Most roof leaks get “fixed” with black asphalt cement that dries out, cracks, and leaks again in three summers — while looking like tar smeared across your shingles the whole time. Sashco’s through the roof sealant is the product category’s opposite: a crystal-clear, elastomeric co-polymer sealant that stretches with the roof, sticks to wet surfaces, and holds up under UV for years instead of seasons. We’ve used it enough to know exactly where it shines and where it’s the wrong tube to reach for. Here is the full review.
What Through the Roof Is
Through the Roof is a solvent-based, UV-resistant co-polymer rubber sealant made by Sashco, the Colorado company behind Big Stretch caulk and Lexel. It comes in a 10.1-ounce cartridge (about $10 – $14), a 1-quart brushable can (about $18 – $25), and a 1-gallon can (about $60 – $75) for larger areas, in clear and white. The headline claims — sticks to wet surfaces, stays permanently flexible, won’t yellow or crack in sunlight, and stretches many times more than asphalt patch — hold up in real use. Sashco rates it for application in rain and down to freezing temperatures, and states roughly 20 times the elasticity of typical asphalt-based roof cements.
Why Clear and Elastic Beats Black and Rigid
Two properties separate this product from a $6 tube of roof cement. First, elasticity: roofs move constantly — shingles expand across a 100°F daily swing, flashing flexes, nails back out fractionally — and rigid asphalt patch cracks at exactly those moving joints. An elastomeric sealant stretches through the movement, which is why the repair lasts 5 to 10+ years instead of 2 to 3. Second, the clear formula disappears. Sealing a skylight perimeter, white trim flashing, or a visible porch roof with black mastic is permanent cosmetic damage; Through the Roof is invisible on everything from copper to white PVC. The wet-surface adhesion is the third trick, and the practical one: real leak repairs happen during rainy weeks, not on the perfect dry weekend, and this formula bonds through damp where water-based sealants wash out.
Where It Works Best
Through the Roof adheres to essentially every roof material: asphalt shingles, metal panels, aluminum and galvanized flashing, PVC, polycarbonate, glass, brick, and wood. The highest-value applications we’ve found:
- Flashing edges: resealing lifted step flashing, chimney counterflashing hems, and drip edge laps — the joints where most shingle-roof leaks actually start.
- Nail heads and screw penetrations: a dab over backed-out nail heads and exposed fasteners on ridge caps and metal trim.
- Skylight perimeters: clear sealant on the frame-to-flashing joint, where black mastic would be visible from inside the yard.
- Plumbing boots: sealing the cracked rubber collar on a vent boot as a multi-year bridge until the boot is replaced.
- Gutter seams and end caps: it stays flexible through freeze-thaw where gutter caulk pops loose.
- Plastic patio covers: one of few sealants that bonds well to polycarbonate and PVC panels without attacking them.
Cure behavior is predictable: a skin forms in 30 to 60 minutes, with full cure over days to a couple of weeks depending on bead thickness and temperature. Being solvent-based, it carries strong fumes — irrelevant on a roof, worth ventilating in an enclosed porch.
Getting a Repair Right, Step by Step
Technique determines whether this sealant delivers its full lifespan, so here is the field-tested sequence for a typical flashing or fastener repair:
- Find the actual entry point. Water travels — trace the interior stain upslope and inspect every penetration and flashing lap in that zone. Sealing the wrong spot is the most common failure mode of any sealant.
- Clear, don’t necessarily dry. Brush away grit, loose granules, flaking paint, and old failed sealant. Damp is fine; standing water and mud are not.
- Cut the tip small and gun it into the joint, not onto the surface. The sealant should fill the gap and overlap each side about 1/2 inch.
- Tool it to 1/8 – 3/16 inch thick with a gloved finger or plastic spreader. Thin, well-adhered layers flex and cure fully; fat blobs skin over and stay soft inside for weeks.
- Give it weather margin where you can. It handles rain within roughly an hour of skinning, but a dry afternoon after application is ideal. Below freezing, warm the cartridge indoors first — cold sealant guns hard and tools poorly.
- Recheck in a season. Good repairs look identical a year later; anything that has pulled an edge gets a second thin pass.
For larger areas — a corroded flashing pan, a run of lapped panel seams — use the brushable quart or gallon and lay in polyester reinforcing fabric between two coats. That membrane approach turns a caulk-grade product into a legitimate multi-year patch over spans a bead could never bridge.
Sizes, Coverage, and Where to Buy
The 10.1-ounce cartridge runs a bead of roughly 25 feet at typical joint sizes — plan one tube per chimney or two or three plumbing boots. The quart covers about 12 to 15 square feet brushed in a single coat; the gallon, 50 to 60. All three sizes are stocked at Ace Hardware, True Value, Menards, and Amazon, and increasingly at the big boxes; the clear cartridge is the fastest-moving SKU, so grab white by order if fascia work is on your list. Shelf life on an unopened cartridge is about two years — stored in the garage, not the freezing shed.
The Honest Limitations
No sealant is a roof, and this one has real boundaries. It is a repair product for joints, penetrations, and small breaches — not a coating to waterproof a failing roof plane; a tube of anything cannot rescue underlayment that has reached end of life. It is not rated for constant water immersion, so ponding areas on flat roofs need a purpose-made ponding-rated mastic instead. Solvent content means you should test first on foam insulation boards and be deliberate around some plastics, and it is not paintable in the way acrylic caulks are (paint adhesion over the flexible film is unreliable — buy the white version rather than painting the clear). Finally, clear formula cuts both ways: it’s invisible when neat, but drips and smears still glisten, so tool it cleanly. If your repair is a wide seam, rusted-through panel, or whole-flashing failure, you’re past sealant and into replacement metal.
Through the Roof vs. the Alternatives
Against asphalt roof cement (Henry 208 and similar): the Sashco product costs about twice as much per tube and lasts three times longer, stays flexible, and doesn’t turn repairs black — asphalt only wins for cheap, temporary, out-of-sight patches. Against silicone: silicone matches the UV life but adheres poorly to asphalt shingles and can’t be topped with anything later; Through the Roof bonds to shingle granules far better. Against butyl and MS-polymer flashing sealants: comparable performance, but few come in optically clear. The niche this product owns is “visible repair on a roof I care about, possibly in damp weather.” For choosing across the whole category — silicones, butyls, brush-grade coatings, and tapes — our complete roof sealant guide breaks down which chemistry fits which failure.
Verdict
Through the Roof is the rare hardware-store product that outperforms its marketing. For sealing flashing joints, fastener heads, skylights, gutters, and plastic panels — especially anywhere visible, or anywhere you can’t wait for dry weather — it is the best cartridge-grade option we’ve used, and worth the $12 over the $6 black stuff every single time. Keep expectations calibrated: it repairs roofs, it doesn’t resurrect them. Pair the cartridge with a caulk gun that has a decent thrust ratio (the sealant is thick) and a box of nitrile gloves, and one tube in the garage, bought before the leak, is the cheapest roof insurance a homeowner can own.
