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

If you are considering the reliable, low maintenance advantages of sheet vinyl for your deck waterproofing solution, you may be presented with the idea that a thicker vinyl is better waterproof protection for your deck; but that is not necessarily accurate.

With vinyl decking, it is best to refer to building code requirements as your guideline because thicker does not mean better.

When Duradek first started waterproofing decks and balconies, the thickness of the PVC membrane used was only 20 mil, and those decks lasted for several years. Today, the requirement for a vinyl sheet membrane for waterproofing decks and balconies is more than double that at 45 mil.

Pedestrian roof decks however, have a Building Code requirement of 60 mils. That is already 25% thicker than a large commercial grade roofing requirement (48 mils thick). Anything over and above the required 60 mil thickness on decks situated over rated or habitable space does not give you any further waterproof protection. The real difference lies in the installation. In fact, a thicker vinyl can come with disadvantages.

Sheet vinyl comes in rolls, typically between 60-72 inches wide. It is rolled out the length of the deck and installed by adhesion to the deck substrate and by heat-welding the seams where the edges of vinyl meet. The seams are usually ¾” to an inch wide, and it this area of overlap for heat-welding the vinyl seams that an increase in thickness can really be a disadvantage.

Installation of Duradek vinyl deck membrane.

Even a 10% difference can be noticeable and make your deck susceptible to things like trapped, ponding water which is something to be avoided with vinyl deck surfaces. Some commercial projects prefer to use an 80 mil vinyl, which is far above building code requirements, but does not give any real added advantage. In fact, that 20 mil difference doubled up at the seam makes a 40 mil difference which is quite noticeable visually as well as by unexpected disadvantages.

Trapped water on a thick 66 mil seam.

Some consideration should be paid to the disadvantages that come with a deck vinyl that exceeds building code thickness.

• Trapped, ponded water.
• Potential tripping hazard.
• Easier to catch seam on snow shovel.
• Difficulties at installation with the fine detailing and handling.

There are actually a number of existing vinyl installations on sundecks from over 30 years ago using 24-32 mil vinyl that are still performing the waterproofing function today. Just a couple of years ago, we pulled up the vinyl from a 32 year old deck that had 32 mil Duradek on it. The plywood, after 32 years, was in perfect shape and was used again as the substrate under a new Duradek vinyl membrane.


This deck in Halifax had 32 year old Duradek vinyl.

When the old Duradek vinyl was lifted,
the plywood underneath was in great shape.

The new Duradek was able to go down over the
existing plywood.

So remember 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.

The reliable protection of vinyl decking is due in large part to the skilled installation techniques of your contractor, and thicker vinyl makes it more difficult to perform the critical details for water-tight protection.

Since these installation skills are so critical, Duradek is available only through one of our trained and authorized Duradek dealers. To talk to an experienced Duradek expert near you, visit our Find A Dealer page or contact us directly for a referral at duradek@duradek.com.