Commercial Roofing Systems
Low-slope commercial roofs use a handful of systems. Each can be repaired, restored with a coating, or replaced.
Foam and Roof Coatings
Spray polyurethane foam goes on as one seamless, insulating layer and is shaped to drain, then protected with an acrylic, silicone or moisture-cured polyurethane coating. On an existing commercial roof, a restoration coating can go over foam, built-up, modified bitumen, single-ply or metal without a tear-off, as long as the roof isn't water-soaked or deteriorated.
TPO Single-Ply Membrane
TPO is a white thermoplastic single-ply membrane, mechanically fastened or adhered over insulation, with heat-welded seams. Like other single-ply roofs, it needs a design slope of at least ¼ inch per foot for drainage.
Modified Bitumen and Built-Up Roofing
Modified bitumen is polymer-modified asphalt in rolled sheets. Built-up roofing is layers of felt and asphalt, often with a gravel or coated surface. Both need a design slope of at least ¼ inch per foot, except coal-tar built-up roofs at ⅛ inch.
Restoration or Replacement
The choice comes down to what's under the surface. A moisture survey and core samples show how much of the insulation and deck is wet. Dry, sound roofs are candidates for restoration coating. Wet or deteriorated roofs can't be recovered and need removal of the wet material or a full replacement.
Why Tempe homeowners call Tempe Expert Roofing
- Free, no-obligation roof estimates
- Written scope: tear-off, underlayment, flashing, coating
- Photos of every finding on your roof
- Permit and code questions answered up front
- One call, one local roofer
What Affects the Cost of a Commercial Roof
- Roof area and building height.
- How much insulation and deck is wet.
- Restoration coating versus tear-off and replacement.
- Rooftop equipment, curbs, drains and penetrations.
- Work scheduled around business hours or tenants.
Commercial Roofing Licenses and Codes in Tempe
License
Arizona's Registrar of Contractors issues C-42 (commercial roofing), R-42 (residential only) and CR-42 (both). A commercial job needs C-42 or CR-42. Look the number up on the ROC website before signing.Codes
Tempe adopted the 2024 International Codes, including the International Building Code, effective July 1, 2026. Commercial roof assemblies fall under IBC Chapter 15. Through December 31, 2026, permit applications may use the 2018 or 2024 codes.Permits
Replacing any roof assembly component beyond the covering, such as insulation or deck, needs a permit in Tempe. Ask the roofer who pulls it.
For flat roofs on smaller buildings and homes, see flat roof repair and foam roofing.