Is Thicker Really Better for a Vinyl Roof Deck?

When deciding on a vinyl decking membrane, one of the factors on which you will base your decision is the thickness of the vinyl and where it will be used. While building codes have not always existed for PVC roof membranes subject to pedestrian traffic (aka vinyl roof deck), today we are fortunate to have this professional resource to turn to.

It are these building code requirements that will be your best guideline because thicker does not necessarily mean better.

Duradek president, John Ogilvie explains in this short video clip.

When you are waterproofing a deck over habitable space, building code requirements state that 60 mil is adequate for a roofing membrane that will be walked on. This seems very reasonable given that commercial flat roofs only need to use a vinyl that is 48 mils thick to meet building codes as a roofing membrane. The only difference in their applications is that the commercial flat roofs are not intended to have foot traffic beyond service requirements. Decks situated over non-habitable space and not requiring building permits need only use a vinyl 45 mil thick which is adequate as a waterproofing membrane and pedestrian traffic surface.

In fact, for quite some time Duradek vinyl was only 32 mil thick and was it was successfully used for many years. Take for example this deck in Halifax. It was one of the first Duradek vinyl decks in Atlantic Canada.  A couple of years ago the homeowner was doing some renovations and decided to freshen up the look of their vinyl deck. When the old 32 mil membrane was pulled up to be replaced, it had performed its waterproofing function so well over the prior three decades that the installers were able to lay the new Duradek membrane over the existing plywood which was in excellent condition. This is a real testament to the waterproofing performance of vinyl membranes!

32 year old Duradek vinyl.

This deck in Halifax had 32 year old, 32 mil Duradek vinyl.


Duradek Vinyl Replacement

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.

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

Thicker Vinyl Does Not Mean Better

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 the vinyl meet. The seams are usually ¾” to an inch wide, and it is this area of overlap for heat-welding the vinyl seams that an increase in thickness can really be a disadvantage.

Duradek 60 mil vinyl decking installation

Duradek 60 mil vinyl decking installation

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.

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 a snow shovel.
  • Difficulties at installation with the fine detailing and handling.
Water can become 'trapped' on a thick seam.

Water can become ‘trapped’ on a thick seam like on this 66 mil vinyl.

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.

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


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