What is Modified Bitumen?
Often chosen for
- Roofs with HVAC equipment or regular foot traffic
- Rowhouse roofs where a thick, multi-layer system is wanted
- Buildings where a no-flame glue-down option is preferred
Types and installation methods
| SBS (styrene-butadiene-styrene) | Rubber-modified sheets that stay flexible in cold weather. Can be torched, cold-applied with adhesive, hot-mopped or self-adhered, depending on the product. |
| APP (atactic polypropylene) | Plastic-modified sheets, typically torch-applied. |
| Torch-down (heat weld) | Sheets are heated with a propane torch so the asphalt melts and bonds. Fast and strong, but it is open-flame work near parapets, wood and insulation, so it needs trained crews and fire precautions. |
| Glue-down (cold process) | Sheets are bonded with cold-applied adhesive, or are self-adhered, so no torch is used. A good choice where open flame is a concern. |
Pros and cons
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How long does Modified Bitumen last?
Estimated life expectancy: about 20 years (modified bitumen), from InterNACHI's Standard Estimated Life Expectancy Chart. InterNACHI says these figures assume regular maintenance and normal wear and are guidelines, not guarantees. Real service life depends on installation quality, drainage, exposure and upkeep.
Signs your Modified Bitumen roof needs repair
- Lap seams separating or curling
- Blisters and splits in the cap sheet
- Granule loss exposing the asphalt
- Cracked flashing at parapets and bulkheads
- Ponding water
Repair or replace?
Blisters, open laps and flashing failures in limited areas can be cut out and patched with new modified bitumen. If the cap sheet is worn across the roof or water has reached the insulation, a tear-off and new two-ply system is usually the better long-term fix.
What affects the cost
We price every job after inspecting and measuring the roof. These are the main factors:
- Roof size, layout and penetrations
- Torch-down vs glue-down vs self-adhered application
- Number of plies and cap sheet type (standard or reflective)
- Tear-off and disposal of old roofing
- Insulation and deck repairs
- Fire-safety measures and access
[Owner: optional typical price range from your own jobs. Leave out if you prefer quoting per job]
Modified Bitumen in Brooklyn & NYC
Open-flame roofing work in NYC is regulated by the FDNY, and our crew is FDNY-certified for torch-applied roofing. Where a torch is not appropriate, for example next to wood framing or in tight spaces, we can use cold-process or self-adhered sheets.
Our process
- Inspection & photos
We inspect the roof, drains and flashing and document what we find. - Written estimate
Scope, materials and options in writing before work starts. - Installation or repair
Modified Bitumen work done to the manufacturer's instructions. [Owner: manufacturers/brands you install] - Clean-up & final photos
Debris removed, final walkthrough and photos.
Compare other flat roofing options
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