Modified Bitumen Roofing in Gilbert, AZ

Modified Bitumen Roofing in Gilbert, AZ

Modified bitumen is a multi-ply roofing system that bridges traditional built-up roofing (BUR) and modern single-ply membranes. It's been in commercial use since the 1970s and remains a top choice for many building types — particularly multi-story buildings, buildings with extensive rooftop equipment, and owners who want the proven redundancy of a multi-ply system.

SBS vs APP Modified Bitumen

SBS (Styrene-Butadiene-Styrene)

SBS modifier gives the bitumen a rubber-like elasticity. SBS membranes remain flexible in cold temperatures, making them the choice for climates with cold winters. In Arizona, SBS performs well — the elasticity allows the membrane to accommodate thermal movement without cracking. SBS systems can be torch-applied, cold-applied with adhesive, or hot-mopped.

APP (Atactic Polypropylene)

APP modifier gives the bitumen a plastic-like quality with excellent UV and heat resistance. APP membranes are stiffer in cold weather but perform exceptionally well in hot climates — Arizona is actually ideal APP territory. APP is almost always torch-applied, which produces a continuous, fully-bonded assembly with no adhesive seams to fail.

Installation Methods

Torch-Applied

A propane torch heats the underside of the membrane roll as it's being unrolled, melting the factory-applied bitumen into the substrate or previous ply. Done correctly, torch application creates a fully bonded, monolithic waterproofing layer. It requires skilled applicators — too much heat damages the membrane, too little creates an incomplete bond.

Cold-Process

Cold-applied systems use a bituminous adhesive rather than heat. They work on structures where open flame is restricted, in occupied buildings with fire suppression concerns, or over substrates that can't handle heat. Cold-process systems require more cure time but eliminate the fire risk of torch work.

Granulated Cap Sheet

Modified bitumen systems almost always terminate with a mineral-surfaced cap sheet — a top ply embedded with ceramic or mineral granules. The granules protect the bitumen from UV degradation (bitumen's primary enemy), add impact resistance, and provide the finished appearance of the roof. White or light-grey granules improve solar reflectance — an important consideration in Arizona.