PVC
Polyvinyl chloride
Made flexible by plasticisers; welded with hot air.
- Top ply: UV-stabilised PVC
- Polyester reinforcing scrim
- Bottom ply: PVC
System pagePVC membranes
▽ +09.00Comparison
PVC vs TPO single-ply roof membranes
Two synthetic single-ply sheets with hot-air welded seams. They differ in chemistry — and that is where the differences in flexibility and compatibility come from.
The two options
TPO
Thermoplastic polyolefin
Flexible without plasticisers; welded with hot air.
- Top ply: UV-stabilised TPO
- Polyester reinforcing scrim
- Bottom ply: TPO
System pageTPO membranes
A reinforced sheet in both: two plies around a scrim. Illustrative drawing, not to scale.
The key difference
PVC is a rigid polymer made flexible by plasticisers; TPO blends polypropylene with ethylene-propylene rubber and is flexible without them. Both are thermoplastic, so their seams are hot-air welded and become the same material as the sheet.
Both are fixed mechanically, adhered or ballasted to the wind design, and neither needs a flame on site. The real differences are compatibility with other materials, ease of detailing and the welding window.
Criterion by criterion
Descriptive criteria, not scores: each cell states the usual behaviour; final values follow the product TDS and the approved specification.
| Criterion | PVCPolyvinyl chloride | TPOThermoplastic polyolefin |
|---|---|---|
| What it is | PVC with plasticisers and stabilisers. | Polyolefin, no plasticisers. |
| Seams | Hot-air welded; a homogeneous seam that can be tested. | Hot-air welded within a narrower settings window; test welds are essential. |
| UV exposure | Exposed roofing grades are UV-stabilised; light colours reflect part of the heat. | Made mainly for exposed roofs in light, reflective colours. |
| Detailing | More flexible, so details are easier. | Stiffer, so details take more care and prefabricated parts. |
| Material compatibility | Must not touch bitumen or polystyrene directly; a separation fleece is needed. | No plasticisers to migrate; separation rules per the manufacturer. |
| Installation method | Mechanically fixed, adhered or ballasted; no flame. | The same methods; no flame. |
| Typical applications | Roofs, and dedicated grades for basements and pools where specified. | Mainly exposed roofs. |
| Protection requirement | Walkway pads on maintenance routes; a protection fleece under ballast. | The same. |
| Substrate & moisture | A clean, smooth deck with no sharp points; a fleece over rough or incompatible substrates. | A clean, even deck; a separation and protection fleece over rough substrates. |
| Repairability | Patches are welded after cleaning the existing sheet. | Weathered sheet needs more cleaning and preparation before a patch is welded. |
| Inspection & testing | Daily test welds, every seam probed, peel samples where required. | The same. |
When to choose which
PVC
Choose PVC when
- Roofs with many details and penetrations.
- Where grades of the same family are wanted for a basement or pool.
- Where the specification names PVC.
TPO
Choose TPO when
- Large, simple exposed roofs.
- Where a plasticiser-free sheet is required.
- Where the specification names TPO.
Either way
- For busy or occupied roofs: a protected system or an inverted roof rather than an exposed sheet.
- For small roofs crowded with details, a liquid membrane may fit better.
- Welding skill and seam testing decide performance in both.
General educational content; final values and requirements follow the manufacturer’s TDS and the approved project specification.
Common questions
Can PVC be welded to TPO?
No — they are chemically different and do not weld together. Where they meet, a transition detail set by the manufacturer is used.
Does a white sheet replace thermal insulation?
No. A reflective surface reduces solar heat taken up at the membrane; heat flow into the building is controlled by the insulation.
References
Standards that cover these materials — named to show what they cover, not to claim that any product complies.
- ASTM D4434Specification for poly(vinyl chloride) sheet roofing.
- ASTM D6878Specification for thermoplastic polyolefin-based sheet roofing.
- EN 13956Plastic and rubber sheets for roof waterproofing: definitions and characteristics.
Technical review
Still weighing the options?
Send the location, area and surface condition, and our engineers will propose the right system after a review.