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Guide · Roofing supplies · Roof cement, sealant, asphalt primer, patch and tar removal

What is the difference between roof cement and roof sealant, and is asphalt primer necessary? Plastic roof cement (ASTM D4586), wet-surface cement, asphalt primer (ASTM D41), how long cement lasts, patching a leak, and getting tar off tools and hands

Roof cement (plastic roof cement, flashing cement, roofing tar in the trade’s loose use) is a trowel-grade asphalt paste with fibers and solvent, made to ASTM D4586, for bedding flashings, sealing around pipes, patching holes with fabric and gluing down lifted shingles; it stays flexible for years and is applied 1/8 inch thick with a trowel. Roof sealant is a gun-grade product (polyurethane, silicone, acrylic, SBS-modified asphalt or butyl in a cartridge) for a bead along a seam or a fastener head; it is thinner, cures faster and does not bridge a gap the way cement with fabric does. Asphalt primer (ASTM D41) is a thin solvent asphalt that seals dust and chalk on a surface so cement, self-adhered membrane and coatings bond to it; it is required on concrete, masonry, weathered metal and old asphalt before those products, and skipped on clean new shingles. Tar and asphalt come off tools and hands with a citrus-based or petroleum-solvent remover, not with dish soap alone.

Bayshore Safety. Industrial safety, roofing tools and jobsite supplies since 2017. · Current as of November 2026 · the C&R roofing supply product data on this site (asphalt primer by the box of 12; 911 emergency roof patch 25 lb pail, which the product data states can be applied when raining, snowing, in melting ice and in standing water; cotton, fiberglass and polyester fabric membranes in 4, 6, 12, 18 and 36 in rolls; Maxkleen 321 tar, asphalt and adhesive remover aerosol; Maxkleen natural citrus cleaner by the gallon; GOJO hand cleaners); ASTM D4586 (asphalt roof cement, asbestos-free), D3409 (asphalt roof cement for wet surfaces), D41 (asphalt primer for roofing), D1227 (emulsified asphalt coatings) and D1079 (roofing terminology) as published designations
Roofing supplies for cement and primer workAll roofing tools
C&R Asphalt PrimerC&R Asphalt PrimerThe product data states the 911 emergency roof patch can be applied when raining, snowing, in melting ice and in standing water
$142.24See the product

Three products, three jobs. Primer prepares a surface. Cement fills, beds and patches, thick, with a trowel, and with fabric where the gap moves. Sealant is a bead from a gun. People mix the names because the big-box aisle does, and the result is sealant squeezed into a hole that needed cement and fabric, or cement smeared over a membrane that needed its own product. The cards below answer the questions as they come: cement vs sealant, what plastic roof cement is, whether primer is necessary, how long cement lasts, how to patch a leaking roof and a flat roof you have to walk on, what cement for roof tiles, what dissolves asphalt, and how to get tar off a windshield, a tool and a hand. The products that are not asphalt-based are covered in the butyl tape, torch-down and seam roller guides linked below.

Roof cement, primer and tar, question by question

ASTM designations are quoted as published; application figures are the ones printed on the product containers; nothing here is a substitute for the roofing manufacturer’s instructions on a warranted roof.

What is the difference between roof sealant and roof cement?Form, thickness and job. Roof cement is trowel-grade: a thick asphalt mastic with mineral fibers that is spread 1/8 inch thick, embedded with fabric for a patch, and stays plastic (hence "plastic roof cement") for years under a flashing or a shingle. Roof sealant is gun-grade: a cartridge or sausage of polyurethane, silicone, acrylic, modified asphalt or butyl that is run as a bead over a seam, a nail head or a joint in metal; it is for narrow lines, not for bridging a hole. Use cement where there is a gap to fill or a flashing to bed, sealant where there is a line to seal, and match the chemistry to the roof: asphalt products on asphalt roofs, silicone or urethane on metal, and the membrane manufacturer’s own sealant on TPO, PVC and EPDM.
What is plastic roof cement, and what is it used for?The standard asphalt roof cement, ASTM D4586 (asbestos-free), Type I (trowel-grade, self-leveling under heat) or Type II (stiffer, for vertical surfaces). "Plastic" means it stays pliable. Uses: bedding step and base flashings, sealing around pipes, vents and chimneys, patching holes and splits with reinforcing fabric (the three-course method: cement, fabric, cement), re-adhering lifted shingle tabs and ridge caps, sealing exposed nail heads on asphalt roofs, and filling pitch pockets. It is applied with a round-nose or pointed-nose trowel from a can or a quart tube in a quart gun. Wet-surface cement (ASTM D3409) is the version that displaces water for emergency work; the 911 emergency patch in our line is a pail product whose data states it can be applied in rain, snow, melting ice and standing water.
Is asphalt primer necessary, and what does it do?On a porous, dusty, chalked or weathered surface, yes; on a clean new asphalt surface, no. Asphalt primer (ASTM D41) is a thin, solvent-cut asphalt that soaks into concrete, masonry, gypsum board, old built-up roofing and oxidized metal, binds the dust and chalk, and leaves a tacky asphalt film that cement, self-adhering modified bitumen, cold-process adhesive and coatings bond to. Without it on those surfaces the cement or membrane sticks to the dust, and the dust lets go. It is brushed, rolled or sprayed thin (a gallon covers about 200 to 300 square feet on concrete), allowed to dry to a tacky, non-stringy film (30 minutes to a few hours), and covered the same day. Our asphalt primer is sold by the box of 12; its product data describes it as a waterproof seal that traps and encapsulates dust before other sealing materials go on.
How long does roof cement last, and do I need it for shingles?Under a flashing or inside a lap, out of the sun, cement stays flexible for ten to twenty years. Exposed to the sun it dries out, shrinks and cracks in two to five years, which is why an exposed patch is covered with fabric and a second coat or with a coating, and why a smear of cement over a leak is a temporary repair. Shingles are installed without cement except where the manufacturer says to use it: hand-sealing tabs in cold weather or high wind, sealing cut shingles at rakes and valleys, bedding step flashing, and the first course and ridge in some wind zones. A dab the size of a quarter under each tab is the standard; more than that and the shingle will not lie flat.
How do you patch a leaking roof, and what is the standard way?The standard way for an asphalt roof is: find the leak (water travels, so look uphill of the stain, at penetrations, flashings and valleys first), dry and clean the area, and for a hole or split use the three-course method: trowel cement 1/8 inch thick over the area 2 inches past the damage, press a piece of roofing fabric (cotton, fiberglass or polyester membrane from our rolls) into it, and trowel a second coat over the fabric feathered to the roof. For a lifted shingle, cement under the tab and press. For a cracked flashing, prime, cement, fabric, cement. For a pinhole in metal, a urethane sealant or foil-backed butyl tape. In rain, the wet-surface emergency patch, then the proper repair when dry. A leak that is not at a penetration or flashing on a roof under fifteen years old is usually a nail that backed out or a cut shingle; one on an old roof is the roof.
What can I put on my flat roof so I can walk on it, and what is a good temporary cover?Walk pads: on a single-ply roof, the membrane manufacturer’s walkway pad heat-welded or adhered in place; on a built-up or modified roof, cap-sheet walk pads or a paver system; on a coated roof, a granulated walkway coat. Plywood laid loose scuffs membrane and traps water; never leave it. A temporary cover for a leaking flat roof is a heavy-duty tarp pitched so it drains, with sandbagged edges (see the tarp guide linked below), or on a small area the emergency patch compound; both are days-to-weeks measures until the roof can be repaired dry.
What cement do you use on roof tiles, and what does roof flashing cost to replace?Clay and concrete tiles are bedded and pointed with a mortar or a tile adhesive the tile manufacturer names (polyurethane foam adhesives and mortar mixes made for tile), not asphalt roof cement, which stains and does not hold tile. Ridge and hip tiles are set in mortar or with a dry-ridge system. Asphalt cement goes on the asphalt underlayment and flashings under the tile. We sell tools and roofing supplies, not labor, and do not quote repair prices.
What chemical dissolves asphalt, and how do you remove tar from a tool, a windshield or a deck?Asphalt and roofing tar are petroleum products and dissolve in petroleum solvents (mineral spirits, kerosene, diesel) and in citrus terpene (d-limonene) cleaners; the citrus products are what the trade uses because they work as well and smell like oranges instead of a refinery. Our Maxkleen 321 is an aerosol tar, asphalt and adhesive remover for that job; the gallon citrus cleaner does buckets, spuds and trowels. Method: scrape the bulk off while it is soft (cold tar chips, warm tar scrapes), apply the remover, wait a few minutes, wipe with a rag, repeat. On a windshield: a razor blade on wet glass takes the bulk, then remover on a rag, then glass cleaner; keep it off the rubber trim. On a wood deck: remover, a stiff brush, then a wash. We do not advise on automotive paint; the car-care products sold for it are made for that finish and this page does not cover them.
Can dish soap remove tar, and can it clean paint brushes?Dish soap alone does not dissolve tar; it lifts what the solvent has loosened, which is why it shows up in every home remedy. For asphalt on skin the order is: a citrus or pumice hand cleaner (see the hand cleaner guide linked below) worked in dry, then soap and water. Vinegar does nothing to tar. Dish soap and warm water do clean latex paint out of brushes; oil-based paint needs mineral spirits first. For bugs on a car, dish soap works; for tar, not without a solvent.
What is the biggest problem with metal roofs, and what material seals roof leaks?We sell tools, not roofs, and do not rate roofing systems. The repair products for a metal roof leak are different from an asphalt roof: foil-backed butyl tape over seams and fastener rows, urethane or silicone sealant at laps and penetrations, replacement fastener washers, and a metal-roof primer and coating for a whole-roof restoration; asphalt cement on a painted metal roof stains and lifts. The butyl tape guide linked below covers it.
What do you use to apply roof cement, and how do you clean the tools?A round-nose or pointed-nose trowel (5 inch for details, 7 inch for spreading), a margin trowel to get it out of the can, a quart caulking gun for the tube version, and a chip brush or roller for primer. Clean trowels with the citrus remover or mineral spirits while the cement is soft; set cement comes off with a scraper and the remover. Wear nitrile or chemical gloves and eye protection; the chemical glove guide linked below has the solvent chart. Primer and cement are flammable while the solvent flashes; no torches near open cans.

Roof cement and primer in plain words

  • Cement (ASTM D4586) is trowel-grade, 1/8 inch thick, for flashings, patches with fabric and lifted tabs. Sealant is a gun bead for a line.
  • Wet-surface cement (ASTM D3409) and the emergency patch go on in rain; the proper repair follows when dry.
  • Primer (ASTM D41) binds dust and chalk on concrete, masonry, old roofing and weathered metal so cement and membrane stick. Skip it on clean new asphalt.
  • Three-course patch: cement, fabric, cement, feathered 2 inches past the damage.
  • Cement lasts ten to twenty years covered, two to five years exposed; cover a patch.
  • Tile is set in mortar or tile adhesive, not asphalt cement.
  • Tar dissolves in citrus (d-limonene) or petroleum solvents; dish soap only lifts what the solvent loosened.
  • Asphalt products on asphalt roofs; butyl, urethane or silicone on metal; the membrane manufacturer’s products on single-ply.

Questions people ask

Can Dawn dish soap remove tar?

Not by itself; a citrus or petroleum solvent dissolves tar and the soap then lifts it. On skin, a pumice or citrus hand cleaner first.

What is the difference between roof sealant and roof cement?

Cement is a thick trowel-grade asphalt mastic for bedding, filling and fabric patches; sealant is a gun-grade bead for seams and fastener heads.

How to patch a roof that is leaking?

Find the source uphill of the stain, clean and dry, then cement, fabric, cement feathered 2 inches past the damage; wet-surface patch if it is raining.

Is asphalt primer necessary?

On concrete, masonry, old roofing and weathered metal, yes; on clean new asphalt, no.

What is the biggest problem with metal roofs?

We do not rate roof systems; metal roof leaks are repaired with butyl tape, urethane or silicone sealant and fastener washers, not asphalt cement.

What is plastic roof cement used for?

Bedding flashings, sealing penetrations, patching with fabric, re-adhering shingle tabs and sealing nail heads on asphalt roofs.

What is the way to patch a roof?

The three-course method for asphalt roofs: cement, reinforcing fabric, cement; the membrane manufacturer’s patch for single-ply.

What can I put on my flat roof so I can walk on it?

Walkway pads from the membrane manufacturer, cap-sheet walk pads or pavers on built-up roofs; never loose plywood.

What cement do you use on roof tiles?

Tile mortar or a tile adhesive the tile manufacturer names, not asphalt roof cement.

What is a good temporary cover for a leaking flat roof?

A heavy-duty tarp pitched to drain with sandbagged edges, or the emergency patch compound on a small area.

How long does roof cement last on a roof?

Ten to twenty years covered under a flashing; two to five years exposed to sun.

Do I need roof cement for shingles?

Only where the shingle manufacturer says: hand-sealing in cold or wind, cut shingles at rakes and valleys, bedding flashings; a quarter-size dab per tab.

What chemical dissolves asphalt?

Petroleum solvents (mineral spirits, kerosene) and citrus d-limonene cleaners.

How do I get tar off my windshield?

Razor blade on wet glass for the bulk, a citrus remover on a rag, then glass cleaner; keep it off the rubber.

What is the material to seal roof leaks?

On asphalt, roof cement with fabric; on metal, butyl tape or urethane sealant; on single-ply, the membrane manufacturer’s product.

What is the way to remove tar?

Scrape the bulk, apply a citrus or petroleum remover, wait, wipe, repeat.

How do I stop my roof leaking in heavy rain?

A wet-surface emergency patch on the source, a tarp over the ridge for a larger area, then the proper repair when dry.

What is considered a minor roof leak?

A single drip at a penetration, flashing or nail on an otherwise sound roof; a leak across a field of old shingles is the roof.

Does vinegar remove tar?

No.

Can I use Dawn to clean my paint brushes?

For latex paint, yes with warm water; oil-based paint needs mineral spirits first.

Related guides

Butyl tape and flashing tapeTypes, uses and what it will not stick toTrowelsMargin, pointing, notched and roofing trowelsRoofing torches and torch-downPropane torches and modified bitumenHeavy-duty hand cleanersPumice, citrus and waterlessTarps: mil, sizes, poly vs vinylAnd how to tarp a roofWhich gloves protect against chemicals?How to read a chemical resistance chart

The ratings, test results and standards shown here are the manufacturers' published values, reproduced as published. Nothing on this page is a recommendation by Bayshore Safety that any product is suitable for a particular task, hazard or workplace. Selecting safety products and protective equipment is the responsibility of the end user and the employer, based on their own hazard assessment and the regulations that apply to their work. Confirm every value on the manufacturer's own documentation before use.

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