Metal, Tile or Membrane: Which Roof Fits Your Commercial Building

You own or manage a strip center, an office, a church, a school building, a shop or a warehouse somewhere in the Upstate, and the roof has come up. Maybe a tenant reported a leak, maybe the building is new to you, maybe the old roof is simply tired.

The useful comparison is not brand against brand. It is how each system behaves on your slope, under your equipment, with your foot traffic, in Upstate heat and summer storms, and how it gets repaired. Anderson Metal Roofing and Shingles installs commercial metal roofs and wall panels and flat roof systems; this guide compares those with the other systems you will be offered, including ones the company's pages do not cover, so you can ask better questions of anyone who bids.

Building codes set a minimum slope for each roof covering, and that one number removes options fast. South Carolina's Building Codes Council adopted the 2021 International Building Code with state modifications, in effect since January 1, 2023 according to the Council's codes-in-effect notice. In Chapter 15 of that code, Section 1507.4.2 allows standing seam metal panels down to one-quarter inch of rise per foot, lapped metal panels with lap sealant down to one-half inch per foot, and lapped panels without sealant only at three inches per foot or steeper. Section 1507.12.1 sets one-quarter inch per foot for single-ply membranes, Section 1507.11.1 the same for modified bitumen, and Section 1507.3.2 requires two and one-half inches per foot or steeper for clay and concrete tile.

The National Roofing Contractors Association recommends more than the code minimums: at least one-half inch per foot for structural metal panel systems and three inches per foot for architectural metal panels, and positive drainage for every membrane roof. The code defines positive roof drainage as a design that still drains within 48 hours of rain after the deck has deflected under load.

IBHS groups anything at three inches per foot or less as low-slope. If your roof is in that range, the realistic choices are a membrane, modified bitumen or structural standing seam metal, and the next guide on TPO versus EPDM versus metal on low-slope roofs goes deeper. Ask the Anderson County or City of Anderson building department how they apply these sections to a reroof.

Each system below is described neutrally. None is right for every building.

• Standing seam metal. Long panels joined at raised seams with concealed clips, so no fasteners sit in the weather. IBHS notes the panels must be allowed to float on their clips to handle thermal movement, and that penetrations cutting through a seam are a potential water entry point. Common on retail, office, school and church roofs with a visible slope, and usable on low slopes when designed as a structural system.
• Exposed-fastener metal. Corrugated or ribbed panels screwed through the face with washered fasteners. Generally less labor than standing seam. Needs more slope and periodic checks of the washers and sealant. Common on warehouses, farm shops and storage buildings. The commercial page lists 22-, 24-, 26- and 29-gauge metal sidings and wall panel options including insulated, single skin, concealed fastener, exposed fastener and interior liners.
• Clay or concrete tile. Heavy, long-wearing and visually specific. The structure has to be designed for the weight, the slope has to meet the code minimum, and walking on it for maintenance can break tiles. Seen on churches, civic buildings and some restaurants and offices. The company's historical restoration page lists clay tile among the materials it works with on older buildings.
• Single-ply membrane (TPO, PVC, EPDM). One layer of sheet material over insulation. IBHS describes thermoplastics (TPO and PVC) as having seams formed by heat or chemical welding, and thermosets (EPDM) as rubber-based. Light, fast to install, and the usual answer for low-slope roofs with equipment on them.
• Modified bitumen. Asphalt-based roll roofing reinforced with polyester or fiberglass, applied with a torch or as peel-and-stick sheets, as the company's flat roof systems page describes. Tolerates foot traffic well and patches with like material. IBHS recommends a written hot work program wherever torches are used.

After slope, think about what sits on the roof and who walks on it. Tile is the heavy option and is only a candidate where the framing was designed for it or an engineer says it can be. Metal and single-ply are light. Modified bitumen sits between them and takes foot traffic better than a bare single-ply sheet.

Roof-mounted HVAC, exhaust fans, vents and solar racks mean penetrations, and every penetration is a detail that can leak. Membranes handle curbs and pipe boots as routine work. On standing seam metal, IBHS advises keeping penetrations to a minimum and placing them in the flat of the panel rather than through a seam. For any system, IBHS recommends a cover board under a new low-slope roof to improve puncture resistance, and periodic inspection that includes clearing debris and keeping the roof shedding water so it does not overload.

Insulation is part of the decision on every low-slope system, since it is what the membrane or panels sit on. The company's post on the importance of commercial roof insulation covers the types; the practical point here is that a roof with wet insulation usually cannot be recovered and has to come off, which the when to replace a commercial roof guide explains.

Upstate summers make roof color a real factor on a low building with a big roof and air conditioning under it. The Cool Roof Rating Council rates roofing products on two properties: solar reflectance, the share of sunlight the surface reflects, and thermal emittance, how well it releases the heat it absorbed. Both run from 0 to 1, and the CRRC publishes initial values and values after three years of weathering in its rated products directory, so you can compare a white membrane, a light painted metal and a granulated cap sheet on the same scale.

The U.S. Department of Energy's guide to cool roofs lists cool thermoplastic membranes, elastomeric coatings and metal products as the cool options for low-slope roofs, and notes that in mixed climates a reflective roof can add a little heating demand in winter that is usually smaller than the summer saving. It also says it is rarely economical to replace a mechanically sound roof only to raise its reflectance. One housekeeping point: the ENERGY STAR specification for roof products was sunset on June 1, 2022, so a current product will not carry that label; use CRRC ratings instead. The what is a cool roof guide covers the rest.

The company's own post on commercial metal roofing makes the case for metal. This guide is the comparison that sits beside it.

Metal is not the fit when the roof has dozens of penetrations in a tight area, when the slope is close to flat and water already stands on it, or when a church or historic building has tile that should stay tile. A membrane, a drainage fix, or restoration are better conversations in those cases, and the company's pages cover metal and flat systems but not new tile roofs, so a tile job may need a different kind of contractor.

Do not pick a system before someone has looked at the existing roof. Under 2021 IBC Section 1512 a new covering may go over an old one only under listed conditions, and never where the existing roof is water-soaked or already has two layers. That finding changes the scope more than the material choice does.

The next step is a free quote. Use the request-a-quote form, choose Commercial as the structure type and describe what is on the roof now. The quote page offers a virtual first look by Zoom or FaceTime, and measurements are verified on site before a price is final.