
whether you're new construction or reroofing.
Ice dam protection
The 2026 code also formalizes ice & water shield requirements:
- Required at all eaves to 36 inches inside the exterior wall line
- Required at all valleys
- Required at all dormers and chimney bases
- Recommended (not required) over the entire deck above 6,500 ft
Most NAZ roofers above 6,500 ft now do full-deck ice & water as
standard practice. The cost premium is real (+$1.10–$1.80/sf) but
one ice-dam leak event costs more.
Ventilation update
The 2024 IRC formalized balanced ventilation requirements:
- 1:300 net free area (with vapor retarder) or 1:150 (without)
- Balanced 50/50 between intake (soffit) and exhaust (ridge)
- Mixing power vents and ridge vents prohibited (creates short-circuit)
Many older NAZ homes have ventilation that "worked" but never met
code. A 2026 reroof has to address it.
What this means for your project
- If your Flagstaff home was built before 2010 and you're planning a
reroof: get a structural review before you sign a contract.
Your roofer should arrange this.
- Budget +$5–8k beyond standard reroof cost for code compliance.
- Plan for 2–3 weeks of permit lead time (longer than the 1–2 weeks
pre-2026).
- Verify your contractor knows the 2024 IRC + local amendments.
Older roofers occasionally still quote to 2018 IRC. Don't accept
that.
A reroof done to 2018 code on a Flagstaff home is technically
non-compliant after March 1, 2026. If sold, the buyer's inspector
will flag it. If insured, future claims may be denied.
Williams and lower-elevation NAZ
Williams, Ash Fork, Seligman, and points west are below the high
snow-load thresholds. Code change is minor (50 → 55 psf). For most
reroofs in these areas, no structural review is required.
Sedona, Oak Creek, and the Verde Valley are exempt from snow-load
amendments entirely — too low and too warm to accumulate.
Flagstaff and the high-altitude communities are where the action is.
Plan accordingly.