Wood Makes a Statement
- By Michael Chazin
- June 1st, 2007
The Gunter Primary School, in Aubrey, TX, is an awesome sight. The building, completed earlier this year, is 37 ft. high at its tallest point and the reaction is that it sets just the right visual impression in this rural community outside of Dallas.It’s very modern looking, says Rick Cohagan, superintendent of the Gunter School District.I’ve had a lot of compliments on the way it looks. Just by looking at the school from the exterior, it’s not possible to know that it’s a wood-framed structure.
For decades, school buildings in Texas have been built exclusively with steel frames. Rigid frames are expected, especially when size requirements of schools often must include both a gymnasium and a cafeteria. While accepted as the standard, steel construction hasn’t always been the first choice of every school district.
At the Gunter School District, Cohagan seemed convinced there had to be a better way. Every metal roof he had ever worked under ended up leaking. Anytime you have a metal roof, they contract in the winter and expand in the summer, he says. If you have a plumbing stack or any kind of penetration they’re going to leak. In 2001, when it came time for the Gunter School District to build a 30,000-sq.-ft. middle school, Cohagan looked around for alternatives.
Time is Money
Time was a vital consideration. Steel frames’ shop drawings have to be approved, he explains, and invariably, time is lost waiting for approvals. Then there is the wait for the steel to arrive. The Gunter School District needed the school to be built in the shortest time possible. Wood seemed to offer the advantage of a shorter total project time.
Materials costs might have had the biggest payback. Wood not only came out less expensive than metal, but it was also possible to hire local tradespeople with wood construction experience. Metal construction workers just aren’t available as readily, and scheduling their time can drag out a project. The commercial framer used on the project had the equipment and crews available. Gunter Middle School, built in 2001, also used a wood frame.
The new primary school under consideration was to be twice as large as the middle school, 60,000 sq. ft., and presented its own set of challenges. Architect Fred Sahs had two issues with the project. The school board wanted the most economical construction possible and was adamant that the project be completed quickly.
Sahs is an independent architect who has spent years consulting on school projects for districts in Central Texas. He has worked for many school districts, some with budgets large enough to build whatever they wanted. More often than not, the rural school districts he worked with had the same demands for space and amenities; all they lacked were the budgets to make that happen.
How to Comply
The big question on the Gunter Primary School was whether a structure that large could be built out of wood and still be compliant with building codes. According to Donald Hampton Jr., the framing contractor who also functioned as the general contractor on the project, based on the size and scope of the structure, observers were certain that a wood structure that big couldn’t be built.
That was about the time that Ed Underwood, senior engineered wood specialist with APA-The Engineered Wood Association, got involved with the project. Underwood had heard about the project and offered his assistance. He showed Sahs how the basic allowable area with wood construction could be increased as long as setbacks were provided around the structure to accommodate firefighting equipment and fire barriers were built. If sprinklers were installed, the allowable areas could be increased.
Underwood also explained how using structural glued laminated timbers (glulam) could improve fire safety. Glulam is fabricated using individual pieces of kiln-dried lumber, laminated together under pressure to form large timbers. Glulam performs beautifully in a fire situation because it chars externally, says Underwood. The char has an insulating effect on the rest of the wood and it slows further burning. Steel fatigues rather quickly under high heat and collapses. Glulam performs much better; the char acts as an insulator and the wood supports the load.
With the knowledge that it would be possible to construct a fire-safe school with a wood frame and meet the rigid building codes, Sahs went to work. He hired a construction cost accountant who ran a comparison between wood and steel construction. That analysis demonstrated that costs would be lower if a wood frame were used. According to Cohagan the school construction cost about $83 per sq. ft. Additional costs were incurred to build three streets around the facility, buy additional land, and build a concrete parking lot.
A Complex Puzzle
Increasing the size of the wood structure from 30,000 to 60,000 sq. ft. required a lot more than just doubling the size. That was why Sahs was glad to learn that the glulam supplier could be called upon to provide engineering assistance. I was looking for them to help me because of the verticality and the volume, as well as the incorporation of the glulam beams,’’ says Sahs. I said you need to look over my shoulder on this, and they didn’t have a problem with that. He adds that he had an engineer on his end reviewing the project every step of the way just to be doubly certain of structural integrity.
The pre-engineered and cut wood pieces were methodically assembled over a period of months. Sahs describes the assembly of the school as reminiscent of a complicated jigsaw puzzle. As with any large project, construction had its share of minor hiccups, but nothing to hinder the framing schedule, says Sahs. We had to buy a few little pieces to fit that jigsaw, he says. That just happens, which is no big deal.
Hampton adds the assembly went quickly with practically no delays. Material was readily available, he says. If I needed anything I could have the material here within two days. You can just do so much more with wood, he adds, we easily made alterations in the field, which did not hurt the integrity of the structure of the building.
Fifteen structural steel columns were strategically placed for the main support. These columns are in the walls in the corridors or on exterior walls, says Hampton, and that leaves the rest of the building wide open. The steel columns help support the two structural glulam beams that are 12-in.-wide and seven-ft.-high. One is 82-ft-long and the second is 65-ft.-long. The longer beam weighed in at 19,000 lbs., and is supported on steel columns, says Hampton.
Making a Statement
When it came to the gymnasium and the cafeteria Sahs wanted to make a statement. In a small community like this, the town revolves around the school. These public areas are frequently sectioned off so they can be used by the community for outside activities such as Boy Scouts, concerts, or even weddings. That was where I wanted to spend some dollars so everybody could appreciate it, says Sahs. Not just the kids, but the parents of the kids and the whole community.
Everybody loves wood, and after seeing exposed laminated beams in some photographs from the supplier, Sahs knew what he wanted to do. The original engineering plans didn’t provide for any exposed glulam beams in the cafeteria or gymnasium. All the beams that we were putting in were going to be covered up, and I just hated that, says Sahs. He wanted to expose more of the beams, and as long as it was safe, the engineers were willing to make the changes.
Originally he had proposed chipboard ceilings in those locations, but he splurged, and for about $8 more per sq. ft. he used tongue and groove decking instead. It turned out beautifully, he says.
Sahs says the result created a visual delight. Everybody that comes in just says wow. One of the school assistants had her parents in from Oregon. After she showed it to them, they couldn’t believe that a space this striking could be built for so little. In the cafeteria, it is the volume of the space, says Sahs. You see how big it is — the vastness of the space, and the natural light open up the area. The gymnasium offers a similar visual impact.
Everyone involved with the project considers it a complete success. Cohagan has yet to see a downside and would definitely choose a wood frame school again. When he considers the money he saved and the aesthetic impact, he is even more likely to choose wood again.