Underlayment is the roofing material nobody sees and everybody depends on. It's the water-resistant layer installed directly over the roof deck, beneath the shingles, tile, or metal panels, and in Central Florida it does more real work than most homeowners realize. Between the daily summer thunderstorm cycle, the hail that sometimes rides in with those storms, and attic temperatures that climb well past what most underlayment products were originally designed for, the choice of underlayment affects how a roof actually performs here — not just how it looks on a spec sheet. Alpine Exteriors installs and repairs roofs across Orlando, Winter Park, Kissimmee, Apopka, Oviedo, Lake Mary, and Windermere, and underlayment selection is one of the more consequential decisions we walk homeowners through on almost every roofing job.
Underlayment falls into three broad categories, and most Central Florida roofs use some combination of them:
All three do the same basic job — keep water off the wood deck if the primary roof covering is breached — but they differ quite a bit in how they hold up to sun, heat, foot traffic, and wind-driven rain before the shingles or tile ever go down, and for the life of the roof after.
Central Florida's roofing conditions are different from the coastal parts of the state, and different again from most of the country, in a few specific ways that matter for underlayment.
Daily convective thunderstorms. From roughly late spring through early fall, Orlando and the surrounding suburbs see near-daily afternoon storms that can drop heavy rain in a short burst, often with gusty, shifting wind. That wind pushes rain sideways and even slightly upward under the lower courses of shingles at eaves and around valleys, ridges, and penetrations like plumbing stacks and skylights. This is exactly the scenario self-adhered underlayment is built for, which is why we install it at valleys, eaves, and roof-to-wall transitions on nearly every job regardless of what's used across the rest of the deck.
Hail. Central Florida's storm cells are strong enough to occasionally produce hail, particularly during spring severe-weather season. Hail can crack or bruise shingles and tile without immediately causing a visible leak, and a quality underlayment is the backup layer that keeps the deck dry during the window between storm damage and repair. It's not a substitute for timely hail damage repair, but it buys time and reduces the odds of a hidden leak turning into deck rot.
Attic heat and UV exposure. Inland Central Florida doesn't get the tempering effect of a coastal sea breeze, and attic temperatures under an Orlando-area roof commonly run well above outdoor air temperature on a sunny afternoon. That heat matters two ways: first, felt and lower-grade synthetics can become brittle faster under sustained UV exposure if a job sits open longer than planned during installation; second, standard (non-high-temp) self-adhered membranes can soften and actually slide down a steep slope under a dark shingle or metal roof baking in Florida sun. Any self-adhered underlayment we install under metal roofing or dark-colored shingles is specified as high-temperature-rated for this reason — it's a small line-item difference that avoids a real problem five or ten years down the road.
Orange County and area permitting. Reroofing in Orlando, Winter Park, and the surrounding jurisdictions requires a permit and inspection under the Florida Building Code, and underlayment type and installation method (fastener pattern, lap widths, and where self-adhered membrane is required) are things inspectors check. Some carriers also give a premium credit on the wind mitigation inspection for a documented secondary water barrier, so the underlayment spec can have a small effect on your insurance paperwork, not just the roof itself.
Synthetic underlayment
Asphalt-saturated felt
Self-adhered membrane
Underlayment isn't a maintenance item in the way gutters or caulking are — once it's under the roof covering, there's nothing to service on a schedule. What matters is how long it lasts relative to the roof covering above it. Felt is generally expected to last the life of the shingles it's paired with on a normal reroof cycle, but it isn't warrantied or intended to function well as a standalone weather barrier for an extended period if shingles are stripped and the deck sits exposed. Synthetic underlayment is often rated by manufacturers for 20-30 years and tends to hold up better to short-term UV exposure during construction, but in practice it's still replaced whenever the roof covering above it is replaced — nobody reuses old underlayment on a reroof. The one time underlayment condition matters outside a full reroof is after storm or hail damage: if shingles are cracked, lifted, or missing, the underlayment underneath should be inspected for tears or UV damage before new covering goes back down, since a compromised deck barrier defeats the point of the repair.
The practical comparison most Central Florida homeowners are actually making is synthetic underlayment versus traditional felt, since both are code-compliant and widely used here. Felt is the lower-cost, long-track-record option; it does the job on a roof that's covered promptly and isn't exposed to weather any longer than necessary during installation. Synthetic costs more but tolerates a delayed install better, is lighter and safer for crews on steep Central Florida roof pitches, and generally holds up longer to the UV load an inland Florida attic and roof deck see. Neither one is "wrong," and Alpine Exteriors installs both depending on the roof system, the homeowner's budget, and the schedule — the decision that actually matters more than felt-versus-synthetic is making sure self-adhered membrane goes in at the valleys, eaves, and penetrations where our storm pattern puts the most water pressure on the roof, regardless of which underlayment covers the rest of the deck.
If the deck is being fully stripped down to bare wood, yes — code requires new underlayment as part of a reroof, and reusing old underlayment isn't standard practice or typically inspector-approved. If it's a smaller shingle repair that doesn't expose the underlayment, it may not need to be touched.
Both are code-compliant options under the Florida Building Code; synthetic isn't mandated. Certain high-wind-exposure areas and self-adhered requirements at valleys and eaves are more about installation method than which base underlayment type you choose.
For a limited time, generally yes — that's its job as a backup barrier. But it's not a permanent roof covering, it's UV-sensitive if left exposed, and any damaged shingles or tile should be repaired promptly rather than relying on underlayment indefinitely.
It can factor into the wind mitigation inspection, specifically the secondary water barrier and roof deck attachment items, which some carriers credit. The effect on your specific premium depends on your carrier and policy, so we'd recommend confirming with your insurer or agent rather than assuming a fixed discount.
If you're planning a reroof or dealing with storm damage anywhere from Orlando and Winter Park out to Kissimmee, Apopka, Oviedo, Lake Mary, or Windermere, Alpine Exteriors can walk your roof, explain what underlayment system fits your budget and roof type, and handle the permitting that comes with it. Reach out for an on-site assessment before you commit to a material.