When it Comes to Vinyl Decking, Does Thicker Mean Better?

When you’re choosing a sheet vinyl membrane for your deck, you might think thicker vinyl means better waterproofing. But when considering vinyl membrane thickness, that’s not true.

Waterproof is waterproof. A thicker vinyl membrane doesn’t make it more waterproof. So once the waterproofing standard is met, extra thickness of material doesn’t add protection.

Understand Building Code Requirements

Don’t rely on vinyl thickness alone, look to the building code:

• If your deck is over 2 feet off the ground and sheds water, it needs a roofing membrane.

• Decks used for pedestrian traffic, must also be approved as a walkable surface.

60 mil vinyl is the industry standard for walkable roof decks. It meets both waterproofing and pedestrian traffic requirements. Anything more than 60 mils doesn’t provide extra waterproofing—it just adds bulk.

Duradek’s History Proves It

Duradek started with a 20 mil thickness. Even at that lower vinyl membrane thickness, decks stayed dry for years. Today, for decks that don’t require permits, 45 mil vinyl is common. And for roof decks, 60 mil remains the standard. In fact, we’ve seen 32-year-old Duradek installations with just 32 mil thickness still protecting the plywood underneath.

Is a Thicker Vinyl Better for A Roof Deck?

By code, pedestrian roof decks require a 60 mil membrane. That’s already 25% thicker than most commercial roofing membranes (48 mil). So, the only real difference in these applications is that commercial flat roofs are not intended to have foot traffic beyond service requirements. Anything over and above the required 60 mil vinyl membrane thickness does not give you any further waterproof protection. The real difference lies in the installation. In fact, a thicker vinyl can come with disadvantages.

Download: Does Thicker Vinyl Really Mean Better? (pdf)

How Vinyl Thickness Effects Installation

Vinyl membranes are rolled out and then adhered to your deck. The seams—where two pieces meet—are heat-welded. Thicker membranes create bulkier seams, which can lead to:

• Trapped or ponded water

• Tripping hazards

• Damage from snow shovels

• Difficult detailing and flashing

Even a 10% increase in vinyl membrane thickness is noticeable at the seam. And when you double that thickness at the overlap, it can cause visual and functional issues.

Many existing vinyl sundeck installations from over 30 years ago, using 24–32 mil vinyl, still perform their waterproofing function today. We pulled up the vinyl from a 32-year-old deck that had 32 mil Duradek on it. After 32 years, the plywood remained in perfect shape, so the installers reused it as the substrate for a new Duradek vinyl membrane.

So for your project, if you want the advantages of a low-maintenance deck vinyl on an elevated deck, balcony, or roof deck, remember that exceeding the building code requirements above 60 mil only provides a thicker seam and no additional waterproof protection.

What is More Important Than Thickness in a Waterproof Vinyl Membrane?

• Quality of the Vinyl
• Product Warranty
• Building Code Requirements
• Installation

Choose a High-Quality Product

Not all vinyl is created equal. Some manufacturers only use quality materials in the top layer and fillers underneath. Duradek uses high-quality PVC throughout the full 60 mil thick material. It’s loaded with UV stabilizers and mold/mildew inhibitors throughout. This means better long-term performance and durability in all conditions.

Warranty Coverage of Vinyl Membranes

An increase in vinyl membrane thickness doesn’t mean better warranty coverage.

Duradek offers one of the most transparent warranties in the industry, including:

• Product performance

• Appearance

• Workmanship

It’s also transferable to new owners—a rare feature in waterproofing warranties.

Does the Vinyl Membrane Meet Building Code Requirements

Building code requires a roofing membrane for any deck that is elevated 2 feet or more and sheds water. If it is subject to foot traffic, it also requires a pedestrian traffic coating. Duradek’s 60 mil vinyl meets building code as both a pedestrian traffic coating and a classified roofing membrane. Many vinyl membranes with a 68 mil thickness do not comply to building code requirements as a classified roofing membrane.

Installation of a Waterproof Vinyl Membrane

Waterproofing success depends on expert installation. Thicker vinyl can actually make it harder for contractors to properly install. Some thick membranes can’t be shaped for critical details. That means installers must buy pre-made accessories—and that limits on-site flexibility. Trained, authorized contractors are the only ones who install Duradek. It’s not available as a DIY product because correct installation is too important to leave to chance.

So, is Thicker Really Better for a Vinyl Roof Deck?

So, Is Thicker Vinyl Really Better?

No. Once you meet the 60 mil code requirement, more thickness adds no waterproof benefit.

It can add:

• More seam visibility

• Increased risk of ponded water

• Harder installation

• Higher cost without added protection

See the Difference for Yourself

Want to hear it straight from the expert? Watch this short video of Duradek President, John Ogilvie, explaining why thicker isn’t better for a vinyl roof deck:

Talk to a Duradek Expert

Get in touch with a Duradek-trained contractor to make sure your project is waterproofed right. To talk to an experienced Duradek expert near you, visit our Find A Dealer page.