A mil is one-thousandth of an inch. Vinyl deck membrane thickness is measured in mils because the differences between products are tiny but meaningful — 60mil is about 1.5mm, 68mil is about 1.7mm. Small numbers, real impact on a twenty-year surface.

45mil

The budget option. Some manufacturers offer 45mil for low-traffic applications, secondary surfaces, or non-permitted work. Typical warranty is 5 years on the material, 1 year on appearance. I wouldn't put this on a residential balcony that needs to last. Fine for a utility deck you don't care about, but if you're reading this guide you probably care.

60mil

The industry standard for walkable roof decks and residential balconies. North American building code requires 60mil minimum for pedestrian-traffic roofing membranes, which is why most manufacturers make this their flagship product. Typical warranty: 10 years waterproofing, 5 years appearance.

60mil does the job. It meets code, it handles normal use, it lasts if installed correctly. The vast majority of Canadian and US residential vinyl decks are 60mil.

68mil

Thicker than code requires. A few manufacturers offer this on their balcony product lines. The argument for it: 13% more material means more puncture resistance, more forgiveness on installation imperfections, and more wear tolerance over twenty years of foot traffic.

The argument against is that waterproofing doesn't improve with thickness. Once a sealed membrane is sealed, water doesn't care how thick it is. That's true.

The thing the "thickness doesn't matter" argument misses: waterproofing isn't the only job the membrane does. Surviving furniture drags, grill feet, dropped tools, and daily traffic is also its job. Thicker handles that better. Not slightly. Measurably.

Does thicker mean better for your project?

Depends on the project.

High-traffic balcony, furniture, pets, kids, twenty-year plan — yes. 68mil gives you margin.

Quiet rooftop, occasional use, want the code minimum — 60mil is fine.

Weekend patio, low expectations, budget constrained — 45mil works if the warranty supports your expectations. Don't expect decades.

What thickness doesn't tell you

Two 60mil membranes aren't necessarily equal. The backing matters (fleece vs PVC vs woven scrim), the seam welding technique matters, the adhesive matters, the UV stabilization matters. Thickness is one variable, not the whole picture.

Don't buy on thickness alone. But when everything else is comparable, more material is better material.

Read how to choose a vinyl deck membrane for the rest of the decision framework.