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Sundeck waterproofing

Sundeck waterproofing

A sundeck over a patio, carport or entry does two jobs at once. It gives you an outdoor room upstairs, and it keeps the space below dry enough to actually use in a Vancouver winter.

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Service life 15-20 years

Why it works

What this actually involves

In short

  • Adds usable living space for a fraction of the cost of an addition
  • Doubles as a roof — the patio, carport or entry below stays dry
  • Membrane tied into the building envelope, not caulked at the surface
  • No annual re-coating, staining or sealing
  • 15 to 20 year service life, with transferable warranty coverage

That only works if the waterproofing is continuous. The point where the deck meets the house is where almost every sundeck fails: water tracks back under the surface, gets behind the cladding, and rots the rim joist out of sight for years before anything shows on the ceiling below.

We integrate the membrane into the building envelope at that connection rather than sealing it at the surface. The sheet runs up the wall, behind the siding and over the flashing, so the drainage plane is unbroken from the deck to the wall. Nothing about that detail is visible when we are finished, which is precisely the point.

Assembly detail

You are not buying a deck surface.
You are buying the ceiling below it.

Duradek is one sheet doing two jobs. It is the waterproofing and it is the floor you walk on, which means there is no seam between the two for water to find.

Where it matters most is the point the drawing shows on the left: the membrane turns up the wall and sits behind the cladding, so the drainage plane runs unbroken from the deck into the building envelope. That detail is invisible when we are finished. It is also the reason the deck is still dry long after a caulked joint would have let go.

Cross-section of a Duradek vinyl deck assembly Rain falls onto a 60 mil PVC membrane laid over plywood sheathing on joists. The membrane slopes to drain and turns up the house wall behind the cladding. The room beneath the deck is shown lit and dry. CLADDING (CUT AWAY) DRY HABITABLE SPACE BELOW WELDED SEAM MEMBRANE TURNS UP BEHIND CLADDING 60 MIL PVC SLOPED TO DRAIN
  • Membrane turns up behind the cladding
  • Hot-air welded seam
  • 60 mil PVC membrane
  • Sloped to drain
Fig. 1 — Duradek assembly at the house connection
Also available

Waterproofing systems

Vinyl deck waterproofing

The core system: a single-ply 60 mil PVC sheet that is the waterproofing and the finished floor at once.

Deck construction

Rooftop deck building

Turn a flat roof into a private terrace with one membrane that is both the roof and the walking surface.

Deck construction

Multi-level deck building

More levels means more transitions, and every transition is somewhere water can get in.

Waterproofing systems

Waterfront decks

Built for the wind-driven rain, salt and constant damp of a West Coast waterfront lot.

Want a number for this?

We measure on site, check what is underneath, and give you an itemised quote with a timeline. No charge and no obligation.

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