Do You Need Flashing on a Deck?

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Peter Overton
WRITTEN BY
PETER OVERTON

Accompanied by over 30 years of experience within the external construction sector, my skill set extends to many areas.

If the decking isn’t correctly installed properly, moisture can seep through the holes that connect the deck to the house, causing water damage to both the deck and your home. This is where deck flashing comes in.

So, do you need flashing on a deck? Deck flashing is necessary to protect your home and deck from water damage, and is required by the International Residential Code. The holes created when attaching the deck to the house are at risk of moisture seeping in, but deck flashing can help to guard against such damage.

Read on to learn more about the necessity of deck ledger flashing.

Is Deck Flashing Necessary?

Deck flashing is not only necessary, but is required by the International Residential Code (IRC), section R703.4 (2018 version). Deck flashing is used to avoid water damage to your home at the points where the deck is attached to the house; the holes created here are at risk of moisture seeping through. 

Without deck flashing, you risk significant water damage to your home, resulting in severe mold and decay, which can be expensive to fix. As such, it is imperative that the deck ledger board is waterproof and protected. 

Where Do You Put Flashing on a Deck?

There are various components of deck flashing; deck ledger flashing, decking board flashing, a third layer, the borel, and a 4th layer, borel flashing, which is then tape flashed to finish.

Deck ledger flashing is the first line of defence against water damage, and the decking board flashing creates a bit of a ridge that the deck will then sit inside of. The flashing sits at a 90 degree, L-shaped angle so that any water drips off of the flashing, rather than compromising both the deck and the house. 

When Should I Flash My Deck?

It’s best to flash your deck as it’s being installed. This way, the desk flashing is installed properly, with minimal hindrance, and any potential water damage that could occur is minimised right from the start

Can You Add Flashing to an Existing Deck?

Whilst it’s best to flash your deck at the time of installation, it can be added to existing decking fairly easily. 

To add flashing to an existing deck, you’ll need to remove some of the decking close to the house. From here, you, or a contractor, can slide the deck flashing up and under the first layer of siding nearest to the deck surface. This then rolls over the edge of the ledger board and the decking boards sit on top. With this in place, water should fall off the flashing to the ground, rather than dripping behind the ledger board where it can cause damage.

Types of Deck Flashing

Deck flashing can be purchased in different forms, including:

  • Flashing on a roll
  • Ridgid Z-shaped flashing
  • Ridgid L-shaped flashing
    • Both Z and L-shaped flashing can be purchased in 10” sheets of stainless steel, aluminum, copper, or vinyl.
    • They come in different widths, so make sure to purchase the right size to tuck behind the house siding.

Tips for Success

To help you get a good finish on your deck flashing, here’s a few tips from the experts:

  • Apply flashing materials in a shingle-like manner, ensuring that materials are overlapped so that water flows appropriately.
  • Use a water-resistant layer, such as asphalt, felt, or other approved water resistive barriers, as explained in section R703.4 of the IRC.

Metal Flashing at Kladworx

Kladworx are providers of aluminum metal flashing to help you decrease water penetration at walls, eaves, windows, doors, and decking. Our metal flashing can be purchased in a variety of sizes, shapes and colors, as well as bespoke profiles to perfectly fit your project.

Need help with your external construction project?

We are suppliers of some of the most bespoke aluminium and uPVC systems on the market. With over 30 years of experience within the external construction sector, it leaves us well placed to offer our advice on the many different systems on the market

See some of our recent work, or get in touch with us today for a free, no obligation quote.

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