Covering treated wood with metal

47832 Views 26 Replies 16 Participants Last post by Tom Struble, May 10, 2012

SC sawdaddy

Discussion Starter · Aug 6, 2009

O.K. I've heard it before... If you cover treated wood with coil it causes a chemical reaction that will:
1. cause corrosion on the coil or
2. cause the treated wood to rot

I'll be honest, if a homeowner wants me to wrap the treated 4x4 posts on the porch, I'll do it.:thumbsup: I will warn about the possible outcomes and offer the solutions of wrapping posts with tyvec or changing out the 4x with two untreated 2x4s. However some of the time I get that look that says "You are just trying to pad the bottom line by adding unnecessary labor/materials"
In those cases I'll let them decide and be sure to waive any warrantee on anything installed against manufactured recc. :no:
What gets me is I have never been called back to any of these projects to repair any corroded coil and seriously doubt that there has been much damage to the post.
Maybe not enough time has passed for the process to take place,:001_unsure: Or maybe it is just a pitch to sell more tyvec. Either way I try to cover my ar$$ when the situation comes up.
My latest run in with the old wood/metal/chemical reaction triangle has a new twist on it though.

Situation:
Building is brick and block cmu. The plan is to strip out with treated 2x4 and cover with metal siding. My supplier tells me that I'll have to use stainless steel self tappers to fasten it or it will be falling off in a year.

OR
furr it out with hat channel. Either way is going to add good bit more to the expense.
I dont know...my boosh hit meter started tinging. I'd love to hear some thoughts on the matter.:notworthy

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neolitic

· #2 · Aug 6, 2009

SC sawdaddy said:
O.K. I've heard it before... If you cover treated wood with coil it causes a chemical reaction that will:
1. cause corrosion on the coil or
2. cause the treated wood to rot

I'll be honest, if a homeowner wants me to wrap the treated 4x4 posts on the porch, I'll do it.:thumbsup: I will warn about the possible outcomes and offer the solutions of wrapping posts with tyvec or changing out the 4x with two untreated 2x4s. However some of the time I get that look that says "You are just trying to pad the bottom line by adding unnecessary labor/materials"
In those cases I'll let them decide and be sure to waive any warrantee on anything installed against manufactured recc. :no:
What gets me is I have never been called back to any of these projects to repair any corroded coil and seriously doubt that there has been much damage to the post.
Maybe not enough time has passed for the process to take place,:001_unsure: Or maybe it is just a pitch to sell more tyvec. Either way I try to cover my ar$$ when the situation comes up.
My latest run in with the old wood/metal/chemical reaction triangle has a new twist on it though.

Situation:
Building is brick and block cmu. The plan is to strip out with treated 2x4 and cover with metal siding. My supplier tells me that I'll have to use stainless steel self tappers to fasten it or it will be falling off in a year. OR
furr it out with hat channel. Either way is going to add good bit more to the expense.
I dont know...my boosh hit meter started tinging. I'd love to hear some thoughts on the matter.:notworthy

Check into the treating.
It's all over the place again.
The new micro pro treating is
less corrosive, and mostly all
one can find here.
Also depends on the siding,
Steel, or aluminum?
Either one would want to be
powder coated on the contact side
at the least.
Find out about the treating,
and do your research on the
Treated Wood Assc. web site,
or here...
http://www.wwpinstitute.org/
or here....
http://www.osmosewood.com/micropro/micropro-eppinformation.html

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SC sawdaddy

Discussion Starter · #3 · Aug 6, 2009

The siding will probably be galvalum (not sure about the spelling) made from a mixture of galvanized and aluminum which is permitted in the use of treated wood according to the bldg. code book. I'll have to check with my supplier again but seems to me if the screws are not galvanized, they should be compatible with anything that the galvalum would be in contact with.

neolitic

· #4 · Aug 6, 2009

SC sawdaddy said:
The siding will probably be galvalum (not sure about the spelling) made from a mixture of galvanized and aluminum which is permitted in the use of treated wood according to the bldg. code book. I'll have to check with my supplier again but seems to me if the screws are not galvanized, they should be compatible with anything that the galvalum would be in contact with.

What ever kind of treated lumber
it is, the screws need to be either
HD Galvi or S.S.
That part is a for sure.

Reactions: 1

fenestrationman

· #5 · Aug 7, 2009

Although I have no data to back up the claim of aluminum coil over pressure treated is a no no, here is what I have seen. We used to have a sunroom division where I am employed. We had a display room set up attached to our building. Deck make up - pressure treated capped off with aluminum coil stock. Within a year and a half, the coil was showing signs of a reaction through color, and metal degradation.
During our installer training sessions, I still recommend not using aluminum over pressure treated. Being cautious on my part.

CharlesD

· #6 · Aug 10, 2009

I capped a couple treated posts on my deck about 8 years ago and they still look good.
My problem with capping treated wood is the shrinkage and movement of the wood can ripple the aluminum stock.
I always had contractors frame garage doors out with treated two by six jambs and I'd cover them.
I always use stainless steel nails with treated wood although I am pretty sure galvanized would do just as well.

Dave Ruc

· #7 · Aug 23, 2009

Wait at least one year

In my experience, PT posts that are more than one year weather cured are much slower at deteriorating the coil stock. After severe homeowner pressure, I wrapped a porch that was brand new with 8 4x4 PT posts and only 4 months later, I was called back to re-do the posts (Payed) and again 6 months later.

The homeowner was well aware of the consequences and I had a clause in the contract that the posts were not guaranteed. The second time I came to replace the trim, I was asked by the homeowner to install tyvek and tyvek tape in hopes that it would stop the deterioration with no prevail.

I have heard before that tyvek would stop the chemical vapors from reaching the trim, however that made no sense to me as Tyvek is not a vapor lock and I explained this to the HO but I was asked to continue anyway. Granted, I am not complaining since I was paid for work performed each time, however, there must be some type of coating that I can spray the inside of the trim with or slather the post with before installing. Any ideas?

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jumbo

· #8 · Aug 24, 2009

I too have been covering with Tyvek for the last couple years. Just had my first call back a week ago. I also wont guarantee these.

quality1stconst

· #9 · Aug 24, 2009

2

I aluminum wrapped my garage door frames (treated lumber) on my house just to test this about 3 1/2 years ago. It still looks great and no signs of any deterioration, fade or anything. I use stainless nails as well. Here are the only pics I can find, it's too dark outside right now.

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SuperGlazier

· #10 · Aug 26, 2009 (Edited)

In my experience in wraping with aluminum over PT... have installed storefront and curtain wall for Target's, Ikea's, etc. There are always situations that we need to wrap PT wood. According to everyone around here you need atleast an 1/8" spacer between the two. My suppliers, (VistaWall, YKK, Tubelite, Kawneer, etc.), all use 1/2" spacers between the two. I have seen the discoloring and chemical reaction when not spaced. A good practice maybe to tar the surface first to seperate the two. Just my opinion and input.

Tom Struble

· #11 · Aug 26, 2009

i think most of the problems are if the trim is in the presence of moisture your gonna have a problem

thing is most lumberyard 4x4s are almost 20% moisture,you wrap it
it will take quite awhile to dry

no more garage door wraps for me
treated or otherwise

lmrivers

· #12 · May 7, 2012

trim coil over PT wood

Someone told me about this today and I'll admit I've been out of full-time contracting for awhile but I've never seen this or heard this. I have four garage doors on my personal house that are pressure treated wood wrapped in trim coil and have been for seven years on two of the doors and twelve years on the other two. None of them are showing any of the reported reaction. Since the wood is in contact with the concrete, it would stand to reason that it will wick up moisture into the wood underneath and, being encased in trim coil, I think rot is the only thing I'm expecting to deal with at some point. Of course, the trim coil I use regularly is fully painted, inside and outside, so that may be the reason I haven't had any issues.

Tom Struble

· #13 · May 7, 2012

3

oh it happens alright

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RobertCDF

· #14 · May 7, 2012

something for people to keep in mind as well, this is to do with NEWER treated (2005+?? is that right? someone correct me if I'm wrong) when PT went from arsenic treatment chemicals to... ummm... garbage... for treatment chemicals. It also needs moisture to really do anything measurable, having paint, powdercoat, tyvek, etc goes a long way in nearly preventing this reaction.

Tom Struble

· #15 · May 7, 2012

ya gotta keep em separated:whistling

every box of coil say do not use on treated lumber,it doesn't say which kind

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Reactions: 1

Tinstaafl

· #16 · May 7, 2012

Tom Struble said:
every box of coil say do not use on treated lumber,it doesn't say which kind

Yes, they say that today. They didn't say that before the newer PT recipes came along.

thing is most lumberyard 4x4s are almost 20% moisture,you wrap it
it will take quite awhile to dry

Unrelated to chemical "rot" of the aluminum, I maintain that slow drying of PT goes a long way in preventing excessive warping and twisting. Every PT post I've ever wrapped (and been back to see) has stayed much straighter than those left unwrapped, particularly those exposed to full sun for at least part of the day.

Reactions: 2

Randy Bush

· #17 · May 7, 2012

Tom Struble said:
ya gotta keep em separated:whistling

every box of coil say do not use on treated lumber,it doesn't say which kind

Do my posts the same way, Have had to replace some over the years before knew better :whistling So now tell builders they have to be covered first.

guardian

· #18 · May 7, 2012

leave it to Tom to have a pic of the rare things in the siding world

sunkist

· #19 · May 7, 2012

i,m lost here?, why wrap use pressure treated wood that will get trimed out?, knowing full well its going to shink warp and make my finnish work look like crap in a few months, all ext screws nails etc s/s all the way. c/k out galvanic table

Tom Struble

· #20 · May 8, 2012

:blink:...your lost?can you translate that a little better?

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