Lately Ive been seeing problematic deck ledger flashing details so Id like to share with you my perspective on how to properly flash and secure your deck to the house. Properly flashing a deck ledger seems to be a lost skill with most weekend warriors..lets discuss how to properly secure the deck ledger and install the .

Building a new deck isnt really that difficult of a project. However, there are some details that must be followed in order to prevent premature failure of your deck and the area of your house that its attached to. The problem with attaching a deck to the house is it creates a great area to collect water. The intersection of the house and deck is extremely vulnerable to moisture problems. As you can see from the diagram and the photo flashing must be done in layers. The best way to think about it to visualize what a drop of water will do as it hits the deck and moves towards the house. First the rain hits the siding, then it gets to the house wrap, then it hits the drip cap flashing and runs out away from the house.

First I like to install a layer of self adhering bitchathane (we like Grace Ice and Water) behind the ledger and above it by at least 12 inches. Make sure the bitchathane is behind the house wrap. The house wrap should extend and overlap the bitchathane.

Next mark the location of the bottom of the ledger board and install a small piece of z flashing. When I bolt the ledger board to the house, I like to install 3 or 4 flat washers between the house and the ledger to allow water and moisture to escape and not get trapped. Id also like to point out that I prefer bolts to lag screws. The reason is lag screws dont hold very well when then only penetrate and inch or so into the rim joist. Make sure you seal all around the bolt heads with some silicone caulking as another line of defense against water.

Next youll want to install a piece of metal drip cap flashing above the ledger board. When you install the floor joists youll need to make some small cuts in the flashing to allow the top of the joist to line up with the top of the ledger board. Make sure the house wrap is long enough to cover over the top of the drip cap. (This is a bit different than the photo.) If there is already house wrap on, then cut a slit in the house wrap just above the top of the ledger. That way you can slide the drip cap up under the house wrap. Just remember its all about layering.

Finally you can install the decking. The siding above should terminate slightly above the surface of the decking to allow air into the space. Just remember, if water gets into that intersection its now going to follow the plane of the drip cap and be pushed out away from the house. If you follow these steps the next time you install a deck youll be sure to eliminate a premature failure due to excess moisture and rotting.

If youre planning on building a new deck get yourself the Complete Guide To Decks.

If you want to make your own flashing you can purchase a Tapco 10558 PRO 19 10-Foot-6-Inch Wide by 19-Inch Throat Portable Brake

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