The average discount for Secondary Water Resistance (SWR) is 8% of the windstorm part of your homeowner’s insurance premium; but it will vary, sometimes significantly, between insurers. Typically this would be a self-adhered and self-sealing modified bitumen roofing underlayment such as Grace Ice and Water Shield or Certainteed WinterGuard. A foam barrier applied to the underside of the roof sheathing is another option, but seldom used. 

    The self-stick underlayment can be applied over the entire surface of the roof sheathing or only in strips at all the plywood joints. Secondary water resistance is not usually added in new residential construction and, since you probably paid extra for your roof to get it, you’ll know if your have it. 

    Some roofers use this underflayment for valleys only, but that does not qualify for the insurance discount because it must protect the entire roof. The inspector will need written documentation from the roofing contractor that the self-stick modified bitumen was applied under the roofing. Typically, a copy of an itemized receipt from the contractor is sufficient. The inspector will also check in the attic at gaps between the roof sheathing for a visual verification.

    Other average discounts that can be verified by a wind mitigation inspection include:

68% - Homes built under the Florida Building Code (permit application after 3/1/2002) or the 1994 Miami-Dade Building Code. This large discount will exclude the possibility of some other discounts listed below because they are included in the FBC/MDBC requirements for hurricane resistance of new homes.

Up to 47% - Hip roof (for roofs that slope downward on all sides like a pyramid). See our blog post How do I get the hip roof discount for my homeowners windstorm insurance? to learn more.

Up to 44% - Shutters, which must be rated by Miami-Dade or Florida Building Code, based on label attached to shutter or other documentation. Lower discount outside wind-borne debris region.

Up to 35% - Metal clips, single-wraps, or double-wraps at roof-to-wall connection. 

Up to 14% - Roof covering that meets Florida Building Code (FBC). Roof permit application date after 3/1/2002 or other documentation necessary.

Up to 5% - Roof deck attachment method. 2-1/2” nails spaced at 6” on center gets best discount.

 • • • • • • • • • • • • • • • • • • • • • • • • • 

Here’s links to a collection of our blog posts about the WIND MITIGATION FORM:

• Why did I get no discounts or only a small discount from my wind mitigation inspection?

• Who can perform a wind mitigation inspection in Florida?

• How long does it take for a wind mitigation inspection? 

• What is checked during a wind mitigation inspection? 

• Is a wind mitigation inspection report (OIR-B1-1802) required for homeowners insurance in Florida? 

• Which building permit date is used for the Building Code section of the wind mitigation form? 

• What are the different roof deck attachment discount categories for a wind mitigation inspection?

• What determines the year of a house? 

• What is the difference between a toe nail, clip, single wrap, and double wrap for the wind mitigation form?

• Can I do my own wind mitigation inspection?   

• What’s the difference between a gable and hip roof for my insurance? 

• What is the wind mitigation inspection for homeowner's insurance?  

• How can I tell how hurricane resistant a Florida house is before I buy it?

• How long does a wind mitigation inspection remain valid? 

• What is a wind mitigation discount? 

• Do I get a a discount for partial hurricane shutters in a Wind Mitigation inspection?

• Why did I get no discount for roof-to-wall-attachment in my Wind Mitigation report? 

• What’s the difference between a four-point and wind mitigation inspection?

   Visit our INSURANCE page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles. 

Average discount data from Florida’s Foundation and insurance documents.
Photo of taped sheathing joints - InterNACHI