bracing applications for wood structural panels

By Jack Merry and Kevin Hayes APA-The Ensineered Wood Association

OSB Producer"'O7

Lpbuilding Products

Louisiana Pacific Corp., Nashville, Tn., the longtime leader in OSB production and sales, curtailed OSB production for one to two weeks at five of its 15 mills last fall.

At the time, executive v.p. Jeff Wagner said, "We cannot continue to operate our mills at full production across the system when the cost of manufacturing OSB exceeds the product's market value."

However, the company's annual production rose slightly last year-to 6.011 billion sq. ft.-as older OSB mills were converted to the production of higher-value spscialty products. Earlier this year, the millin Hayward, Wi., began producing LP SmartSide OSB siding on both ot its two lines. In Houlton, Me., a new OSL facility is being constructed on the site of an older OSB mill. ln addition, LP has obtained marketing rights to additional LVL capacity being constructed on the West Coast, scheduled to come on line early next year.

Peace Valley OSB, a mill in Fort St. John, 8.C., that is jointly owned with Canfor, should reach full production early next year.

A S CONTRACTORS strive to .Cl,meet building code requirements in high wind and seismic areas, they seek efficient solutions. APA is at the forefront in bracing research that defines those solutions.

Some test results are now accepted practice, while other recommendations are working through various code committees. Here is a look at where wood structural panels have made significant gains in codes and building guidelines and what's on the research horizon.

Narrow Walls, SlPs Make 2OO7 IRG Supplement

APA's Narrow Wall Bracine

NNorbord

Norbord Industries, Toronto, Ont., started up a second line at its OSB millin Cordele, Ga., last December. The facility is now running at 80o/o of plant design and is expected to be fully operational by the end of the year. When fully operational, the new line will boost production-which was 4.37 billion sq. ft. last year*by 15%.

When conversion work is completed at the mill in Nacogdoches, Tx., by year's end, all of the company's nine plants will be run on biomass energy-reducing natural gas use by more than 50%, at an annualsavings of more than $10 million.

Method (NWBM) was accepted for use anywhere in the house, including over raised wood floors and second stories. Previously limited to the garage, it has achieved widespread use by builders who fully sheath their houses. They recognize it as a cost effective solution to meet bracing requirements in narrow wall applications and provide the best value to their customers.

The APA method was also expanded for use in any Seismic Design Category (SDC) permitted by the International Residential Code (IRC). whereas it was previously limited to

nWeyerhaeuser

Ylleyerhaeus€t, Federal Way, Wa., responded to decreased OSB demand by curtailing production late last year at its OSB mill in Miramichi, $ask. ln February, annual production was decreased more than 500 million sq. ft. at the mills in Drayton Valley, Alb., and Sutton, W.V.

"Despite the best efforts of our mill employees, we cannot avoid reducing supply,' said Phil Dennett, vice president of ilevel Strand Technologies, We're taking this action to balance our production with market demand."

The company's nine North American mills have annual capacity of 4.3 billion sq. ft. and produced 4,166 billion sq. ft. last year.

A-C. Builders now have a code compliant bracing option for use throughout the home. The 2007 supplement to the 2006 IRC will continue to limit the use of this user-friendly system to walls that are continuously sheathed with plywood or OSB. (No more than four NWBM segments are permitted for each wall line and they may not be stacked. APA will address these restrictions in the next round of code hearings.)

Structural Insulated Panels were also adopted into the IRC for wall applications. APA, on behalf of the Structural Insulated Panel Association, submitted the prescriptive specifications and installation details after conducting several series of tests in support of the proposal. Builders using SIP walls in residential projects will no longer be required to conduct additional engineering to show equivalency to the prescriptive method for other framing systems in the IRC, thus facilitating the use of SIPs in residential construction and potentially doubling the use of OSB wall sheathing panels along the wall line.

Arnsworth

Ainsworth, Vancouver, 8.C., permanently closed one production line at its mill in Bemidji, Mn., last August, reducing annual production by 300 million sq. ft., for a combined capacity of 3.135 billion sq. tt. a year at its seven OSB plants.

"The high costs of production, coupled with current market conditions, made it economically unsustainable to continue operating this line," said chairman and c.e.o. Brian Ainsworth.

In September, production was suspended at the company's mills in Grand Rapids and Cook, Mn., although Cook reopened in March of this year. Construction costs for a second line at the mill in Grande Prairie, Alb., rose to $260 million when a continuous press allowing flexible production of OSB, OSL and LSL was included. Final installation of machinery and startup programming at the Grande Prairie millwould take 90 days with a lull crew. However, due to market conditions, only a small crew is currently onsite.

Using Wood Structural Panels for Shear, Uplift

In 2005, the Institute for Business & Home Safety (IBHS) published Guidelines for Hurricane Resistant Residential Construction. The document is based on the Standard Building Code Congress International legacy standard SSTD 10-99, the first U.S. standard written to address hurricaneresistant residential structures and still referenced in both the IRC and International Building Code. In the 2005 Guidelines, IBHS updated this existing standard to more closely reflect current IBC and ASCE-7 wind loads, wind speed maps. and conventions.

In 2006, APA worked with IBHS to contract full-scale combined shear and uplift testing at Clemson University to verify the analytical work done previously by APA staff. The tests were successfully completed and the previous tables were then adopted with minor modifications by the IBHS through the issuance of errata. This

Georgia-Pacific Corp.,

Atlanta, Ga., which became part of Koch Industries at the end of 2005, continues to operate under its own name as part of Koch Forest Products.

The company has seven OSB mills with annualcapacity of 2.7 billion sq. ft. Production last year totaled 2.5 billion sq. ft.

Grant Forest Products is now negotiating with workers at its millin Timmons, Ont., who were locked out nearly a year ago after a new contract was denied. Many believe that the workers would have been laid otf eventually, due to the high price and low supply of wood. The company's other Canadian OSB mill, in Englehart, was not affected by the strike.

Granl's first U.S. mill, in Allendale, S.C., is currently in start-up phase. An identical plant is currently being constructed in Clarendon County, S.C.

document has been adopted by the state of Florida for residential structure design. Wood structural panel sheathing or siding may be used to resist shear and uplift simultaneously provided the following are met:

. Anchor bolt spacing shall be 16 inches or less on center.

3x3xo.229" steel plate washers shall be used at anchor bolt locations.

. Nails in any single row shall not be spaced closer than 3" on center.

These conditions effectively eliminate cross-grain bending as a failure mode in the bottom plate, as shown by full-scale test results reported by independent testing organizations. This concept is also in the International Code Council/American National Standards Institute document that will replace SSTD 10-99, which is in the final stages of development.

Vanguard of ResearchWhole House Testing

The impetus for APA's whole house test program, which began early last year, was a contentious IRC code change hearing in October 2005 at which APA proposed a change to the code's narrow wall bracing provisions.

Ironically, although APA lost its

EHGII{EERED woons

Huber Engineered

Woods, Charlotte, N,C., has responded to decreased demand by making more value-added, specialty product$ at its five OSB mills, which have annual capacity of 2 billion sq. ft.

'We dont make a lot of commodity OSB," said new president Brian Carlson. "Our strategy for over a decade has been specialty and value-added O$B products." He added that a challenge for the company is to get more osB into each home, since fewer homes are being built. "Plywood is probably a pretiy good target for us" in this effort, he said.

Construction of a proposed mill in EmanuelCounty, Ga., has been put on hold, although land was purchased and permits are going forward. oWe're going to base the decision b move forward on overall market conditions," said Carlson.

bid to gain approval of its proposal at that time, the code hearing outcome gave rise to APA's whole house test program, formation of new wall bracing advisory committees, and initia- tion of efforts to revise the American Society for Testing and Materials (ASTM) standard method for cyclic testing of walls-developments that in the end helped vindicate APA's engineering conclusions. The new test program also laid the groundwork for the aforementioned code approvals and should provide the basis for a variety of new prescriptive wall bracing designs gaining code acceptance.

Tolko Industries, vernon, 8.C., began production last winter on a new tongue & groove and sanding line at its millin Meadowlake, Sask. However, production here and at the mill in High Prairie, Alb., was curtailed severaltimes this year. After three-week production shutdowns lhis summer, bolh mills are now operating at reduced levels.

The company's mill in Slave Lake, Alb., which was purchased from Weyerhaeuser in 2004 and was slated for improvement, also experienced several cuilailments.

A larger $250 million Slave Lake plant-which has a 70.3 meter continuous Bres$ and an annual capacity of 750 million sq. ft.-is expected to begin producing margin-added products such as OSL and webstock this fall.

More broadly, notes APA Quality

-trANQR-

Canfor, Vancouver, 8.C., lowered production at its PolarBoard OSB millin Fort Nelson, B.C., early this year, then again during the summer,'The lumber and panel markets today are extremely difficult," said president and c.e.o. Jim Shepherd. "Add to the mix the disruption of a CN railstrike, which requires us to change our operating plan."

Canfor also co-owns with L-P a newer, larger OSB mill in Fort St. John, 8.C., which expmts to ramp up to full production of 820 million sq. ft. annually by early n€xt year.

and Technical Services v.p. Tom Williamson. the test program is advancing "overall understanding of building performance under extreme loads and thereby serves the life safety interests and aesthetic preferences of both the design and construction community and the home buying public."

APA now operates one of the few laboratories in the country capable of full-scale three-dimensional structure testing.

"We're very excited about this project because of its long-term potential for supporting the structural wood panel industry's wall sheathing market goals," said APA senior engineer Tom Skaggs, P.E., Ph.D. Skaggs designed the test equipment and supervises the day-to-day tests.

The tests employ a state-of-the-art device that applies a maximum 65,000-lb. lateral load to a full-scale three-dimensional house. The test setup is designed to record the response of both the wall and overall building with different bracing methods and configurations. The equipment has the capability of testing the structure to complete collapse.

The results of the ongoing tests are being summarized in progress reports posted at www.wallbracing.org. To date, seven reports have been issued.

Although data from whole house testing is expected to carry substantial weight in future code change deliberations. the data alone won't automatically safeguard or advance scientifically credible treatment of wood panel bracing designs. An ongoing challenge, notes Williamson, will be to make the data and conclusions understandable to code committees and to stay involved in committee-level code debates, discussions and negotiations.

- More information about APA's whole house test program, wall bracing, design issues and recommendations, code development updates, and related topics can be fitund on APA's wtt:w.wallbracing.org and on its blog.for design pro.fessionals ( w'wv'.apawood. o rg/pabkt g ). Among othe r backgrounders and articles, the blog site includes "The Evolution of Lateral Load

Design in Residential Construction," an overview of lateral load design developments over the past several decades. It.s primary uuthttr was APA senior engineer Ed Keith, P.E., also the author o/Wood Structural Panel Sheathing or Siding Used for Combined Shear and Uplift (Form H335). APA also hcts several publications on the subject of wall bracing, including Introduction to Lateral Design ( Form X305), Introduction to W all Bracing ( Fo rm F430), and Whole House Wall Bracing (Form G410). All can be downloaded.free from www.apawood.org.

l.ANGBOARD

Roy O. Martin, Alexandria, La., shui down its OSB mill in LeMoyen, La., January 31, 2007. That same day, the first board was produced at a larger, $200 million O$B planl in Oakdale, La. A grand opening was held in April.

The new mill can produce a full range of OSB products, from sheathing to oversize panels.

"Over the next 12 months, the new millwillreach its 950 million sq. tt. capacity," said sales mgr.

Bobby Byrd.

Langboard Inc., Quitman, Ga., continues to process almost all pine, rather than sott hardwoods, at its newly remodeled OSB mill in Quitman.

The biggest shifi, said sales mgr. Chuck Rigoni, is how much more the company is exporting. "Years ago, never thought we'd be doing so much exporting. We've been pleasantly surprised at the volume," he said. "Even if the domestic market goes up, it makes sense to stay diversified."

Arbec Forest Products, Saint-Leonard, P.Q., has been operating the former Tembec OSB plant in St. Georges de Champlain, P.Q., since early 2006. The facility was acquired from a debl-ridden Tembec by Emanuele Saputo, Jolina Capital, who soon afier purchased softwood lumber and pulp manufacturer Arbec.