Flashing over existing deck?

[MikeFrogTN]

We have a deck on the back of our house with a bay window that extends out onto the deck. I recently discovered that no one had ever caulked/sealed the area where the deck meets the wood siding that covers the bay window (we've only lived here for 2 years, house is 12 years old). The house is brick, only the window area is siding. Water has been leaking in under the siding and has damaged the framing underneath...not too bad yet, I don't think the framing needs to be replaced. I tried caulking the entire area with no luck. I even caulked between all the deck boards. Water is still getting in. I'm wondering if I can install metal or vinyl flashing against the outside of the siding and onto the top of the deck boards to prevent water from getting in underneath. I hate to have to rip up all the deck boards, install siding underneath, and reinstall decking if that's not necessary. Any ideas? Advice?

Thanks,
Mike

[Mike K]

Sounds like your best bet will be to remove a deck board or 2, cut back the siding to gain access to replace/repair the water damage and properly flash from underneath the siding to prevent more water intrusion. Also, double check to see that the ledger (if present) is properly fastened and flashed. Then replace the deck boards making sure to leave a gap to the house where water does not sit against the siding and flashing.

Good luck

[Bobby Parks]

Something else to consider here. Is there a post and beam supporting the vertical load where the deck fraing meets the cantilevered bay area? You can bolt or lag all day long but what you're bolting to an edge band nailed to the end of the joist. I believe this should be done as a rule, but if there is any question as to whether rot or softening of the house floor band has occured, this is something to address. Otherwise, someone could go on a big ride. Down. Bobby

[Mike K]

Good point Bobby...I guess I had taken it for granted that nobody would dare put a ledger onto cantilevered framing of a bay. but one never knows.

[Andy Engel]

Mike, I'd also vote to remove decking and siding, and to flash the wall properly. By that I mean that the flashing needs to go up behind not only the siding, but behind the building paper as well. All siding leaks - your true weather barrier is the building paper or housewrap, assuming that's installed correctly. Caulk is really only intended for asthetics, not for keeping out serious water.

Of larger concern perhaps is whether the deck is attached to the brick. Doing so is a code violation, and potentially dangerous. Take a look at the article in the last issue (available on line) that covers challenging ledger attachments.

[Mike K]

Good point Andy!

This brings another topic to bear: I know they can be more cumbersome to build, but all of the flashing and proper ledger board attachment issues make freestanding decks all the more attractive. I'd rather utilize a few more posts and beams than deal with the hassle of installing and flashing a ledger with joist hangers...that is unless it is a very convoluted, multi level and extremely tall deck.