anchor bolt corrosion by PT mudsills
I’m considering replacing the mudsill under my10 foot long sliding glass patio door sill next year. My house is from the fifties with 2×6 mudsills combined with ordinary steel anchor bolts that are permanently set in the poured concrete foundation.
But FHB Dec/Jan04 pp.82-85 states that the CCA form of pressure-treated wood(presumably DugFur #2 in my application) is being phased out 1/1/04, and new formulations such as ACQ and CBA are highly corrosive to steel.
What will my options be if I can’t find some CCA boards? I’m guessing I would need to look for some special plastic or stainless sleeves and washers to protect my anchor bolts.
It also seems as if Hemlock has replaced DugFur in the new (non-CCA) PT wood available in California at most lumber outlets. But isn’t this substandard wood for mudsills? Or is there a new practice for the material to be used in replacement mudsills in my situation?
This is all news to my city Building Inspector, who only says to use “PT wood or Foundation Grade Redwood”. BTW FG redwood is no longer available here.
Replies
I've been wondering about this a lot in the past few months since I just built my largest deck to date and used ACQ lumber for the first time just as the news about corrosiveness came out. In your case, I wouldn't worry about it too much. Since your sills shouldn't have much free water flowing around, the steel may not be repeatedly bathed in a fresh salt solution. You might consider slathering them with some bearing grease and using hot-dip galvanized washers and nuts to replace the originals.
Al Mollitor, Sharon MA
I gotta tell you this is a question that has been driving me crazy for a few months. I cannot get a straight answer on how corrosive the new stuff is. I am a framing contractor in SoCal., and I have heard that we will be required to use stainless steel nails when nailing through the bottom sill or sole plate. If that is true, I am wondering what the cement guys are going to have to use for anchor bolts. And then there is Simpson Strong-Tie and all the fun stuff they require for their products. There is never a dull moment in the fun filled construction industry. Hopefully, some of the more informed members of this board can shed some light?
All I can say is from what I've gleaned water isn't the worry - it's a metallurgy issue. The chemistry in ACQ adds enough copper to the mix that you get a reaction of dissimilar metals. True/false? I'm with you there. I can't wait for the day someone gives the collective "us" something resembling a difinitive answer."The child is grown / The dream is gone / And I have become / Comfortably numb " lyrics by Roger Waters
I don't know the chemistry of it, but some manufacturers are in denial and the worst reports and photos I have seen seem to be in locations where excess water washes across the metal when in contact. Maybe it activates a galvanic action.
I like the idea of creating a sleeve of some sort. Caulk, grease, whatever..
Excellence is its own reward!
From what I understand, the chemistry is the very high amount of copper (67% Copper Oxide in ACQ) in the new PT wood, causing galvanic corrosion. Moisture only speeds the process. Having spent many years in the Navy, I can testifiy to the power of galavanic corrosion in a moist (and salty) environment - it's not pretty.
As an aside, I just ran across this interesting document that is one city's attempt at dealing with the ACQ problem:
http://www.ci.arlington.tx.us/build/pdf/TREATED%20WOOD%20&%20FLUX%20120503.pdf
Here's some good additional info on the new stuff courtesy of your federal tax dollars:
Technical data on new treatments:
http://www.fpl.fs.fed.us/pres_fire/types.htm
FAQ on new treatments:
http://www.fpl.fs.fed.us/pres_fire/Preservation_FAQ.htm#faq
An interesting point I read in here is the the US Forest Products Lab hasn't had a chance yet to thoroughly test the new stuff to see how it performs.
Edited 12/14/2003 10:52:43 PM ET by Andy
"All I can say is from what I've gleaned water isn't the worry - it's a metallurgy issue. The chemistry in ACQ adds enough copper to the mix that you get a reaction of dissimilar metals. True/false? I'm with you there. I can't wait for the day someone gives the collective "us" something resembling a difinitive answer."
From what I have read, this reaction cannot happen without water. Whether there is enough water absorbed in the wood, or enough simply in the air to feed the reaction, I would not speculate.
The whole situation is a massive over-reaction. At the very least, the CCA material should have been made available as a consumer choice. Evidence suggests that the high arsenic levels in the soil are not from leaching, but from the sawdust generated during assembly. This part is simply a matter of education on the 'care and handling' side.
If folks do not want to spec it for playgrounds, that's fine and good, but eliminating CCA from the marketplace is setting the stage for a whole new set of problems.
So great, the PT manufacturers are acting pre-emptively to headoff litigation.
What about the litigation that will whack them when fasteners start failing, and structures collapse? Will they say "the WOOD did not fail", so blame them?. Have they thought this through? Simpson has, which is why they are warning us now. What about the contractors? What will protect them from mass litigation?
If everything has to be stainless or copper, construction the costs are going to soar. The cost of fasteners and other related hardware is certain to be much greater than the lumber involved. Bet this will give other construction materials quite a boost, since the 'upcharge' for composites and such might be a wash after buying all that stainless!
Unfortunately, I have already repaired a structure using aluminum flashing in direct contact with AQT. Even used aluminum nails to prevent galvanic corrosion...
Read my message 37752.6?
When I went to my HD where I got the "new" stuff, they told me the lumber producer had not instructed them about corrosion. When I asked about lawsuits against HD, the just told me "we will sue the manufacturer".
I cannot get into the space I built (see "the deck we built this summer" in Photo Gallery) to do repairs without destroying about $15,000 of work and finding a place to store his wine. What choices do I have? If there is a failure, my insurance company will want proof, the lumber supplier will deny liability, Simpson will bring in their lawyers ... meanwhile, my reputation will be shot.Quality repairs for your home.
Aaron the HandymanVancouver, Canada
Manufacturers are recommending double hot dipped fasteners. There are already adds for such in many magazines. G185 is the heavier-than typical galvanized coating they are recommending. Another thought would be to use Boardwalk decking, Trex or the like for uses like deck boards. You know, PVC/wood components. Trust me, there will be an influx of information about all of this new stuff and the fasteners in the near future. I guess we just wait until then.
You can use trex and the like, but it's not structural, so you'll in all likelyhood, still be nailing into PT wood.
FWIW I would think that a good coat of any decent oil based paint would stick quite well to a clean, you might have to degrease a little, galvanized anchor bolt. I would think that excluding any transfer from the treated wood and additionally exclude any moisture.
I would be tempted to paint the bolts after the concrete sets, maybe better to paint them before setting but not too far down the bolt. Once the sill was set I might slop some paint down the hole around the bolt just to be sure. Place a plastic washer over the bolt, set the washer and nut. Even if it got sloppy it wound be in the wall so no worries.
Just an idea seeing as that many industrial paint are quite effective preventing corrosion.
What about using No-Ox (sp?, the stuff used for aluminum wiring)? It seams better than a paint.
Talked to the lumber salesman last night and he said that the contractors will have to have a license to purchase CCA. But it won't matter if you have a license and get supplies, you will get a fine for using it in residential applications.
Ya gotta wonder who is going to enforce that. The Pressure Treated Police? Whomever it is, they sure as God made little green apples have too much time on their hands.
Gotta be the government. Building inspector, right? I'm gonna call him next time a replace a rotting skirt board on a porch? I don't think so.
I may not agree with the new PT lumber changeover, but will switch. Grudgingly. But let's keep the government out of it as much as possible. (Too late, I know.)
I never met a tool I didn't like!
As soon as someone has their sill plate rot out and ask for replacement under insurance the insurance company, the people who really run the nation, will need standards, conventions and rules.
On the other end, the anchor bolt giving up and someone getting hurt or loosing the side of a house in a storm there will also be a standard needed. People want to be able to live in a house with the reasonable expectation of it not falling down around their ears without requiring that every home owner be an engineer.
Same goes for drinking the water and eating the food. As long as there are those who cut corners or dupe people into dangerous situations there will always need to be rules and someone to enforce those rules.
Materials and requirements change. Given time I'm sure a solution will be worked out for this situation. Who knows. Maybe you could come up with a simple low cost solution that would keep everyone happy and you could sell at a profit. Welcome to the wonderful world of free enterprise where there are no problems. Just opportunities to make money.
My point wasn't that there should be no rules or laws, my kids will tell you I have more rules than they know what to do with. But I also know there is a point at which there is too much intervention. You are correct, there must be codes and standards to maintain a safe environment, but sometimes it goes too far. I have seen a whole industry fall into stagnation and now decline because government rules made producing power by nuclear reaction cost-prohibitive. Clearly the industry must be regulated, but I can guarantee you that once the government steps in with both feet, costs will skyrocket and rules and laws will be implemented that will seem utterly absurd to you and I.
My point is best said by a verse in the Bible; 'In all things moderation. . .' That's something I don't believe the fed has any concept of, moderation.
Sorry for the rant, some old (and long festering) feelings boiling to the surface.
Happy Holidays!
I never met a tool I didn't like!
Well, one thing that is worse than government is waiting for private industry to do something for the general good. I worked as an industrial engineer and the stated policy I got regarding dumping polutants directly into the river was to do absolutely nothing until we received a court order.
I'm an electrician so I will probably not be worrying about all this, unless I build my own house, but I got thinking last night. I liked my paint idea but thought it was too hit or miss. A missed or galled spot in the paint could allow corrosion and a false sense of confidence.
So I came up with a better plan, it's what I do:
I would cut a bunch of half inch PEX into 6" pieces. Once the anchor bolts, inserted into the wet concrete or attached to the forms, are surrounded by concrete I would slip the PEX tubes over the bolts. I would try to get something like 2 or 3" of it into the concrete but leave enough to cover the threaded end, maybe just a bit less. Once the sill was set and the nuts ready to screw down I would cut off the tube from around the bolts. Follow with an plastic washer, a bit bigger than the steel washer, then washer and nut.
I think this is better than the paint because PEX is fairly tough, long lived and resistant to chemicals. Less likely to be damaged by the concrete or trowel work as long as some care is taken.
Check this link out for "Simposon Strong-Tie"
http://www.strongtie.com/news/index.html
two points about your comments about the government,
First in the end everything will be done by humans,, some are good and some are bad.. It doesn't matter if the paycheck comes from private sources or public sources.. there are good and bad in everything.. so please accept that not all the things done by us (remember it's,.. "we the people") are bad.
Second,
the government can be changed.. if you don't like a rule and can convince more than half of the people that you are correct, change the rule.....
(unless you're lazy and don't really care but would rather just complain)
I was first thinking about that but considering that the anti-oxidant compounds are like grease, subject to flowing in heat or washing off, I thought any of the better industrial paints, stable and pretty much impervious to anything short of straight MEK or strong acid, would be a superior choice.
"I would be tempted to paint the bolts after the concrete sets..."
That's what I was thinking - A spray can and a quick coat of metal primer.
Maybe paint the washers too, and hit the bolts again after the treated plate is bolted down.If you get out of the shower clean and dry off with a clean towel, then why do you have to wash the towel?
Those are some great ideas. Until they come out with something better, those ideas sure beat what we've got now.
I purchased my first ACQ lumber in September . The Sales rep for the Manufacturer happened to be in the yard approached me and asked if I was going to be using this for a deck. When I replied yes he stated that the preservative they now use does not have the water repelling capabilities that the old lumber had . This is causing severe checking on the deck surface. They are trying to correct this problem but had been unsuccessful at that time. He recommended a good coat of Thompsons or another brand that I can't recall. I live in Ontario but a lot of our chemicals come from south of the Border. Attaching deck railings that contain aluminum is also a no no.
You aren't the only one.
I used what I think is the new PT stuff as sills bolted to the ledger boards, with Simpson hangers and nails holding roofing joist for a roof deck above/wine room underneath.
$40,000 deck; $100,000 of wine, and nobody can give me answers if I have ACQ or not (not even the lumberyard - they had new and old intermixed) and even Hilti does not have definitive answers on this, never mind Simpson.
I emailed my insurance agent as soon as the problems started popping up here, and I told the lumberyard.
Right now, there is no answer.Quality repairs for your home.
Aaron the HandymanVancouver, Canada
You might try to sleave the old bolts, but you might be better off to drill new holes in the foundation for stainless or galvanized anchor bolts. Not sure if you have the clearance to get a hammer drill in there though.
Good luck,
Andy
Galvonic corrosion occurs when two different metals come in contact in the presence of an electrolyte, like water. The more reactive metal in your case are the steel bolts. I personally would put a moisture barrier between my ACQ treated lumber and concrete, prime and paint my existing bolts, and use hot dipped galvanized washer and nut if the threads are compatible. There seems to be a lot of CYA when it comes to the new treatments.
That proposal brings us to the idea of getting rid of PT for sills, since many codes call for PT sills, or a barrier to separate lumber from contact with 'crete. So if you are going to separate the PT, theere is no reason to have it..
Excellence is its own reward!
FYI if you go to
http://www.osmose.com/wood/usa/preserved/naturewood/product/
and click on the flashing red "Important Fastener Info" you end up at
http://www.osmose.com/acrobat/NaturewoodFastenerInfoSheet.pdf
which states half way down,
"2003 International Residential Code - Fastener Statement - Section R319.3: Fasteners for pressure-preservative treated wood shall be of hot-dipped galvanized steel, silicon bronze or copper. Exception: One-half inch (12.7mm) diameter or greater steel bolts."
The last part of this statement implies that steel anchor bolts greater than 1/2 inch are ok as is with any PT mudsill.
The first link Andy gives in post #9 also mentions this, although less clearly, and only by reference to the IRC.
Perhaps Osmose Research has more info regarding ACQ vs. CCA as to corrosion. I'll post if I find it.
"That proposal brings us to the idea of getting rid of PT for sills, since many codes call for PT sills, or a barrier to separate lumber from contact with 'crete. So if you are going to separate the PT, theere is no reason to have it."
Good point. Frankly, separation is better practice anyways. They make those nice EPDM sill gaskets now. Around here, inspectors really do want to see the 'glow' of PT on the sills.
Also, being at the bottom, sills are the 'weakest link' for rot from bad water shedding details. Does not take much of a leak to cause troubles over time. While not needed in theory, in practice the PT provides some measure of insurance against sloppy workmanship, or deterioration when materials start to fail down the road.
Actually, sills are probably not the top area of concern for corrosion. Sill anchor bolts do not normally 'do' anything. Structures around here have been standing for hundreds of years with only gravity to keep them on their foundations. Takes an extraordinary event to test a sill anchor bolt... earthquakes, hurricanes, tornados....
Something under constant shear load and weather exposure (like a deck ledger) would be more worrysome.
I'm with you on this issue Piffin,
I use a sill sealer between the concrete and the sill board and lately selected tamarack as a naturally decay resistant wood.
when I run out of my source for Tamarck I'll switch to white oak..
Any accumulated wisdom you would care to pass on regarding the various "barrier to separate lumber from contact with 'crete"? Particularly if the "crete" doesn't exactly have a pristine finish where the barrier needs to go...
Peel and stick or a metal flashing.
Excellence is its own reward!
In the meantime, does anyone know of a good source or manufacturer for (higher) corrosion-resistant metal connectors? Big box stores seem to only carry Simpson, and Simpson says don't use their hardware on PT lumber. I'm open to suggestions.
Go here and then investigate ZMax for your PT connectors. Outside of stainless, these are recommended for the new kind of PT.
http://www.strongtie.com/ii_Coatings.html
Remodeling Contractor just outside the Glass City.
Quittin' Time
Edited 12/17/2003 6:14:17 PM ET by calvin
Get Simpson Zmax connectors and joist hangers or USP's Triple Zinc (TZ) hangers. Zmax is in my Home Depot, look over by the pressure treated wood area, look for the sticker. See my article, there's photos of the good stuff.
DanDan MorrisonOne happy assistant editor
First of all, you could use borate treated lumber. It's less corrosive than CCA.
If you can't find that, why don't you just cut off the steel anchor bolts and install expansion bolts?
But if it's only a ten foot section, it's probably not that critical for the plate to be bolted down. (But you should ask someone smarter than me about that).
About species, I'm unaware of a species switch as a result of the chemical switch, in fact I'm pretty sure they're unrelated.
Hope that helps,
Dan
One happy assistant editor
Some things worthy of consideration:
In regards to working with ACQ lumber, I have found stainless steel hangers in the McFeelys catalog. Not sure of the manufacturer but the description states that the the hangers utilize Simpson's Strong Tie Double Shear Nailing System so maybe they are made by Simpson. Obviously, ordering out of a catalog for items that we are accustomed to picking up at any old lumber store is frustating and not timely. McFeelys also sells the Joint Hanging Nails in stainless steel as well as a plethora of other stainless steel fasteners one may use in deck building.
As for mud sills, I have not seen stainless achor bolts. However, stainless all-thread is reasonably available and one could easily make their own j-bolts from such. Again, more effort and one cannot just "grab" some at the store. Stainless steel does not generally have quite the strength properties as carbon steel but as someone pointed out, the anchor bolts are rarely "challenged." Use stainless steel washer and nuts.
I recently was looking for a mud sill material to use with a water cistern and wanted to avoid all the pressure treated products. Our lumber yard could not get foundation-grade redwood (although they could get a particular heartwood grade of redwood). I looked into a product called Polywood. It is a structural product (not just for decking like Trex) and it is commonly utilized for railroad ties. I figured if it could handle trains speeding above, surely being a passive mudsill wouldn't be difficult. Shipping was difficult to arrange but I live far away from commerce.
http://www.polywood.com (their web site is a bit lame, IMHO)
I found it better to call them.
Edited 12/22/2003 1:27:55 PM ET by ADGUSTUM
Seems to me that one issue is the anchor bolts but another is the nails you use to nail the bottom of the sheathing to the sill. Once those corrode away the house no longer has any holddown. Our local yard sells stainless steel siding nails but nothing like a 10d nail and I've never seen stainless nails in a gun.
I just bought CCA framing material for two decks I'm building next year. Maybe avoid the issue for a while...
McFeelys also carries stainless steel nails all the way up to 16d. The are available only in ring shank which, in some cases, just aren't "what the doctor ordered."
Maybe down around the mud sill ring-shanks wouldn't be a bad idea. Seems like that environment sees enough temperature/humidity swings that nails tend to push themselves out.
Having to hand drive just the stainless nails that actually fasten to the treated lumber of the mud sill wouldn't be that bad. But stainless nails that worked in you favorite gun would be nice in the case of building a deck.