Galvanized Flashing With ACQ Treated Lumber? - General DIY Discussions - DIY Chatroom Home Improvement Forum

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Old 05-09-2008, 09:23 AM   #1
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Galvanized Flashing with ACQ Treated Lumber?

Does anyone know if the treated lumber at Lowes (Top Choice) is ACQ?? I just bought a bunch of wood to begin building my deck and I picked up some galvanized flashing. I read on that you shouldn't use galvanized flashing with ACQ treated wood.

Can anyone confirm this?

Is Top Choice lumber from Lowes ACQ or CCA?

Assuming it's ACQ, should I not use all of the galvanized hardware I already bought, such as carriage bolts, joist hangers, ect.?




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Old 05-09-2008, 10:36 AM   #2
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"New pressure treated lumber uses alkaline copper quat (ACQ) as a preservative, which is less harmful to the environment and to you. The problem with this new pressure treated lumber, however, is that the ACQ product contains much higher levels of copper. Copper is not a safety issue by itself, however it is more corrosive when put in contact with steel and other metals. In time this corrosive action could lead to deck flashing failure if aluminum or galvanized flashing were used with this newly treated lumber.
Consequently, if you are building a pressure treated deck it is best to use a copper based deck flashing to prevent corrosion. It is also important to use copper nails when securing the copper deck flashing to the deck ledger board and home, again to prevent corrosion."


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Old 05-09-2008, 11:21 AM   #3
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ACQ is known to eat fasteners and metals faster than CCA would. You must use HOT DIPPED GALVANIZED (not electro-galvanized) fasteners in it. The joist hanger manufacturers are making hangers with more zinc to resist corrosion of the hangers, but they won't say that you HAVE to use them.

As for flashing, copper is your best bet. It would be exxageration for someone to say that a galvanized piece of flashing won't work...Chances are it will last for years. The inspector might fuss, might not.

I have an ACQ fence, and four years later the staples that hold the mill tags on the end grain of the lumber are still going strong with minimal corrosion. I think there has been a lot of hype about this issue for sure.
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Old 05-09-2008, 12:16 PM   #4
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I was planning to use galvanized flashing on my deck as well. Someone told me to just put a membrane over the top of the ledger before placing the metal flashing. You could also place the same membrane (Grace Deck Protector) on the face of the ledger and ends of the joists to isolate the joist hangers, if you want to go that far. In 10 years we will all know if it is really necessary.
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Old 05-12-2008, 09:42 AM   #5
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Thanks for the replies. I ended up buying vinyl flashing for behind the ledger board and vinyl z-flashing for the top. I put the ledger board up this weekend and everything went well. I through-bolted it using 3/8" carriage bolts every 16", staggered top and bottom the whole way across.
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Old 05-18-2008, 10:59 AM   #6
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Not sure about lowes but I know the treated lumber home depot carries is approved for use in direct contact with aluminum. It is not ACQ but rather micronized copper, which is not nearly as corrosive as ACQ, but it also is not approved for ground contact so you must still use standard acq lumber for posts.


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