The underlayment beneath your roof covering is your last line of defense against water intrusion. If a hurricane rips off shingles or tiles, the underlayment is all that stands between the storm and your home's interior. In Florida, choosing the right underlayment is not just a best practice. In many areas, it is a code requirement. This guide compares the three main types of underlayment used in Florida roofing and explains when each is appropriate.
What Underlayment Does
Underlayment is a sheet material installed directly on the roof deck (the plywood or OSB sheathing) before the primary roof covering (shingles, tile, or metal) is installed on top. It serves three critical functions.
Water barrier. Underlayment prevents water from reaching the roof deck and the interior of the home. Even on an intact roof, wind-driven rain can penetrate beneath shingles and tiles. The underlayment catches this water and channels it to the eaves.
Secondary water resistance. If the primary roof covering is damaged or removed by a hurricane, the underlayment is the only barrier protecting your home from rain. A properly installed underlayment system can keep a home dry for days or weeks after the primary covering is gone. This is the core reason Florida building codes emphasize underlayment quality and installation.
Deck protection. Underlayment protects the roof deck from moisture damage during and after construction. Between the time the old roof is torn off and the new covering is installed, the underlayment keeps the deck dry. In Florida's afternoon thunderstorm climate, this protection is critical during the construction window.
Type 1: Felt Underlayment (Traditional)
Felt underlayment, also called tar paper, has been used in roofing for over a century. It is made from a fiberglass or organic mat saturated with asphalt.
Specifications. Florida Building Code accepts ASTM D226 Type I (15-pound) or Type II (30-pound) felt. The 30-pound variety is thicker, more durable, and the standard for Florida applications. The weight designation refers to the weight per 100 square feet of material.
Pros. Felt is the least expensive underlayment option. It provides a basic water barrier and has a long track record. It is widely available at every roofing supply house.
Cons. Felt tears easily during installation, especially in windy conditions. It absorbs water and wrinkles when wet, which can create ridges visible through thin shingle profiles. It degrades rapidly when exposed to UV radiation, which means it must be covered with roofing material quickly. In Florida heat, felt can dry out and become brittle within months if left exposed. It has no self-sealing properties, meaning it does not seal around nail penetrations. Every nail hole is a potential water entry point.
When it is appropriate. Felt is acceptable for budget-conscious projects outside the HVHZ where the homeowner does not need the secondary water resistance insurance credit. It meets minimum code in most of Florida outside Miami-Dade and Broward counties. However, it is increasingly being replaced by synthetic underlayment even in non-HVHZ areas because synthetic offers better performance at a modest cost increase.
Cost. $0.08 to $0.15 per square foot for material, or $150 to $300 for a typical 2,000-square-foot roof.
Type 2: Synthetic Underlayment
Synthetic underlayment is made from woven or non-woven polypropylene or polyethylene. It was introduced in the early 2000s and has rapidly become the most popular underlayment type for shingle and metal roofs outside the HVHZ.
Specifications. Products must meet ASTM D226 Type II equivalent performance standards. Major brands include Owens Corning ProArmor, GAF FeltBuster, CertainTeed RoofRunner, and Atlas Summit. Each has slightly different specifications but all meet the same performance threshold.
Pros. Synthetic is significantly stronger than felt. It resists tearing during installation even in windy conditions, which reduces waste and installation time. It does not absorb water, so it lies flat on the deck without wrinkling. It has superior UV resistance and can be left exposed for 30 to 180 days depending on the product, giving the crew flexibility on multi-day projects. It is lighter than felt, making it easier and faster to install. Some synthetic products have textured surfaces that improve traction for workers walking on steep slopes, a significant safety advantage.
Cons. Synthetic costs roughly double the material price of felt. Like felt, it does not self-seal around nail penetrations. It does not qualify as secondary water resistance for the wind mitigation insurance credit. It can be slippery on steep slopes (though many modern products have addressed this with textured surfaces).
When it is appropriate. Synthetic is the standard choice for shingle roofs outside the HVHZ where the homeowner does not require the secondary water resistance credit. It provides a better water barrier than felt, installs faster and with less waste, and provides a flatter, more professional substrate for the roof covering.
Cost. $0.15 to $0.30 per square foot for material, or $300 to $600 for a typical 2,000-square-foot roof.
Type 3: Peel-and-Stick (Self-Adhering) Underlayment
Peel-and-stick underlayment, also called self-adhering modified bitumen underlayment, is the premium option and the Florida standard for hurricane-zone roofing. It consists of a rubberized asphalt compound on a polyester or fiberglass reinforcement with a removable release film on the bottom.
Specifications. Products must meet ASTM D1970 Standard Specification for Self-Adhering Polymer Modified Bituminous Sheet Materials. In the HVHZ, products must also have a Miami-Dade County NOA or Florida Product Approval specifically for use as a secondary water barrier.
Pros. Peel-and-stick adheres directly to the roof deck, creating a sealed, waterproof membrane. This is the key advantage: the adhesive bond seals around every nail penetration, eliminating the leak points that exist with felt and synthetic underlayment. If the roof covering is torn off during a hurricane, the peel-and-stick underlayment keeps the home dry because there are no unsealed nail holes. It qualifies as secondary water resistance on the wind mitigation inspection form, earning a significant insurance premium credit. It provides the best overall water protection of any underlayment type.
Cons. Peel-and-stick costs 3 to 4 times more than felt in material costs. It requires a clean, dry roof deck for proper adhesion, which adds preparation time during installation. It cannot be installed in temperatures below 40 degrees (rarely a concern in South Florida). It requires careful alignment during installation because once the release film is removed and the sheet contacts the deck, it bonds immediately and cannot be easily repositioned. Improper installation, such as wrinkles, gaps, or failure to roll the material for full adhesion, reduces its effectiveness.
When it is appropriate. Peel-and-stick is required by code in the HVHZ (all of Miami-Dade and Broward counties). Outside the HVHZ, it is the recommended choice for any homeowner who wants the secondary water resistance insurance credit, lives in a coastal or high-wind area, or wants the best possible protection for their home. The insurance savings from the SWR credit typically pay for the upgrade within two to three years.
Cost. $0.30 to $0.60 per square foot for material, or $600 to $1,200 for a typical 2,000-square-foot roof.
What Florida Code Requires
Florida Building Code requirements for underlayment vary by location and roof type.
HVHZ (Miami-Dade and Broward counties). Full coverage with a self-adhering modified bitumen underlayment providing secondary water resistance is required. No exceptions. This applies to all new roofs and reroofs regardless of the roof covering type.
Non-HVHZ (rest of Florida). Minimum one layer of ASTM D226 Type II (30-pound) felt or approved synthetic underlayment. Peel-and-stick is not required but is recommended for the insurance credit and superior protection.
The 25 percent rule. If more than 25 percent of the roof covering is replaced in any 12-month period, the underlayment must be brought up to current code, which means peel-and-stick in the HVHZ.
The Insurance Credit Math
The secondary water resistance credit on the Florida wind mitigation form is one of the most valuable credits available. Here is how the math works for a typical South Florida homeowner.
Without SWR credit. Annual insurance premium: $4,000. This is the baseline with standard underlayment that does not qualify for secondary water resistance.
With SWR credit. Annual insurance premium: $3,400 to $3,600. The SWR credit alone saves $400 to $600 per year.
Upgrade cost. The additional cost of peel-and-stick over synthetic underlayment during a reroof: $400 to $800.
Payback period. The insurance savings pay for the underlayment upgrade in one to two years. Over the 20 to 30 year life of the roof, the total insurance savings from the SWR credit range from $8,000 to $18,000.
Making Your Decision
If you are in the HVHZ. You have no choice. Peel-and-stick is required by code. Make sure your contractor uses a product with a valid Miami-Dade NOA and installs it to manufacturer specifications.
If you are outside the HVHZ and budget is tight. Synthetic underlayment is the minimum recommended option. It provides better performance than felt at a modest cost increase and will last the full life of your roof covering.
If you are outside the HVHZ and want the best value. Peel-and-stick is the smart choice even though it is not required. The insurance savings pay for the upgrade within two years, and you get genuine secondary water resistance that could save your home during a hurricane.
Never choose felt. While felt still meets minimum code outside the HVHZ, there is no scenario where it is the best value. The modest savings in material cost are offset by shorter lifespan, more difficult installation, and zero insurance credit. Synthetic costs just $150 to $300 more and is superior in every measurable way.
Frequently Asked Questions
Is peel-and-stick underlayment required in Florida?
It is required in the HVHZ (Miami-Dade and Broward counties). Outside the HVHZ, it is not required but is strongly recommended for the insurance premium credit it provides. The credit typically saves $400 to $600 per year, paying for the upgrade within one to two years.
How much more does synthetic or peel-and-stick underlayment cost compared to felt?
For a typical 2,000-square-foot roof, felt costs $150 to $300, synthetic costs $300 to $600, and peel-and-stick costs $600 to $1,200 in material costs. Installed cost differences are smaller because synthetic installs faster. Peel-and-stick pays for itself through insurance savings within two to three years.
Can I install new underlayment without replacing the entire roof?
No. Underlayment is installed directly on the roof deck beneath the roof covering. The covering must be completely removed to access the underlayment. Choose the best underlayment you can afford during your next roof replacement since the decision will last 20 to 40 years.