How about making that cut in the siding say your siding is 3/4'' make a 3/8'' cut 1 1/2'' above the decking trail it out on both sides, install the flashing made with a little 3/8'' bend in it to fit into the cut,the flashing comes down and lands on the decking.Finish off with a high grade construstion adhesive. John

I've thought about that as an option. It may work reasonably well. But it still leaves the deck boards running up to the cedar. So they will still wick moisture up to the cedar. The other problem I've got to deal with if I flash it in some fashion, is the kerf into the siding must be fairly deep. It will need to go about 1/2 inch deep into the rough sawn cedar. So I don't know how to cut that kerf neatly and uniformly. (Route it with a jig to hold the router? Or buy a Fein Multimaster? A circular saw?) In places the kerf must butt up to each side of three different doors an electrical outlet and several downspouts. Finally, if I'm going to go the flashing route, it seems I should go all out, pulling up the deck boards and running the flashing under them.

I'll admit the reason I've not done the flashing route already is I'm not sure how to cut that kerf.

John

sawdust,

I don't think that flashing over the deck boards is a good idea. As you said, it will still get wet underneath, and rot even faster in the dark...and you won't be able to get under there to clean it out. Short of major surgery, I only see 1 option. Clean the gaps again, and get some fungicide/insecticide preservative, and soak the area between the cedar and the board ends. At least it shouldn't rot.

steve

John mon,
flashing under the decking is the way to go. if the boards ran parallel to the house, he could rip up 1 row, flash, reset the row...bang, you're done. but his boards intersect the house at different angles...for 66'. Major surgery.
Flashing over the deck in that situation wouldn't keep out moisture. not a good idea.

steve

Steve,

I agree. I really don't like the idea of flashing on top of the decking. This will assuredly just encourage the same problem I'm trying to get away from.

How does this plan sound?

There are 20 feet or so of decking that runs parallel to the house. I'll pull up those two boards, ripping about 1/4 inch off the width of these boards. I'll clean out any trash thats in the area now, then spray the area with a fungicide/insecticide.

Then I'll run a simple copper flashing with a single 90 degree bend, along the bottom of the deck board, and along its edge. Any water that gets into this board will now be isolated from the house.

Screw the board back down. The extra 1/4 of an inch I ripped off leaves me with room to fill between the flashing and the cedar siding with a high quality exterior grade silicon caulk. This way there is no place at all for any water or junk to get in. Any water will be directed off to the flashing, away from the house.

I'll do much the same for those boards that butt up to the house at whatever angle, just one or two boards at a time.

An advantage of doing it this way is I do not need to run a kerf into the existing siding. I also will not have a visible copper flashing that SWMBO will complain about when I'm done. The only visible sign will be a neat bead of caulk that will match the color of the siding fairly closely.

John

If you start out depending on the caulking,you will be caulking from now on.

As a given the ledger should be fastened to the rim joist,the siding comes down, with the flashing behind it running on the deck joists at a 90 the decking is fastened thru it.

John I dont know what a swmbo is but if your talking about the wife, if moma's not happy there is nobody happy so you go on and do what you want to do. If she and you dont like that copper showing just go on and nail the stuff to the siding and be done with it.

However there is no differance making that cut tucking the flashing in it and landing on top of the decking up against taking out the decking installing the flashing on the joists, nailing the flashing to the existing siding, reinstalling the decking and caulking the flashing far as closing that little area goes,its exactly the same thing.With the slight diffeance in caulking everytime the cedar siding bucks up with the weather.

Looks are important,if visble and wife pleasen are your main goal, you dont want to go to all the trouble of making that cut, Go for it Bro. J

Sorry. SWMBO - She Who Must Be Obeyed. Typically used as an online reference to the wife. I've seen a few different origins suggested.

http://www.hbd.org/hbd/archive/3483.html#3483-2

It would not have taken that much effort to have flashed the deck properly when they did it in the first place. Drat.

John

Soooooooo Funny...sounds like something out of an aol chat room,not that I know anything about that.

Thats true John,its much more easy to do it right than do it wrong, time and money both. But there you are Ol Son,, Did those ol boys install the ledger right to the Cedar?? ghessssss anyway it seems to me it would take less time and hassle to just make that cut and fit the flashing to it.
If you do it that way a worm drive skill saw and a sharp blade will do it for Ya,( be real carefull with that worm drive saw) work safe and keep the Little Lady happy. J