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TPO and EPDM roofing in St. Louis
TPO and EPDM are the two single-ply membranes we install on low-slope roofs. They are both sheets. They are not the same sheet, and the bid should say which one and how it is attached.
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TPO and EPDM
TPO is a thermoplastic membrane. The laps are welded with hot air until the two sheets become one piece. The membrane is usually white or another light color, so it reflects more of the sun than a black roof. That matters on a low-slope commercial roof through a St. Louis summer, when the surface temperature of a dark roof climbs well above the air temperature.
EPDM is a synthetic rubber sheet. People still call it a rubber roof. It is often black, though white EPDM exists. The seams are not welded. They are joined with seam tape or adhesive, and the strength of the roof depends on those joints being clean and rolled. EPDM stays flexible in cold weather, which is why it has been on Midwest roofs for a long time.
We install both. We do not pick one for every building. A light-colored welded membrane and a black rubber membrane behave differently in heat, at the seams and under foot traffic. The written scope names the membrane, the thickness and the attachment. If a building already has one of them, a repair uses materials matched to that sheet, and the repair itself is on the repair site.
Thickness and attachment
Both membranes are sold in more than one thickness. A thicker sheet costs more and takes more abuse from hail, foot traffic and a dropped tool. Thinner sheet is not automatically wrong on a roof nobody walks. The thickness belongs in the bid as a mil number, not as the word "commercial grade," so two proposals can be compared.
Fully adhered means the sheet is glued to the cover board or insulation underneath. The surface is smoother, and the wind has less of a loose sheet to pull on. The glue is only as good as the board it sticks to, so a wet or dusty substrate is not a place to adhere a roof.
Mechanically attached means plates and screws fasten the sheet through the insulation into the deck, usually in the laps, and the laps are then welded or taped over the plates. It is a common way to put down a large open roof. In wind the sheet can flutter between the rows of fasteners. That is not a defect by itself. It is a reason the fastener layout has to match the wind exposure of that building, and a reason some owners prefer a fully adhered roof over a quiet office.
We use the attachment the deck and the building call for, and we write it down. We do not describe a third method on this page.
- Thickness named in the scope, not hidden behind a grade name
- Fully adhered when the substrate is sound and the building wants a quieter, smoother roof
- Mechanically attached when the deck and the wind layout support it
How long they last
We do not publish a year count as a promise. A membrane's life is the thickness, the attachment, the drainage, how often people walk it, and whether small seam problems are fixed before they run. A well-drained roof outlasts the same sheet left in a pond. A roof that is already ponding will age at the water line no matter whose name is on the roll.
What we will say is practical. Seams and flashings fail before the field of the sheet does, on both TPO and EPDM. A maintenance look at those details extends the roof. Ignoring an open weld, or a loose tape edge on EPDM, spends the rest of the membrane early. When the sheet itself is cracked, shrunk or patched beyond reading, the conversation is replacement, not another repair.
Heat and hail in St. Louis
Heat is the argument for a light-colored TPO on a building that takes the afternoon sun with no shade. The membrane still gets hot. It gets less hot than a black EPDM in the same place, and the rooms under it feel that. EPDM handles the cold and stays flexible. On a roof that is in shade, or on a building where the existing roof is already EPDM and the flashings match it, staying with EPDM is often the cleaner repair and the cleaner replacement.
Hail hits both. It can bruise TPO and it can fracture an aged EPDM surface without opening a hole the day of the storm. Edge metal and any exposed fastener heads show the hits more clearly than the field of the sheet. After a hail storm the useful inspection maps the bruises and looks at the seams. A dry ceiling the next morning does not mean the membrane was spared.
Ponding is harder on both systems than a single hail event. Water that stands in a lap attacks the weld or the tape every day it sits there. Replacement that copies a dead-flat deck copies the pond. Tapered insulation or a relocated drain is part of the system choice, not an upgrade to talk about later.
How an installation runs
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We inspect the roof and the deck, and we cut a test opening if the insulation may be wet.
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The scope names TPO or EPDM, the thickness, fully adhered or mechanically attached, and the insulation.
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The old roof comes off, or a recover is laid, only when the deck and the existing layers allow a recover.
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Seams are welded on TPO and taped or cemented on EPDM, then checked. Flashings and edge metal are part of the same day the field goes down, not a punch-list after the crew has left.
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You get photos of the deck, the insulation and the finished seams. The building stays on the phasing we agreed if it is occupied.
Warranties we will state
The warranty we state is our written workmanship warranty. The term is on the certificate for the job. We do not publish manufacturer system-warranty terms on this page. A building owner who wants those terms asks, and we only repeat what we can actually provide.
TPO and EPDM repair
A weld that has opened, a tape seam that has let go, a puncture from a foot or a dropped tool, and a flashing that has pulled off a curb are repairs when the rest of the sheet is sound and the insulation is dry. That repair work is on the repair site, matched to the membrane that is already there. We do not weld a TPO patch onto EPDM or tape a rubber patch onto a thermoplastic sheet.
If the repair visit finds wet insulation or a sheet that has shrunk off the walls, the honest result is a replacement scope, written on the replacement page.
Questions about TPO and EPDM
- Which lasts longer, TPO or EPDM?
- Whichever one is thick enough, attached correctly and drained. We do not publish a year count. Ponding and failed seams end either membrane early.
- Is EPDM the same as a rubber roof?
- Yes. EPDM is the synthetic rubber sheet people mean by a rubber roof. Seams are taped or adhered. TPO seams are heat-welded.
- What does fully adhered mean?
- The membrane is glued to the board under it. Mechanically attached means plates and screws hold it down, usually in the laps. The scope says which one.
- Does a white roof stay cooler?
- A light-colored membrane reflects more sun than a black one, so the surface runs cooler. It does not replace insulation, and it does not fix a roof that ponds.
- Can you repair TPO and EPDM?
- Yes, when the sheet and the insulation are worth keeping. Repairs are matched to the existing membrane and are written up on the repair site.
- Will you state a manufacturer warranty term?
- Not on this page. We state our written workmanship warranty, and the term is on the job's certificate.
- What thickness should the bid name?
- The mil thickness. Two bids that both say single-ply and do not say the thickness are not the same roof.
- Do I get photos from the inspection?
- Yes. We photograph what we find and go through it with you, so you see what we saw.
Why building owners work with us
- GAF Certified
- BBB Accredited, rated A+
- We pull the permit on every job that requires one.
- Our office reads every request and calls you back.
- Inspections documented with photos of what we found.
Where we do this work
- Jefferson County
- St. Louis City
- St. Louis County
- St. Charles County