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PropertyRoofs

Straight answers for the people who own the roof

How TPO, EPDM, PVC, metal and the other commercial roof systems go on, where each falls short, how they handle hail and what the warranties cover. Written for building owners and facility managers, not sold by a roofer.

Compare roof systemsTPO vs EPDM
Roof lengthRooftop unitCricketDrainSlope to drainRoof areaParapet wallSlopeDrainRidge or cricket
A low-slope roof plan: the roof slopes to two drains, with a cricket between them and a rooftop unit above it.

Which system fits your building

Start from what the building does. Its use, the traffic on the roof and what lands on it narrow the choice before price does.

BuildingUsually consideredWhy
Warehouse or distribution centerTPO, EPDMLarge, open roofs, where wide sheets leave fewer seams: TPO comes up to 12 to 16 feet wide and EPDM up to 50.
Restaurant or food processingPVCPVC resists grease and oils from kitchen exhaust, which attack EPDM and modified bitumen.
Office or retail with rooftop equipmentModified bitumenPolyester-reinforced plies hold up to service crews walking to the units.
School, hospital or other occupied buildingTPO, Modified bitumenLow-odor methods with no kettle or torch: self-adhered TPO, and cold-applied or self-adhered modified bitumen.
Flat roof that holds waterSpray foam, MetalFoam can be sprayed thicker in low spots to slope the roof to its drains; metal goes on new sloped framing over the old roof.
Pre-engineered metal buildingMetalNew panels can be screwed through the old ones into the existing purlins, so the old roof stays in place.

Compare the main systems

SystemWhat it isSeams
TPOSingle-ply thermoplastic sheet with polyester reinforcementHot-air welded
EPDMSingle-ply sheet of cured synthetic rubberPrimed and taped; adhesive at some details
PVCSingle-ply thermoplastic made flexible with plasticizersHot-air welded; some panels factory-welded
Modified bitumenPolymer-modified asphalt rolls laid in two or more pliesLapped, sealed with heat, hot asphalt or adhesive
Built-upPlies of felt set in bitumen, topped with gravel, a cap sheet or a coatingLapped plies set in bitumen or adhesive
Spray foamFoam sprayed in place as one seamless layer, then coatedNone; the foam is seamless
MetalSteel panels on a sloped roofMachine-seamed, snap-together, or lapped

Seams as each system page documents them, with its sources. How we build these pages

Sources (29)

  1. Johns Manville, JM TPO 80 mil Thermoplastic Polyolefin Membrane data sheet (RS-8634)
  2. Elevate (Amrize Building Envelope), UltraPly TPO Roofing Systems: membrane
  3. Carlisle SynTec Systems, Sure-Weld TPO Reinforced Membrane Product Data Sheet (01.28.26)
  4. Carlisle SynTec Systems, Sure-Seal EPDM Dusted Non-Reinforced Membrane Product Data Sheet
  5. Elevate (Amrize, formerly Holcim Elevate), RubberGard EPDM brochure
  6. Duro-Last, Membrane Reference Guide
  7. Johns Manville, JM PVC - 60 mil MIN Product Data Sheet (RS-9275)
  8. USACE / NAVFAC / AFCEC (via WBDG), UFGS 07 53 23 Ethylene-Propylene-Diene-Monomer Roofing (August 2025)
  9. Elevate (Amrize, formerly Holcim Elevate), Lowslope Fire Retardant (LSFR) RubberGard EPDM, Technical Information Sheet TIS 103
  10. USACE / NAVFAC / AFCEC (Whole Building Design Guide), UFGS 07 52 00 Modified Bituminous Membrane Roofing (August 2025)
  11. Elevate (Amrize), APP 160 Technical Information Sheet (TIS 401)
  12. Tremco Roofing and Building Maintenance, Modified Bitumen roofing systems (POWERply)
  13. Elevate (Amrize Building Envelope), UltraPly TPO Roofing Systems
  14. Johns Manville, JM TPO SA - 60 mil
  15. The Garland Company, Garland High-Performance Membranes brochure
  16. Insurance Institute for Business & Home Safety (section by the Spray Polyurethane Foam Alliance), RICOWI Roof Guide: Spray Foam
  17. American WeatherStar, Application Guideline: Coated Spray Polyurethane Foam System over Single-Ply (Foam-Gard, rev. 9/18/25)
  18. MBCI, How to Retrofit Existing Roofs with New Metal Roofing Systems
  19. McElroy Metal, Metal Over Low Slope Retrofit
  20. USACE / NAVFAC / AFCEC (Unified Facilities Guide Specifications, via WBDG), UFGS 07 61 14 Steel Standing Seam Roofing (August 2025)
  21. McElroy Metal, Retrofit and Recover
  22. Johns Manville, JM TPO Roofing Membrane
  23. Johns Manville, JM EPDM NR 60 mil Data Sheet (RS-3005)
  24. Sika Corporation, Sarnafil G 410-60 Product Data Sheet
  25. Versico Roofing Systems, Non-Compatible Substrates for PVC
  26. National Institute of Standards and Technology, NISTIR 4972: Observations From a Field Study of the Performance of Polymer-Modified Bitumen Roofing (1993)
  27. FM Approvals, Approval Standard 4470: Single-Ply, Polymer-Modified Bitumen Sheet, Built-Up Roof (BUR) and Liquid Applied Roof Assemblies (April 2022)
  28. USACE / NAVFAC / AFCEC (via WBDG), UFGS 07 51 13 Built-Up Asphalt Roofing (August 2025)
  29. MBCI, Selecting Metal Panels Based on Roof Slope

Updated October 2026.