Boulder Roof Wind Speed Requirements

Boulder sits at the foot of the Flatirons, where downslope winds can be strong, and the City has adopted local amendments to its building code that set higher design wind speeds than many places. Those rules affect which roofing products can be used, how they are fastened, and what inspectors check.

This guide summarizes the City's published wind speed requirements and how they show up in a reroof.

The design wind speeds

The City's Roof Inspection Guide lists the basic design wind speed by risk category and by location relative to Broadway:

Most single-family homes fall under Risk Category II, which means 150 mph east of Broadway and 165 mph west of Broadway. The Residential Building Permit Guide states the same 150 and 165 mph figures for structural design of new structures and additions and says roofing materials must meet the wind speed requirements of B.R.C. Section 10-5-2(ff).

Ultimate and allowable stress speeds

Under B.R.C. §10-5-2(ff) and the City's Roof Inspection Guide, most homes (Risk Category II) use design wind speeds of 150 mph east of Broadway and 165 mph west of Broadway. Under B.R.C. §10-5-2(ff) and the City's Roof Inspection Guide, most homes (Risk Category II) use design wind speeds of 150 mph east of Broadway and 165 mph west of Broadway. Product listings may use either form, so ask your roofer which value the product's listing covers and confirm it meets the requirement for your side of Broadway.

What this means for shingles

Shingle products carry wind ratings tied to specific installation methods, commonly a required number of nails per shingle and special starter strips at eaves and rakes. Shingles must carry a listing for the design wind speed that applies to the property. Ask the roofer for the product's wind listing and the installation instructions that achieve it, and keep a copy with your permit documents.

Flat membrane roofs

For low-slope membrane assemblies, the Roof Inspection Guide offers two ways to verify wind resistance. One is an engineered design submitted at permit application that details materials, installation methods, load calculations and the number and layout of fasteners or bonding, followed by City inspection of the fastening or bonding. The other is a deferred design, where a sealed letter from a qualified design professional certifying that the installed assembly meets applicable codes is provided at the mid-roof inspection. Either way, a City mid-roof inspection also verifies the assembly's Class A fire rating.

The guide notes that uplift pressures are determined under the ASCE 7 standard and that roof assembly test standards such as FM Global can be used to specify a tested assembly.

Inspections that check wind design

The Roof Inspection Guide lists ultimate wind speed design and fastener installation on the mid-roof checklist. Mid-roof inspections are required when pitch is less than 4/12 or for any roof type other than asphalt shingles, regardless of pitch. Inspectors may request additional documentation such as the Class A listed assembly, wind design or material specifications, so have them ready.

Knowing which side of Broadway you are on

Because the requirement changes at Broadway, homes west of Broadway, closer to the foothills, need the higher wind speed. If your property is near the line or you are unsure, ask the City's Planning and Development Services through Inquire Boulder. Note that unincorporated Boulder County sets its own wind requirements; this guide covers the City of Boulder.

Questions to ask your roofer

Which side of Broadway is the house on, and which design wind speed applies? What wind rating does the product carry, and which installation method achieves it? How many nails per shingle and what starter strips will be used? For flat roofs, which design verification option will be used, and is the design professional's fee included? Ask for answers in writing with the bid.

Comparing bids on these points helps you avoid low prices that skip required installation steps.

Wind and insurance

Wind damage claims are often subject to the same percentage wind/hail deductibles that apply to hail. A properly rated and installed roof reduces the risk of blow-offs.

Retrofitting for wind

During a reroof, ask about upgrades that improve wind resistance, such as additional nailing, enhanced starter courses at eaves and rakes, and secure ridge caps. These may already be required by the product listing for Boulder's wind speeds, but confirming them in writing helps ensure they are done.

Older roofs and wind

Roofs installed before current requirements may not meet today's wind design. That does not require immediate replacement, but a permitted reroof must meet current rules, which can affect product choice and cost.

Keep the listing

Save the product's wind listing with your permit documents for future insurance or resale questions.

Properties near the foothills on the west side of town face the higher requirement, so confirm the location early when comparing products and bids.

Risk categories explained

Risk categories reflect how important a building is; most homes are Risk Category II, while essential facilities use higher categories and speeds.

Published roofing cost estimates

Sources: Angi: Emergency roof tarping cost; Angi: Slate roof cost; Angi: Roof replacement cost (2026); Angi: Roof repair cost (2026). Figures are published national or regional estimates compiled by those sites, labeled as estimates; they are not quotes and not prices from any provider on this site. Boulder's high wind-speed requirements, Class A assemblies and WUI rules can push local prices above national averages.

Local rules and code references

• City of Boulder Roof Inspection Guide: inspection checklist items: Class A assembly documentation, ultimate wind speed design, fastener installation, mid-roof inspection for asphalt shingles below 4/12 pitch.
• City of Boulder Building Permits and Inspections: lists Roofing Replacement among single-trade permit types and Electrical (including solar arrays) separately; refers to the Roof Inspection Guide for the City\'s roofing requirements; electrical permits applied for on or after Aug. 1, 2026 are reviewed under the 2026 NEC.
• City of Boulder Residential Building Permit Guide: Class A roofing materials are required and wood roofing materials are prohibited; roofing must meet B.R.C. §10-5-2(ff) wind speeds; WUI properties must show compliance with the IWUIC as amended by B.R.C. §10-8.5-2.
• Boulder Revised Code Title 10, Chapter 5, Building Code (Municode): the City's adopted building code and local amendments, including roof covering requirements.

Code text and department procedures change; confirm current requirements with the jurisdiction before work starts.