01
ROOF DECK
The structural deck must be sound and compatible with the selected attachment method and roof assembly.
ASPHALT-BASED • REINFORCED SHEETS • MULTI-LAYER SYSTEM
MODIFIED BITUMEN ROOFING IN ATLANTA, GA
Modified bitumen roofing combines asphalt with polymer modification and reinforced sheets to create a durable low-slope commercial roof system with multiple application and surfacing options.
COMMERCIAL LOW-SLOPE
SBS + APP SYSTEMS
MULTI-LAYER OPTIONS
ATLANTA, GA
QUICK ANSWER • WHAT IS MODIFIED BITUMEN ROOFING?
Modified bitumen is an asphalt-based low-slope roofing system manufactured in reinforced rolls. SBS and APP are the two major modifier families, and systems may use base sheets, cap sheets and different attachment methods depending on the product. Installation can involve hot asphalt, torch application, cold-process adhesive, mechanical attachment or self-adhered materials where permitted and specified.
MODIFIED BITUMEN SYSTEM ANATOMY
ASPHALT TECHNOLOGY. MORE CONTROLLED THAN A SINGLE SHEET.
Modified bitumen systems can be assembled in different ways, but the recurring idea is redundancy. Deck preparation, insulation, cover board, base layers, cap sheets, laps, flashings and surfacing all influence how the roof handles water, foot traffic and repeated service work.
02
INSULATION / COVER BOARD
Thermal layers and a stable surface support drainage, attachment and long-term membrane performance.
03
BASE SHEET
Some assemblies include a mechanically attached, adhered or asphalt-set base ply beneath the cap sheet.
04
MODIFIED BITUMEN PLY
Reinforced SBS- or APP-modified sheets create the primary waterproofing layers.
05
CAP SHEET / SURFACING
Granulated cap sheets or other approved surfacing protect the asphaltic membrane from ultraviolet exposure and traffic.
06
FLASHING + LAPS
Transitions and sheet laps must follow the product-specific installation method and temperature requirements.
WHERE MODIFIED BITUMEN MAKES SENSE
A TOUGH SYSTEM FOR ROOFS THAT SEE SERVICE TRAFFIC AND COMPLEX DETAILS.
Modified bitumen is often evaluated for commercial roofs where owners want an asphalt-based assembly with reinforced sheets, multiple plies, durable surfacing and repair methods that are familiar on many existing built-up or modified roofs. It can be useful around frequent rooftop service activity when the assembly is detailed and protected correctly.
- Low-slope commercial roof replacement
- Existing asphalt-based roof assemblies
- Roofs with recurring maintenance traffic
- Buildings with many curbs, penetrations and transitions
- Projects where multi-layer redundancy is a priority
- Owners evaluating recover versus full tear-off
MODIFIED BITUMEN VS. OTHER LOW-SLOPE SYSTEMS
MULTIPLE PLIES CHANGE THE FAILURE PATH.
| System | Type | Seams / Joints | Standout Advantage | Watch Closely |
|---|---|---|---|---|
| Modified Bitumen | Polymer-modified asphalt sheets | Product-specific laps | Redundancy + durable surfacing | Application method, heat, weight, detailing |
| Built-Up Roofing | Alternating bitumen + reinforcing plies | Hot/cold-applied field plies | Multiple waterproofing layers | Weight, odor/logistics, surfacing, drains |
| TPO | Thermoplastic single-ply | Heat welded | Reflectivity + broad commercial use | Welds, punctures, drainage |
| EPDM | Synthetic rubber single-ply | Tape / adhesive seams | Flexibility + large sheets | Seams, punctures, rooftop traffic |
OTHER COMMERCIAL ROOF SYSTEMS
COMPARE THE ALTERNATIVES BEFORE LOCKING THE SPECIFICATION.
The right system starts with slope, deck, drainage, rooftop use, exposure, existing materials and ownership goals. These related commercial roof systems solve different problems and should not be treated as interchangeable products.
01
TPO ROOFING
Thermoplastic single-ply with heat-welded seams for low-slope commercial roofs.
EXPLORE TPO ROOFING → 02
EPDM ROOFING
Synthetic-rubber single-ply roofing with flexible sheets and proven repair methods.
EXPLORE EPDM ROOFING →
03
PVC ROOFING
Thermoplastic membrane with welded seams and strong resistance to many grease and chemical exposures.
EXPLORE PVC ROOFING →
04
BUILT-UP ROOFING
Multi-ply bitumen and reinforcement for redundant commercial waterproofing.
EXPLORE BUILT-UP ROOFING → 05
COMMERCIAL METAL
Panel and standing-seam systems built around movement, attachment and flashing control.
EXPLORE COMMERCIAL METAL →MODIFIED BITUMEN INSTALLATION PRIORITIES
THE APPLICATION METHOD HAS TO FIT THE BUILDING, PRODUCT AND CREW.
01
ASSEMBLY IDENTIFICATION
Determine the existing roof composition, moisture conditions and whether the project is repair, recover or replacement.
02
PRODUCT + METHOD SELECTION
Match SBS or APP products and the approved attachment method to the building, substrate and manufacturer system.
03
SUBSTRATE PREPARATION
Create a clean, dry, stable surface with compatible insulation or cover board and corrected drainage transitions.
04
PLY INSTALLATION
Install base and cap sheets with proper side laps, end laps, offsets and adhesion according to the system.
05
FLASHING DETAILS
Build curbs, walls, penetrations, drains and edge transitions with compatible reinforced flashing materials.
06
SURFACE + PUNCH LIST
Protect exposed asphalt, inspect laps and terminations, and correct wrinkles, voids or incomplete bonds before closeout.
THE POINT:
Torch-applied modified bitumen is only one installation category, not a synonym for the entire system. Product choice and application method need to account for fire risk, occupied-building conditions, substrate compatibility and local requirements.
REPAIR, RECOVER OR REPLACE?
START WITH THE ROOF THAT IS ACTUALLY THERE.
Before recommending a commercial roof project, Ameristar Roofing can evaluate membrane or panel condition, moisture, insulation, deck concerns, drainage, penetrations, previous repairs and the remaining usefulness of the existing assembly.
A small leak does not automatically mean full replacement. The opposite is also true: a roof covered in patchwork is not automatically a good repair candidate just because another bucket of sealant can be purchased.
The decision should be based on the extent of deterioration, trapped moisture, attachment, recurring leak history, building plans and whether a repair or recover can reasonably restore dependable performance.
MODIFIED BITUMEN ROOFING FAQS
THE QUESTIONS THAT SHOULD BE ANSWERED BEFORE THE PROJECT.
What is modified bitumen roofing?
Modified bitumen is an asphalt-based low-slope roofing system manufactured as reinforced membrane sheets. Polymer modifiers such as SBS or APP are used to change flexibility and performance characteristics.
What is the difference between SBS and APP modified bitumen?
SBS and APP use different polymer modifiers and are commonly associated with different handling and installation characteristics. The right choice depends on the specific manufacturer system and project requirements.
Does modified bitumen have to be torch applied?
No. Depending on the product, modified bitumen may be installed with torch application, hot asphalt, cold-process adhesive, mechanical attachment or self-adhered methods.
Can modified bitumen be repaired?
Often, yes. Localized splits, punctures, open laps and flashing defects may be repairable with compatible asphaltic materials when the surrounding roof and substrate remain suitable.
Is modified bitumen the same as built-up roofing?
No. Both are asphalt-based systems, but built-up roofing is traditionally assembled from alternating layers of bitumen and reinforcing felts, while modified bitumen uses factory-manufactured reinforced membrane sheets.
Is granulated modified bitumen good for foot traffic?
Granulated cap sheets provide a durable surface, but repeated service traffic should still be controlled and protected. No roof membrane should be treated like a sidewalk.
When should a modified bitumen roof be replaced?
Replacement may be appropriate when moisture is widespread, plies are extensively deteriorated, repairs are recurring across the roof, attachment is compromised or drainage and substrate problems cannot be solved reliably with localized work.
AMERISTAR ROOFING • ATLANTA, GA
BUILD THE ROOF AROUND THE BUILDING.
Ameristar Roofing can inspect the existing commercial roof, evaluate the assembly and help determine whether modified bitumen roofing belongs in the repair, recover or replacement plan.
(770) 338-6361