Texas Windstorm Insurance, TDI Certification, and What It Means for Your Roof

Most San Antonio homeowners never have to think about TDI (Texas Department of Insurance) windstorm requirements — they apply primarily to the coastal Tier 1 counties. But understanding the system matters because pieces of it affect all Texas roofing, and if you own property in multiple regions it comes up fast. Here's what you need to know.

What TDI windstorm certification actually is

TDI administers the Texas Windstorm Insurance Association (TWIA), which provides wind and hail coverage in designated "catastrophe areas" where private insurers have largely withdrawn — the 14 coastal Tier 1 counties (Aransas, Brazoria, Calhoun, Cameron, Chambers, Galveston, Jefferson, Kenedy, Kleberg, Matagorda, Nueces, Refugio, San Patricio, Willacy) and parts of Harris County east of I-45. Structures built or repaired in these areas must comply with specific wind-resistant construction standards and be certified by a TDI-appointed engineer.

The certification is documented on a WPI-8 form (for completed construction) or WPI-3 (for in-progress inspections). Without proper documentation, coastal properties typically cannot get TWIA wind coverage.

Does this affect San Antonio?

Directly, no. San Antonio is not in a designated catastrophe area — private insurers underwrite wind and hail coverage here, and TDI windstorm compliance is not required for roofing work.

Indirectly, yes — in three specific situations:

1. You own coastal property. If you have a second home in Port Aransas, Corpus Christi, Galveston, or anywhere in the designated counties, work on that property does require TDI compliance. Ask your contractor if they're experienced with WPI-8 certification requirements — not all are.
2. You're moving from or to the coast. Homeowners who relocate often don't realize the insurance rules differ — what was a simple roof replacement at the coast required engineering inspection and certification, which adds cost and time.
3. TDI best practices inform all Texas roofing. Wind ratings, nail patterns, edge details, and underlayment specifications developed for TDI windstorm zones have raised standards industry-wide. A contractor experienced with TDI work brings those best practices to inland jobs too.

What TDI-grade roofing looks like

Even though it's not required in San Antonio, there's value in understanding what TDI-compliant roofing involves — these are defensible best practices anywhere in Texas:

• 6-nail pattern minimum on asphalt shingles rather than 4-nail, with specific placement in the designated nail zone.
• High-wind rated shingles (110+ mph rating in standard zones, 150+ mph in extreme exposure).
• Synthetic or peel-and-stick underlayment, not 15-pound felt.
• Ring-shank or screw-shank nails rather than smooth-shank, for better pullout resistance.
• Metal edge closure — proper drip edge at eaves and rakes, hemmed where exposed.
• Ice-and-water shield in valleys, around penetrations, and at eaves (3 feet minimum).
• Roof-to-wall and roof-to-deck connection details specified and documented.

We install to these standards by default — not because TDI requires it in San Antonio, but because they're simply better construction.

The "wind-resistive" policy discount

Even outside TDI zones, many Texas insurers offer premium discounts for wind-resistive construction. The discount varies by carrier — State Farm, Allstate, USAA, and Farmers all have versions. Typical requirements:

• Shingles rated for 110+ mph wind
• 6-nail installation pattern
• Properly installed drip edge
• Secondary water barrier (peel-and-stick underlayment at penetrations)

Discounts typically run 5–15% on the wind/hail portion of your premium. Ask your insurer whether your roof qualifies. If you're about to replace, ask us to install to the wind-resistive spec — the incremental cost is minimal and the discount recurs annually.

How to find a contractor experienced with TDI work

If you need WPI-8 certified work (coastal property), look for roofing contractors who specifically list TDI or TWIA compliance experience. The roofing contractor doesn't issue the WPI-8 — a TDI-appointed engineer does — but the contractor installs to the spec the engineer inspects against. Experienced TDI contractors know what to document and how to stage inspections.

For San Antonio work, TDI certification isn't a requirement — but a contractor who's done coastal work brings practices that benefit your inland roof too. Ask about specifications, not just price.