TPO Roofing Cost Calculator

TPO runs roughly $5.50 to $12 per square foot installed, so a 2,500 sq ft flat roof lands around $14,000 to $30,000, and larger commercial roofs scale up from there. The membrane thickness sets the base (45 mil is cheapest, 60 mil is the common standard, 80 mil is heavy-duty), then the attachment method and whether the old roof is torn off adjust it. The number people most often underestimate is insulation — rigid board beneath the membrane is a real part of the system and can add a couple of dollars per square foot on its own.

All three are single-ply flat-roof membranes, but they differ in a few key ways. TPO is a reflective white thermoplastic with heat-welded seams — energy-efficient and moderately priced, which is why it dominates commercial flat roofs. EPDM is a rubber membrane, usually black, that's proven and flexible but absorbs heat (less efficient unless you buy white) and uses glued or taped seams rather than welded ones. PVC is a thermoplastic like TPO with the same welded seams and reflectivity, and it's the most chemical- and grease-resistant (good for restaurants) — but it costs more. TPO sits in the middle: cheaper than PVC, more energy-efficient than standard EPDM, with strong welded seams.

Thickness (in mils) trades cost against durability and lifespan. 45 mil is the economical option for budget projects or low-exposure roofs, but it's thinner and shorter-lived. 60 mil is the most popular choice and the usual recommendation — a solid balance of puncture resistance, longevity, and cost for most roofs. 80 mil is the heavy-duty pick for high-traffic roofs, rooftop equipment, hail-prone or harsh climates, and maximum lifespan and warranty length. Thicker membrane generally lasts longer and resists punctures better, so unless budget is tight, 60 mil is the safe default and 80 mil is worth it for demanding conditions.

These are the three ways the membrane is held to the roof. Mechanically fastened uses screws and plates along the seams (then the next sheet welds over them) — fast, economical, and the common standard, though fasteners can leave slight ripples. Fully adhered glues the membrane down across the whole surface for a smooth look and excellent wind-uplift resistance, preferred on exposed or high-wind roofs, but it costs more in adhesive and labor (about +15%). Ballasted lays the membrane loose and holds it down with stone or pavers — cheaper on attachment (about −5%) but heavy, so it needs adequate structure and isn't right for every roof. Your wind zone and roof deck usually decide it.

Insulation is a core part of a TPO system but is usually a separate line, and it's the item that most affects the total after the membrane itself. In a typical assembly, rigid board (like polyiso) goes over the deck, then often a cover board, then the TPO. It provides the R-value your energy code requires, cuts heating and cooling costs, and gives the membrane a smooth, stable base. On a re-roof you may be adding fresh insulation — especially if the old board is wet from a past leak. This calculator treats insulation (~$2.50/sq ft) and a cover board (~$1/sq ft) as add-ons so you can budget them; skipping insulation hurts efficiency and can violate code.

Sometimes TPO can be installed as an overlay (recover) over a sound existing roof — saving tear-off and disposal — but only if there's a single existing layer, the deck and insulation are dry, and code allows it (most codes cap a roof at two total layers). The risk is trapping moisture or problems you can't see. A tear-off down to the deck is often preferred or required because it lets the crew inspect and repair the deck, remove any wet insulation, and install a clean, warranty-compliant system — many manufacturers require it for full warranties. The calculator lets you include tear-off (about $1.50/sq ft) or skip it for an overlay or new construction.

Expect about 20 to 30 years, with thickness, installation quality, climate, and maintenance driving the range. Thicker membrane lasts longer, so an 80 mil roof generally outlives a 45 mil one. Installation quality is critical because TPO's seams are heat-welded — properly welded seams are what make the roof watertight, and poor welding is a leading cause of premature failure, so an experienced installer matters more than the brand. The reflective white surface helps it shrug off UV and heat, but standing (ponding) water and extreme conditions shorten life. Warranties commonly run 15 to 30 years depending on the system and thickness.

Most flat-roof TPO jobs run a few days to about two weeks, depending on size, complexity, and whether tear-off and new insulation are involved. A small-to-medium roof of a few thousand square feet is often several days to a week; large commercial roofs take longer. The work runs through any tear-off and deck repair, insulation and cover board, rolling out and fastening or adhering the membrane, heat-welding the seams, and flashing all the edges, drains, and penetrations. Because TPO comes in large sheets and welds quickly, it usually installs faster than a steep-slope shingle or tile roof on a comparable building — but the detail work around penetrations and dry-weather welding conditions set the pace.