Texas Windstorm Construction Standards for Coastal Counties

If you own or plan to build on the Texas coast, your structure has to be built to a specific wind-resistant building code and inspected by a state-appointed engineer before it can be insured against wind and hail through the Texas Windstorm Insurance Association. The Texas windstorm construction standards for coastal counties currently point to the 2018 International Residential Code or International Building Code, but every new WPI-1 application filed on or after April 1, 2026, must comply with the 2024 editions of those codes.¹ A building that passes inspection gets a Certificate of Compliance from the Texas Department of Insurance. Without one, the owner either pays a 15% surcharge on a TWIA policy or can’t get TWIA coverage at all.²

Which Counties and Areas Are Covered

Texas defines a “Seacoast Territory” made up of two rings of counties. Fourteen first-tier counties sit directly on the Gulf: Aransas, Brazoria, Calhoun, Cameron, Chambers, Galveston, Jefferson, Kenedy, Kleberg, Matagorda, Nueces, Refugio, San Patricio, and Willacy. A second ring of fourteen counties sits behind them, including Harris, Fort Bend, Hidalgo, Orange, and Liberty.³

Being in a second-tier county doesn’t automatically mean your property is subject to the certification mandate. TDI draws boundary lines inside some of those counties to mark the “designated catastrophe area” where windstorm certification is required. In Harris County, that line runs along Highway 146, with properties east of the highway falling inside the zone. Structures inside the zone need a Certificate of Compliance for TWIA eligibility. Structures outside typically have access to private windstorm coverage and don’t face the same mandate.

The Building Code You Have to Build To

The technical backbone of the standard is the adopted building code. For any WPI-1 application filed on or after April 1, 2026, the structure must be certified under either the 2024 International Residential Code or the 2024 International Building Code. Projects with a WPI-1 already on file under the 2018 editions may continue under those older standards.¹ If you’re planning construction that will kick off in 2026 or later, your engineer and contractor should be working from the 2024 editions from the start.

Texas layers state-specific amendments onto the international codes, tailored to Gulf Coast conditions and focused on how a structure holds together when wind pushes hard on one side and pulls on the other.

Design Wind Speed

There isn’t a single wind speed number that applies across all coastal counties. The required design wind speed depends on where the structure sits relative to the shoreline. TDI directs builders and engineers to use web tools like the ASCE 7 Hazard Tool to pull the specific three-second gust value their project must resist.¹ Structures closer to the water face higher numbers, and the calculation accounts for both the lateral push of sustained winds and the uplift forces that try to lift a roof off the walls.

What Inspectors Look At

The inspection covers the full building envelope, every component that stands between the storm and the interior:

Roofing materials, attachment methods, and underlayment appropriate for the location’s wind speed.
Exterior wall sheathing and cladding, which must resist wind pressure without separating from the frame.
Windows and other glazed openings, protected by impact-resistant glass or approved coverings so windborne debris can’t breach the envelope.
Exterior doors and garage doors, rated for the same impact and pressure loads as windows. A failed garage door can let in enough wind to lift the roof from below.
The foundation, engineered against both uplift and lateral forces.
The structural frame, including studs, trusses, and every connection between them, using specific hardware and nailing patterns.

These requirements aren’t limited to new construction. Replacing a roof, installing new windows, adding a room, or making major structural repairs all trigger the need for a new inspection. If you’re touching the building envelope or the structural frame, plan on going through certification.

Getting Certified: WPI-1, Inspection, WPI-8

The process starts with the WPI-1 (Application for Certificate of Compliance), which must be filed with TDI before construction begins.⁴ The form is downloadable from the TDI website and asks for the property location, a description of the planned work, and the contact information for the professional engineer overseeing the design.⁵ Be specific in the scope-of-work description. Vague entries cause delays when inspectors can’t match what they see in the field to what’s on the form.

Inspections are performed by Appointed Qualified Inspectors (AQIs), licensed Texas professional engineers who have completed a TDI orientation and demonstrated windstorm design experience.⁶ TDI keeps a searchable list of appointed engineers on its website. Engineering fees for windstorm inspections generally run from roughly $650 to over $2,700, depending on project scope and whether the work is inspected in progress or after the fact.

Filing the WPI-1 before breaking ground matters because it determines which certificate you receive:

A WPI-8 is issued for new or ongoing construction inspected during the build. This is the standard path when the WPI-1 was filed before work started.⁷
A WPI-8-E is issued after a post-construction inspection, used when the work is substantially complete or title has already transferred from builder to owner. Post-construction inspections cost more and are more limited, because the inspector can’t see structural connections hidden behind finished drywall.⁷

Once TDI processes the inspection data, the certificate appears in the department’s online database, typically within a few days. Owners and agents can search by address to confirm status and print the documents needed to bind a TWIA policy.

What It Costs You to Skip It

Certification does more than open the door to TWIA. It sets your premium. Structures built to code qualify for mandatory building code credits on wind and hail coverage. For new residential construction certified under the IRC or IBC, dwelling credits range from 26% to 33% depending on whether the property sits in the Seaward, Inland I, or Inland II zone. Personal property credits on the same policies run from 20% to 28%. Older homes built before 1998 or 2003, depending on the area, can earn a separate 10% retrofit credit if all exterior openings have windborne debris protection like impact-resistant shutters.⁸

Structures that lack a required Certificate of Compliance but still qualify for TWIA through the waiver program pay a 15% surcharge on top of standard premium. The surcharge is non-refundable and non-commissionable, and the structure receives no building code credits while it applies.⁸ You pay more and lose credits that would otherwise cut the premium by a quarter or better.

Older Buildings and Other Exceptions

Not every coastal structure has to go through the certification process. The Texas Insurance Code carves out a handful of exceptions:

A structure built before January 1, 1988, in an area that had a TWIA-recognized building code at the time is eligible for TWIA coverage without inspection.⁹
A structure built before 1988 outside any recognized code area is eligible if it was previously insured by an authorized insurer and remains in essentially the same condition, aside from normal wear.⁹
An uncertified residential property built between 1988 and 2009 can still get TWIA coverage, but pays the 15% surcharge.⁷
A residential property insured on or after June 19, 2009, by a private carrier that later non-renews or cancels may be eligible for TWIA coverage even without a WPI-8, if the certificate was missing when the private policy ended.⁷

None of these exceptions covers new construction or major renovations. If you’re building, adding on, or making significant repairs, the full certification process applies regardless of the building’s history.

Buying or Selling a Coastal Home

Texas law requires a written seller’s disclosure of property condition, but the statutory form has no specific line for windstorm certificates.¹⁰ Buyers in coastal counties should treat certification as a key piece of due diligence anyway. Without a valid WPI-8, the new owner pays the surcharge, funds a post-construction inspection to try to get certified, or goes without windstorm coverage.

Before closing, search TDI’s online database for the address. If a certificate exists, confirm it still matches the structure’s current condition, including any additions or roof work done since it was issued. Post-certificate work can void the existing certificate. Finding this out before you own the property gives you room to negotiate repairs, a price reduction, or a requirement that the seller obtain a new certificate before the sale closes.

1
Texas Department of Insurance. Adopted Building Codes
2
Texas Windstorm Insurance Association. Coverage and Eligibility
3
State of Texas. Texas Insurance Code INS 2210.003
4
Texas Department of Insurance. What Is the Windstorm Inspection Process
5
Texas Department of Insurance. PC350 WPI-1 Application for Certificate of Compliance
6
Legal Information Institute. 28 Texas Admin Code 5.4609 – Application for Qualified Inspector
7
Texas Windstorm Insurance Association. Windstorm Certification
8
Texas Windstorm Insurance Association. TWIA Rating Rules Manual
9
State of Texas. Texas Insurance Code INS 2210.251
10
State of Texas. Texas Property Code 5.008 – Sellers Disclosure of Property Condition