Peel-and-Stick vs. Torch-Down: Which Low-Slope Roofing Should You Buy?

Buy peel-and-stick if you want a low-slope roof without an open flame, and torch-down if a trained crew will heat-weld it. Both are modified bitumen sheets; the difference is the bond. Polyglass says its self-adhered ADESO membranes "do not require torching," while its Polyflex torch sheet goes down "with traditional torch roofing techniques." The model residential code allows modified bitumen on slopes as low as 1/4 inch per foot, far below the 2 in 12 minimum for asphalt shingles.

Cold weather narrows the choice less than you might expect. Polyglass's self-adhered cap and base sheets go down only when air and surface temperatures are "40°F (5°C) and rising," and its torch specification "advises against installing modified bitumen membranes" below 40°F to 45°F. The exception is its Elastoflex SA P Polar Cap, a self-adhered sheet rated for 25°F to 60°F. This guide compares the two systems, the sheets in each, slope and temperature limits, and fire safety.

What Is the Difference Between Peel-and-Stick and Torch-Down Roofing?

Modified bitumen roofing is asphalt blended with APP or SBS polymers, reinforced with a mat and sold in rolls for low-slope roofs. Both systems use it.

• Peel-and-stick (self-adhered). Polyglass's ADESO sheets combine "a true APP or SBS compound top weathering surface with an aggressive self-adhesive compound on the bottom surface." You peel the release film and roll the sheet down.

• Torch-down (heat-welded). Polyflex has "a factory applied burn-off film for heat welding applications." Polyglass says to install it with a torch and "do not use cold adhesives or hot asphalt."

The two can also be combined. Polyglass's Stick1-Torch1 system pairs a self-adhered Elastoflex SA V or SA V Plus base sheet with a torch-applied Polyflex G or Polyfresko G cap sheet.

Why Not Just Use Shingles on a Low-Slope Roof?

Shingles need more pitch. The model residential code says asphalt shingles "shall be used only on roof slopes of 2 units vertical in 12 units horizontal" or greater, and requires two layers of underlayment from 2:12 up to 4:12.

Modified bitumen has a much lower floor. The same code says it needs "a design slope of not less than one-fourth unit vertical in 12 units horizontal" for drainage, must meet listed ASTM membrane standards, and must be installed per the maker's instructions. Polyglass's own specifications also list 1/4 inch per foot as the minimum recommended slope for both its self-adhered and heat-welded systems.

That makes modified bitumen the material to look at for a porch roof, a garage, a shed dormer or a rear addition that is too flat for shingles. If you are unsure of the pitch, CGR's guide to understanding roof pitch shows how to read it.

Which Polyglass Sheets Make Up Each System?

Polyglass's two-ply systems use a base sheet against the deck and a cap sheet on top. Polyglass says its Polyflex SA P cap "is to be applied as the uppermost layer of a multi-ply roof system over a film top Polyglass base or interply sheet."

Polyglass sheet	Type	Thickness	Coverage per roll	Weight
Polyflex SA P	Self-adhered APP granulated cap	142 mils	100 sq ft	89 lb
Elastoflex SA P	Self-adhered SBS granulated cap	140 mils	100 sq ft	86 lb
Elastoflex SA V Plus	Self-adhered SBS base	100 mils	150 sq ft	Not listed here
Elastoflex SA Base	Self-adhered SBS base, polyester mat	100 mils	150 sq ft	Not listed here
Polyflex	Torch APP, smooth sand surface (base, interply or cap)	160 mils	100 sq ft	102 lb
Polyflex G	Torch APP granulated cap	180 mils	100 sq ft	Not listed here

Sources: Polyglass product data sheets, editions 2021 to 2026.

The torch sheets are thicker on paper. Both systems rely on correct laps and a full bond for their performance, so follow each data sheet's lap and rolling instructions.

How Cold Is Too Cold to Install Each One?

Polyglass sets about the same floor for both:

1. Self-adhered caps and bases: "only in dry weather and when air and surface temperatures are 40°F (5°C) and rising."

2. Torch sheets: Polyglass advises against any modified bitumen install below 40°F to 45°F, says "the rolls must be at least 40°F (4°C) at the time of application," and reminds crews that "wind chill will have an effect on the application temperature."

3. Cold-weather self-adhered: the Elastoflex SA P Polar Cap is "designed for cold weather applications" from 25°F to 60°F, and Polyglass's two-ply spec pairs it with Elastoflex SA V Polar Base for that range.

Storage matters too. Polyglass calls for a minimum storage temperature of 55°F to 60°F, and its install guide says to let membranes "acclimatize in the sun for at least 15 minutes" before rolling them out. For a late fall job, keep the rolls in a heated garage until you need them.

Do You Need Primer for Peel-and-Stick Roofing?

It depends on the sheet and the deck. Polyglass's Polyflex SA P data sheet says to "prime required substrates prior to application with PG 100 Fast-Drying Asphalt Primer or WB-3000 Water-Based Primer." Elastoflex SA Base, by contrast, is made for "application directly to approved insulation, cover boards and wood decks without a primer."

Laps differ by product. Elastoflex SA Base calls for "a minimum 6" end lap and 3" side lap," and Polyflex SA P uses "the 5" FASTLap at the endlap and 3" SEALLap ULTRA granule free side lap." Polyglass's 2026 self-adhered specification calls for rolling the sheets with "a 75# split-face linoleum roller." Plan drip edge and flashing details before the first roll goes down. CGR's posts on drip edge and the types of roof flashing cover those pieces.

Is Torch-Down Roofing a Fire Risk?

It can be, which is why torch work is a trade skill. Polyglass's heat-welded specification warns that "surfaces which contact the melted bitumen or torch may ignite." The National Roofing Contractors Association runs the CERTA program for "roofing workers who want to be trained in safely applying torch-related roofing products," and says CERTA is required "as a condition of general liability coverage by some insurance companies." Certification is valid for three years and belongs to the individual worker.

NRCA's concern is greatest "over combustible substrates," and where fire hazards "cannot be adequately mitigated," it recommends avoiding direct torching of membrane flashings. OSHA's construction rule for welding, cutting and heating work requires "suitable fire extinguishing equipment" in the work area.

Polyglass pitches its self-adhered line as a "safe, no open flame application" that "may reduce insurance costs."

Which Low-Slope Roofing Should You Buy?

Match the system to who is installing it and when:

• Homeowner or crew without torch training: a self-adhered base and cap. No flame, and Elastoflex SA Base can go on an approved wood deck without primer.

• CERTA-trained crew: torch-down with Polyflex or Polyflex G, or the Stick1-Torch1 combination.

• Late season job below 40°F: the Polar self-adhered products, rated from 25°F.

• Part of the roof at 2 in 12 or steeper and part too flat for shingles: shingles on the pitched section and modified bitumen on the low-slope section, flashed where they meet.

CGR's comparison of peel-and-stick underlayment vs felt paper covers the steep-slope underlayment side.

FAQ

Is peel-and-stick roofing as good as torch-down?

Both are modified bitumen built to ASTM membrane standards. Polyglass's self-adhered caps run about 140 mils, and its torch caps run 160 to 180 mils, so compare the full two-ply system and the install conditions.

Can peel-and-stick roofing go directly on plywood?

Elastoflex SA Base can. Polyglass says it applies "directly to approved insulation, cover boards and wood decks without a primer." The cap sheet goes over a base.

What is the minimum slope for modified bitumen roofing?

The model code sets 1/4 inch per foot, and Polyglass lists the same minimum for its systems.

How cold can you install peel-and-stick roofing?

Standard Polyglass self-adhered sheets need 40°F and rising. Its Polar Cap is rated for 25°F to 60°F.

Do you need two layers of modified bitumen?

For Polyflex SA P, yes. It is the uppermost layer "over a film top Polyglass base or interply sheet."

Can you torch a cap sheet over a self-adhered base?

Polyglass's Stick1-Torch1 system does exactly that, with an Elastoflex SA V or SA V Plus base under a torch-applied Polyflex G or Polyfresko G cap.

Get Polyglass Low-Slope Roofing at CGR Wholesale

CGR Wholesale Roofing & Siding Supply Center says it "always has Polyglass SA Granulated Low Slope Cap Sheet/SA Base Sheet along with Torch Down smooth in stock" on its Polyglass page. Measure the low-slope area, note the deck type and ask the counter which cap and base are on the shelf. The Rostraver showroom is open Monday through Friday 7:00 AM to 4:00 PM and Saturday 7:00 AM to 12:00 PM, and orders can be called in for pickup or delivery.

Visit CGR Wholesale Roofing & Siding Supply Center or call 724-268-3671 today. Contact us for more information.