Fit, form and function

Commerce Construction takes insulated forming systems to new heights, building a five-story dormitory, the tallest building ever to be built in the Western U.S. with the system.

It’s ironic that polystyrene – the same material used to make cheap styrofoam coolers that often don’t last as long as the beverages inside them – is being used as an effective concrete forming material on more and more jobsites.

Insulated concrete forming (ICF) systems have been around since the late ’80s. With roots in Canada where winters are cold and basements are often wet, designers there developed a system of using hollow polystyrene building blocks as in-place forming systems. Its high insulating properties and ease of use are gaining fans among engineers, architects, contractors and owners.

Commerce Construction, is a Los Angeles-based tilt-up construction contractor. “We self-perform construction in the southern California area, but also do general contract work in Las Vegas, Atlanta  and Denver. Our work is mainly tilt-up buildings for the industrial, retail, office and hospitality markets and some five- to seven-story buildings,” says Dan Rivett, vice president at the company.

Commerce Construction is taking ICF to new heights at Azusa Pacific University, where student enrollment tops 7,600, an over 11 percent increase in the last year. The Azusa, California-based Christian college faces a severe housing shortage where many dormitory rooms, originally built for two students, must house three students.

Commerce Construction is using the ICF system to build a five-story dormitory, the tallest building ever to be built with this system in western North America, says David Zeidman, Commerce Construction project superintendent.

"Most of our work is tilt-up construction. We don’t self-perform masonry work. This is our first experience building with the ICF and we are doing things no one else has tried. We went through training to learn how to use this product and we are coming up with many ways to adapt it to this jobsite," he says, "I think we are taking it to the next level of performance."

Tallest building yet
The 100,000 sq.-ft. five-story, 350-bed dormitory will be topped with a parapet roof, making it the tallest building to be built with ICF in the western United States. The facility has nearly 400 windows, which complicates the construction process.

"The selling factor for this type of construction is energy efficiency," says Russ Wiersma of Paramount Ready-Mix Concrete, which supplies Commerce Construction with the ICF supplies and accessories. "By insulating the concrete between two layers of polystyrene, it becomes a thermal barrier that repels heat or cold, depending on the climate. It has a three-hour firewall rating and has great noise control properties," he says. It’s also mold- and termite-resistant.

The ICF process is a proven performer for retaining walls and foundations in developments on California hillsides where contractors bench-excavate, but this is the first time it has been used in the area to build a multi-story commercial building of this size. The project offers many challenges to Zeidman and his crews.

"If this was just a box building, we could really fly putting it up. The ICF system would be very easy to install. But because of the number of windows and height of the building, we had to modify the polystyrene forms to meet our needs," says Ziedman.

The ICF systems commonly are poured in 3’ lifts, but to tie the spancrete floors into the building, Commerce Construction modified the forming system so the walls could be poured in two 4’ lifts. The final 12" of the wall is poured at the same time the spancrete floor panels are capped with 2 1/2" of concrete. "We use a laser to make sure we are staying level from floor to floor," says Zeidman.

The ICF blocks have handy snap-in rebar connectors for precise rebar placement. "Because of seismic concerns and the size of this building, we must use #5 or #6 rebar.  The snap-in holders built into the blocks’ webs accept only #3 or #4 rebar. So we must wire-tie the rebar to the webs to assure proper placement," Zeidman says.

To achieve the 4’ lift height, Zeidman and his crews use a spacer or adjuster block between the two lifts. Because of the tremendous vertical pressure of the poured concrete from the second lift, the crews screw 1/2" plywood straps into the plastic webs of the block forms to tie the spacer blocks between the two lifts together. "The screws go right into the webbing and the engineers say it has a greater pullout resistance than screwing into wood," says Wiersma.

"When pouring the first floor, we had three blowouts. We learned quite a bit about what we needed to do. If there is a blowout, though, it is easier to repair than a conventional form. You let the concrete come out, then because the blocks are modular, you just patch a new one in, reinforce the spot and repair it," he says.

The concrete must come to the site with a 5" to 6" slump so it flows consistently around the rebar and through the forms. For best results, the concrete must be consolidated with a vibrator no larger than one hp.

Because of the size and complexity of the building, all of the corners needed additional bracing. "We had to stiffen the corner forms with two pieces 3/4" plywood fastened at 90 degrees then fastened to the webbing with #6 drywall screws," Zeidman says. "We learned from the school of hard knocks. By the time we poured the third floor, we didn’t have any blow-outs."

Windows present challenges
Window placement and construction greatly affects the project. "It takes 28 days for the concrete to reach its compressive strength, but we can’t wait that long between floors. So we had to come up with a way to provide support across the window lintel so the spancrete panels could be put in place and the floor and final 12" of wall could be poured," says Zeidman

To protect the vinyl window frames from bending or failing under the weight of the spancrete floor panels, Zeidman and his crews worked with the engineers to devise a way to transfer the weight through a frame built with 4"x8" and 4"x4" members.

"We cut 5" holes in the vinyl window bucks which allows the concrete to form pedestals through the frame. These pedestals transfer the weight to the 4"x8" header without compressing the vinyl window frame," says Zeidman.

Setting the polystyrene blocks in place is easier than working with conventional forming, which is used around doorways and other difficult areas. "A pallet of the ICF blocks weigh about 200 lbs., and four workers can carry a pallet easily. This is a very congested jobsite, so any time we can move something without using forklift helps," Zeidman says.

Fall protection plans
To protect workers and provide a solid working platform, two types of scaffolding are used. "We decided to go with conventional scaffolding on the outside of the building because it provides easy access for workers who install the plywood forms that tie the walls and the floors together. It’s much faster for workers than using a man-lift, and the stucco contractor can use it when it comes time to finish the building," he adds.

On the inside walls, the crews use an ARXX alignment system which also offers a scaffold on the inside of the building. The workers plumb up the forms by adjusting the turnbuckles in the supports. Expanding foam bonds the polystyrene to the concrete base or footing and fills any gaps. "We pour within 1/4" accuracy so the foam fills in any low areas," Zeidman says.

Design speeds construction
Setting the polystyrene blocks in place is easier than setting conventional forms. The rabbeted edges help workers effectively lock the blocks in place vertically and horizontally. Rebar or conduit that must be placed in the form is also easy to install because it can be snapped or strapped to the plastic support webs.

Contractors achieve other efficiencies with the ICF system because the plastic webbing molded into the blocks provides an easy attachment point for drywall or other exterior finish.

"Electricians can use a hot knife to cut through the polystyrene to make conduit runs that will be flush and allow drywall installation over the top of them. If the wiring layout changes during the construction process, it’s no big deal," Zeidman says.

Published in the January/February, 2003 issue of Contractor Tools and Supplies magazine.

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