By The Roofing Brief Team. Last reviewed: October 2026.
Tar roof repair means sealing a roof leak with asphalt-based roofing cement, troweled 1/8 to 1/4 in thick at least 2 in past the damage and reinforced with fabric on anything over 1/4 in wide or 2 in long (Henry 208R data sheet). It works as a fast, low-cost stopgap on asphalt shingles, roll roofing, and built-up (tar and gravel) roofs. It is the wrong fix for EPDM rubber, TPO, and PVC membranes: Henry and Gardner-Gibson both warn against rubber and PVC sheet roofing on their cement data sheets.
Three choices decide whether a tar patch works: which surface you are standing on, which product matches it (a tube for a crack, where 29 fl oz of 208R lays about 39 ft of 3/8 in bead; a gallon tub for a patch), and whether the surface is wet. The tables below answer each from the makers’ own sheets.
What roofing tar actually is in 2026
Most products sold as roofing tar today are not true tar. They are asphalt (bitumen) roof cement, a trowel-grade mastic made to ASTM D4586, the specification for asbestos-free asphalt roof cement. Henry’s 208R Rubberized Wet Patch data sheet (rev. 03/11/2015), for example, lists ASTM D4586 Type I, a refined-asphalt base, 78 percent solids by weight and 9.1 to 9.5 lb per gallon. True coal-tar pitch is now rare outside commercial built-up roofing.
Cold-applied cement comes ready to use in a tub or a caulk tube. You spread it with a trowel or a caulk gun, and it cures as the solvents flash off; Henry’s label says to close roof air intakes until the solvents dissipate. Named products include Henry 208R Wet Patch, Gardner-Gibson Black Jack 2172 All-Weather Roof Cement, and Henry 204 Plastic Roof Cement. For the full breakdown of grades and how to apply each, see our guide to roofing cement types and how to apply them.
Hot tar is a different job. Asphalt or coal-tar pitch is melted in a kettle and mopped between plies of felt on low-slope built-up roofs; HomeWyse’s built-up roofing estimate assumes a base sheet plus 3 plies hot-mopped between each ply. That is professional work, not a homeowner patch.
Tar, roofing cement, and wet patch: the terms untangled
Roofing tar, roof cement, and wet patch describe overlapping products with different jobs. The deciding spec for a damp roof is wet-surface adhesion, tested under ASTM D3409, which Henry cites for 208R. Black Jack 2172 is labeled for use in wet or dry conditions.
| Term | What it is | Best use | Bonds to a wet surface? |
|---|---|---|---|
| Roofing tar (generic) | Loose name for asphalt cement or coal-tar pitch | Marketing catch-all | Check the label |
| Plastic roofing cement (ASTM D4586) | Trowel-grade asphalt mastic | Flashing, seams, small holes | Only if the label claims wet use or ASTM D3409 adhesion |
| Wet patch cement (e.g. Henry 208R) | Asphalt cement formulated for damp surfaces | Emergency leaks in the rain | Yes: 100% wet-surface adhesion per ASTM D3409 (Henry) |
| Roof sealant or caulk (e.g. Sashco Through the Roof!) | Elastomeric co-polymer rubber in a tube, not asphalt | Fine cracks, fastener heads, flashing | Yes on damp surfaces, per Sashco |
| Hot tar or coal-tar pitch | Melted bitumen mopped between felt plies | Built-up and tar-and-gravel roofs | No, pro application |
Roofing tar products compared
| Product | Base | Wet surface? | Temperature | Coverage | Not for | Listing, Oct 19, 2026 |
|---|---|---|---|---|---|---|
| Henry 208R Rubberized Wet Patch | Refined asphalt, SBS rubberized | Yes (ASTM D3409) | Adheres 5 to 120 F | 12.5 sq ft per gal at 1/8 in; 39 LF of 3/8 in bead per 29 fl oz tube | Gravel, rubber or PVC sheet, wood shingles | $22.99 per gal, Agri Supply |
| Gardner-Gibson Black Jack 2172 | Asphalt | Yes, per label | Apply at 50 to 120 F surface | 25 LF of 1/4 in bead per tube | EPDM, Hypalon, PVC, single-ply | Not priced here |
| Henry Plastic Roof Cement, 0.9 gal | Asphalt | Check label | Henry names its 204 Plastic Roof Cement for vertical surfaces in hot weather | Check label | Check label | $14.99, Agri Supply |
| Sashco Through the Roof! 10.5 oz | Co-polymer rubber, clear | Yes, even active leaks | Not stated | Tube | EPDM and other rubber membranes | $13.48, Lowe’s (MSRP $12.49) |
Sources: Henry 208R TDS, Black Jack 2172 TDS, Sashco product page; prices are Google Shopping listings checked October 19, 2026.
Roofing tar in a tube: when the caulk gun beats the trowel
Roofing tar in a tube is the same asphalt roof cement, packed in a 10 or 29 fl oz cartridge that fits a standard caulk gun. The 29 fl oz Black Jack tube measures 2.5 in by 16 in, per its data sheet, and some stores shelve it as tar caulking or roof caulk. Use the tube for narrow cracks, seams, fastener heads, and flashing joints, where a bead lands exactly on the leak. Use a tub and trowel for anything wider, because a fabric-reinforced patch needs more cement than a bead delivers.
Cartridge coverage is modest. Gardner-Gibson sells Black Jack All-Weather Roof Cement in 10 and 29 fl. oz. tubes and rates a tube at about 25 linear feet of 1/4 inch bead. Henry rates a 29 fl. oz. cartridge of 208R Rubberized Wet Patch at 39 linear feet of 3/8 inch bead. That is plenty for sealing nail heads and a flashing seam, and not much for a torn section of roof.
A bead alone is not a patch. Both makers tell you to spread the bead flat with a putty knife or trowel and to reinforce larger damage with fabric. Henry’s line: any hole over 1/4 inch wide or 2 inches long gets Henry 181 or 183 roof repair fabric between two layers of cement. Gardner-Gibson calls for 1/8 to 1/2 inch of cement worked two or three inches past the problem area, with fabric embedded and a second layer on top.
Read the label before you load the gun. Black Jack 2172 is meant for surface temperatures between 50 and 120 degrees Fahrenheit, and in cold weather Gardner-Gibson says to store the tube at 70 to 80 degrees for at least 24 hours first. The tube does not change the chemistry either: the same sheet says not to use it on EPDM, Hypalon, PVC, or any single-ply roof. And do not confuse it with the elastomeric sealants in the table above, such as Sashco Through the Roof!, which also come in tubes but are not asphalt.
The cement also keeps curing long after it feels firm. Henry says to wait 30 days before putting a roof coating over 208R, and Gardner-Gibson says to let Black Jack 2172 cure 30 to 60 days before a reflective coating.
Which roofs tar works on, and which it ruins
Asphalt roofing tar bonds to other asphalt-based and porous surfaces and can damage single-ply rubber and plastic membranes. GAF’s technical bulletin TAB R-157 warns that oils from asphaltic roofing can migrate into rubber such as EPDM, and both cement makers above exclude rubber and PVC on their data sheets. TPO and PVC need heat-welded or manufacturer-approved patches. If your roof is EPDM, our guide to rubber roof repair covers leak, seam, and tear fixes by damage type.
| If your roof is | Asphalt tar or cement? | Why |
|---|---|---|
| Asphalt shingles (3-tab or architectural) | Yes, as a spot patch | Same asphalt chemistry; Henry lists composition roofs |
| Roll roofing or mineral-surface cap sheet | Yes | Listed on the Henry 208R sheet |
| Built-up, tar and gravel (BUR) | Yes, after removing embedded gravel | Henry: remove embedded gravel and cut away old cement first |
| SBS modified bitumen | Yes | Listed on the Henry 208R sheet |
| APP torch-down modified bitumen | Ask the membrane maker | Henry: may not give satisfactory results over some APP membranes |
| Metal flashing and seams | Yes, on clean metal | Henry: wire-brush rust and scale first |
| Concrete or masonry | Yes | Listed on the Henry 208R sheet |
| EPDM rubber | No | Henry and Black Jack both exclude it; GAF R-157 notes oil migration into EPDM |
| TPO or PVC single-ply | No | Black Jack excludes PVC and single-ply; use a welded or maker-approved patch |
| Wood shingles or shakes | No | Henry 208R: not recommended over wood shingles |
How to patch a roof leak with tar, step by step
On an asphalt shingle, roll, or built-up roof, a reinforced cement patch is a solid emergency fix. These steps follow the Henry 208R and Black Jack 2172 data sheets. For the wider set of options beyond tar, our step-by-step roof leak fix covers when to patch and when to stop.
- Check the temperature and the label. Black Jack 2172 wants a 50 to 120 F surface; Henry 208R adheres from 5 to 120 F and on wet surfaces. Below 50 F, store the tube at 70 to 80 F for 24 hours first (Gardner-Gibson).
- Find and clean the leak source. The entry point is often uphill of the interior stain, so inspect above the wet spot. Sweep off debris and loose granules, remove embedded gravel, and cut away old cement that would stop a smooth patch (Henry 208R TDS).
- Prepare metal. Wire-brush rust and scale from any metal flashing in the repair area, per Henry’s preparation step.
- Trowel on the first coat. Spread cement 1/8 to 1/4 in thick and at least 2 in past the damage, feathering the edges (Henry 208R). A gallon covers about 12.5 sq ft at 1/8 in.
- Embed reinforcing fabric. If the damage is over 1/4 in wide or 2 in long, press Henry 181 or 183 roof repair fabric (or polyester or glass fabric) into the wet cement. Henry ties its 10-year warranty on 208R to using its fabric.
- Apply the second coat. Trowel cement over the fabric until the mesh disappears, feathering the edges so water runs off instead of pooling.
- Seal nearby fasteners. Dab cement over any exposed nail or screw heads next to the repair.
- Let it cure, then coat. Wait 30 days before a Henry roof coating over 208R, or 30 to 60 days before a reflective coating over Black Jack 2172.
Patching a shingle tear or nail pop with tar
A torn tab or a popped nail is the most common asphalt shingle repair, and tar handles it in four steps. Work when the shingle surface is at least 50 F, the low end of the Black Jack 2172 range, so the tab bends without cracking.
- Lift the damaged shingle tab gently.
- Apply a coat of cement under the tear, using it as a glue, then press the shingle back down.
- Re-nail the shingle if it lifted, using roofing nails that reach 3/4 in into sound decking or through it (IRC R905.2.5).
- Cover the tear and each nail head with a top coat of cement.
Hot tar roof repair, and when it is a pro job
Hot tar roof repair, the job many people call tarring or re-tarring the roof, means melting asphalt or coal-tar pitch in a kettle and mopping it onto a built-up or tar-and-gravel roof, then re-embedding gravel or a cap sheet. It repairs the same low-slope systems it built. A new hot-mopped system priced by HomeWyse (May 2026) runs $7.91 to $9.82 per sq ft for a base sheet plus 3 hot-mopped plies, which shows why spot repair, not re-tarring, is the usual call on a sound roof.
Have a gravel-surfaced flat roof? Read how these systems are built and fail in our tar and gravel roof guide before choosing patch or recover.
How long a tar patch lasts, and what it costs
A tar or asphalt cement patch is a stopgap, not a permanent repair. Henry’s 208R sheet gives the two levers that extend it: fabric reinforcement, which it requires for its 10-year warranty, and a roof coating after 30 days. An unreinforced bead left in full sun is the shortest-lived version, so plan a real repair at the next dry spell. The materials cost little.
| Item | Listing (Google Shopping, Oct 19, 2026) | Notes |
|---|---|---|
| Henry 208 Wet Patch, 10 oz tube | $7.38, PlumbersStock | Small cracks and fasteners |
| Henry Plastic Roof Cement, 0.9 gal | $14.99, Agri Supply | Multiple dry-surface patches |
| Henry 208R Wet Patch, 1 gal | $22.99, Agri Supply | Bonds to damp surfaces; about 12.5 sq ft at 1/8 in |
| Henry HE181195 roof patch fabric | $16.97, Home Depot | Required by Henry for the 10-year warranty |
| Sashco Through the Roof! 10.5 oz | $13.48, Lowe’s | Non-asphalt alternative for flashing and metal |
| Pro small roof repair | $361 to $439 per repair | HomeWyse, January 2026, shingle roofs |
Worked example. A 2 ft by 2 ft patch is 4 sq ft. Two 1/8 in coats over fabric use about 8 sq ft of coverage, or roughly 0.64 gallon of 208R at 12.5 sq ft per gallon (Roofing Brief arithmetic: 8 / 12.5). One $22.99 gallon plus a $16.97 fabric roll covers it for about $40. When you need a fix to hold only until a real repair, a temporary roof repair and tarping plan may protect the interior better than tar alone during a storm.
When tar will not save your roof
Tar covers a symptom. If the leak comes from failed flashing, widespread granule loss, rotted decking, or a roof near the end of its life, a patch hides the problem while water keeps moving inside the assembly. Repeated patches on the same roof are a signal for a professional repair or replacement; HomeWyse’s $361 to $439 small-repair estimate is the benchmark to compare against another round of DIY cement.
Call a roofer instead of reaching for the tar when you see any of these:
- Multiple leaks appearing across the roof, not one clear spot.
- Decking that feels soft, spongy, or sags underfoot.
- Daylight visible through the deck from the attic.
- An asphalt roof past roughly 20 years of age.
- Leaks around chimneys, skylights, or valleys, which are usually flashing failures, not field damage.
- Ponding water: Henry warns that roofs under 1/2 in per foot of slope or with poor drainage concentrate asphalt residue and deteriorate faster where water stands.
For the wider picture on materials, systems, and when a patch is the right call, start at our roofing basics hub.
Frequently asked questions
Is roofing tar good for a roof leak?
Roofing tar, usually asphalt roof cement, can stop a roof leak quickly as a temporary fix on asphalt shingles, roll roofing, SBS modified bitumen and built-up roofs. It is not a permanent repair, and Henry and Gardner-Gibson both say not to use their cements on rubber (EPDM) or PVC roofing. Spread it 1/8 to 1/4 in thick, 2 in past the damage, with fabric on anything over 1/4 in wide or 2 in long.
How long does roof tar last?
A cement patch is a stopgap. How long it holds depends on reinforcement and sun: Henry ties a 10-year warranty on 208R to using its roof repair fabric and says to coat the patch after 30 days to extend its life, while an unreinforced bead in full sun is the shortest-lived version. Hot-applied tar on a built-up roof lasts far longer because it is part of the roof system.
Does roofing tar get hard?
It firms up but stays pliable at first. Cold-applied roofing cement cures as its solvents evaporate, and makers say to wait 30 days (Henry 208R) or 30 to 60 days (Black Jack 2172) before coating it, which shows how long full cure takes. Rubberized grades such as Henry 208R are made to stay flexible. Hot tar hardens as it cools.
Can you put tar on a roof in the rain?
Only with a product labeled for wet use. Henry 208R is rated for 100% wet-surface adhesion under ASTM D3409 and can be applied in rain or under water, and Black Jack 2172 is labeled for wet or dry conditions. Treat any rain repair as an emergency measure and redo it properly once the roof dries.
What is the difference between roofing tar and roofing cement?
In everyday use the terms overlap. Roofing cement is a trowel-grade asphalt mastic made to ASTM D4586, sold in 10 and 29 fl oz tubes and gallon tubs for patching. Roofing tar is a looser term that can mean the same cold asphalt cement or true hot coal-tar pitch mopped onto built-up roofs. Most consumer roofing tar is asphalt cement.
Can you use roofing tar on a rubber roof?
No. Henry’s 208R sheet says it is not recommended over rubber or PVC sheet roofing, Black Jack 2172 says not to use it on EPDM, Hypalon or PVC, and GAF’s TAB R-157 notes asphalt oils can migrate into EPDM. Rubber roofs need EPDM-compatible primer, seam tape, and patches, such as EternaBond RoofSeal, which its maker lists for EPDM and TPO.
How much does hot tar roof repair cost?
For scale, HomeWyse prices a new hot-mopped built-up roof (base sheet plus 3 plies) at $7.91 to $9.82 per sq ft in May 2026, and a small roof repair at $361 to $439 per repair in January 2026. A localized hot tar repair on a built-up roof is quoted by the job, so ask for the area in square feet and the number of plies being replaced. It is a licensed contractor job, not a DIY patch.