I recently replaced the 5/4 x 6 preassure treated decking boards on a deck. The ledger is a 2×10. It has 1/2 inch lags at least every 16 inches on center, and all the 2×8 joists have joist hangers installed. The original builder of the deck also had a piece of aluminum flashing on the top of the ledger. It comes down the face of the sheathing from behind the siding, bends over the 1 1/2 inch top of the ledger , and bends down the face od the ledger about 3 inches. Sounds typical, I know. I am unsure whether or not the builder also installed flashing behind the ledger , before it was attached to the house. Now, I pulled of the old decking, and reinstalled new decking. Same type of material. The decking runs at 45 degree angles to the ledger. The joists run at 90 degree angles off the ledger. The decking needed to be screwed to the ledger, to secure the ends of the boards. Otherwise , in the worst cases, the last screws in the board would be 12 inches from the end of the decking board, where the decking lays on top of the ledger and meets the house. Now, here comes the concerning scenarios. Where the original builder had nailed galvanized nails through the decking, through the flashing, and into the ledger, the aluminum flashing had corroded. Now, I replaced these boards a couple at a time. Most of the flashing was in good condition, so I did not replace it. If I was able to pull up the whole deck at once, I may have replaced it all. But thats not the cause of my concern, exactly. Just keep in mind the oxidation of the aluminum where the galvanized steel nail penetrated it. So, where the flashing had been corroded, which was maybe under 5 – 10 boards out of I think about 50- 60, I applied liberal amounts of Flashmate, which is the 50 year flashing caulking they sell at Home Depot in the roofing department. Then I installed the board over it. I am not concerned with water getting through the flashing where the flashmate is. I dries to a very flexible rubberlike form. Now, why I am worried IS that I put 2 screws in the end of each board THROUGH the aluminum flashing INTO the ledger. I felt I HAD to in order to properly attach the decking board. So lets say I put about 100 screws THROUGH the flashing. I did not take any out and leave an OPEN penetration through the flashing. But I did penetrate the flashing with 100 screws ( 50 boards, 2 screws each into the ledger). Finally, my QUESTIONS. Did I comprimize the watershedding quality of the aluminum flashing by screwing the deck boards to the ledger through it? I am unsure and afraid that water will find its way around the screws, through the flashing, and behind the ledger where it will rot the sheathing, then rot the rimjoist that the ledger is attached to with 1/2 inch lags, and this second story deck, which is about 12 feet off the ground, will collapse and possibly kill someone. Also, the screws I used where the “coated” exterior decking screws. They are coated with green, whatever it is, I actually don’t know what they coat extreior screws with, although I think I should. Point being they were NOT galvanized screws. Question is, will the coating cause the aluminum flashing to corrode, just like the galvanized nails did? I am cosidering a couple different fixes if I decide I need to. I need your guys expert opinions, and experience to let me know, did I screw this one up? Do I need to fix this, or am I being overly concerned. THANK YOU for any help you would be gracious enough to offer!
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Here's an idea for the next time.
I also flash the ledger in a manner similar to what you found. Behind the siding, out over the ledger and down with a kickout.
However, rather than poke holes in the flashing, I install blocking between all those joists near the downturned flashing-maybe 3" from the ledger. I fasten the decking to those blocks. Secure, and no holes in the flashing.
I'm not familar with the brush on flashing, but a layer of vicor might have done the same "sealing" at that point
Can't give you an opinion on the corrosivemess of the "green" deck screws. I suggest you contact the manufacturer on that question.
I recently replaced a bad board on a deck we did about 18 yrs ago. We used Greycote Deck Screws on that. All the screws I removed showed signs of corrosion. This was done in the old style Wolmanized treated wood. Before ACQ and those corrosion fears. What they say now about compatibility of material might just turn out different down the road.
Best of luck.