Structural Engineer Serving Block Island (New Shoreham), Rhode Island

South County Design Group, Inc. is a local Rhode Island engineering firm focusing on structural engineering services. Since 2003 we have served clients throughout the state, with particular focus on coastal residential projects in Block Island (New Shoreham) — among Rhode Island's most exposed coastal municipalities, a small island roughly 12 miles off the mainland in the open Atlantic. The firm is led by Kenneth A. Hayes, Rhode Island Professional Engineer (License #7252).

This page summarizes the structural and coastal design parameters that apply to Block Island under the Rhode Island State Building Code as revised effective December 1, 2025, and describes our professional approach to determining design wind loads for specific sites on the island. "Block Island" is the common name; "New Shoreham" is the incorporated town name used for legal and municipal purposes.

Block Island Design Parameters Under the New Code

Rhode Island's State Building Code (RISBC) was updated effective December 1, 2025. For the first time, the code publishes a single set of design values per municipality — used by both residential (RISBC-2) and commercial (RISBC-1) projects.

Below is a plain-English summary of the wind, snow, temperature, and frost-depth values that apply to structures on Block Island, followed by how we translate them to a specific property. Block Island's values stand apart from the rest of Rhode Island in two respects: its design wind speeds are the highest published in the state, and its frost depth is the shallowest.

Block Island (New Shoreham) · RISBC Design Parameters

Parameter	Value
Ground snow load	30 psf
Flat roof snow load	30 psf
Ultimate design wind speed (Vult), Risk Category I	124 mph
Vult, Risk Category II	134 mph # — WBDR applies within 1 mile of coast
Vult, Risk Category III	143 mph * — WBDR applies regardless of coast proximity
Vult, Risk Category IV	149 mph * — the highest Vult in Rhode Island
Frost depth (residential, RISBC-2)	2'-6" — unique in RI
Frost depth (commercial, RISBC-1)	2'-6" — same as residential, also unique
Winter design temperature (Washington County)	5°F
Mean annual temperature	50°F
Air freezing index	1,200 degree-days below freezing

Note Block Island's frost depth — 2'-6" for both residential and commercial structures — is shallower than elsewhere in Rhode Island. This reflects the island's ocean-moderated winter climate.

Risk Category II is the default for most residential and commercial structures. Risk Category III applies to important facilities (assembly occupancies of more than 300, schools with more than 250 students, certain healthcare uses). Risk Category IV covers essential facilities (hospitals, fire stations, emergency operations centers, designated emergency shelters).

The Wind-Borne Debris Region on Block Island

The Wind-Borne Debris Region (WBDR) is the coastal zone where windows are most likely to be struck by flying debris during a hurricane. Inside the WBDR, openings must either use impact-resistant glazing or approved shutters — otherwise the structure must be designed as partially enclosed, which substantially increases the wind loads it has to resist. Glazing inside the WBDR must pass the Large Missile Test of ASTM E1996 and ASTM E1886.

Under the new RISBC, a site falls within the WBDR when both conditions are met:

1. The structure's Risk Category design wind speed (V_ult) exceeds 130 mph; and
2. The structure is within 1 mile of the "mean high coastal water line."

For Block Island at Risk Category II, V_ult is 134 mph — well above the 130 mph threshold, carrying the # flag. Given Block Island's geography — a small island entirely surrounded by the open Atlantic — virtually every property on the island falls within 1 mile of a qualifying coastal shoreline. Effectively the entire island is within the Wind-Borne Debris Region.

What Counts as "Coastal" on Block Island

The new RISBC references "mean high coastal water line" without defining the term. In our practice, we interpret "coastal" consistent with the ASCE 7-16 Exposure Category D framework — the wind-load engineering standard the code references. Under ASCE 7-16, a water body produces coastal conditions when its upwind fetch exceeds 5,000 feet — enough open water to generate the wind characteristics that put a structure in Exposure Category D.

Applied to Block Island, this interpretation identifies the qualifying shorelines as:

• The entire Atlantic perimeter of the island, including Crescent Beach, Ballard's Beach, the Mohegan Bluffs, Black Rock Beach, and the coastal stretches around Southeast Light and North Light
• The Great Salt Pond — the large interior tidal pond, with extensive open-water fetch
• Old Harbor (the town landing) and New Harbor (the Great Salt Pond entrance)

Given the island's small footprint (about 10 square miles) and its perimeter exposure, nearly all of Block Island produces Exposure D conditions.

For a full plain-English explanation of how Exposure Categories B, C, and D work in Rhode Island, see Understanding Wind Exposure Categories in Rhode Island.

Two Distance Rules, Two Distinct Zones

Under ASCE 7-16 §26.7.3 (preserved in ASCE 7-22 §26.7.4), coastal proximity drives two separate design requirements with different distance thresholds:

ASCE 7-16 / 7-22 · Coastal Distance Framework

Distance From Qualifying Shoreline	Effect
Within 600 feet (or 20 × mean roof height, whichever is greater)	Exposure Category D — the highest wind exposure category, producing the largest design wind pressures
Within 1 mile of mean high coastal water line (and Vult > 130 mph)	Wind-Borne Debris Region — impact-resistant glazing or approved shutters required
Beyond the 600-foot Exposure D zone but still within the 1-mile WBDR zone	Exposure Category C with WBDR requirements — standard open-terrain wind pressures, plus impact-rated openings
Beyond 1 mile from any qualifying shoreline	Exposure Category C — no WBDR requirement

On Block Island, the 1-mile WBDR zone covers the entire island. The 600-foot Exposure D zone, measured from both the Atlantic perimeter and the Great Salt Pond shoreline, covers nearly all building sites on the island as well. A typical Block Island residence therefore sits within all three concentric conditions — Exposure D, WBDR, and V_ult well above the 130 mph threshold.

How We Determine Wind Load for a Specific Block Island Site

The RISBC publishes a single V_ult value per municipality (134 mph for Block Island at Risk Category II). ASCE 7-16 — which RISBC references as the engineered-design standard — defines wind loads as a continuous geographic surface rather than a per-town value.

For any Block Island project we:

1. Locate the actual site coordinates from the property deed or survey.
2. Query the ASCE 7-16 Hazard Tool at those coordinates to obtain V_ult for each Risk Category.
3. Design to the higher of the RISBC table value or the ASCE 7-16 Hazard Tool value — the more conservative figure governs.
4. Assess the site's Exposure Category based on actual upwind surface roughness: open water, flat marsh, pasture, woodland, or suburban development within the relevant fetch distance.
5. Apply WBDR requirements across the island given that the 130 mph threshold is exceeded at Risk Category II and the 1-mile coastal test is met everywhere on the island.

This approach ensures that the design reflects the actual wind hazard at the site as determined by the referenced engineering standard, rather than relying on a single per-town lookup value that may not capture local exposure conditions.

Coastal Residential Engineering Services

For Block Island coastal residential projects, our services typically include:

• FEMA floodplain analysis and structural elevation design — elevating the lowest floor above the Base Flood Elevation plus one foot, in compliance with IRC R322 and ASCE 24
• Helical pile foundation design — the preferred deep foundation system for coastal sites with marginal soil bearing or high water tables
• Reinforced concrete grade beam and pier design — spanning between helical piles to support elevated framing
• Shear wall design and uplift connection specification — consistent with ASCE 7-16 wind pressures and the AWC Wood Frame Construction Manual (WFCM) or engineered analysis
• Wind-borne debris region opening specification — coordination with the owner and architect on impact-rated glazing or approved shutter systems, applied across the entire island
• ASCE 7-16 engineered wind load analysis for structures exceeding the prescriptive thresholds of IRC 2021 R301.2.1.1 or WFCM Chapter 3
• Coordination with FEMA Flood Insurance Rate Map (FIRM) designations — determining A, AE, AO, VE, or Coastal A Zone (LiMWA) requirements at the specific property

Permitting and Regulatory Coordination

Residential projects on Block Island typically navigate four layers of regulatory review:

1. Local zoning — property-line setbacks, height limits, coverage, buffer zones
2. Local building permit — plan review by the building official and the local fire marshal
3. Rhode Island Coastal Resources Management Council (CRMC) — CRMC jurisdiction is particularly significant on Block Island given the island's entirely coastal character. The Block Island SAMP may apply to specific zones; CRMC Contiguous Areas and the 200-foot MHW jurisdiction reach nearly every project.
4. Rhode Island Department of Environmental Management (RI DEM) — jurisdictional over wetlands, Individual Sewage Disposal System (ISDS) approval, and related environmental review

In our experience, the longer lead times on Block Island projects come from the state agencies and from the logistics of working on an offshore island — CRMC review in particular can add several months to the design schedule. Our structural design work can proceed in parallel with the CRMC application rather than waiting on it.

About the Engineer

Frequently Asked Questions

Is my Block Island property in the Wind-Borne Debris Region?

Essentially yes. Under the new RISBC (effective December 1, 2025), a Block Island property falls within the Wind-Borne Debris Region (WBDR) when it is within 1 mile of a qualifying coastal shoreline and the applicable Risk Category design wind speed exceeds 130 mph. Block Island at Risk Category II has V_ult of 134 mph — above the 130 mph threshold. Because the island is roughly 3 miles by 7 miles and surrounded entirely by the open Atlantic, every property on the island is within 1 mile of a qualifying shoreline. Effectively the entire island is within the WBDR and requires impact-resistant glazing or approved shutters.

What wind speed does my Block Island home need to be designed to?

The RISBC table publishes a single V_ult of 134 mph for Block Island at Risk Category II — among the highest values in Rhode Island, reflecting the island's open-Atlantic exposure. For engineered design we use the ASCE 7-16 Hazard Tool at the actual site coordinates and design to the more conservative of the two figures. Most of Block Island's building sites fall within 600 feet of a qualifying shoreline and are designed to Exposure Category D — the highest wind exposure category.

Do I need CRMC approval for a Block Island project?

CRMC jurisdiction is particularly significant on Block Island given the island's entirely coastal character. CRMC review typically applies to structures within 200 feet of Mean High Water, within the Contiguous Area of a coastal feature (beach, dune, barrier beach, cliff, rocky shore, or salt pond), or within any applicable Special Area Management Plan. CRMC review runs in parallel with structural design rather than sequentially.