By The Roofing Brief Team. Last reviewed: October 2026.
The best ice and water shield for most asphalt shingle roofs in 2026 is Grace Ice & Water Shield from GCP Applied Technologies: a 40 mil rubberized asphalt membrane with a slip-resistant polyethylene film, listed under ICC-ES ESR-1677 and rated to stay uncovered for up to 90 days, per GCP’s March 2026 data sheet. Under metal panels, step up to a high-temperature membrane: Grace Ultra (300°F), Grace HT or Owens Corning WeatherLock Specialty Tile & Metal (both 260°F), or GAF StormGuard (250°F). On a tight budget, GAF WeatherWatch listed at $80.52 for a 200 sq ft roll at Lowe’s on October 19, 2026, about $40 per square.
An ice and water shield (also called a leak barrier or self-adhered underlayment) is a peel-and-stick membrane installed at eaves, valleys, and penetrations to stop water driven uphill by ice dams and wind. It matters because the standard roofing felt underlayment shingles sit on does not seal around fasteners or block ice-dam backup. In cold-climate counties, the IRC (Section R905.1.2) requires an ice barrier extending at least 24 inches inside the exterior wall line for asphalt shingles, metal shingles, slate, and wood roofs, per the 2021 IRC, Chapter 9.
How we picked the best ice and water shield
This is an editorial ranking compiled from manufacturer data sheets and product pages (GCP Applied Technologies, GAF and Owens Corning), the ASTM D1970 standard for self-adhered ice-barrier underlayments, the IRC ice-barrier rule, and retail roll prices listed on Google Shopping on October 19, 2026. We did not run hands-on lab or field tests. Per-square prices below are the listed roll price divided by the roll’s square footage, so treat them as planning figures rather than quotes.
Three published specs decide most jobs. Surface type (granular, smooth film, or high-heat film) controls where a membrane can go. The high-temperature rating (240°F to 300°F among the membranes here that publish one) determines whether it can sit under hot metal panels without the adhesive migrating. The UV-exposure window, which runs from 30 days for Owens Corning WeatherLock G to 180 days for Titanium PSU30 and WeatherLock Specialty Tile & Metal, sets how long it can stay uncovered before shingles or panels go on. We weighted those first, then price per square.
Best ice and water shield brands compared (2026)
Published high-temperature ratings in this group run from 240°F (Titanium PSU30) to 300°F (Grace Ultra). “Not published” means the current maker sheet we checked does not state the value.
| Product | Surface | Max temp | UV exposure | Roll size | Best for | Source |
|---|---|---|---|---|---|---|
| Grace Ice & Water Shield (GCP) | Slip-resistant poly film, 40 mil | Not published; GCP points copper, zinc and COR-TEN roofs to Grace Ultra | Cover within 90 days | 225 sq ft (36 in x 75 ft), 61.4 lb | Overall pick: eaves and valleys on shingle roofs | GCP data sheet, updated Mar 20, 2026 |
| Grace Ultra (GCP) | Poly film, 100% butyl adhesive | 300°F | Up to 120 days | 198 sq ft | Metal roofs and extreme heat | GCP Grace Ultra data sheet, Jun 2025 |
| Grace Ice & Water Shield HT (GCP) | Poly film, rubberized asphalt | 260°F | Up to 120 days | 225 sq ft | Metal and tile at a lower price than Ultra | GCP HT data sheet |
| GAF StormGuard | Smooth film | 250°F | Up to 90 days | 200 sq ft (36 in x 66.7 ft) | Mixed shingle and metal, GAF system warranty | GAF StormGuard sell sheet RESUL116 (2018) |
| Owens Corning Titanium PSU30 | Sure-Foot polymer mesh over asphalt adhesive | 240°F | Up to 6 months (180 days) | 216 sq ft (36 in x 72 ft), 48 lb | Walkability and long UV exposure | Owens Corning PSU30 page; 240°F from an earlier Titanium data sheet |
| GAF WeatherWatch | Mineral granules, fiberglass mat | Not published | Up to 60 days, if necessary | 150 sq ft or 200 sq ft | Budget granular for shingle eaves | GAF WeatherWatch sell sheet RESUL103 (June 2020) |
| Owens Corning WeatherLock G | Granulated, fiberglass mat, 53 mil | Not published | Up to 30 days | 200 sq ft (3 ft x 66.7 ft) | Pairing with an Owens Corning shingle system | Owens Corning WeatherLock G page; 53 mil from OC’s 2017 data sheet; 30-day UV limit from OC Pub. 10009578-P (Nov 2025) |
Ice and water shield price per square (retail listings, October 19, 2026)
| Product | Listed roll price | Roll size | Price per square (100 sq ft) | Source |
|---|---|---|---|---|
| GAF WeatherWatch | $80.52 to $99.97 | 200 sq ft | $40 to $50 | Lowe’s; Lakefront Supply (Google Shopping, Oct 19, 2026) |
| Owens Corning WeatherLock Mat | $108.00 | 200 sq ft | $54 | Home Depot (Google Shopping, Oct 19, 2026) |
| Owens Corning WeatherLock G | $119.00 to $139.00 | 200 sq ft | $60 to $70 | Menards; Lowe’s (Google Shopping, Oct 19, 2026) |
| GAF StormGuard | $119.00 to $148.94 | 200 sq ft | $60 to $74 | Woodson Lumber; Builders Warehouse (Google Shopping, Oct 19, 2026) |
| Owens Corning WeatherLock Specialty Tile & Metal | $146.00 | 214 sq ft | $68 | Arbor (Google Shopping, Oct 19, 2026) |
| Owens Corning Titanium PSU30 | $159.00 | 216 sq ft | $74 | S.W. Collins (Google Shopping, Oct 19, 2026) |
| Owens Corning WeatherLock Flex | $189.00 | 225 sq ft | $84 | S.W. Collins (Google Shopping, Oct 19, 2026) |
| Grace Ice & Water Shield | $179.00 to $251.17 | 225 sq ft | $80 to $112 | Schafer Metals; Home Depot (Google Shopping, Oct 19, 2026) |
| Grace Ice & Water Shield HT | $292.83 | 225 sq ft | $130 | Home Depot (Google Shopping, Oct 19, 2026) |
| Grace Ultra | $372.00 | 198 sq ft | $188 | Schafer Metals (Google Shopping, Oct 19, 2026) |
Per-square figures are the listed roll price divided by roll square footage, rounded to the dollar. Listings exclude tax, delivery and contractor discounts, and one retailer’s price on one day can differ from your supplier’s.
1. Grace Ice & Water Shield: best overall (top pick)
Grace Ice & Water Shield ranks first because it carries the most complete public documentation in this group: a dated data sheet, ICC-ES ESR-1677 approval under AC-48, Miami-Dade and Florida product approvals, and a UL Class A fire classification under fiberglass shingles. GCP describes it as a rubberized asphalt adhesive backed by a slip-resistant, cross-laminated polyethylene film, with a 35-plus-year track record. The 225 sq ft roll (36 inches by 75 feet) weighs 61.4 lb, and the membrane is 40 mil thick with permeance of 0.05 perms, so it acts as a vapor barrier as well.
Its ceiling is heat. GCP’s sheet publishes no high-temperature rating for the standard membrane, warns that some applications are prohibited in hot southwestern deserts, and says not to use it under copper, COR-TEN or zinc roofs at high altitude, where Grace Ultra is required instead. For metal, GCP sells Grace Ice & Water Shield HT (rated to 260°F) and the butyl Grace Ultra (300°F). Retail listings on October 19, 2026 ran $179.00 to $251.17 per 225 sq ft roll, or $80 to $112 per square, which puts standard Grace above the budget granular options.
2. Grace Ultra: best for metal roofs and extreme heat
Grace Ultra is the strongest choice for metal roofs and high-heat assemblies because its 100% butyl rubber adhesive contains no asphalt and is formulated to withstand 300°F, the highest rating in this group, per GCP’s June 2025 data sheet. Butyl does not soften and migrate the way rubberized asphalt can under a hot standing-seam panel, and GCP also names Ultra for tie-ins to EPDM and TPO, which standard Grace is not compatible with.
Ultra is the most expensive membrane here: Schafer Metals listed a 198 sq ft roll at $372.00 on October 19, 2026, about $188 per square. GCP rates it for up to 120 days of exposure. On a shingle roof in a mild climate that heat headroom is unnecessary, so Ultra earns its place on copper, zinc, dark standing-seam and low-slope metal roofs where a 180°F to 250°F membrane would be pushed past its rating.
3. GAF StormGuard: best for mixed roofs and system warranty
GAF StormGuard is the pick when you want one membrane for both shingle and metal work or you are building a warranted GAF system. GAF’s StormGuard sell sheet (RESUL116) lists a 250°F high-temperature rating, UV exposure of up to 90 days if necessary, a 2-square roll that is 36 inches by 66.7 feet, ICC-ES ESR-1322, and passing results on the ASTM D1970 nail-sealability and low-temperature (-20°F) tests. The same sheet says most codes require ice-dam protection at eaves where the January average temperature is 25°F or lower.
Retail listings on October 19, 2026 ran $119.00 to $148.94 per 200 sq ft roll, about $60 to $74 per square. On a full GAF roof, StormGuard is one of the GAF accessories that can count toward the maker’s enhanced system warranties, so read GAF’s current warranty terms before swapping in another brand’s membrane.
4. Owens Corning Titanium PSU30: best for walkability and long exposure
Titanium PSU30 suits crews who value footing and a long exposure window. Owens Corning lists a Sure-Foot dimensional mesh walking surface, up to six months of UV exposure protection, a Lifetime Limited Warranty, use on slopes of 1/2:12 or greater, and a roll that is 72 feet by 36 inches (2.16 squares) weighing 48 lb. An earlier Titanium PSU30 data sheet rates it for service from -20°F to 240°F in metal applications.
PSU30 pairs a synthetic polymer top sheet with an asphalt adhesive, and it laps asphalt to asphalt. S.W. Collins listed a 3 ft x 72 ft roll at $159.00 on October 19, 2026, about $74 per square. It fits steep-slope work where grip matters and phased re-roofs where the deck may sit exposed for weeks, within its 180-day limit.
5. GAF WeatherWatch: best budget granular barrier
GAF WeatherWatch is the value pick for asphalt-shingle eaves and valleys. GAF’s sell sheet (RESUL103) describes a mineral-surfaced, fiberglass-reinforced membrane that meets ASTM D1970 and ICC-ES ESR-1322, sold in 1.5-square (36 in x 50 ft) and 2-square (36 in x 66.7 ft) rolls. Lowe’s listed the 200 sq ft roll at $80.52 on October 19, 2026, about $40 per square, the lowest price in this comparison.
The trade-offs: GAF’s June 2020 sell sheet (RESUL103) publishes no high-temperature rating and allows UV exposure of up to 60 days only if necessary, and the granular top makes it a shingle product, not a metal-panel underlayment. For a shingle re-roof in IRC ice-barrier territory, it delivers code-compliant eave and valley protection at the lowest material cost. Cover it with shingles the same day or as soon as the schedule allows.
6. Owens Corning WeatherLock: best for an Owens Corning system
Owens Corning WeatherLock is the leak barrier to use when the rest of the roof is an Owens Corning system, sold in granular (WeatherLock G), smooth (WeatherLock Mat), flexible (WeatherLock Flex) and high-heat (WeatherLock Specialty Tile & Metal) versions. Owens Corning lists WeatherLock G and Flex as engineered for asphalt shingle, wood shake and quarry slate roofs, and recommends full-deck coverage on 2:12 to 4:12 pitches with proper ventilation.
Retail listings on October 19, 2026: WeatherLock Mat at $108.00 per 200 sq ft roll (Home Depot, about $54 per square), WeatherLock G at $119.00 (Menards, about $60 per square), and WeatherLock Flex at $189.00 per 225 sq ft roll (S.W. Collins, about $84 per square). Owens Corning includes WeatherLock in its Total Protection Roofing System, so choosing it keeps the underlayment inside the system that its upgraded warranties cover.
Owens Corning water and ice shield: WeatherLock G, Mat, Flex, and Specialty Tile & Metal
Owens Corning WeatherLock is the brand’s self-adhered ice and water shield, sold as four lines that split by surface and job: WeatherLock G (granulated), WeatherLock Mat (smooth), WeatherLock Flex (flexible detailing), and WeatherLock Specialty Tile & Metal (high-heat). Matching the Owens Corning water and ice shield line to the roof area matters more than the brand badge, since each line is built for a different spot on the deck. For line-by-line data sheet figures, see our Owens Corning WeatherLock review.
| WeatherLock line | Surface | Where it is used | Roll coverage | Notes | Source |
|---|---|---|---|---|---|
| WeatherLock G | Granulated asphalt, fiberglass mat | Eaves and valleys on shingle, wood-shake, and slate roofs | 200 sq ft (3 ft x 66.7 ft); 100 sq ft roll also sold | 53 mil; UV exposure up to 30 days (OC Pub. 10009578-P); full deck recommended on 2:12 to 4:12 | Owens Corning WeatherLock G page; OC 2017 data sheet |
| WeatherLock Mat | Polymeric coating, fiberglass mat (SureStep traction) | Secondary barrier under shingles, wood shakes, and quarry slate | 200 sq ft (3 ft x 66.7 ft) | Non-granular alternative to G for the same assemblies | Owens Corning WeatherLock Mat page |
| WeatherLock Flex | Flexible poly over modified asphalt | Pipes, chimneys, skylights, inside corners, and tight details | 225 sq ft roll (3 ft x 75 ft) | Adheres in cold-weather applications to 40°F | Owens Corning WeatherLock Flex page |
| WeatherLock Specialty Tile & Metal | Polyester walking surface | Foam-set or mechanically fastened tile and metal panel systems | 214 sq ft (3 ft x 71.3 ft) | Rated to 260°F; UV exposure up to 180 days; 30-year limited warranty | Owens Corning Specialty Tile & Metal page |
Coverage, temperature and exposure figures are from Owens Corning product pages checked October 19, 2026, except where a dated data sheet is named. This is a specifications review, not a hands-on lab test.
Where each line fits comes down to the surface and the heat:
- Standard shingle eaves and valleys: WeatherLock G for a granular surface that grips shingles, or WeatherLock Mat for a smooth-surface equivalent.
- Detail work and penetrations: WeatherLock Flex, which bends around pipes, chimneys, skylights, and inside corners and still adheres in cold weather down to 40°F.
- Tile or metal panels: WeatherLock Specialty Tile & Metal, the high-heat line rated to 260°F with a 180-day UV window, since Owens Corning publishes no high-temperature rating for G, Mat or Flex and does not list them for metal panels.
Which ice and water shield should you buy?
Match the membrane to the roof covering and the hottest expected deck temperature first (ratings of 240°F to 300°F for metal), then to price per square ($40 to $188 in the October 19, 2026 listings).
| If your roof is… | Buy | Why (published threshold) |
|---|---|---|
| Asphalt shingles, cold climate, budget under $50 per square | GAF WeatherWatch | $40 to $50 per square listed Oct 19, 2026; meets ASTM D1970 |
| Asphalt shingles, Owens Corning system warranty | WeatherLock G or Mat | Listed in OC’s Total Protection Roofing System; $54 to $70 per square |
| Asphalt shingles, longest documented track record | Grace Ice & Water Shield | ESR-1677; 90-day exposure limit; 35-plus years per GCP |
| Standing seam or exposed-fastener steel, deck heat up to 250°F | GAF StormGuard | 250°F rating; $60 to $74 per square |
| Metal or tile, deck heat up to 260°F, roof open for up to 180 days | WeatherLock Specialty Tile & Metal or Grace HT | 260°F; 180 days (OC) or 120 days (Grace HT) |
| Copper, zinc, COR-TEN, dark metal at altitude, or tie-in to EPDM/TPO | Grace Ultra | 300°F butyl; GCP names Ultra for these roofs |
| Steep slope that crews walk for weeks before cover-up | Titanium PSU30 | Sure-Foot mesh; up to 6 months UV; 240°F |
| Pipe boots, chimneys, skylight corners | WeatherLock Flex | Conforms to corners; adheres to 40°F |
- Asphalt shingle, moderate climate: Grace Ice & Water Shield for the most complete documentation, or GAF WeatherWatch and Owens Corning WeatherLock to cut material cost to $40 to $70 per square.
- Metal roof or hot climate: Grace Ultra (300°F) or Grace HT (260°F); GAF StormGuard (250°F) as a mid-priced film option, or Owens Corning WeatherLock Specialty Tile & Metal (260°F) to stay inside an Owens Corning system.
- Long exposure or steep, walked-on slopes: Owens Corning Titanium PSU30 for its non-slip surface and six-month UV window.
- Warranted manufacturer system: match the membrane to your shingle brand (GAF StormGuard or WeatherWatch, Owens Corning WeatherLock) so it counts toward system coverage.
Whatever you choose, install it where water backs up: at the eaves to at least 24 inches inside the exterior wall line (IRC R905.1.2), in valleys, and around every penetration. GCP’s installation section calls for side laps of at least 3.5 inches, end laps of at least 6 inches, and air, deck and membrane at 40°F or warmer. Pair it with correct eave and gutter flashing so the membrane and metal shed water together, which limits the interior water damage an ice dam can cause.
Do you need ice and water shield everywhere?
No. The IRC requires an ice barrier only at the eaves, and only where the jurisdiction marks ice-dam damage as a local hazard in its design criteria table (IRC Table R301.2). The 2021 IRC text sets the minimum at two cemented layers of underlayment or a self-adhering polymer modified bitumen sheet from the eave to 24 inches inside the exterior wall line, and adds 36 inches along the slope on roofs of 8:12 or steeper. That 8:12 clause was removed in the 2024 IRC, so the rule depends on which edition your jurisdiction adopted. Valleys and penetrations are the maker-recommended priority spots beyond that.
Full-deck coverage is a deliberate choice, not a default. Grace’s data sheet states its membrane is an air and vapor barrier at 0.05 perms, so a fully covered deck needs the attic ventilation to dry the sheathing from below; Owens Corning recommends full-deck WeatherLock on 2:12 to 4:12 pitches only with proper ventilation. Across the open field of a shingle roof at 4:12 or steeper, the IRC underlayment table (R905.1.1) calls for a single layer of felt or approved synthetic underlayment, not a self-adhered membrane. Our guide to the best synthetic underlayment brands covers that field layer. If you are weighing a full DIY roof replacement, confirm your local amendments, since some jurisdictions and post-storm-damage rebuilds expand the requirement.
Frequently asked questions
What is the best ice and water shield brand?
Grace Ice & Water Shield from GCP Applied Technologies is our editorial top pick for shingle roofs: it is a 40 mil rubberized asphalt membrane with ICC-ES ESR-1677 approval and a 90-day exposure limit, per GCP’s March 2026 data sheet. For metal roofs, Grace Ultra is rated to 300°F. On a budget, GAF WeatherWatch listed at about $40 per square on October 19, 2026.
How much does ice and water shield cost?
Retail roll prices listed on October 19, 2026 worked out to about $40 per square (100 sq ft) for GAF WeatherWatch, $54 to $70 for Owens Corning WeatherLock Mat and G, $60 to $74 for GAF StormGuard, $80 to $112 for Grace Ice & Water Shield, and $188 for Grace Ultra. Installed cost adds labor, and the total depends on how many linear feet of eave, valley and penetration you cover.
Is Grace or GAF ice and water shield better?
They solve different jobs. Grace Ice & Water Shield has the longer published record (35-plus years per GCP) and a 90-day exposure limit, but no published high-temperature rating. GAF StormGuard is rated to 250°F with up to 90 days of exposure and counts toward GAF system warranties. For a warranted GAF roof, use GAF’s barrier; for a standalone shingle roof, Grace is our editorial pick.
Does code require ice and water shield?
Where the local jurisdiction marks ice-dam damage as a hazard, IRC Section R905.1.2 requires an ice barrier at the eaves, extending at least 24 inches inside the exterior wall line, for asphalt shingles, metal shingles, mineral-surfaced roll roofing, slate, and wood roofs. The 2021 IRC adds 36 inches along the slope on 8:12 and steeper roofs; the 2024 IRC dropped that clause. Check which edition and amendments your county adopted.
Can you use ice and water shield under a metal roof?
Yes, but use a high-temperature grade. Choose a membrane with a published rating such as Grace Ultra (300°F), Grace HT or Owens Corning WeatherLock Specialty Tile & Metal (260°F), GAF StormGuard (250°F), or Titanium PSU30 (240°F). Standard granular barriers such as WeatherLock G and WeatherWatch have no published high-temperature rating. Confirm the rating against the panel maker’s underlayment requirements before installing.
How long can ice and water shield be left exposed?
It depends on the product’s published limit: Grace Ice & Water Shield and GAF StormGuard up to 90 days, Grace HT and Grace Ultra up to 120 days, and Owens Corning Titanium PSU30 and WeatherLock Specialty Tile & Metal up to 180 days. GAF WeatherWatch is rated for up to 60 days if necessary, per GAF sell sheet RESUL103, and Owens Corning WeatherLock G for up to 30 days, per OC data sheet Pub. 10009578-P.
Is Owens Corning WeatherLock a good ice and water shield?
Owens Corning WeatherLock makes the most sense when the rest of the roof is an Owens Corning system, because it is part of OC’s Total Protection Roofing System. It comes in granular (G), smooth (Mat), flexible (Flex) and high-heat (Specialty Tile & Metal, 260°F) lines, with 200 to 225 sq ft rolls listed at $108 to $189 on October 19, 2026. Use the Specialty line, not G, under metal or tile.
What is the difference between WeatherLock G, Mat, and Flex?
WeatherLock G has a granulated surface for eaves and valleys on shingle, wood-shake, and slate roofs. WeatherLock Mat is the smooth, polymer-coated equivalent with SureStep traction, used under those same assemblies. WeatherLock Flex is a flexible poly-surfaced membrane made for detailing around pipes, chimneys, skylights, and inside corners, and it still adheres in cold weather down to 40°F.