Underdecking 101
Dry-Deck and Underdecking
When decks are built high enough to have useable space beneath them, they can have under-deck systems added to make the deck waterproof. This adds even more outdoor living space to a home which will be sheltered and dry.
The terms are usually used interchangeably. Dry-deck usually means any product that keeps the space under a deck dry. Underdecking often refers to all these products, but especially refers to paneling systems installed to the underside of the deck framing.
Dry-deck systems vary by their appearance and how they integrate into the deck: they either get installed between deck boards, beneath the framing, or beneath the decking but above the framing. Either the panels or the deck are sloped so that water can drain into a gutter at one or more sides of the deck frame.
Style
Gap-Filling Systems
Dexerdry is currently our only dry-deck product that takes advantage of the pre-cut grooves in modern low-maintenance decking. Putting a special gasket between each board as it is installed seals the gap between them, and makes the entire top surface of the deck waterproof.
When the decking surface is waterproof and the decking gaps are filled, this also keeps the framing dry, and keeps debris from getting stuck between deck boards. Dexerdry can also be used as a premium bug-proof alternative on screen porch floors.
Dexerdry must be installed at the same time as the decking, and cannot be added later unless all the decking is removed.
Style
Membrane Systems
A thin membrane can be suspended across the framing, and installed just before the decking. The membrane can either be a solid piece or strips, with the edges stapled to each joist.
Trex Rain Escape uses long sections of flexible plastic 12 or 16 inches wide, with the edges secured to the joists, and they create a sloped trough that drains water towards the gutter.
When done correctly, membrane systems will keep the framing dry, and the water will be redirected in such a way where the deck boards won't sit in standing water.
Style
Paneling Systems
Underdeck panel systems can be installed on a completed deck, either days or years after the frame and decking was installed. Membrane systems cannot be installed after the decking, which makes panel systems popular on decks that are already built.
Timbertech Dryspace is a basic vinyl panel system that will hide the deck framing and waterproof the deck area, but doesn't provide a clean, flat finished look like Inside Out paneling would.
Metal Inside Out panels are attached to a carrier piece so that the ceiling is even and flat.The seam between each panel interlocks and creates a visual gap, but doesn't allow water through.
Features
Additional Ceiling Paneling
If Dexerdry or a membrane system has been installed with the deck, additional paneling can be installed on the underside of the deck frame to hide the framing and create a bright, clean ceiling.
Cedar or Azek tongue-and-groove boards are common choices, which are weatherproof but not waterproof, hence the need for a dry-deck to be used with them.
Tongue and groove boards cannot be installed over panel underdeck systems, since they both need to be secured directly to the deck framing.