Water that can get behind the deck ledger board can lead to sill and band joist
dry rot as well as connector corrosion. In addition, mold and mildew growth can
also occur. All of these issues can eventually cause the deck to pull away from
the home leading to catastrophic deck failure. Unfortunately, the catastrophic
deck failure often occurs when extra weight is placed on the deck, such as when
the deck is holding several people. As a result, it is critical to prevent water
intrusion behind the deck ledger by properly installing deck flashing.
Equally important to installing deck
flashing when constructing a deck is to install the right type of flashing. Deck
flashing is available in galvanized, copper, aluminum and stainless steel, as
well as PVC. Deck flashing is most commonly sold in roll form that can be
shaped, or in Z or L pre-shaped sections. A waterproof membrane is also
frequently used in conjunction with the deck flashing to provide extra
protection against water leaks and to isolate certain deck flashing types from
ACQ (Alkaline Copper Quaternary) treated lumber.
When fastening metal deck flashing to house siding and ledger boards, use
fasteners of the same type of metal. Using fasteners that are of dissimilar
metals can lead to chemical reactions and corrosion between the metal deck
flashing and fasteners. The chemical reaction between the two dissimilar metals
can eventually lead to catastrophic deck failure. In addition, aluminum or
electro-galvanized deck flashing should not be used with ACQ treated lumber as
it contains copper. Again, the chemical reaction between the dissimilar metals
can cause deck failure.
Photos by Mark Donovan
This said, hot dipped galvanized (G185) perimeter and ledger deck flashing is specifically
designed to be used with ACQ treated lumber. The company
Everflashing sells this
type of specialty deck flashing product as well as many other types of unique
perimeter flashing products.
PVC, Stainless steel, and Copper deck flashing can also be used with ACQ
treated lumber. Stainless steel flashing is also the perfect type of deck
flashing for salt water environments. Aluminum deck flashing can often be found
in various colors and is limited for use with L3 and Micropro lumber
applications, or with a membrane barrier. Again,
Everflashing offers a unique
Aluminum deck flashing product that is available in a variety of colors.
It is also important to use the proper width deck flashing. Deck flashing
should tuck up at least 2 to 3 inches behind the house siding to ensure the
prevention of water intrusion.
So if you have plans to build a deck, make sure to include deck flashing, use
the right type, and install it per the manufacturer’s recommendations.
For help on building a new Deck, see HomeAdditionPlus.com's
Deck Installation Bid Sheet.
Deck Installation Bid Sheet
will teach your how to hire the right deck contractor, and help to
ensure that your deck project is completed on time and budget.
How to Finance your Deck Project
can help provide funds for your new home improvement project if
financing is required.
Additional Deck Information