Modified Bitumen Roofs
A durable, UV-resistant, and heat-welded solution for long-lasting flat roof protection.
Get a Flat Roof EstimateWhat is APP Modified Bitumen?
APP modified bitumen is essentially a "plasticized asphalt." It is created by adding APP (Atactic Polypropylene), a type of plastic polymer, to roofing-grade asphalt. This modification gives the resulting membrane plastic-like characteristics, particularly when heated. When installed with a torch, the plasticized asphalt melts into a liquid state, allowing for a powerful, seamless, and monolithic bond to the roofing substrate, creating a highly durable and waterproof surface.
Key Characteristics of APP Roofing
High Temperature Tolerance
APP membranes have a high melting point, making them exceptionally stable in hot climates and resistant to softening from intense sun.
Excellent UV Resistance
The plastic modifiers in APP provide strong resistance to ultraviolet (UV) radiation, preventing premature aging and cracking.
Seamless Torch Application
When heated, the material melts into a liquid, allowing for a strong, monolithic (seamless) bond to the substrate and at all overlaps.
Puncture & Tear Resistant
Its tough, plasticized nature offers robust resistance to punctures, tears, and foot traffic once cooled and cured.
Choosing The Right System: SBS vs. APP
Choose SBS If...
SBS (Styrene-Butadiene-Styrene) modified bitumen behaves more like rubber. It is generally preferred in colder climates due to its superior flexibility in low temperatures, which helps it resist cracking. It's an excellent choice for roofs that experience building shifts or movement.
Choose APP If...
APP (Atactic Polypropylene) modified bitumen behaves more like plastic. It often excels in hotter, sunnier climates due to its high-temperature stability and superior resistance to UV degradation. It forms a hard, durable surface ideal for high sun exposure.
Flat Roof Replacement Process
Replacing a flat roof is a detailed process that requires precision at every stage to ensure a long-lasting, watertight system.
Roof Tear-Off
All existing roof layers are completely removed down to the structural roof decking.
Deck Inspection & Repair
The exposed decking is thoroughly inspected for signs of rot, moisture, or sagging, and any damaged sections are replaced.
Vapor Barrier (Optional)
If required, a vapor barrier is installed over the deck to prevent moisture transfer and condensation within the system.
Insulation Board Installation
Rigid Polyiso board insulation is mechanically fastened or adhered to the deck, providing thermal resistance.
Modified Bitumen Installation
The base and cap sheets are carefully laid out and torch-adhered to create a multi-layer, waterproof membrane.
Flashing & Edge Detailing
Critical areas like vents, drains, and walls are meticulously flashed to create a watertight seal at all transitions.
Final Inspection & Cleanup
A final walkthrough ensures all components are properly installed and sealed. The site is then cleared of all debris.
Why Expert Installation Matters
By understanding the differences between SBS and APP modified bitumen, homeowners can feel confident in choosing the product for their home. However, the best material can fail without expert installation. Always choose a reputable and experienced roofing contractor specializing in low-slope applications to ensure a quality, lasting investment. Flat roofs are more complex due to water pooling and higher foot traffic, so it's important to hire a company that has years of flat roof experience under their belt.
APP Roofing FAQs
A professionally installed APP modified bitumen roof can last between 15 and 30 years. Its lifespan is influenced by factors like climate, quality of installation, proper drainage, and regular maintenance.
Yes, when performed by a trained, certified, and fully insured professional. Reputable contractors follow strict safety protocols, including having fire extinguishers readily available and using heat shields to protect flammable surfaces. It is not a DIY project and requires expert handling.
Yes, modified bitumen roofs are durable and can handle regular foot traffic for maintenance purposes (e.g., servicing HVAC units). The surface is tough and less prone to scuffs or punctures compared to some other single-ply membranes.
Maintenance is generally low. It involves semi-annual inspections to check for and clear any debris, ensure drains are not clogged, and inspect seams and flashings for any signs of damage or deterioration. Promptly addressing minor issues will significantly extend the roof's life.
APP stands for Atactic Polypropylene. It is a type of thermoplastic polymer that is added to asphalt to enhance its properties, particularly its stability at high temperatures and its resistance to UV degradation, making the final product act more like a plastic.
Secure Your Flat Roof
Ensure your property is protected with a durable, professionally installed modified bitumen system. Contact Revma for a detailed inspection and estimate.
Get Your Free Estimate