The NAU Sky Dome

During the late 1960’s, a citizen’s group in Flagstaff, Arizona suggested that a major activity center be built in town with the major consideration that it be large enough to accommodate Northern Arizona University athletic events. Nothing came of this recommendation but NAU President Dr. Lawrence Walkup did not give up on the idea.

Dr. Walkup followed through by conducting a study and polling the students who expressed a desire for a covered multi-purpose facility on the Northern Arizona campus. The students wanted an on-campus facility that would include a skating rink plus room for athletic events and entertainment programs. Dr. Walkup then developed a plan to build a covered multi-purpose complex for multiple uses. He began by consulting Architectural firms and asked for proposals.

The Architectural firm of Rossman & Partners of Phoenix was selected to design the facility and they presented the idea of a glued laminated timber dome that would cover 6 acres under one roof. Most of the funding for this project was provided by the Arizona State legislature and after plans were completed the University accepted the $6.6 million base bid from Mardian Construction Co. in August of 1975. Western Wood Structures acted as a sub-contractor to Mardian for design and construction of the VARAX style timber dome.

The 502’ diameter facility was very economical even by 1975 standards because of its unique style of construction. A natural bowl at the site was further excavated to allow for the domed roof to rest on 36 concrete buttresses at ground level. This “Ensphere” design eliminated the need for expensive outside support walls. As a result, athletic events as well as most of the spectator seating takes place 30 feet below ground level. There are 15,200 permanent seats but capacity can be increased to 20,000 with temporary end zone seating. The timber roof is designed to support the huge volumes of snow that accumulate in Flagstaff.

When it was completed, the 502’ diameter NAU Sky Dome was the largest clear-span timber roof in the world. Since then, Western Wood Structures has constructed two larger domes – the 530’ diameter Tacoma Dome and the 532’ Superior Dome on the Northern Michigan University campus.

The Cathedral of Christ The Light

When the Cathedral of Francis de Sakes was rendered unusable following the 1989 Loma Prieta earthquake, the Archdiocese wanted to build a new Cathedral with a 300 year design life span. Glulam was selected as the main structural building component for its strength, durability, and aesthetic appeal.

The roof is composed of a large steel compression ring and a glass oculus. The oculus is supported by glass enclosed Glulam space frames consisting of 10-3/4” x 15” Glulam mullions that measure 103’ in length, 10-3/4” curved Glulam ribs that vary in depth from 30” to 19-1/2” and measure 97’ in length, and pre-tensioned steel rods that were manufactured in Germany.

Lathe turned Glulam compression struts connect the outer mullions to the interior ribs. Glulam louvers that vary in depth from 22-1/2” to 39” are set between each rib at seven different angles to optimize light effects.

Special attention was given to the appearance of the Glulam products. Lumber was hand selected by the manufacturers to minimize knots and voids on the exposed surfaces. Any voids were then left natural since standard fillers used to bring Glulam to Premium Appearance is often objectionable.

Western Wood prepared 67 pages of shop details from a three dimensional computer model to fully describe the Glulam components. In total, there are 26 vertical mullions, 26 curved ribs, 720 louvers, and 88 compression struts. The frames are connected with 249 unique steel assemblies and 42 unique rod assemblies.

Each Glulam member was pre-fabricated off site and many of the steel connector assemblies were plant installed to reduce jobsite costs. There were nearly 15,000 holes to pre-drill, all of which had to be accurately located. A hundegger machine was used to fabricate the louvers while the struts, ribs, and mullions were fabricated by hand. The long, curved ribs were trucked to the site from Minnesota and the rest of the Glulams were manufactured and fabricated in Oregon.

The jobsite’s proximity to busy downtown Oakland contributed to the construction challenges faced by Western Wood crews but assembly and erection of the Glulam system was achieved in just 3 months.

Wood Design & Building article.

Glulam Specifications

Specifications for Glued-Laminated Timber or “Glulams” are usually found in Division 06180 of the CSI numbering format. Specifications are written by the specifier in order to establish the standards by which the supplier or installer of the product is expected to adhere. We are providing a sample specification for those who wish to keep current as many things have changed over the years. By clicking on the link below you will be able to view and copy this sample specification.

The Ford Foundation Building

Roseburg, Oregon







Specifications of Glued-Laminated Timber Sample

Lower Burnett Road Bridge

The Foothills Rails-to Trails coalition of Buckley, Washington working in conjunction with Pierce County, had been seeking a link to connect the north and south sides of the Foothills Trail to replace the original railroad trestle that had been removed some years prior. The result is this stunning Arched Bridge that Western Wood Structures designed, fabricated, and installed.

The use of 3D modeling made possible for the bridge components to be fully fabricated prior to pressure treatment which in turn allowed Western Wood crews to complete the complex installation in less than two months. The overall length of the 3-span bridge is nearly 400 feet including approach spans and when complete the trail will measure more than 28 miles in length.

The use of pressure treated Douglas Fir Glulam as a bridge material perfectly complements the natural beauty of the wooded site.

STRUCTURE Magazine, October 2010 article

Dominion Creek Trestle

This 100 year old former Milwaukee Railroad trestle that once carried freight trains through the Montana backcountry is being retrofitted as part of a Rails to Trails project to accommodate bicycles, ATVs, and snowmobiles. This project was made possible thanks to $850,000 in Federal stimulus funding and will open miles of the Milwaukee Road passage through the dense forest toward St. Regis, Montana.

Western Wood Structures supplied the pressure treated 6.75” thick Glulam deck panels which were segmented to match the curve of the trestle. The walkway, which measures about 650 feet and rests 100-feet above Dominion Creek, is 12’ wide with 3-foot pedestrian walkways on either side. The project will be 80% complete before the snow flies this year with final completion scheduled for next spring.

The General Contractor is Dick Anderson Construction of Great Falls, Montana. Western Wood Structures met the tight shipping schedule by having the pressure treated Douglas Fir Glulams delivered in 8 to 9 weeks.

Nisqually River Estuary Boardwalk

Federal stimulus money was used to finance construction of the Nisqually River estuary boardwalk at the Nisqually River National Wildlife Refuge. The mile-long boardwalk is nearly half done and when complete it will be used to provide access out into the world of mudflats and tidal sloughs teeming with marine life and birds.

The project has reclaimed about 762 acres of the refuge, turning the delta back into the estuary and saltwater marsh it was before it was diked 100 years ago to create farmland. The goal is to restore habitat for salmon, shorebirds, and other creatures that thrive in estuaries.

The boardwalk superstructure is constructed from pressure treated Douglas fir. The preservative is ammoniacal copper zinc, or ACZA, which is approved for use by the U.S. Environmental Protection Agency. The decking is Port Orford Cedar Glulam. The boardwalk will have a life expectancy of 50 to 75 years. The U.S. Fish & Wildlife Service considered re-cycled materials for construction of this boardwalk but wood was chosen for its durability and strength.

Western Wood Structures designed this timber boardwalk and is in the midst of fabricating and shipping materials as of this writing. The General Contractor is Five Rivers Construction of Longview, Washington.

Award Winning Bridges

Western Wood Structures has been designing and selling treated timber bridges for 40 years. We have been fortunate enough to have been involved in some very interesting projects and our bridge sales have led us to nearly every state in the union plus Japan, Taiwan, and China. We are proud to show off some of our award winning bridges.

Award Winning Timber Bridges