Commercial TPO Roofing — Orlando

Commercial Roofing

TPO (thermoplastic polyolefin) is a single-ply membrane, typically 45 to 80 mils thick, installed over insulation and a cover board and joined at the seams with hot air. The weld fuses the sheets into one piece rather than gluing them, which is what makes a well-installed TPO roof watertight at the laps for a long time. The white surface reflects most of the sun that hits it, and on an Orlando roof in August that reflectivity shows up as a real reduction in cooling load and rooftop temperature.

Almost every TPO problem we are called to look at traces to how it was installed rather than to the membrane itself. Cold welds that looked fine on day one open under a few summers of thermal movement. Flashing at curbs, walls and pipes was done with the wrong accessory or not welded at all. Membrane was run up to equipment with no walk pad, and service technicians punctured it. This page is about what a TPO roof should look like when it is done properly, and how to tell whether yours was.

Mechanically attached or fully adhered

There are two ways to hold a TPO membrane down. Mechanically attached systems screw the sheet through the insulation to the deck along each lap, with plates under the membrane. They install fast, cost less and suit steel decks well; the trade-off is that the sheet flutters between fasteners in wind, which is why Florida wind uplift code drives fastener spacing tighter at the corners and perimeter than in the field. Fully adhered systems bond the membrane to the cover board with adhesive across the whole surface: no flutter, a cleaner look, better performance where uplift pressures are high, and easier to detail around dense equipment, at a higher cost and more sensitivity to the weather on install day.

Which one is right depends on the deck, the building height and exposure, the wind zone and the uplift rating the permit will require. We size the attachment to the engineering, not to a habit.

Where TPO roofs fail in Central Florida

• Seam welds that were cold, contaminated or too narrow, opening after a few seasons of heat cycling
• Flashing at HVAC curbs, parapets and pipe boots, especially where the membrane was not fully welded to the accessory
• Punctures around rooftop equipment from service traffic, dropped tools and unprotected walk paths
• Membrane run without a cover board, so the insulation facer telegraphs through and the sheet wears at every fastener plate
• Ponding that keeps a seam wet and hot for days at a time

UV in Orlando is harder on membrane than data sheets written for a national market suggest, and the thin end of the thickness range shows it first. We specify a heavier sheet than the minimum where the roof will see foot traffic, and we probe every field seam before handing the roof over.

Insulation and cover board

The membrane gets the attention, but the layers under it decide how the roof performs. Polyisocyanurate insulation gives the R-value the energy code asks for and can be tapered to build slope toward drains on a dead-flat deck, which is the single most effective ponding fix there is. A cover board, typically a high-density polyiso or a gypsum board, goes between the insulation and the membrane. It resists hail and foot traffic, gives the adhesive a solid surface to bond to, and keeps a puncture from going straight into wet insulation.

Skipping the cover board is a common way to make a TPO bid look cheaper, and it is the first thing we check on a roof that is failing early. We show the full assembly in the scope, layer by layer, so a bid comparison is a fair one.

New construction, re-cover or tear-off

On new construction, like the new-construction building near Orlando International Airport in the photograph at the top of this page, TPO goes straight onto the deck and insulation with nothing to work around. On an existing roof there is a choice. Florida code allows one roof over an existing one in many cases, so a re-cover can put new insulation and membrane over the old roof if that roof is dry and the deck is sound. It saves the tear-off cost and the landfill trip. It is the wrong move when the old insulation is wet, when the deck needs repair, or when the building already has two roofs on it. A moisture survey tells us which case you are in, and we will not re-cover over wet insulation regardless of how much it would save on the bid. The commercial roof replacement page lays out the full decision.

When TPO is the wrong answer

TPO is not the right membrane for every low-slope roof, and we will say so. A restaurant with kitchen exhaust fans dumping grease onto the roof will shorten a TPO membrane badly; that is PVC territory. A roof with heavy, constant foot traffic from maintenance crews is often better served by modified bitumen, which takes abuse a thin thermoplastic sheet does not. And a TPO roof that is aging uniformly but is still dry underneath may not need replacing at all; a coating can be the better spend. If you are weighing options for a building anywhere from downtown Orlando to Kissimmee, call (407) 871-6159 and we will walk the roof before recommending a system.

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