Published underlayment exposure time limits run from 30 days to 180 days depending on the exact product, and the UV rating on the data sheet is the spec that decides whether a dried-in roof can sit over a weekend, a two week weather delay, or a phased job that runs into the next season. GAF prints 180 days on Deck-Armor and Tiger Paw but only 90 days on FeltBuster. Owens Corning prints 90 days on ProArmor and 60 days on RhinoRoof U20. Asphalt felt carries no UV rating at all.
Two things trip crews up. The clock starts the day the sheet is fastened down, not the day the weather cleared. And in some jurisdictions a product approval cuts the manufacturer’s number by a factor of six.
What an underlayment UV exposure rating actually covers
A UV exposure rating is the manufacturer’s published maximum number of days the underlayment may stay uncovered before the primary roof covering goes on. It is a materials claim about the sheet itself, and nothing more. GAF states it directly in the footnote on its FeltBuster sell sheet: the day count “refers to standardized testing conducted by GAF to ensure the product will not physically degrade when exposed to UV. It is NOT related to withstanding water, snow, or wind.”
The same footnote runs on GAF’s Deck-Armor and Tiger Paw sell sheets, alongside an instruction in capitals not to use the product as a temporary roof to protect property or possessions. A sheet inside its rating can still leak at a lap, at a fastener, or under wind driven rain.
The rating is also not a code number. ICC-ES report ESR-2808, reissued July 2026, evaluates Deck-Armor, Tiger Paw and FeltBuster against the ICC-ES Acceptance Criteria for Roof Underlayments (AC188) for physical properties and fire classification. It assigns no UV exposure period at all. The day count you plan around comes from the manufacturer, not from the evaluation report.
Published UV exposure limits by product
Every figure below is the number printed on that manufacturer’s own data sheet, warranty or technical letter. Where a manufacturer publishes no number, the table says so rather than borrowing a sibling product’s figure.
| Product | Manufacturer | Published exposure limit | Where the figure is published |
|---|---|---|---|
| Titanium UDL25 | Owens Corning (InterWrap) | Up to 6 months (180 days) | UDL25 technical data sheet |
| Titanium UDL30 | Owens Corning (InterWrap) | Up to 6 months (180 days) | UDL30 technical data sheet |
| Titanium UDL50 | Owens Corning (InterWrap) | No UV rating printed on the data sheet; warranty voids past 180 days uncovered | UDL50 technical data sheet and UDL50 Limited Warranty |
| Deck-Armor Premium Breathable Roof Deck Protection | GAF | 180 days | Deck-Armor sell sheet |
| Tiger Paw Premium Roof Deck Protection | GAF | 180 days | Tiger Paw sell sheet RESUL179 |
| FeltBuster High-Traction Synthetic Roofing Felt | GAF | 90 days | FeltBuster sell sheet |
| ProArmor Synthetic Roof Underlayment | Owens Corning | 90 days | ProArmor product data sheet |
| RhinoRoof U20 | Owens Corning | 60 days | RhinoRoof U20 product data sheet |
| Grace Tri-Flex XT | GCP Applied Technologies | 180 days | GCP Technical Letter 3 |
| Grace Tri-Flex 15 | GCP Applied Technologies | 30 days | GCP Technical Letter 3 |
| Grace Ice and Water Shield | GCP Applied Technologies | 90 days | GCP Technical Letter 3 |
| Grace Ice and Water Shield HT | GCP Applied Technologies | 120 days | GCP Technical Letter 3 |
| Grace Ultra | GCP Applied Technologies | 120 days | GCP Technical Letter 3 |
| Grace Select and GCP granular underlayments | GCP Applied Technologies | 30 days | GCP Technical Letter 3 |
| 15 lb and 30 lb asphalt saturated felt (ASTM D226) | Various | No published UV exposure rating | Felt data sheets list ASTM type, weight and coverage only |
Two patterns are worth reading off that table. Within a single brand the spread is wide: Owens Corning sells a 180 day sheet, a 90 day sheet and a 60 day sheet, so “we used Owens Corning underlayment” tells you nothing about the window. And self-adhered leak barriers usually get shorter windows than the mechanically attached synthetics above them, which is why the Grace Ice and Water Shield line tops out at 90 to 120 days. For the grade by grade differences inside one family, see our breakdown of Titanium UDL25, UDL30 and UDL50 specs.
Felt has no UV rating, and it fails a different way
No. 15 and No. 30 asphalt saturated organic felt to ASTM D226 carries no meaningful UV exposure rating. Felt data sheets list the ASTM type, roll dimensions and coverage, and stop there. Tarco’s asphalt saturated organic felt sheet is typical: Type I and Type II listings, roll sizes, no exposure figure anywhere on the page.
Felt does not embrittle the way a UV stabilized polypropylene sheet does. It dries out. The asphalt saturant volatilizes in sun and heat, the organic mat loses flexibility, and the sheet curls at the edges, buckles between fasteners, and tears at the nail heads. A felt roof left out reads as wrinkled and lifted long before a synthetic of the same age looks like anything at all.
One caveat on the “no rating” claim. Some felt makers publish a durability statement rather than a UV number. GMC’s organic felt sheet says the product “Remains viable even after prolonged exposure. Minimum of 60 days in single ply and 6 months in two ply applications.” That is a claim about staying serviceable, not a UV exposure rating, and it is not comparable to the tested day counts the synthetics publish. If you are choosing between the two materials, our felt vs synthetic underlayment comparison covers the rest of the tradeoff, and the roofing felt reference covers 15 lb against 30 lb.
What actually degrades while the deck sits bare
Three separate mechanisms run at once on an exposed roof, and only one of them is what the UV rating measures. A sheet can be well inside its published window and still be compromised by the other two.
UV embrittlement
Polypropylene and polyolefin sheets are UV stabilized with additives that are consumed over time. As they deplete, the polymer chains break down, the sheet loses elongation and tear strength, and it begins to crack or powder at the surface. This is the failure the published day count is calibrated against, and it is the slowest of the three. It is also the one you can least easily see from the ground.
Heat and thermal cycling
Heat works on the sheet independently of UV. GCP is unusually candid about this in Technical Letter 3: during the exposure period the two factors at work are heat and UV radiation, and UV “will not affect the membrane in any significant way during its maximum exposure limit.” What heat does instead is move the sheet. GCP says that after a long exposure it is normal for self-adhered membranes to appear slightly wrinkled, to show a slight color change in the non-slip coating, and to curl at the edges.
That movement matters where it crosses a lap. GCP’s instruction is to inspect before covering: a wrinkle that extends to the edge of a lap must be cut, pressed down and patched with a round patch extending 6 inches past the damaged area in all directions, and any curling at edges or corners must be cut and patched if the affected area is more than half an inch wide. Titanium UDL sheets carry a published service temperature range of minus 40F to 240F, which is the band the material is expected to cycle through.
Wind flutter at the fasteners
Flutter is the fastest failure mode and the one that actually loses roofs. Wind lifts the field of the sheet between fasteners, the sheet works back and forth against the nail head, and the fastener hole elongates until the sheet tears free. Manufacturers respond by changing the fastening schedule for exposure rather than by changing the UV number.
Owens Corning’s RhinoRoof U20 data sheet is explicit: if the product will be exposed longer than 24 hours and up to 60 days, it must be attached with minimum 1 inch diameter plastic or metal cap roofing nails, and for extended exposure the recommendation is to anchor at every printed fastening position on the facer. Where driving rain or strong winds are expected, the sheet calls for doubling lap widths, or sealing between laps with a compatible sealant or peel and stick tape. GAF’s Miami-Dade notice of acceptance 18-1023.10 makes a similar move, directing that all end and side laps be taped with an approved butyl adhesive if the roof is exposed to rain or snow. Lap and fastening rules by pitch are covered in our guide to underlayment slope and lap requirements.
The clock starts at installation, not at the last dry day
Every published limit is worded from the moment the sheet goes down, and rainy days do not pause it. Owens Corning’s RhinoRoof U20 sheet says the product “must be covered by primary roofing within 60 days of application.” The InterWrap Titanium warranty language keys off the product having been “installed and left uncovered without roof cladding” past its limit. Florida’s evaluation report language is “after installation.”
The practical version: a deck dried in on 1 March with a 90 day product has to be covered by roughly 30 May, whether or not half of those days were unworkable. A phased re-roof that dries in the whole house and then shingles one slope at a time is measured from the original dry-in date on every slope, including the one nobody has touched yet. Winter days count too, even though degradation is slower in low sun angles, because the published limit is a flat calendar figure and not a UV dose budget.
Where a code approval overrides the data sheet number
In Florida, the state product approval sets the exposure limit, not the sell sheet. Trinity ERD evaluation report FL15487, issued 23 April 2012 for GAF Synthetic Roof Underlayments, states under Exposure Limitations that Deck-Armor, RoofPro, Shingle-Mate, StormSafe anchor sheet, Tiger Paw and VersaShield “shall not be left exposed for longer than 30-days after installation.”
That is 30 days for the same Tiger Paw sheet GAF markets at 180 days, a factor of six. A contractor planning a Florida dry-in around the marketing figure is planning around a number the approving engineer did not accept.
Miami-Dade applies a comparable 30 day cap in a different place. Notice of acceptance 18-1023.10 instructs that WeatherWatch mineral surfaced leak barrier and StormGuard film surfaced leak barrier not be left exposed for more than 30 days without a roof deck protection underlayment over the secondary water barrier.
Approvals are revised, and they vary by jurisdiction, product revision and roof system. Before quoting a 180 day window to an inspector or an adjuster, pull the current approval for that product in that state. For a wider read on which brands publish what, see our roundup of synthetic underlayment brands.
What blowing past the limit does to the warranty
The underlayment warranty is usually the first thing to go, and the wording is generally unconditional. The InterWrap Titanium limited warranty covering UDL25, UDL30 and UDL50 promises the product will retain its ability to shed water for 40 years from the invoice date, then states that the warranty does not apply if “any part of the product is exposed to UV after roof cladding installation” and if “the product has been installed and left uncovered without roof cladding for more than 180 days.”
Note that this is a two part exclusion, and the second half is the exposure clause. It does not ask whether the sheet still looks fine at day 200. Titanium’s claim procedure also runs tight: written notice within 30 days of discovering the defect, with field samples showing production codes, application details and photographs.
Coverage on the rest of the assembly may or may not follow. Shingle manufacturers often sell system warranties that require qualifying accessories to be installed per their instructions, so an overexposed underlayment can in some cases put enhanced system coverage at risk even when the shingle itself is fine. Whether it does depends on the specific warranty document, the jurisdiction and how the failure presents, so read the certificate rather than assuming either way.
How to plan a dry-in that has to sit
- Read the day count off the specific product data sheet, not off the brand. Owens Corning alone spans 60, 90 and 180 days across RhinoRoof U20, ProArmor and Titanium UDL.
- Record the dry-in date in the job file the day the sheet is fastened. That date, not the weather, is day zero.
- Check the product approval for the jurisdiction. In Florida, 30 days may apply to GAF synthetics regardless of the sell sheet.
- Fasten for exposure from the start. Cap fasteners at every printed position beats going back to add them after the first wind event.
- Treat the laps if wind or driving rain is in the forecast: double the lap width, or seal the laps with a compatible sealant or butyl tape per the manufacturer’s instruction.
- Walk the roof before covering. Cut, press and patch any wrinkle that runs into a lap, patch edge curling wider than half an inch, and replace any area torn at the fasteners.
- If the limit will be blown, ask the manufacturer in writing. GCP, for example, allows Tri-Flex to be applied over its self-adhered membranes to extend the exposure period where the application allows it.
Frequently asked questions
How long can roofing underlayment be left exposed?
Published limits run from 30 days to 180 days depending on the product. GAF rates Deck-Armor and Tiger Paw at 180 days and FeltBuster at 90 days. Owens Corning rates ProArmor at 90 days and RhinoRoof U20 at 60 days. GCP rates Tri-Flex XT at 180 days and Grace Select at 30 days. Asphalt felt has no published UV exposure rating.
What does a 180 day UV rating actually mean?
It means the manufacturer’s testing showed the sheet will not physically degrade from UV within 180 days of exposure. GAF’s own footnote says the rating “is NOT related to withstanding water, snow, or wind.” It is a materials claim about the underlayment, not a promise that the roof is watertight, and GAF instructs that the product not be used as a temporary roof.
Does the exposure clock pause during rain or winter?
No. Manufacturers word the limit as a flat calendar count from installation. Owens Corning requires RhinoRoof U20 to be covered by primary roofing within 60 days of application, and the Titanium warranty measures from the product being installed and left uncovered. Days when nobody could work still count, and on a phased job every slope is measured from the original dry-in date.
Does felt underlayment have a UV rating?
No. Data sheets for 15 lb and 30 lb asphalt saturated felt to ASTM D226 publish the ASTM type, roll size and coverage, with no UV exposure figure. Felt also fails differently: rather than embrittling, it dries out, curls at the edges, buckles between fasteners and tears at nail heads. Some makers publish a general durability statement, which is not the same thing.
What happens if underlayment is left exposed past its limit?
Expect three things: loss of tear strength and elongation from UV, wrinkling and edge curl from heat cycling, and elongated fastener holes from wind flutter. Before covering, GCP directs that wrinkles crossing a lap be cut, pressed and patched with a round patch extending 6 inches past the damage, and that edge curling wider than half an inch be cut and patched.
Does exposed underlayment void the warranty?
It can void the underlayment warranty outright. The InterWrap Titanium limited warranty does not apply where the product “has been installed and left uncovered without roof cladding for more than 180 days,” regardless of condition. Effects on shingle or system coverage vary by the specific warranty document and jurisdiction, so check the certificate rather than assuming the underlayment clause carries across.
By The Roofing Brief Team. Last reviewed: August 2026.