Owens Corning WeatherLock is the self-adhered ice and water barrier line from Owens Corning Roofing and Asphalt (Toledo, Ohio), sold in four current US versions: WeatherLock G (granulated, 200 sq ft roll), WeatherLock Mat (SureStep surface, 200 sq ft), WeatherLock Flex (40 mil poly film, 225 sq ft) and WeatherLock Specialty Tile & Metal (65 mil, 260°F, 180 days of UV exposure, 214 sq ft). All four list ASTM D1970 on their Owens Corning data sheets. The first three must be covered within 30 days and carry a 5-year limited warranty when used under another brand’s shingles.
This review is built from the Owens Corning documents themselves: four data sheets dated August 2024 to December 2025, the installation instructions, the WeatherLock limited warranties and the August 2026 shingle warranties, plus retailer listings checked on October 19, 2026. It also covers what retail and maker pages leave out: where those documents contradict each other, how many rolls a real eave takes, and when a WeatherLock roll counts toward an extended Owens Corning warranty.
Owens Corning WeatherLock at a glance
The figures most buyers search for are roll coverage, exposure window, heat rating and warranty term. Each value below comes from the named Owens Corning publication or a dated retailer listing, and Owens Corning labels its typical values as approximate.
| Item | Figure | Source |
|---|---|---|
| Standard roll (G and Mat) | 3 ft x 66.7 ft, 200 sq ft (2 squares) | OC data sheets Pub. 10009578-P (Nov 2025), 58107-O (Aug 2024) |
| Flex roll and thickness | 3 ft x 75 ft, 225 sq ft, 40 mils | OC data sheet Pub. 10009579-O (Dec 2025) |
| Specialty Tile & Metal | 3 ft x 71.3 ft, 214 sq ft, 65 mils, up to 260°F | OC data sheet Pub. 10011679-G (Feb 2025) |
| Maximum uncovered time | 30 days (G, Mat, Flex); 180 days (Specialty Tile & Metal) | OC installation instructions; Pub. 10011679-G |
| Minimum slope and install temperature | 2:12; 40°F and rising | OC WeatherLock installation instructions |
| Warranty with non-OC shingles | 5 years (G, Mat, Flex); 30 years (Tile & Metal) | OC Pub. 10009004-C (Oct 2019); Pub. 10009003-C (Mar 2022) |
| Retail price, Oct 19 2026 | $99.98 (Mat, Lowe’s) to $189.00 (Flex, S.W. Collins) per roll | Google Shopping listings, retrieved Oct 19 2026 |
The four WeatherLock products and their data sheet specs
WeatherLock G, Mat and Flex are rubberized (modified) asphalt membranes engineered for asphalt shingle, wood shake and quarry slate roofs. Specialty Tile & Metal is the high-temperature version for foam-set or mechanically fastened tile and metal panels. G and Mat carry a FIBERGLAS mat reinforcement; Flex uses a cross-laminated poly surface instead, and Specialty Tile & Metal a polyester non-woven fabric.
| Spec | WeatherLock G | WeatherLock Mat | WeatherLock Flex | Specialty Tile & Metal |
|---|---|---|---|---|
| Surface | Granulated asphalt | Polymeric asphalt, SureStep walking surface | High-strength cross-laminated poly | Polyester non-woven fabric |
| Reinforcement | FIBERGLAS mat | FIBERGLAS mat | None listed | Fabric surface |
| Roll size | 3 x 66.7 ft, 200 sq ft | 3 x 66.7 ft, 200 sq ft | 3 x 75 ft, 225 sq ft | 3 x 71.3 ft, 214 sq ft |
| Published thickness | Not published | Not published | 40 mils | 65 mils |
| UV exposure limit | 30 days | 30 days (install sheet) | 30 days | 180 days |
| High-temperature rating | None published | None published | None published | 260°F |
| Lap edge | Taped selvedge edge | See conflicts section | Marked ply line, 3 in lap | Sticky selvage edge |
| Limited warranty term | 5 yr alone, or shingle term | 5 yr alone, or shingle term | 5 yr alone, or shingle term | 30 years |
| Data sheet | Pub. 10009578-P, Nov 2025 | Pub. 58107-O, Aug 2024 | Pub. 10009579-O, Dec 2025 | Pub. 10011679-G, Feb 2025 |
Owens Corning publishes test methods for tensile strength (ASTM D412 or D2523), tear resistance (ASTM D4073), vapor permeance (ASTM E96) and plywood adhesion at 40°F and 73 to 75°F, but the G, Mat and Flex data sheets list no numeric results for them. The only published thickness figures are 40 mils for Flex and 65 mils for Specialty Tile & Metal, so any mil figure quoted for G or Mat comes from somewhere other than the current Owens Corning sheet.
Code listings and approvals by version
All four versions list ASTM D1970, the standard the 2021 IRC references for self-adhering polymer-modified bitumen underlayment. The listings differ on fire class, Miami-Dade approval and tile-specific tests, which matters in Florida and Texas.
| Listing | G | Mat | Flex | Tile & Metal |
|---|---|---|---|---|
| ASTM D1970 | Yes | Yes | Yes | Yes |
| UL 790 / ASTM E108 fire class | Class A under asphalt shingles | Class A | Class A under asphalt shingles | Class A under clay, concrete tile and shingles; Class C under metal |
| PRI evaluation report | ER 1378E01 | Not listed on sheet | ER 1378E01 | ER 1378E02 |
| Florida Product Approval | Yes | Yes | Not on data sheet | Yes |
| Miami-Dade NOA | Yes | Yes | Not on data sheet | Yes |
| TAS 103 tile slippage and puncture | No | No | No | Yes |
| Texas Department of Insurance listed | Product page | Product page | Product page | Data sheet |
Source: the four Owens Corning data sheets named above; the Texas Department of Insurance and CSA A123.5 listings for G, Mat and Flex appear only in the standards filter on owenscorning.com product pages, checked October 19, 2026.
WeatherLock G vs Mat vs Flex vs Specialty Tile & Metal: which one to pick
Pick by roof covering first, then by exposure time and detailing. Under metal or tile, or on a job that will stay open more than 30 days, only Specialty Tile & Metal fits the Owens Corning documents. Under asphalt shingles, the choice between G, Mat and Flex comes down to surface grip, roll weight and how much cutting around penetrations the roof needs.
| If your job is… | Pick | Why, per Owens Corning documents |
|---|---|---|
| Asphalt shingles, eaves and valleys, 4:12 to 12:12 | WeatherLock G | Granulated slip-resistant surface; taped selvedge edge for 3 in side laps |
| Full deck on a 2:12 to 4:12 shingle roof | WeatherLock Mat or G | OC recommends full-deck coverage at 2:12 to 4:12 with proper ventilation; Mat is sold as the lighter roll |
| Chimneys, skylights, pipe clusters, inside corners | WeatherLock Flex | Pliable poly surface adheres around irregular shapes; granule-free; 225 sq ft roll |
| Standing seam, metal shingles, foam-set or nailed tile | Specialty Tile & Metal | 260°F rating, TAS 103 tile slippage listing, Class A under tile |
| Roof stays uncovered 31 to 180 days | Specialty Tile & Metal | Only WeatherLock rated past 30 days of exposure |
| Roof with BAPV solar panels fastened through the deck | Specialty Tile & Metal | Data sheet cites Class A with BAPV panels and sealing at panel fasteners |
| Shingles from GAF, CertainTeed, IKO or another brand | Consider the shingle maker’s own membrane | WeatherLock G, Mat and Flex drop to a 5-year warranty under non-OC shingles |
For a side-by-side ranking across brands rather than within the Owens Corning line, see our best ice and water shield comparison.
Where the WeatherLock documents disagree
Owens Corning’s own data sheets, web install pages, product filters and warranties do not always say the same thing. Six conflicts showed up in the documents current on October 19, 2026, and each one changes what a buyer or installer should do. The safer reading is listed in the last column.
| Topic | Document A says | Document B says | Safer reading |
|---|---|---|---|
| Mat UV exposure | owenscorning.com product filter: 60-day | Mat install instructions: do not leave exposed more than 30 days | Cover Mat within 30 days |
| Mat selvage edge | Data sheet Pub. 58107-O (Aug 2024): “no selvage” | Web install steps: back-nail through the selvedge edge; 3 in lap on the selvedge | Check the delivered roll before planning laps and back-nailing |
| Flex over old membrane | Flex data sheet (Dec 2025): can be applied over existing single-layer ice and water barriers | Flex install page: apply after existing shingles and underlayment are removed; Platinum, Preferred and System Protection warranties require old ice and water membrane removed | Strip to the deck if you want an extended OC warranty |
| Flex roll size | OC data sheet: 75 ft, 2.25 squares | QXO listing: 1.95 square roll, 65 ft | Count rolls from the label on the delivered product |
| Valley end overlap | G and Mat: 6 in | Flex: 3 in; Specialty Tile & Metal: 4 in minimum | Use 6 in in valleys for all versions |
| Warranty under OC shingles | WeatherLock warranty Pub. 10009004-C (2019): the shingle warranty period applies | Standard Product warranty Pub. 10023873-I (Aug 2026): components match the shingle warranty only when 3 of 5 OC component categories are installed | Install at least 3 OC component categories |
The Series installation instructions (Pub. 10011693-A, October 2019) also print OSHA’s fall protection rule as “20 CFR 1926.500”; the federal rule is 29 CFR 1926 Subpart M, and 29 CFR 1926.501(b)(13) requires fall protection on residential roofs at 6 feet or more.
How WeatherLock counts toward Owens Corning warranties
A WeatherLock roll can carry its own limited warranty, borrow the shingle warranty, or count as a required component for an extended system warranty. Which one applies depends on the shingle brand, how many Owens Corning components go on the roof, and who installs it. The August 2026 Owens Corning warranties are the current text for shingles bought after August 1, 2026.
| Situation | WeatherLock coverage | Source |
|---|---|---|
| G, Mat or Flex under non-OC shingles | 5 years from installation; OC pays reasonable cost to repair or replace defective membrane, including labor to reinstall only the membrane, excluding shingles, metalwork and flashing | Pub. 10009004-C |
| G, Mat or Flex with OC shingles plus 2 more OC component categories (3 of 5) | Components match the shingle warranty coverage and period | Standard Product Limited Lifetime Warranty, Pub. 10023873-I (Aug 2026) |
| Fewer than 3 OC component categories | Each component keeps its own product warranty | Pub. 10023873-I |
| Specialty Tile & Metal | 30 years, non-transferable; years 1 to 10 repair, replace or refund product cost excluding labor; years 11 to 30 prorated over 360 months | Pub. 10009003-C (Mar 2022) |
| Platinum or Preferred Protection | OC shingles, OC synthetic underlayment, OC Hip & Ridge, plus any 2 of: OC ice and water barrier (WeatherLock, Titanium or RhinoRoof), OC starter, VentSure ventilation | Pub. 10020608-O and 10020609-P (Aug 2026) |
| Full-deck WeatherLock on a Platinum or Preferred roof | Satisfies both the synthetic underlayment requirement and the ice and water barrier category | Pub. 10020608-O, section 4(b) |
The five categories in the August 2026 Standard Product warranty are Hip & Ridge shingles, VentSure products, OC synthetic underlayment (RhinoRoof U20 or Titanium), OC starter shingles, and WeatherLock, Titanium or RhinoRoof self-adhered ice and water barriers. On owenscorning.com, Owens Corning states that only Platinum or Preferred contractors may register an extended warranty and that they are “authorized, but not obligated” to offer one. Our Owens Corning shingle line guide lists which shingles those warranties attach to.
WeatherLock price per square in October 2026
On October 19, 2026, Google Shopping listings showed WeatherLock from $99.98 per 200 sq ft roll (Mat at Lowe’s) to $189.00 per 225 sq ft roll (Flex at S.W. Collins). Divided by roll coverage, that is $49.99 to $84.00 per square of membrane before laps. Listings change daily and vary by ZIP code, so treat these as a dated snapshot, not a quote.
| Product | Seller (listing) | Roll price | Roll coverage | Price per square (100 sq ft) |
|---|---|---|---|---|
| WeatherLock Mat | Lowe’s | $99.98 | 200 sq ft | $49.99 |
| WeatherLock Mat | Home Depot | $108.00 | 200 sq ft | $54.00 |
| WeatherLock G | Menards | $119.00 | 200 sq ft | $59.50 |
| WeatherLock 180 Specialty Tile & Metal | Arbor | $146.00 | 214 sq ft | $68.22 |
| WeatherLock Flex | S.W. Collins | $189.00 | 225 sq ft | $84.00 |
Source: Google Shopping results for each product name, retrieved October 19, 2026; coverage from the Owens Corning data sheets. Price per square = roll price divided by gross roll coverage in squares. Supply houses that sell to contractors, such as QXO (formerly Beacon), require a login to show pricing.
Worked example: how many WeatherLock rolls a roof needs
A single 36 in course does not reach the code line on most houses, so roll counts based on eave length alone come up short. On a 6:12 roof with a 12 in overhang, the barrier must cover 36 in of horizontal run, which is 40.2 in measured up the slope, so two courses are needed at every eave.
| Step | Input or rule | Result |
|---|---|---|
| 1. Horizontal run to cover | 12 in overhang + 24 in inside the exterior wall (IRC R905.1.2) | 36 in |
| 2. Along-slope length at 6:12 | 36 in x 1.118 slope factor (square root of 1 + 0.5 squared) | 40.2 in, more than one 36 in roll width |
| 3. Two eave courses, 60 ft of eave | Cut into 15 ft pieces; 3 end laps x 6 in per course | 2 x 61.5 ft = 123 ft |
| 4. Two 15 ft valleys | Full 36 in width, 18 in each side of centerline | 30 ft |
| 5. Total membrane length | Step 3 + step 4 | 153 ft |
| 6. Rolls of G or Mat | 153 ft / 66.7 ft per roll = 2.29 | 3 rolls: $357.00 (G, Menards) or $299.94 (Mat, Lowe’s) |
| 7. Rolls of Flex | 153 ft / 75 ft per roll = 2.04 | 3 rolls: $567.00 (S.W. Collins) |
Roofing Brief estimate using the October 19, 2026 listing prices above. The second course laps the first by 3 in, so two courses cover 69 in along the slope, which also clears the 36 in along-slope minimum that the 2021 IRC adds on roofs of 8:12 and steeper.
Full-deck coverage on a low-slope roof
Owens Corning’s G and Flex pages recommend covering the entire deck on 2:12 to 4:12 shingle roofs, with proper ventilation, because the membrane is a vapor barrier. A 3 in side lap leaves 33 in (2.75 ft) of net width per course, which sets the roll count.
| Item | WeatherLock G or Mat | WeatherLock Flex |
|---|---|---|
| Deck area (example) | 1,800 sq ft | 1,800 sq ft |
| Net length per roll after 6 in end laps | About 64.7 ft | About 72.5 ft |
| Net coverage per roll (x 2.75 ft) | 177.9 sq ft | 199.4 sq ft |
| Rolls needed, before hip and valley waste | 1,800 / 177.9 = 10.1, so 11 rolls | 1,800 / 199.4 = 9.03, so 10 rolls |
| Material at Oct 19 2026 listings | $1,309.00 (G) or $1,099.78 (Mat) | $1,890.00 |
Roofing Brief estimate. Under the August 2026 Platinum and Preferred warranties, a full deck of Owens Corning self-adhered membrane also meets the synthetic underlayment requirement, so no separate RhinoRoof or Titanium roll is needed on those roofs.
How to install Owens Corning WeatherLock
Owens Corning’s web instructions for WeatherLock G and Mat set out a 10-step sequence: valleys first, then eaves, with each course rolled by an 80 lb roller. The deck must be clean, frost free and dry for 24 hours, at least 3/8 in plywood or 7/16 in OSB, with gaps no wider than 1/4 in. Flex and Specialty Tile & Metal differ on laps and nailing.
- Check the slope is 2:12 or steeper and the air and deck are 40°F or warmer, below 100°F. Below 40°F the membrane will not fully adhere until it warms up.
- Nail the metal drip edge at the eave first. WeatherLock goes over the drip edge at the eave and under the drip edge at the rake, where the WeatherLock G instructions say to fit the drip edge only after the membrane has adhered.
- Line valleys first, starting at the low point, with the full 36 in width centered so it runs 18 in on each side. Overlap pieces by 6 in and hand-roll the laps.
- Cut the roll into 10 to 20 ft lengths and let them relax 3 to 5 minutes. Owens Corning warns that skipping this step can cause wrinkles that may not be covered by the warranty.
- Lay the first eave course flush with the outside edge of the drip edge, peel the lower half of the split release sheet, press it down, then fold back and peel the upper half. Above 90°F the release backing can stick; Owens Corning says to move the roll into shade until it cools.
- Roll the whole course with an 80 lb roller from the center outward to remove trapped air.
- On slopes over 3:12 or in high-wind areas, back-nail G and Mat at 12 in on center through the selvedge edge with smooth-shank galvanized roofing nails. Do not use staples.
- Lap each upper course 3 in on the selvedge or marked ply line, lap end joints 6 in, and offset end laps at least 6 ft between courses.
- Continue to 24 in inside the exterior wall, measured horizontally, or farther if the local code says so. At rakes, overlap the eave material by 6 in.
- Cover with the finished roofing within 30 days (180 days for Specialty Tile & Metal). Store rolls upright and below 90°F before use.
| Install rule | G and Mat | Flex | Specialty Tile & Metal |
|---|---|---|---|
| Side lap | 3 in on selvedge | 3 in to marked ply line | 3 in |
| End lap | 6 in, offset 6 ft | 6 in | 6 in |
| Valley overlap | 6 in | 3 in | 4 in minimum |
| Fastening | Back-nail 12 in on center over 3:12 | Nails 18 in on center on steeper slopes | Nails in selvage 12 in on center if needed |
| Primer | None on plywood; OSB may need priming | None | Per install sheet |
| Tile loading | Not for tile | Not for tile | Tile direct on membrane up to 6:12; loading boards above 6:12; stacks of no more than 10 tiles |
Source: owenscorning.com installation instruction pages for WeatherLock G, Mat and Flex, the WeatherLock Series instructions (Pub. 10011693-A) and the Specialty Tile & Metal instructions (Pub. 10021222-B). Our underlayment UV exposure limits guide compares the 30, 60, 90 and 180 day windows across brands.
Do you put roof underlayment over or under WeatherLock?
WeatherLock goes directly on the wood deck (at least 3/8 in plywood or 7/16 in OSB), never on top of felt or synthetic underlayment. Owens Corning’s Flex and Series instructions state “Do not apply shingle underlayment beneath” the product. Upslope synthetic underlayment then laps over the top edge of the WeatherLock course so water sheds onto the membrane, the same shingle-fashion order used for every lap on the roof.
On a full-deck WeatherLock roof there is no separate underlayment layer at all, and the August 2026 Platinum and Preferred warranties accept that full-deck membrane in place of RhinoRoof U20 or Titanium synthetic underlayment. Owens Corning’s warranties exclude damage from inadequate attic ventilation, which is why its G, Mat and Flex pages tie full-deck use to “proper ventilation”.
WeatherLock vs GAF, CertainTeed, Grace and Titanium
Against the other big-brand membranes, WeatherLock G and Mat sit in the middle on listed price per square, while Flex costs more per square than Grace Ice & Water Shield. The bigger difference is published data: GAF, CertainTeed (through ICC-ES) and Grace print thickness figures for their granular sheets, while Owens Corning prints none for G or Mat.
| Product | Surface | Roll | Published thickness | UV exposure | Listed price, Oct 19 2026 | Spec source |
|---|---|---|---|---|---|---|
| OC WeatherLock G | Granulated | 200 sq ft | Not published | 30 days | $119.00 (Menards), $59.50/sq | OC Pub. 10009578-P |
| OC WeatherLock Flex | Poly film | 225 sq ft | 40 mils | 30 days | $189.00 (S.W. Collins), $84.00/sq | OC Pub. 10009579-O |
| OC Titanium PSU30 | Sure-Foot nodular | 36 in x 72 ft, 2.14 gross sq | 45 mils nominal | 180 days | $136.00 (Schafer Metals), $63.55/sq | OC Pub. 10028605 (May 2026) |
| GAF WeatherWatch | Mineral | 150 or 200 sq ft | See GAF sheet | Up to 60 days, if necessary | $80.52 (Lowe’s), $40.26/sq | GAF sell sheet RESUL103 |
| GAF StormGuard | Film | 200 sq ft | 40 mils min (ASTM D5147) | Up to 90 days; 250°F rating | $119.90 (Go Build Supply), $59.95/sq | GAF data sheet RESUL116 |
| CertainTeed WinterGuard Granular | Mineral | 36 in x 65 ft | 70 mils nominal | See CertainTeed sheet | $87.95 (Lowe’s); $45.10/sq if 195 sq ft | ICC-ES ESR-1492 (Jan 2026) |
| Grace Ice & Water Shield | Granular | 36 in x 75 ft, 225 sq ft | 40 mils (ASTM D3767) | 30 days | $179.00 (Schafer Metals), $79.56/sq | GCP data sheet |
CertainTeed’s ESR-1492 also requires 4 in side laps on WinterGuard Granular, against 3 in on WeatherLock, so a WinterGuard roll nets slightly less width per course. Deeper single-product reviews: Grace Ice and Water Shield review and GAF StormGuard review.
Where code requires an ice barrier
Under 2021 IRC Section R905.1.2, an ice barrier is required where the local jurisdiction marks “a history of ice forming along the eaves” in Table R301.2. It must be two layers of underlayment cemented together or a self-adhering polymer-modified bitumen sheet, running from the lowest roof edge to at least 24 in inside the exterior wall line. Every WeatherLock version lists ASTM D1970, the product standard used for that self-adhering sheet.
The same section adds a 36 in minimum measured along the slope on roofs of 8:12 and steeper, and exempts detached accessory structures with no conditioned floor area. Valleys are governed by R905.2.8.2, which permits ASTM D1970 self-adhering membrane in place of valley lining. State-by-state triggers, including New Jersey’s 25°F January rule, are in our ice dam membrane code guide, and general sizing and cost math is in our ice and water shield guide.
Frequently asked questions
What is Owens Corning WeatherLock?
Owens Corning WeatherLock is a family of self-adhered, ASTM D1970-listed ice and water barriers that go directly on the roof deck at eaves, valleys and penetrations. The 2026 US line is WeatherLock G (granulated), Mat (SureStep surface), Flex (40 mil poly film) and Specialty Tile & Metal (65 mil, 260°F). G and Mat come in 200 sq ft rolls, Flex in 225 sq ft and Tile & Metal in 214 sq ft.
How do I install Owens Corning WeatherLock Ice and Water Shield?
Apply it to a clean, dry deck at 40°F or warmer on slopes of 2:12 or more. Line valleys first, then lay eave courses over the drip edge, peel the split release sheet and roll each course with an 80 lb roller. Lap sides 3 in and ends 6 in, back-nail G and Mat at 12 in on center above 3:12, and cover within 30 days.
Is there a class action lawsuit against Owens Corning shingles?
There has been. In Gonzalez v. Owens Corning, 885 F.3d 186 (3d Cir. 2018), consumers in four states alleged Oakridge shingles were defective, and the Third Circuit affirmed the denial of class certification. In October 2026, neighbors of the Minneapolis shingle plant filed a nuisance class action over odors, per Sahan Journal. A search on October 19, 2026 found no lawsuit or recall naming WeatherLock.
Do you put roof underlayment over an ice and water shield?
Only at its top edge. WeatherLock goes directly on the deck, and Owens Corning says not to apply shingle underlayment beneath it. Synthetic underlayment higher on the roof laps over the membrane’s upper edge, shingle fashion. On a full-deck WeatherLock roof no separate underlayment is needed, and Owens Corning’s August 2026 Platinum and Preferred warranties accept the full-deck membrane in its place.
Does Owens Corning require an ice and water shield?
Not for the shingle warranty itself. The August 2026 Platinum and Preferred warranties require OC shingles, OC synthetic underlayment and OC Hip & Ridge, plus any 2 of 3 categories: OC ice and water barrier, OC starter shingles or VentSure ventilation. Your local code may still require an ice barrier under IRC R905.1.2, whatever the shingle brand.
What is the difference between WeatherLock G and WeatherLock Mat?
Both are 3 ft by 66.7 ft, 200 sq ft FIBERGLAS-reinforced rolls for shingle, shake and slate roofs. G has a granulated surface and a taped selvedge edge; Mat has a polymeric asphalt surface with SureStep traction and is marketed as the lighter roll. In October 19, 2026 listings, G was $119.00 at Menards and Mat $99.98 at Lowe’s. Both must be covered within 30 days.
Is it okay to put ice and water shield on the entire roof?
Owens Corning recommends full-deck WeatherLock on 2:12 to 4:12 shingle roofs, provided attic ventilation meets code, because the membrane is a vapor barrier. On an 1,800 sq ft deck that is about 11 rolls of G or Mat with 3 in side laps. Inadequate attic ventilation is a listed exclusion in the WeatherLock limited warranty, Pub. 10009004-C.
Is ice and water shield completely waterproof?
Owens Corning classes all four WeatherLock versions as waterproof, and ASTM D1970 tests nail sealability and lap integrity. That holds only as installed: laps must be hand-rolled, the deck must be dry, and G, Mat and Flex must be covered within 30 days because sunlight degrades them. It is a secondary barrier under the roofing, not a finished roof surface.
Sources
- Owens Corning, WeatherLock G Data Sheet, Pub. No. 10009578-P, November 2025.
- Owens Corning, WeatherLock Mat Data Sheet, Pub. No. 58107-O, August 2024.
- Owens Corning, WeatherLock Flex Data Sheet, Pub. No. 10009579-O, December 2025.
- Owens Corning, WeatherLock Specialty Tile & Metal Data Sheet, Pub. No. 10011679-G, February 2025; installation instructions Pub. No. 10021222-B; limited warranty Pub. No. 10009003-C, March 2022.
- Owens Corning, WeatherLock Series Installation Instructions, Pub. No. 10011693-A, October 2019; WeatherLock G, Mat and Flex installation pages on owenscorning.com, checked October 19, 2026.
- Owens Corning, WeatherLock Self-Sealing Ice & Water Barrier Products Limited Warranty, Pub. No. 10009004-C, October 2019.
- Owens Corning, Standard Product Limited Lifetime Warranty (Pub. No. 10023873-I), Platinum Protection (10020608-O), Preferred Protection (10020609-P) and System Protection (10020610-P) limited lifetime warranties, all August 2026.
- Owens Corning, Titanium PSU30 Technical Data Sheet, Pub. No. 10028605, May 2026.
- ICC-ES, ESR-1492 (CertainTeed WinterGuard series), reissued January 2026. GAF data sheets RESUL116 (StormGuard) and RESUL103 (WeatherWatch). GCP Applied Technologies, Grace Ice & Water Shield data sheet.
- International Code Council, 2021 International Residential Code, Sections R905.1.2 and R905.2.8.2. OSHA, 29 CFR 1926.501(b)(13).
- Gonzalez v. Owens Corning, 885 F.3d 186 (3d Cir. 2018). Sahan Journal, reporting on a nuisance class action against the Owens Corning Minneapolis plant, October 2026.
- Retail prices: Google Shopping listings for Lowe’s, Home Depot, Menards, S.W. Collins, Arbor, Go Build Supply and Schafer Metals, retrieved October 19, 2026.