Having been happy with a four-story tilt-up dorm building and in great need of more, Boca Raton's Florida Atlantic University tapped Woodland Construction of Jupiter, Fla., a 20-year tilt-up specialist, to put up an even bigger, 600-bed student housing facility.

"Tilt-up is a fairly common construction system in this market," said Clayton Fischer, founder and president of Woodland. "It is probably one of the methods of choice over masonry because it is fairly economical compared to it. You have a finished wall that you don't have to stucco or plaster.

It is a load bearing wall, so you don't need a perimeter structure. It has the durability to meet hurricane codes on wind loads, and it is a little less labor-intensive than masonry. Everything is basically done flat on the ground, so you don't need scaffolding."

When Fischer went into business, nobody else was doing tilt-up as a subcontractor; so it turned into quite a niche market. They were the experts for a long time, but now there are a tremendous number of contractors doing it. Woodland differentiates itself by doing the "Houdini jobs," the tough, more complex type projects - those that call for casting on difficult sites, creating panels with different layers, a lot of corners, circles, arcs or different openings. They add to all that considerable, precise engineering to make sure everything fits the way it should.

One of the challenges in building the student housing facility was the site. "The site was tight because it was surrounded by occupied buildings," Fischer said. "We had an active construction site, some panels as large as 30 feet wide and 50 feet tall, and a number of construction vehicles. Even though we fenced the site, we had to be extremely cautious about everything we did."

Time was another challenge. The university needed to get the students in the rooms before the fall semester. If the building wasn't ready, Fischer would have had to pay to house 600 students in hotels and motels, so speed was key. They started construction in November, and finished in July on schedule.

A little different
"The student housing facility was a hybrid building, with a structural steel frame," Fischer said. "We built two and three-story panels outside the building on temporary casting beds and attached them to the steel frame, so the walls were a closure rather than load bearing. We did that for speed. As we were putting up the steel, we were building the wall panels. As soon as they got to the second story, we attached the panels to the frame and poured the floors. That way the trades on the bottom floors could get started sooner than in a conventional building."

Two identical seven-story towers are joined to a center core lobby area that accesses the two towers. There are 600 beds, or about 300 sleeping rooms. Rooms averaged about 600 to 700 square feet. There are units called "double doubles," which have two bedrooms, closets, a common bath with a shower, and a little entry hallway. Then there also are guest apartments, which have a dining and living area and a bedroom - probably for married couples. In the north tower, there is a staff apartment, which has a living room, dining room, little kitchen and two bedrooms. The lobby, which can be entered from both sides of the building is divided into a reception desk area and 10 rooms: a computer lab, three study rooms, a classroom, a laundry room, a conference room and four offices behind the reception area.

The interior was finished with drywall and sheetrock on walls and ceilings; the floors are vinyl tile. The exterior was stuccoed with color and a sand type texture. There were some applied moldings and a random pattern of reveals cast into the panels.

"We wanted to keep it pretty simple," Fischer said. "The reveals would kind of box in two sets of windows and leave a space. We changed colors on either side of the reveal to make the building more interesting. Actually, the main building is cream colored, areas in reveals were a kind of peach/tan color. The first floor is a dark tan up to the bottom of the second floor windows. At the top of the first floor, the fifth floor and the roof parapet, we ran a horizontal molding that projects off the building to give the exterior design some depth."

The entry, which is striking, has a walkway lined with Royal Palms, a courtyard with large concrete planters and a tilt-up covered walkway leading up to the lobby entrance. The large windows, using glazing impact systems on a par with bulletproof glass, are designed to withstand 145 mile-an-hour winds without shutters. The whole building is engineered to survive a category 3 storm.

Step by step
There was a tremendous amount of engineering that went into this project. For the foundation, it depended on the bearing capacity of the soil. In this area, Fischer could have encountered either coral rock or sand. The sugar sand is tough to work in. Fortunately, he had rock, which provided better load bearing capacity and could be driven on. He did isolated, big pad footings for each column. Then a concrete slab floating floor was poured.

There was also a tremendous amount of engineering to determine the structure's wind loads and the panels themselves had to be engineered for in-place loads. More importantly, because they are cast on the ground, they have to be engineered for the lifting. They will never go through more stress than in the erection process. Individual bars are tied in place before the pour, so the panels are reinforced to withstand the lifting.

"We also cast in special lifting hardware and connection plates," Fischer said. "The lugs are placed to incur the minimum amount of stress on the panel. Their location is determined by a lifting engineer using a computer program, so the panels come up plumb. We produce shop drawings for each individual panel, which has the dimensions for windows and doors as well.

"Layout for all this stuff prior to casting is extremely critical. There are very small tolerances. The way we build these panels is to chalk-line dimensions on temporary slabs and attach wood forms. The slabs are three inches thick with a nice smooth surface. We spray on a chemical bond breaker before we pour, so the panels don't stick to the beds. When we are totally done with the casting beds, we break them up and recycle them."

Fischer cast the panels' exterior face down. The reveals are "inneys," the moldings are "outies," attached later. The amount of steel added varied according to the panel. Because panels for this project were closure panels, they weren't heavily reinforced. They placed No. 5 rebar every 16 inches vertically and No. 4 rebar every 12 inches, horizontally. For tilt-up, this is considered pretty light reinforcement.

"The panels were attached to the frame every 10 feet on center, vertically, and every five feet on center, horizontally, so the frame was taking the wind." Fischer said. "At that stage, we tried to get 20 or 30 panels ready, and set up a big six-inch pump to pour 500 or 600 yards of panels. The average panel is about 18 feet wide by 30 feet tall. The lobby, which is one story, was the only part of the project with load bearing tilt-up panels."

Getting it done
"We ordered 500 or 600 yards of concrete and tried to produce a bunch of panels a day to keep the crew busy and get maximum use out of our equipment and manpower. The big trouble we had was getting as much concrete as we needed as fast as we needed it, in a busy market. They are so over booked, we would request 100 yards an hour and were lucky to get 30. It made for some long days."

Fischer poured the panels, let them cure for three days and then started erecting them. He did a compressive strength test, then a flexural strength test. To get the lifting strength he needed a little earlier, he beefed up the concrete mix a little bit.

Because of the summer rainy season, Fischer did a lot of the casting at night when it doesn't rain. They started at two or three o'clock in the morning. The panels cured enough to walk on in seven hours, but didn't have lifting strength for about three days. If they got caught in several days of rain, they would cover up the panels with plastic and fix them when the rain stopped. The concrete mixes have the right amount of retardants, so the heat is not a problem.

"On that project," Fischer said, "we used a 200-ton, 40-foot long crawler crane with a 150-foot boom to reach up seven stories. We had eight lift points for each panel, so we ran the cable through rolling blocks to produce even pressure through all the lifting inserts. To attach it to the steel frame, we set it in place, temporarily held it with 10 welds, then cut it lose and went to hook up to the next panel, while the guys finished up the welding. On a typical tilt-up project, on a good day, we could probably erect 30 panels in eight hours. For more detail on the tilt-up erection process, see woodlandconstruction.com.

Building a workforce
"Tilt-up is so common there is no problem finding trades that are experienced with it; but because there is a terrible labor shortage here, finding the crew is a different matter," Fischer said. "Our company has a pretty intensive recruitment/training program. Our workforce is predominantly Hispanic from Central and South America. We get families - fathers, sons and cousins. They are smart guys, who pick it up quickly and see that they can advance. I have one man from Guatemala who started as a laborer, but today, he is one of my best superintendents. We train and promote from within.

"Some of the workers don't have much construction experience when they come, but they have motivation. They are very loyal, and we take good care of them. Ten or 15 years ago, we could get kids here out of high-school. But it is hot, tough work, so we hardly get any of them anymore."

Woodland is widely known as an excellent tilt-up contractor, according to Fischer. Predominantly, the way he gets exposure is the work he does with architects and design engineers to familiarize them with tilt-up and make them comfortable with it.

"They can call me any time and ask questions - sort of some free consulting on how to panelize," Fischer said. "I'm their go-to guy. Once they have confidence in you, they spread the word around. We also have a lot of repeat customers.

"In the future, for residential, you will see more tilt-up in southern markets where you have hurricanes. Actual onsite residential is just starting to take hold."