In This Guide
NH Building Code Overview: IBC/IRC Amendments
New Hampshire adopts the International Building Code (IBC) for commercial structures and the International Residential Code (IRC) for one- and two-family dwellings, with state-specific amendments administered by the NH Building Code Review Board under RSA 155-A. Understanding these amendments is essential because they add requirements beyond the base IBC/IRC that address New Hampshire's severe winter climate, variable terrain, and specific regional conditions.
Key NH Amendments Affecting Roofing
- Enhanced snow load tables: NH provides municipality-specific ground snow load values that often exceed the base IBC tables, ranging from 50 psf in the southern tier to 120 psf in mountain areas. These values are the legal minimum design loads.
- Ice barrier requirements: Mandatory ice and water shield membrane from eave edge to at least 24 inches past the interior wall line on all heated buildings. This exceeds the base IRC requirement in colder climate zones.
- Ventilation standards: Attic ventilation requirements of 1:150 (net free area to attic floor area), reducible to 1:300 with a vapor retarder or balanced ventilation. These are enforced more stringently due to ice dam risk.
- Energy code integration: R-49 minimum attic insulation is required under the NH energy code. This directly impacts roofing projects that involve attic access or modifications to the building envelope.
- Local authority: NH municipalities may adopt codes stricter than the state minimum. Cities like Concord, Manchester, and Portsmouth may have additional local requirements.
Code Enforcement in New Hampshire
Code enforcement varies significantly across NH municipalities. Larger cities have full-time building inspectors, while smaller towns may share inspectors or rely on third-party inspection services. The NH Building Code Review Board provides oversight, but day-to-day enforcement is local.
The NH Building Code Review Board can be reached at (603) 271-1585. Their website provides the current adopted codes and amendments at nh.gov/safety/boardsandcommissions/bldgcode.
Snow Load Requirements by Town
New Hampshire's ground snow load requirements vary dramatically across the state. The design snow load for your roof depends on the ground snow load for your municipality, roof geometry (slope, shape, exposure), and whether drifting or sliding snow conditions apply.
| Municipality | County | Ground Snow Load (psf) | Region |
|---|---|---|---|
| Nashua | Hillsborough | 50 psf | Southern |
| Salem | Rockingham | 50 psf | Southern |
| Manchester | Hillsborough | 55 psf | South-Central |
| Portsmouth | Rockingham | 55 psf | Seacoast |
| Concord | Merrimack | 60 psf | Central |
| Keene | Cheshire | 60 psf | Southwest |
| Lebanon | Grafton | 60 psf | Upper Valley |
| Laconia | Belknap | 70 psf | Lakes Region |
| Plymouth | Grafton | 80 psf | Central Mountains |
| Littleton | Grafton | 80 psf | North Country |
| Berlin | Coos | 90 psf | North Country |
| Conway/N. Conway | Carroll | 80–100 psf | White Mountains |
| Lincoln/Woodstock | Grafton | 100–120 psf | White Mountains |
| Pittsburg/Colebrook | Coos | 100–120 psf | Great North Woods |
Important Snow Load Considerations
Ground snow load is not the same as roof snow load. Your engineer or contractor calculates the design roof snow load by applying factors for roof slope, thermal conditions, exposure category, and importance factor. A steeply pitched roof in an exposed location sheds snow more readily than a low-slope roof in a sheltered valley.
Drifting snow behind parapets, dormers, and adjacent higher roof sections can create localized loads far exceeding the uniform ground snow load. Sliding snow from upper roofs onto lower roofs is another critical consideration in New Hampshire's multi-level housing stock.
Ice and Water Shield Requirements
Ice and water shield (self-adhering modified bitumen membrane) is one of the most important code requirements for New Hampshire roofs. It is the last line of defense against water intrusion from ice dams, which are a pervasive problem throughout the state during winter months.
NH Code Minimum Requirements
- Eaves: From the eave edge extending upslope to at least 24 inches past the interior wall line. On typical NH homes with 12 to 16 inch eave overhangs, this means approximately 3 to 4 feet up the roof from the drip edge.
- Valleys: Full-width ice barrier in all roof valleys, extending at least 36 inches from the valley centerline on each side.
- Around penetrations: Ice barrier around skylights, chimneys, vent pipes, and other roof penetrations where water can pool or ice can form.
- Low-slope transitions: Where a low-slope area (below 4:12) transitions to a steeper slope, ice barrier should extend at least 24 inches past the transition point.
NH Best Practices: Beyond Code Minimum
Experienced NH roofing contractors typically exceed the code minimum:
- Extending ice barrier 6 feet from the eave instead of code minimum (especially on north-facing slopes and in heavy snow areas above 70 psf)
- Full ice barrier coverage on roof slopes below 4:12
- Double-width valley ice barrier in complex roof geometries
- Ice barrier at all dormer-to-main-roof intersections, a common ice dam formation point on NH colonial and Cape Cod homes
Wind Speed and Fastener Requirements
While snow load is the primary structural concern in New Hampshire, wind is the leading cause of acute roof damage. NH code requires roofing materials to be installed to withstand design wind speeds that account for the state's exposure to nor'easters and localized wind events.
Design Wind Speeds by Region
- Southern NH (interior): 110–115 mph — standard fastener patterns
- Central NH (Lakes Region, Upper Valley): 110–115 mph — standard risk with terrain considerations
- Seacoast (Portsmouth, Hampton, Rye): 120–130 mph — enhanced fastener patterns required
- White Mountains (exposed elevations): 120–130 mph — terrain-amplified winds require enhanced installation
Fastener Requirements for NH
- Standard zones (110-115 mph): Minimum 4 nails per shingle, 6 nails in high-wind roof areas (eaves, rakes, ridges)
- High-wind zones (120+ mph): 6 nails per shingle across the entire roof, with starter strip and ridge cap enhancements
- Nail length: Minimum 1.25 inches with 3/8-inch head diameter, penetrating at least 3/4 inch into the deck
- Metal roofing: Concealed fastener panels with clips rated for design wind speed; exposed fastener panels with neoprene-washer screws at manufacturer spacing
Ventilation and Insulation Standards
Proper attic ventilation and insulation are the primary defense against ice dams in New Hampshire. Code-compliant ventilation and insulation prevent the heat transfer that causes snow to melt unevenly on your roof.
NH Ventilation Requirements
| Requirement | Standard | Notes |
|---|---|---|
| Net Free Ventilation | 1:150 ratio | Reducible to 1:300 with vapor barrier or balanced vent |
| Intake vs. Exhaust | 50/50 balanced | Equal soffit intake and ridge/gable exhaust |
| Soffit Baffles | Required per rafter bay | Prevents insulation from blocking soffit vents |
| Attic Insulation | R-49 minimum | NH energy code; critical for ice dam prevention |
| Air Sealing | Required before insulation | Seal penetrations, bypasses, and attic hatches |
Permit Requirements by Municipality
Unlike states with uniform statewide permit requirements, New Hampshire leaves building permit administration to individual municipalities. Requirements, fees, and processes can vary from one town to the next.
When Permits Are Required
In most NH municipalities, a building permit is required for:
- Complete roof replacement (tear-off and re-roof)
- Structural modifications to the roof (adding dormers, changing pitch, snow load reinforcement)
- Adding new roof penetrations (skylights, chimneys, large vents)
- Converting unvented to vented attic assemblies
- Changes to the building envelope affecting energy code compliance
Some municipalities may not require a permit for simple re-roofing over existing shingles with no structural changes, but always check with your local building department first.
Typical NH Permit Process
- Contact your local building department (town hall or city building inspection office)
- Submit a permit application with project description, contractor information, and scope of work
- Pay the permit fee (typically $75 to $300 based on project value)
- Receive permit approval (usually 1 to 5 business days for straightforward replacements)
- Post the permit at the job site during construction
- Schedule inspections as required (typically a final inspection after completion)
- Receive certificate of completion or inspection sign-off
Contractor Licensing in New Hampshire
New Hampshire does not have a statewide roofing license requirement, which places more responsibility on homeowners to verify contractor qualifications.
What NH Requires
- Business registration: All contractors must register with the NH Secretary of State
- General liability insurance: Required to protect homeowners against property damage during the project
- Workers' compensation insurance: Required for any contractor with employees
- Local registration: Some municipalities require contractors to register locally
What to Verify Before Hiring
- Business registration with the NH Secretary of State (search at sos.nh.gov)
- Current general liability insurance (ask for a certificate of insurance)
- Workers' compensation coverage (verify through the NH Department of Labor)
- Experience with NH-specific requirements (snow load, ice barrier, ventilation)
- Manufacturer certifications (GAF Master Elite, CertainTeed SELECT ShingleMaster, or Owens Corning Platinum Preferred)
- References from recent NH projects in your snow load zone
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Get Your Free NH Roof EstimateFrequently Asked Questions: NH Building Codes & Snow Load
What building code does New Hampshire follow for roofing?
New Hampshire adopts the IBC and IRC with state-specific amendments through the NH Building Code Review Board. The current edition is based on IBC/IRC 2018 with NH amendments addressing snow load, ice barrier, and wind exposure requirements. Local municipalities may adopt additional requirements but cannot reduce state minimums.
What is the ground snow load requirement for my NH town?
Ground snow loads range from 50 psf in southern communities like Nashua and Salem to 120 psf or higher in the White Mountains. Common values: Concord 60 psf, Manchester 55 psf, Laconia 70 psf, Lebanon 60 psf, Berlin 90 psf, and Coos County mountain areas 100-120 psf.
Does New Hampshire require ice and water shield on roofs?
Yes. NH code requires ice barrier from the eave edge extending at least 24 inches past the interior wall line on all heated structures. Many contractors install further up the roof, especially in valleys and around penetrations, as best practice for NH winters.
Do I need a permit for a roof replacement in New Hampshire?
Permit requirements vary by municipality. Most towns require a building permit for full replacements and structural changes. Some smaller towns may not require permits for like-for-like re-roofing. Contact your local building department before starting work. Permits typically cost $75 to $300.
What are the wind speed requirements for roofing in New Hampshire?
Design wind speeds range from 110 to 130 mph (3-second gust) depending on location. The seacoast and exposed mountain areas have the highest requirements. High-wind areas require enhanced nailing patterns, typically 6 nails per shingle instead of 4.
How many layers of shingles are allowed in New Hampshire?
NH follows the IRC standard allowing a maximum of two layers of asphalt shingles. If two layers exist, a complete tear-off is required. Many contractors recommend full tear-off even over one layer to inspect for ice dam damage, rot, and structural issues.
What ventilation requirements does NH have for roofs?
NH requires a minimum net free ventilation area of 1:150, reducible to 1:300 with a vapor barrier or balanced ventilation. Proper ventilation is critical to prevent ice dams. The state also requires R-49 attic insulation for energy code compliance.
Does NH require contractors to be licensed for roofing work?
NH does not have a statewide roofing license. Contractors must register with the NH Secretary of State and carry general liability and workers compensation insurance. Some municipalities require local registration. Always verify insurance and check references.
Related Resources
NH Roof Replacement Costs (2026)
Average costs by material, city, and roof size for New Hampshire homeowners.
NH Roof Insurance Claims Guide
Step-by-step guide to filing and settling your NH roof insurance claim.
New England Snow Load Guide
Regional snow load overview across all six New England states.
Ice Dam Prevention & Repair
Complete guide to preventing and managing ice dam damage.