Ask any contractor where a deck is most likely to fail and, chances are, they’ll point to the ledger board and the deck frame. If not correctly installed and protected, these elements can be the Achilles’ heel of a deck’s structure. To better understand this issue and how to prevent it, we tapped the expertise of professional deck builders.

Identifying the Issue

“Deck failure happens at the connection point to the home,” said Ed Pacylowski, owner of ProBuilt Construction, Inc. in Highland, Md. “Either decks are not connected properly or there is rot on the wood - most commonly caused by exposure to water over time.”

In almost every case, pros pointed to moisture as the primary source of deck framing failures. Easily one of wood’s worst enemies, moisture poses a serious threat not only to the frame itself, but also to other critical areas, such as the ledger board. When left exposed, water can seep into screw holes and sit on the wood causing it to rot and the screws to rust. Additionally, the natural expansion and contraction of wood can cause framing, and the ledger board, in particular, to weaken, split and deteriorate over time, posing serious safety issues.

“The biggest cause of deck failure is moisture getting on or into lumber,” confirmed Scott Seal of Seal’s Building and Remodeling in Lexington, KY. “This is actually going to be a larger issue because of younger trees not having closer growth rings. Moisture will be able to penetrate even easier.”

A Simple Solution

In most cases, boards rot prematurely due to lack of proper flashing. When it comes to protecting the ledger board, there are two main approaches – metal flashing and flashing tape.

The biggest advantages of metal are that it’s inexpensive and can be installed in any type of weather. It requires bending, which is time consuming, and can be dangerous to handle due to its sharp edges. Metal also requires nails or screws for installation, which creates opportunities for moisture penetration. While it diverts water away, it doesn’t seal water out. In fact, many counties no longer allow metal flashing because it is so prone to leaks.

Flashing tape is better for waterproofing. It creates a tight seal on boards and around hardware. Some tapes can be difficult to control due to their stickiness and, historically, have not come in an optimal size for ledger-specific applications.

These concerns have been addressed in a new product called Trex Seal, which combines the best performance features of metal and tape flashing. Reinforced with an aluminum liner, this 11-inch-wide butyl-based tape creates a waterproof barrier that provides complete coverage of the ledger board. It is self-adhering and seals any gaps between the ledger and the substructure for optimal protection. Featuring a convenient 5.5-inch double-release liner, Trex Seal is easy to apply for accurate installation and is Code AAMA711 compliant.

“Trex Seal is designed specifically for deck installations,” commented Pacylowski. “Trex Seal comes in the appropriate sizes for proper flashing of framing members, and it can be set in place without flexing back like other flashing tapes. We also use Trex Protect Rim Tape around the perimeter of the deck between the treated wood and fascia trim to protect the frame from exposure to water that drips between the decking boards.”

Flashing tapes are proven to preserve a deck’s integrity and longevity. And, with the selection of easy-to-apply options now available, there’s no reason for any deck to be left vulnerable to the elements and premature failure.

For more information about deck flashing, visit