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Deck Ledger Flashing

Deck Safety deck ledger

The Importance of Deck Ledger Flashing:

Recently I have been spending my time working up off of Monument Street performing exterior rot replacement in anticipation of having the house  painted. This normally means going over the house with a fine tooth comb looking for problem areas to fix.

Deck ledger flashing problem areas typically seem to repeat themselves from house to house.

Deck Ledger Flashing Typical problem Areas Are:

1. Touching or low to the ground trim.

2. Horizontal surfaces: deck boards, railings, window sills.

3. Areas adjacent or below roof run off.

4. Flashing issues: missing, or improperly installed.

5. Trim or house siding continually wet from lawn sprinklers.

Below is a photo of the clapboards meeting the mahogany decking.  The two story roof above does not have gutters and the client does not want them.

The problem is that the paint on the first and second clapboard courses continues to peel off due to the beating they take from the rain pouring off the roof and splashing off the deck.

The plan was to remove two courses of cedar clapboards and replace them with a 1×10″ pvc trim board that would weather the roof run off better.

Once the clapboards were removed we discovered rotted plywood sheathing and a deck ledger flashing problem.

The flashing used on this deck ledger was inadequate and basically is what we normally use to flash the top window trim boards.

The photo below shows the flashing extended above the decking approximately 1″. With all the rain splashing and snow build up
this flashing should extend higher.

In addition to the ledger flashing a second layer of tin, copper or rubber flashing should have run up the house behind and above
the ledger.

Another issue was that the original carpenters installed the Typar house wrap behind the ledger flashing.This wrap should be installed over the flashing so any moisture draining down it can end up on the outside edge of the flashing and not behind the ledger board where it could potentially get into the house framing.

We pulled off the rotted sheathing to discover that carpenter ants had started to chew into the structural rim joist.

The siding was replaced and we needed to come up with a plan to address the lack of flashing. In the photo below the flashing was at the same height as the deck board.  The corner board was 5/4″ thick and was the only thing that prevented water from pouting in behind the deck ledger board.

We installed 8″ Vycor flashing over the ledger and up the house side wall.

The deck boards on the right of the picture is protected and

does not get the same abuse from roof run off.

Once the rubber was installed we counter flashed the ledger with pvc ledger flashing.  If you look at the fourth decking board out from the house you’ll see wearing away of the wood from the the roof “drip line.”

The last decking board was replaced and a 1 x 10″ pvc board covered it all.
We used window top flashing to flash the top of the 1 x 10″ before replacing the cedar clapboard siding.

~ concord carpenter

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