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Isolating Truss Connector Plates from Treated Lumber

Isolating Truss Connector Plates from Treated Lumber

Assembly time for Hansen Pole Buildings’ client BRAD in MOUNT VERNON. Construction has begun upon his new post frame building. Brad had some great questions for Technical Support!

“I’m not sure if you can answer my question or can possible point me in the correct direction.  We are about to attach trusses.  I thought that I had read somewhere that we needed to isolate the truss connector plates from the treated poles, if they were in a position where they would contact the columns.  Also, is it OK to fasten through these connector plates?

Thank you for your time and help on all of the questions we have had so far.”

Mike the Pole Barn Guru responds:

This Construction Manual caution regards ACQ pressure preservative treated lumber only. Each piece of pressure preservative treated lumber will be marked or tagged with an identification of chemicals used for treatment (as well as level of treatment).

 Truss plates are produced from sheet steel which is galvanized to ASTM A 653 specifications. The galvanized coating is suitable for use with non-corrosive lumber treatments, including most sodium borate-based preservatives.

  This galvanizing is not suitable for direct contact with ACQ treated lumber. A waterproof barrier, such as polyethylene roof underlayment (Vycor or similar), must be placed between any truss plates and ACQ treated lumber. An application example is where the truss heel is attached to a treated wood post. The entire truss plate must be covered with barrier, and care shall be taken not to rip or damage barrier when drilling or installing any fasteners.

  In lieu of a waterproof barrier, exposed truss plate surface may be painted as recommended by ANSI/TPI 1-2002 Section 6.51:

Epoxy-Polyamide Primer (SSPC-Paint 22)

Coal-Tar Epoxy-Polyamide Black or Dark Red Paint (SSPC-Paint 16)

Basic Zinc Chromate-Vinyl Butyral Wash Primer (SSPC-Paint 27) and cold applied Asphaltic Mastic (Extra Thick Film) Paint (SSPC-Paint 12).


Keep in mind we, as manufacturers, have to deal in a perfect world where everyone follows everyone else’s rules of best practice and instructions. I’d like to tell you as long as you keep this connection dry, you are highly unlikely to ever have an issue, however there still exists a rare possibility.

If location of a steel connector plate happens to make it impossible to otherwise fasten a truss, place fasteners so they go through “holes” in truss connector plate. BCSI-B8 addresses a similar issue of connectors being placed through a truss plate, “Toe-nailing through a metal connector plate of a truss does not adversely affect the uplift capacity of the Connection provided the truss plate and lumber are not damaged during installation.” https://www.sbcmag.info/sites/sbcmag.info/files/article/2007/01/bcsi_chapter_8_pdf__15339.pdf.

Of interest, some metal plate connected wood truss manufacturers use nail guns to set steel plates, prior to trusses being pushed through a roller press, setting them permanently.

 

 

This entry was posted in Lumber, Trusses and tagged , , , on by .

Wood Rot and Bugs in South Carolina

Hansen Pole Buildings’ Designer Dave Gross sent me this note recently: “I have a client questioning steel versus wood. I have gone through the blogs and discussed the pros and cons with client. Her main comeback is wood rot and bugs in South Carolina.

She is a sharp cookie. 30 year business owner. Just built her 4500 SF house and was the GC on it.  She is direct and wants the truth.”

Dave was certainly right in sharing some of my articles with his client. Among these would be why wood decays to begin with: https://www.hansenpolebuildings.com/blog/2011/07/how-untreated-wood-decays/ and what the Code requirements are for pressure preservative treated wood: https://www.hansenpolebuildings.com/blog/2012/10/pressure-treated-posts-2/

One of the questions I posed of Dave was, did your client happen to build her house out of all pressure preservative treated wood? Of course the answer was “no”.

Wood is an inherently durable material which is resistant to most biological attack provided it remains dry. However prolonged wetting leads to a risk of decay by wood rotting fungi. Various insects also use wood as a food source.

“Dry Rot” is a term most often used to describe a particular kind of dry, cracking, rotting wood. However, dry rot occurs because of a variety of brown rot species, most notably the “true” dry rot fungus known as Serpula lacrymans. It originally got its name from the thought that it did not need water to survive and used a fermentation process to survive. Research has long since been proven untrue, and it is now called, more appropriately, “brown rot“, although the old name hangs on. Dry rot needs much less moisture than other types of wood rotting fungi–a wood moisture content of at least 28-30% — to survive.

Treated Wood StampThe solution to wood rot problems is to prevent it from ever starting – the use of properly pressure preservative treated lumber in critical areas can reduce or altogether eliminate the potential for insect and fungal decay.

And yes, Hansen Buildings uses lumber which is treated to UC4B standards for all structural in ground use.

Read more about this here:

https://www.hansenpolebuildings.com/blog/2012/10/pressure-treated-posts-2/

 

 

 

 

 

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Treated Wood

Treated Wood Industry Looks to Toughen Standards

post holePrior to the EPA (Environmental Protection Agency) dipping its nose into the pressure preservative treating chemical industry in 2002, buying treated wood was pretty darn easy. Chromated Copper Arsenate (CCA) was the treatment of choice for most everything.

CCA was so much cleaner to work with than its most common predecessor, penta (pentachlorophenol), was cost competitive and enjoyed a lengthy lifespan.

For more reading on penta treated lumber see: https://www.hansenpolebuildings.com/blog/2012/11/pcp/

I’ve been ranking on the post frame building industry to put the pressure (pun intended) on lumberyards, wholesalers and pressure preservative treatment companies for some time, so it is nice to see another industry (the deck builders) jumping on the wagon for improvements as well.

My most popular rant on pressure treating can be reviewed at: https://www.hansenpolebuildings.com/blog/2012/10/pressure-treated-posts-2/

This recent article by Ted Cushman in the Journal of Light Construction (https://www.jlconline.com/wood/treated-wood-industry-looks-to-toughen-standards_o.aspx?dfpzone=home) lays out the challenges posed by the deck construction industry with pressure preservative treated wood.

Ted also wrote a great article in Professional Deck Builder (https://www.deckmagazine.com/lumber/treated-wood-update_o.aspx) which gives an interesting recent history on the “players” in the pressure preservative chemical industry. This article also has some great explanations as to how different chemicals work to preserve wood.

My hope – the post frame (pole building) industry will organize to put suppliers on notice – we (and our consumers) both want and need products which will withstand the test of time.

Investing in a new pole barn? Then know what it is you’re a buying when it comes to the treatment levels of the columns for your new building. Don’t be satisfied if the vendor says their columns “are treated for in-ground use”. Ask them to specify the treatment level! All treated posts are not the same! Whether building yourself, or buying a “turnkey” building – your hard earned dollars should be spent on something which will indeed last for as long as the rest of the building!

This entry was posted in Columns and tagged , , , , on by .

Incising Lumber

Incising

My former wife (mother of my two youngest children – Allison and Brent), was by training an RDH (Registered Dental Hygienist). In order to keep her registration current, she had to obtain CEUs (Continuing Education Credits). One way to generate CEUs was to attend the annual state dental convention.

One year I went along with her and as we perused the trade show floor, the assumption was somehow made of me being a dentist – so I received lots of attention. Also tons of free stuff – I don’t think I needed to purchase a tooth brush, tooth paste or dental floss for the next decade!

Other than my annual visits to the dentist, about the only thing I remotely knew in regards to teeth were the incisors are the front four teeth on the top and bottom.

With my tremendous knowledge of incisors – I was able to easily translate to incising of lumber.

For those in the east and south – you may have never seen pressure preservative treated lumber which has been incised. Most treated lumber in those regions is Southern Yellow Pine – which is highly treatable (think of it as being a chemical sponge).

Travel west and north, the lumber species of choice for pressure treating is grade stamped as Hem-Fir. Hem-Fir is not a species unto itself, it is a lumber species “group” which includes California Red Fir, Grand Fir, Noble Fir, Pacific Silver Fir, Western Hemlock and White Fir.

Incised LumberDifficult-to-treat (refractory) lumber species, such as Hem-Fir, must be incised prior to preservative treatment to meet minimum penetration requirements for preservative-treated wood. Incising is a pretreatment process in which small incisions or slits are punched into the wood. To me, the resultant product looks as though the lumber has been walked on by someone wearing golf shoes!

Incising increases preservative retention and penetration during the treating process by increasing the amount of exposed, easily penetrated end-grain and by decreasing the side-grain surface area. While incising has been used since the 19th century, the process appears to have developed casually with little consideration given to optimizing the process to maximize preservative treatment and minimize strength loss. While AWPA (American Wood Preservers Association) standards require incising, they do not define or recommend what type, how deep, or how many incisions are required. Generally, it appears the more effective an incising pattern is in achieving preservative penetration, the more it reduces strength.

AF&PA’s National Design Specification® (NDS®) for Wood Construction includes provisions for the downward adjustment of lumber strength characteristics for incised lumber by use of an Incising Factor known as Ci. Referenced design values are multiplied by Ci when dimension lumber is incised parallel to grain a maximum depth of 0.4”, a maximum length of 3/8”, and a density of incisions up to 1100 per square foot.

E values are to be multiplied by 0.95, while other values (with the exception of compression perpendicular to the grain of the wood) are multiplied by 0.80.

Sound engineering design of incised lumber (which includes pole building columns) take into account these strength reductions.

If you see Hem-fir and it has all these little cuts – don’t panic. It just means it’s been incised for adequate infiltration of chemical treatment. This ensures preserving a longer life of whatever you are building, be it a deck, garage or even a new pole building house.

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TimberSIL® – A Great Idea?

Great Ideas May Not Always Bring Great Results

Much ado has been made about alternatives to CCA (Chromated Copper Arsenate) pressure preservative treated lumber. CCA has been used to pressure treat lumber since the 1940s. Since the 1970s, the majority of the wood used in outdoor residential settings (as well as pole buildings) has been CCA-treated wood. Effective December 31, 2003, no wood treater or manufacturer may treat wood with CCA for residential uses, with certain exceptions.

Treated Wood StampThis resulted in a plethora of alternative pressure preservative treatment chemicals being introduced which, on the surface, sound like a veritable alphabet soup – ACQ, CA-B, CA-C, MCA, etc.

Although not used for preservation of timbers for structural in ground use, there have been some interesting alternatives, not all of which have necessarily worked in all cases.

Brad Pitt’s Make It Right Foundation has built 100 energy-efficient and eco-friendly houses in New Orleans to replace homes damaged by Hurricane Katrina. Unfortunately, the organization believes that some of the wood it used is now rotting, reports The New Orleans Advocate.

The organization used TimberSIL®, an innovative glass-infused wood product produced by a South Carolina manufacturer, to build porches and outside steps. The absence of chromated copper arsenate and other chemicals typically used to prevent rot and decay was a selling point for Make It Right.

“Instead of treating the wood with toxic chemicals, it’s actually infused with sand, or silica, such that it takes on the properties of treated lumber,” Tom Darden, the executive director of Make It Right, said in a 2010 interview. “At the end of its life cycle, which is estimated to be about 300 years, it can be mulched and composted, believe it or not.”

Unfortunately, Make It Right has found TimberSIL® can’t stand the moisture in the balmy city and has turned dark gray and begun falling apart. The organization has replaced wood in 30 homes and is considering legal action. TimberSIL® has reportedly caused trouble for at least one other client: a project in Western Massachusetts which had to be repaired when the builders found the wood retained too much moisture and couldn’t hold paint.

With more and more pole buildings being used for residential purposes, with alternative sidings to the traditional steel, as well as attached decks, it would behoove some serious research and consideration (in this author’s humble opinion) before utilization of this particular product

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MCA: Micronized Copper Technology

Particulate (micronized or dispersed) copper preservative technology has recently been introduced in the USA and Europe. In these systems, the copper is ground to micro sized particles and suspended in water rather than being dissolved in a chemical reaction as is the case with other copper products such as ACQ and Copper Azole. There are currently two particulate copper systems in production. One system uses a quat biocide system (known as MCQ) and is a take-off of ACQ. The other uses an azole biocide (known as MCA or μCA-C) and is a take-off of Copper Azole.

Treated Wood StampProponents of the particulate copper systems make the case the particulate copper system perform as well or better than the dissolved copper systems as a wood preservative, but other industry researchers disagree. None of the particulate copper systems have been submitted to the American Wood Protection Association (AWPA) for evaluation, thus the particulate systems should not be used in applications where AWPA standards are required. However, all of the particulate copper systems have been tested and approved for building code requirements by the International Code Council (ICC). The particulate copper systems provide a lighter color than dissolved copper systems such as ACQ or copper azole.

Proponents of the micronized copper systems claim the systems are subject to third party inspection under a quality monitor program. However, the monitoring program is not subject to oversight by the American Lumber Standards Committee (ALSC) as is required for the AWPA standard systems.

Two particulate copper systems, one marketed by Osmose as MicroPro and the other as Wolmanized using μCA-C formulation, have achieved Environmentally Preferable Product (EPP) certification. The EPP certification was issued by Scientific Certifications Systems (SCS), and is based on a comparative life-cycle impact assessments with an industry standard.

The copper particle size used in the “micronized” copper products ranges from 1 to 700 nm with an average under 300 nm. Larger particles (such as actual micron-scale particles) of copper do not adequately penetrate the wood cell walls. These micronized preservatives use nano particles of copper oxide, for which there are alleged safety concerns.

A competitor of Osmose, Viance, has waged what Osmose terms as a “negative public relations campaign questioning the effect”.

Osmose President Paul A. Goydan calls the campaign, “desperate, deceptive and damaging to the entire treated wood industry, including preservative manufacturers, wood treatment companies, distributors, retailers, contractors and deck builders.”

The chemical retention level of Micronized Copper is 0.23 lb/ft3 in order to meet the IBC (International Building Code) requirement of a UC-4B for structural in ground use in post frame buildings.

East of the Rocky Mountains, MCA has become the pressure treatment of choice for one of the large “box stores” as it requires no special fasteners (unlike ACQ treatments). ACQ treatments have been found to more quickly erode fasteners in contact with the treated lumber than the former CCA, and now….MCA.

Based upon the evidence at hand…although there is not a ten year or more history of MCA use, Osmose has obtained approval by the Building Codes for their product, and I’d not think one of the largest Big Box stores in America would endorse it’s use without close scrutiny.  At this point, I would have no reservations using MCA treated lumber in any building of my own.

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Pressure Treated Lumber: Copper Azole

Most of us – both those who specify wood treating and those who use it, look upon the litany of possible wood treatments like alphabet soup.

Lumber Treatment PlantOr maybe more like Scrabble – where my 19 year old daughter always seems to either draw the right letters, or make otherwise incomprehensible words (to her Dad anyway) out of a total jumble.

Copper azole preservative (denoted as CA-B and CA-C under American Wood Protection Association/AWPA standards) is a major copper based wood preservative which has come into wide use in Canada, the USA, Europe, Japan and Australia following restrictions on CCA (Chromated Copper Arsenate). Its use is governed by national and international standards, which determine the volume of preservative uptake required for a specific timber end use.

Copper azole is similar to ACQ (Alkaline Copper Quaternary – read more at https://www.hansenpolebuildings.com/blog/2012/06/acq-treated-lumber/) with the difference being the dissolved copper preservative is augmented by an azole co-biocide like Tebuconazole instead of the quat biocide used in ACQ. The azole co-biocide yields a copper azole product which is effective at lower retentions than required for equivalent ACQ performance.

Here in North America it is marketed widely under the Wolmanized brand in North America.

The AWPA standard retention for CA-B is 0.10 lb/ft3 for above ground applications (UC-3) and 0.21 lb/ft3 (pounds of pressure treating chemical retained per cubic foot of wood) for ground contact applications (UC-4A). Type C copper azole, denoted as CA-C, has been introduced under the Wolmanized brand. The AWPA standard retention for CA-C is 0.06 lb/ft3 for above ground applications and 0.15 lb/ft3 for ground contact applications. Both CA-B and CA-C require a retention of 0.31 lb/ft3 in order to meet the IBC Code requirement of a UC-4B for structural in ground use in post frame buildings.

For detailed information on pressure treated lumber for structural in ground use: https://www.hansenpolebuildings.com/blog/2012/10/pressure-treated-posts-2/

The copper azole preservative incorporates organic triazoles such as tebuconazole or propiconazole as the co-biocide, which are also used to protect food crops. The general appearance of wood treated with copper azole preservative is similar to CCA with a green coloration.

Every piece of pressure treated lumber will have a tag on it stating what treatment chemical was used and to what level it was treated.  Be sure for look for these tags.  Don’t get fooled by companies stating they use wood treated for in ground use, only to be sent lumber with inadequate treatment.  Your future question to me will be “why did my posts rot?”  With the right chemicals, and the right level of treatment, your letter will have two words, “Thank You.”

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ACQ Treated Lumber

Pressure-treated lumber has been available for about 60 years. Most original formulas centered on arsenic as the main preservative, to help lumber withstand the extremes of outdoor use. While over time small amounts of chemicals from treatments such as CCA may have leached out of the treated timbers, a 2004 report in Wood and Fibre Science stated soil contamination due to the presence of CCA treated wood after 45 years is minimal.

As one might expect, the use of a potentially-poisonous substance like arsenic was cause for considerable concern, particularly when children are exposed to such installations. However, a Florida Department of Health panel of physicians found no published clinical evidence in the medical literature of arsenic poisoning in children resulting from CCA treated playground equipment exposure.

To address the pressure treated wood safety concerns, in 2002, the United States’ Environmental Protection Agency convinced lumber manufacturers to find a non-arsenic based formula for treated. The result was ACQ (Alkaline Copper Quartenary) treated lumber.

The new ACQ treated lumber contains a very high level of copper to replace the arsenic. While this reduces the desired risk of poisoning, it does present a different, but very dangerous problem: increased levels of corrosion.

Simply put, ACQ treated lumber is extremely corrosive to metal fasteners such as nails, screws, framing hangers as well as metal siding and flashings. The problem is you end up with two metal compounds in direct contact with each other in an exterior application so water contact is going to happen.  When two metals in direct contact with each other are surrounded by an electrolyte (water) rapid corrosion of the metal on the lower end of the electromotive series will occur.

Significant issues were seen early on in the outdoor deck industry. Here, standard joist hangers decayed rapidly due to the chemical interactions.

In post frame construction, the biggest concern was with contact of the pressure treated skirt boards (splash planks) with steel base trims or steel siding. Most quality providers went to isolating the skirt boards from the steel by uses of waterproof barriers and fastening the steel at the base of the walls with stainless steel screws. Nails with higher levels of zinc coating became prevalent as well, for fastening ACQ treated lumber.

The end solution was the short popularity of ACQ treated lumber. Copper Azole (CA) and Micronized Copper Quaternary (MCQ) have now become the pressure treatments of choice, as they have significantly lower tendencies towards the electrolysis issues seen with ACQ. While MCQ is less corrosive to metals, one of the “big box stores” continues to recommend the use of galvanized fasteners with it.

This entry was posted in Lumber and tagged , , on by .
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