Types Of Deck Flashing

Types of deck flashing

Building and installing a deck in your home is no small feat, and there are many factors you have to consider to design and build it correctly. Getting the correct deck flushing for your ledger board is one of these. Let’s discuss the various types and which you should perhaps choose.

There are four main deck flashing types: vinyl, Z-shape, L-shape, and 10-inch flashing. Vinyl flashing is made from polyvinyl chloride or another polymer. Common galvanized steel is used for Z and L shape flashing. 10-inch flashing can be made from galvanized steel, aluminum, copper, or vinyl.

We’ll look at all the various flashing types you get along with what materials they come in. Then we’ll discuss which is best suited for different situations and which could perhaps be best for you.

Types Of Deck Flashing

There are a few types of flashing that you can use to insulate your home’s deck and, more specifically, the leger board where it comes into contact with your house frame. Depending on your situation and the code requirements, you will need to use or might prefer to use one rather than the other.

Moreover, some modern types of flashing are preferred and are generally seen to be easier to install and maintain. Let’s look at the various types and discuss them in detail.

Vinyl (Membrane) Flashing

Vinyl flashing is an insulated, water-resistant material that is made up of polyvinyl chloride or some related polymer. It is used for deck flashing, but this flashing (unlike other types) can be used for protecting floor tiles, roofs, fencing, goods shipping, billboards, and automotive materials.

Additionally, vinyl flashing is resistant to corrosion (again, unlike other types of flashing) and is resilient to moisture damage, chemical damage, or even structural failure.

Cutting and installing vinyl flushing is typically much easier to accomplish because you only require tin snips. You will only need to peel away the back layer and stick it to the deck that requires it.

This is because most modern vinyl flashing is built around a “peel and stick” membrane. Conversely, other types of flushing (which we will discuss next) will require a much more involved DIY approach that will entail screwing, bolting, or nailing the flashing into place.

Rigid Z Shape Flashing

As you would have guessed, Z shape flashing refers to a piece of metal shaped in the form of a “Z.”. This metal “Z” shaped flashing has channels and provides a transition between two different materials by allowing these channels to act as a receiver for these panels. Instead of panels, they will work together with ridge caps and headwall flashing.

Preventing water absorption or penetration is achieved by the transition of the different materials and doing so by directing water and dispersing it away from the vulnerable sections (in this case, the deck ledger board). Z-shaped flashing also facilitates not only the redirection of water but water drainage.

Typically these flashing panels are custom-made, and as such, they are designed to fit perfectly. Thus sometimes necessary adjustments of the channels are needed to facilitate and anticipate potential hazards.

*Builders Tip*

Not a perfect fit like custom bent flashing (1 ¼” not 1 ½”), but drip cap is similar in design and can be picked up at your local building supply store.

Typically for decks, Z-type flashing will tuck under the siding, and then it will wrap over the top of the ledger board. Directing the water down and away from the ledger unlike “L” flashing which water can wick around the lip and under the flashing.

Rigid L Shape Flashing

Similar to that of the “Z” shaped flashing, “L” shaped flashing is a universal and versatile type of flashing that is used to finalize a 90-degree surface and make it robust by uniformly strengthening it. Due to this type of design, the flashing is able to safeguard against moisture and then the elements at the section where the house meets the deck.

It will help if you remember that water is the enemy of wood, and protecting your decking against water damage should be your first concern.

10-Inch Sheet Flashing

10-inch flashing, also known as galvanized steel flashing, is technically a roll of galvanized steel that you will measure, cut, and bend to size. Besides vinyl flashing, this is probably the most versatile because you can cut and mould it to the desired size and structure.

The advantage over “Z” and “L” shaped flashing is the ability to make custom modifications and designs on site. You can measure the exact dimensions and then bend the metal accordingly. Removing any need to compromise to make the flashing work.

It should also be noted that besides galvanized steel, you can purchase 10-inch sheets in different materials such as copper, aluminum, or vinyl. Depending on your situation, one material may be more beneficial than the other. Keeping your deck (specifically the ledger board) protected from moisture and the elements is the main factor to consider.

Take note that if you decide to opt for copper, you should use copper nails to secure the flashing, as this will prevent any rust. Using nails made of other materials will cause oxidation and deteriorate the wood.

*Builders tip*

Joist membrane tape can be taped on the ledger to protect the flashing from reacting to the ACQ treatment of the wood.

Furthermore, you should ensure that galvanized steel or aluminum flashing does not come into contact with ACQ pressure-treated woodOpens in a new tab.. This is because corrosion will occur if it does.

Which Deck Flashing Provides The Best Protection?

There are various types of deck flashing due to there being many scenarios where one may be more applicable than the other.

However, vinyl flashing is regarded nowadays as the most versatile and easy-to-use type of flashing. Additionally, it is easy to install and maintain, not to mention that in most cases, it is less expensive than the other deck flashing types. 

Take note, though, that steel is not permeable to any degree. Hence, any form of steel flashing will completely repel any liquid. However, you will need to consider the cost and the involvement in installation if you choose to use it. Moreover, steel lasts for a very long time and would last longer than vinyl. Consider that the time span here for both steel and vinyl can be in the decades, so this might be a moot point.

If you are building your deck yourself, then perhaps vinyl flashing would be better suited because of the longevity, good protection, ease of installation, and cost.

How to Install Preformed Metal Flashing on a Deck Ledger

If you decide to use metal flashing here is how to install it.

  1. Measure carefully.
  2. With tin snips, cut the flashing piece to the correct length. If using multiply pieces overlap the ends a minimum 4″.
  3. Slip the flashing behind the siding. Make sure to overhang the end of the ledger by at least 2″. This will prevent water from getting behind the flashing.
  4. Attach the flashing under the siding, at least 3′′. With wood siding, you may need to pry up the siding first. Pull out any nails that are in the way. Do this by prying the siding out near a nail, then push the pry bar against it as you press down on the siding with your other hand. Which should raise the nail head enough to pull out.

With vinyl siding is best to remove the initial row of siding above the deck ledger. Install the flashing on top of the ledger tight to the wall. Then reinstall the siding once complete.

  1. If your deck includes a corner of your house. Cut the bottom of the flashing with a tin snip. Fold the flashing to fit tight to the corner and then either squirt caulk or silicone in between the two flaps or seal with deck membrane tape.
  2. Make sure you caulk any exposed flashing. Seal any joints that do not overlap 4″ or more with gutter caulk sealant or silicone sealer. You may now also caulk the inside corner of the ledger at this point.

Looking at all the steps shows why people often choose vinyl. It’s just so much easier. But tin is more durable with a stronger corner preventing water penetration. 


We discovered that there are four types of deck flushing specifically. However, you do get other types of flashing, but those types are for other parts of your home.

The four types of flashing include

  • Vinyl (Membrane)
  • Z-shape
  • L-shape
  • Sheet roll

Usually, you will find sheet flashing in various kinds of material, while you might be able to find the Z and L shaped flashing in your more common steels.

Most individuals who have experience with deck building and specifically deck flashing are adamant that if you are able to (and if your situation allows you to), then vinyl flashing is the easiest to use and should be considered first.

If you are looking for the best joists tape membraneOpens in a new tab., click the link to see my recommended tapes and why. Yes, a quick switch of names, but it is the same product. Just order the larger widths, for you can tape up the wall a minimum of 3″ (75mm) and fully cover the deck ledger for no water gets trapped behind the ledger.

If you are looking for more ways to protect your deck’s substructure, for you can enjoy your decking longer. Check out my complete articles on Ways to Prevent Joists from RottingOpens in a new tab.. More than a dozen ways, including my top 3 that I regularly use when building decks.

Source list

Types of Deck Flashing

What Is Deck Ledger Flashing?

Deck Flashing Code Requirements

Deck flashing

What is Vinyl Flashing?

The Different Uses of Z-Flashing and L-Flashing and When to Use Each