How to Install Deck Flashing

What You'll Need
Copper deck flashing
Hot dipped galvanized roofing nails
Ice and water shield

Learning how to install deck flashing can be a simple process if you know what you’re dealing with. Determining what kind of lumber you will be using to make your deck is very important before deciding what type of deck flashing to use. Whichever type you choose, the deck flashing will help protect your deck from rot and mildew problems. Use this step-by-step guide to help choose the right type of deck flashing and to learn how to install it. The tools and materials required for the job are given below. 

Step 1 – Choose the Type of Deck Flashing 

You first have to determine what type of lumber you want to build the deck with. You could have normally used copper, aluminum or vinyl deck flashing in recent times but now the lumber preserving process has changed. Lumber is now pressure-treated and coated with alkaline copper quat (ACQ). This is probably the lumber you will be using for building your deck. Use copper deck flashing if you are using this type of lumber. It will not get corroded easily by the ACQ.

Also, make sure the nails and other hardware you use are hot dipped galvanized types. They will be corrosion-resistant too and will add longevity to your deck and all the deck flashing fittings. Also, deck flashing comes in different sizes (i.e. lengths and widths). The size you decide to use will depend entirely on the size of deck you are willing to build. 

Step 2 – Cut the Copper Deck Flashing 

If you’re going to use a 10 feet ledger board, use a 10 feet 4 inches copper deck flashing. This will make sure you have plenty of room for the deck flashing to run past the ledger board. 

Step 3 – Install Deck Flashing on Top and Underneath the Deck Board 

Once you have cut the deck flashing material to size, install the deck flashing on top of the ledger board and underneath the ledger board. Fasten it into place by using staples or roofing nails. 

Step 4 – Install Grace Ice and Water Shield 

When installing the deck flashing on the top side of the ledger board and underneath the board for prevention of water accumulation, make sure you apply it over a sheet of grace ice and water shield. This will further prevent any water to enter into the sides of your deck and will protect it from rotting. The trick is to make sure that there is no space between the housing panels and the deck lumber.

The water shield and the copper deck flashing should be placed in between the deck’s lumber and the house panels so that during a rainy season for example, no water can seep into the edges and cause harm to the construction. If you do not do this well or have not cut the copper deck flashing to the right size, the damage can be bigger long-term. Over years, the deck can gradually separate itself from the house wall panels and you don’t want to be standing over the deck during a party or BBQ when that happens.