Quick Answer
Flat (low-slope) membrane roofs such as TPO and modified bitumen cost less upfront and work on nearly flat roofs, but often need more maintenance and earlier replacement. Metal roofs last longer and resist hail better, but they need enough slope to drain. Some buildings can be converted from flat to metal with a sloped framing retrofit. The right choice depends on your building's slope, use, and long-term plans.
Flat Roof Membranes
Most commercial flat roofs use single-ply membranes like TPO or PVC, or built-up and modified bitumen systems. They are designed for very low slopes and large roof areas.
- Lower initial cost on large flat roofs
- Works on nearly flat roof decks
- Seams and penetrations need regular inspection
- Ponding water can shorten roof life
- Hail can puncture or bruise some membranes
Metal Roofing
Metal roofing needs a minimum slope to shed water. Some standing seam systems are rated for low slopes, but true flat roofs are usually not suitable without changes.
Metal offers longer life, better hail resistance, and lower long-term maintenance.
Converting Flat to Metal
For buildings with chronic flat roof problems, a retrofit system can add sloped framing over the existing roof and then install metal panels on top. This improves drainage and can add insulation space.
Retrofits require an engineering review of the structure, but they can end a cycle of leaks and repairs.
Drainage Is the Deciding Factor
The biggest issue on flat roofs is water that does not drain. Ponding water adds weight, speeds membrane breakdown, and finds its way through any weak seam.
Metal roofing solves drainage by design, since it requires slope. When a building has persistent ponding problems, adding slope with a retrofit system and installing metal can be a long-term solution rather than another round of patches.
Which Is Right for Your Building?
Consider how long you will own the building, your maintenance budget, hail exposure, and roof slope. A lower upfront cost can mean higher costs over time.
We can inspect your building and walk you through the options for San Antonio commercial properties.
Frequently Asked Questions
Can you put a metal roof on a flat roof?
Not directly in most cases, but a retrofit system can add slope so metal panels can be installed.
How long do flat commercial roofs last?
It varies by membrane and maintenance, but they generally need replacement sooner than a quality metal roof.
Which commercial roof handles hail better?
Metal generally resists hail better than many flat roof membranes.
Contact Sanchez Metal Roofing
Phone: (210) 708-3308. Email: sanchezmetalroofing123@gmail.com. Address: 520 Fredericksburg Rd, San Antonio, TX 78201. Hours: Monday through Saturday 8:00 AM to 5:00 PM. Free roof inspections across San Antonio. Call (210) 708-3308.