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Ditchmonkey
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# Posted: 4 Mar 2016 13:45
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I'm skeptical of the value of pressure-treated wood in non-ground contact situations due to the corrosion of metal hangers and fasteners. Last year, I saw a Zmax (supposedly made for PT wood) hanger break off because it had corroded through completely. I'm wondering if an outside feature like a deck would last just as long with non-treated lumber due to the fact that the fasteners and hangers would last as long as the wood.
Any thoughts on this?
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Ditchmonkey
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# Posted: 4 Mar 2016 13:57
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Actually I just discovered that joist hangers can be bought in stainless steel. Expensive, but potentially worth it in the right circumstances.
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Don_P
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# Posted: 4 Mar 2016 15:58
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And no, untreated wood will not outlast treated even with fastener corrosion issues. For the decking itself you may use naturally decay resistant species. That resistance is quite variable, I wouldn't.
Chances are unless you are in a coastal environment the continuing evolution of the treatment chemicals likely means that treatment now is less corrosive than what you witnessed. In the immediate aftermath of the changeover from CCA to ACQ the mix was very corrosive, they have reformulated that mostly and we see several other treatment methods as well. All are more corrosive than the old CCA so still use at least Zmax and galvy nails or all stainless... do not mix, once you go stainless go all stainless. I made the comment at the time that we were saving children from an arsenic scare and inviting them to a deck collapse about the time they hit college.
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Littlecooner
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# Posted: 4 Mar 2016 16:46
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The old CCA appears to be a better choice for long life, but the arsenic appears to have everyone afraid to use it, causing the conversion to the ACQ mixes.
Depends on your location. Like Don_P says, there are naturally decay resistant species out there. The outside of my cabin under construction will be one inch boards of Black Locust. They will be as solid in 2116 as they are today. It took finding a Forester running a sawmill before anyone would talk to me about buying and sawing Black Locust, but I have 800 board feet and it was the same price as about anything else and less that what ACQ pine would have cost.
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Don_P
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# Posted: 4 Mar 2016 20:05
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Good score! There is a porch in it locally that is beautiful but was a nightmare to source. You've got to open a lot of logs of really dense stuff to get a few good boards. I've been slowly accumulating parts for a timberframe barn rebuild.
There are tropical woods as well, I sort of hate going there though.
Copper Azole, CA-C is another one here as well as micronized ACQ. The copper is the primary cause of corrosion when it can react with steel and these have less. I've read somewhere that it was the chromium part of the old CCA that buffered the copper/steel galvanic reaction.
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turkeyhunter
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# Posted: 4 Mar 2016 20:10 - Edited by: turkeyhunter
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Quoting: Littlecooner sawing Black Locust, but I have 800 board feet
that will last for EVA!!!! tough as woodpecker LIPS
I saw old black locust "gap posts" / I bet they had been in use for 100 years or so on some old southern farms....
GAP  for city folks that means ...a gate/ break in the fence ...made of barbwire and a post on each side and couple small sapling to hold the wire up as a gate.
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1tentman
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# Posted: 4 Mar 2016 21:51
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turkeyhunter I havent heard the word GAP used for years and yes I know what it is. Starting when I was 6 years old that was my job to open and close the gap when I was with dad or grandpa in the fields. The worse part about this was they would always give that top loop of wire a twist and make it tighter, I can hear grandpa now ,pull a little harder buddy you can get it. I wish I had a dollar for every GAP I opened and closed I would be a wealthy man. Oh the memories THanks!
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turkeyhunter
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# Posted: 5 Mar 2016 07:02
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Quoting: 1tentman I wish I had a dollar for every GAP I opened and closed I would be a wealthy man. Oh the memories THanks!
You are welcome Sir~~I hope my grand boys have memories like that when they get to adults .....as the have a lot of gates and gaps to open for PawPaw....while I sit on the MULE ( UTV)
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KinAlberta
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# Posted: 6 Mar 2016 10:09
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When I built a deck behind my house I covered the frame with that Grace tar-like tape to prevent water from getting between doubled up joists. I also used it behind some non resistant hangers as a separator. I also used some duct tape to do the same separation job. My deck is almost on the ground and tied my joists in with screws anyway, but I don't see why a separation won't be effective at preventing the hangers from corroding.
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KinAlberta
Member
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# Posted: 7 Mar 2016 11:22 - Edited by: KinAlberta
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Note the photo Of the Grace Vycor wrapping at the bottom of this page:
http://deckfailure.com/df/component/content/article?id=93
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KinAlberta
Member
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# Posted: 23 Jul 2018 12:05 - Edited by: KinAlberta
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A “must read†for any DIY’er:
Nails and other Hardware in ACQ Lumber (Retrofit Shear Walls and ACQ Lumber)
"This article was written as a research report to prove to an engineer I know that there is nothing wrong with ACQ lumber so long as galvanized nails are used. I proved myself wrong. Stainless steel is the only acceptable fastener. Special thanks to the engineers at Simpson StrongTie. "
https://www.bayarearetrofit.com/acq-lumber-shear-walls/
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KinAlberta
Member
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# Posted: 18 Feb 2019 09:50
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Interesting video on a 100 year old untreated wood structure
Untreated Wood walls of Norway - What happens to untreated wooden walls?
https://m.youtube.com/watch?v=azHGAHJsKew&list=PLQTCyoPa-q5-BU0CMijfoQyXRykFpPNZu&ind ex=3&t=0s
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KinAlberta
Member
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# Posted: 25 May 2019 22:02
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http://www.buildmagazine.org.nz/assets/Images/Build_162_44_Feature_Corrosion_And_Mate rials_Degeration_Why_Timber_Eats_Metal/a044-3-online.png
Why timber eats metal | BRANZ Build
http://www.buildmagazine.org.nz/index.php/articles/show/why-timber-eats-metal
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KinAlberta
Member
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# Posted: 30 Jul 2019 16:27 - Edited by: KinAlberta
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Good article. At a minimum just check out the photos of corrosion.
Corrosion of Steel Hardware
Caused by Pressure-Treated Lumber
http://www.ggashi.com/wordpress/wp-content/uploads/PT-Lumber-Causes-Steel-Corrosion.p df
More:
The corrosive problem of ACQ treated lumber “... First, you need to know that today’s pressure treated lumber is far different than the treated lumber used and sold just a few years ago. In 2002 the Environmental Protection Agency coerced the companies that produce pressure treated lumber to ‘voluntarily’ change their treatment methods. The old treated lumber used an Arsenic-based preservative solution, and was known as CCA treated lumber (chromated copper arsenate). The new chemical formula is known as ACQ treated lumber (Alkaline Copper Quaternary). Unlike the old formula, ACQ contains no arsenic but has high copper content. Switching to a high copper content created a major problem. If you remember your high school chemistry, copper is extremely conductive. That means ACQ lumber has a very corrosive affect on most metals — like the nails and screws that are used to hold boards together. The government and lumber industry initially ignored this potential safety hazard. They started paying attention to it after people fell to their deaths when ...†https://www.buildloghomes.org/the-corrosive-problem-acq-treated-lumber/
Pressure-treated Wood: A new look at a traditional product September 1, 2012 This year has seen changes in the residential pressure-treated wood market as the next generation of new wood preservatives are being launched. Making its way into the market this year is a carbon-based wood preservative that is colourless and gives the treated wood a natural appearance without the customary green colour of most other residential treated wood preservatives. Wood treated with this preservative is limited to use in above-ground applications. Also poised to enter the Canadian market is micronized copper azole (MCA). Sub-micron particles are physically deposited in the wood cells in solid form without the use of solvents, fixing to the wood like a coating. Wood treated with MCA can be used both above ground and in ground contact. It can range in colour from a pale green to natural brown and cedar shades. https://www.constructioncanada.net/pressure-treated-wood-a-new-look-at-a-traditional- product/
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Princelake
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# Posted: 30 Jul 2019 21:59
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I'm unsure of the process they use but there is preserved wood that is used for wood basements. They have a 100year warranty and that's below grade. I'm not sure why this product hasnt become more popular and used instead of pressure treated.
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ICC
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# Posted: 30 Jul 2019 22:34
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One needs to read the labels that are attached to every piece of PT wood. Some are rated for above ground use, like deck floors. Others are rated ground contact, like landscape timbers. The PWFoundations use a foundation grade of PT wood. As you move up the scale from above ground, to ground contact, to foundation, the concentration of the preservative increases. That increases the cost. There are also timbers treated suitable for immersion in salt water, used for piers. You cannot find the foundation grades and pier grades at the usual common sources.
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KinAlberta
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# Posted: 30 Jul 2019 23:19
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Quoting: Princelake I'm unsure of the process they use but there is preserved wood that is used for wood basements. They have a 100year warranty and that's below grade. I'm not sure why this product hasnt become more popular and used instead of pressure treated.
How many of these companies survive 10 yrs let alone 100 yr years? I suspect the warranties have little worth beyond their propaganda value.
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Princelake
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# Posted: 31 Jul 2019 06:26
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2hrs north of me up in the area where I'm building my cabin theres a town there. There are quite a few homes with wooden basements some 30+ years old and the wood is still like brand new. The basements dont feel damp and it's in a cold climate and are insulated very well. Right by my house theres a nice house probably built in the 80s it's kinda like a hybrid. Wood foundation walls with poured floor. They poured the floor after the walls and its holding up perfectly fine.
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snobdds
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# Posted: 31 Jul 2019 11:04
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I absolutely hate pressure treated wood. If you don't use it immediately it will twist and warp. The shrinkage on a 2x6 board can be as much as 1/2 -5/8 of an inch. The strength does not seem to be as great as non pressure treated wood, they always seem to develop long cracks.
When I built my deck at the cabin, I used pressure treated wood. This past year we had about 15 feet of snow and every single rim board on the deck cracked. I think it had more to do with the wood drying out and being fastened down and something had to give, as opposed to the snow load. I have the decks covered so the snow was not covering the porch.
I ripped all the cracked wood out and put back regular old 2x12 rim boards. I will use my trusted blend of wood preservative to keep it good for years to come...50/50 blend of new 30wt motor oil and diesel fuel. I coat my trailer decks in the stuff and the wood never rots.
The old pressure treated wood with CCA was decent. This new stuff they use is garbage.
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Brettny
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# Posted: 1 Aug 2019 08:09
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Personaly for deck boards i wouldnt mess with anything wood. It will look like total crap in 5yrs unless you mantain the crap out of it. For the frame im not really sure. I guess you could use flashing membrane ontop of every joist and this may really help normal wood survive. It all depends on the climate though
Snobdds im sure 15ft of snow had nothing to do with your rim boards cracking. Have you thought about doubling them up?
I have had non PT lumber on a trailer for 8yrs now with no rotting. I never stained or oiled it. It has plents of air space around it though.
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KinAlberta
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# Posted: 18 Nov 2024 16:35 - Edited by: KinAlberta
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Here’s a good article:
How Long Will Treated Wood Deck Last? - Building Advisor
April 23, 2022
https://buildingadvisor.com/how-long-does-treated-wood-deck-last/
Here’s another from 2016:
Why Should I be Concerned About Galvanic Corrosion? | Warren Forensics
https://www.warrenforensics.com/2016/04/22/why-should-i-be-concerned-about-galvanic-c orrosion/
Here’s a photo of corroded screws
from an earlier post showing
the old CCA vs the new ACQ:
https://www.buildmagazine.org.nz/assets/Images/Build_162_44_Feature_Corrosion_And_Mat erials_Degeration_Why_Timber_Eats_Metal/a044-3-online.png
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