Modified Bitumen Roofing

SBS-modified (styrene-butadiene-styrene). Rubber polymer that gives the asphalt flexibility at low temperatures. SBS handles freeze-thaw cycles better, stays pliable through NJ winters, and is the standard recommendation for any roof in NJ's climate zones 4 and 5. Most major manufacturers (Soprema, GAF Liberty, Johns Manville Dynalastic, Polyglass) make SBS products.

APP-modified (atactic polypropylene). Polymer that gives the asphalt high-temperature stability. APP handles hot roof surfaces better than SBS but is less flexible in cold. Right for shore-county roofs with intense summer sun exposure; standard in southern US climates. Less commonly spec'd for NJ than SBS.

Two-ply vs three-ply systems. Two-ply is the residential standard — base sheet + cap sheet. Three-ply (base + interply + cap) is the premium commercial spec — more redundancy, longer warranty class, higher cost.

Base sheet options. Fiberglass-reinforced base (most common, lower cost) or polyester-reinforced base (stronger, more dimensionally stable, premium spec). For mechanically fastened systems, polyester is required because fiberglass tears at fastener points.

Cap sheet finish. Granulated cap (sand or ceramic granules on the surface) is the standard — provides UV protection and walkable surface. Smooth cap (no granules) is used when the roof will be coated or covered. White cap (reflective granules) meets cool-roof spec and Energy Star where required.

Torch-applied. Propane torch heats the back of the cap sheet, melts the asphalt, and adheres it to the base sheet. Fast install, strong bond, the traditional commercial method. Requires fire-safety protocols on every install — torch work near flammable substrates (wood siding, soffit overhangs) requires extra precautions and is sometimes prohibited near specific building types. Not allowed at all on some occupied buildings.

Mop-applied (hot asphalt). The original BUR method. Hot asphalt is mopped between plies. Increasingly rare on new installs because of the safety hazards of moving hot asphalt around the roof and the smell during install. Some commercial buildings still spec it for compatibility with existing BUR.

Peel-and-stick (self-adhered). Cap sheet has a release liner; peel it off and roll the sheet down. No torch, no hot asphalt, no fire risk. Standard for residential mod-bit and for any project where torch work is prohibited. GAF Liberty is the dominant peel-and-stick system; Polyglass Polyflex and Soprema Sopralast also have peel-and-stick options.

Cold-applied (adhesive). Cap sheet is set in cold-applied asphalt adhesive — no torch, no flame, no hot asphalt. Middle-ground cost between peel-and-stick and torch. Less common than the other two methods.

We default to peel-and-stick for residential and many small commercial — eliminates fire risk, faster install, comparable performance to torch-applied for warranty purposes.

Residential porch roofs and additions. The dominant application. Most NJ homes built before 1970 with a porch or addition have mod-bit (or BUR predecessor) on those flat sections. When we replace, we typically install a new two-ply SBS mod-bit (peel-and-stick) — drops in fast, compatible with surrounding asphalt shingle on the steep-slope sections, lasts 15-20 years.

Small commercial under 5,000 sq ft. Strip malls, small office buildings, churches. Below the scale where TPO welding equipment is economical. Mod-bit two-ply or three-ply with granulated cap is the standard install. White cap if cool-roof is required.

Renovations integrating with existing BUR. Adding to a building that already has a BUR roof. Mod-bit is chemically compatible with BUR for tie-ins; TPO and EPDM are not. We use mod-bit for BUR-integration projects, then plan the entire-roof replacement (typically to TPO or EPDM) for the next capital cycle.

Budget-driven commercial. Lower upfront cost than TPO or EPDM on small commercial. Right when the building owner has a tight capital budget and the building doesn't need premium warranty class or reflective surface.

Restoration with silicone coating overlay. Aging mod-bit can be restored with silicone coatings (GE Enduris, Mule-Hide 100% Silicone) instead of full replacement — extends service life 15-20 more years at meaningful cost savings. See our Flat Roof Coatings page for details.