The Clayton Residence is one of the largest and most remarkable homes built in the U.S. recently.

Completed last year in an affluent suburb northeast of Phoenix, Ariz., the home has more than 28,000 sq. ft.

With a home of this size in the Arizona heat, it was obvious energy efficiency would be essential. The design also included a large number of radius walls, which made many alternative building methods cost-prohibitive. “The owner and architect knew that ICF was the way to go with the build,” says Rod Fetters of Castle Rock Homes. “We just had to convince them that we could do smooth radius walls.”

Of the 1,000 linear feet of walls, more than 40% were radiused. Some reach 25 feet without intermediate floors.

Castle Rock is one of the most experienced ICF contractors in North America, and they got job. Based on installer preference, BuildBlock ICFs were the block of choice.

Fetters says, “The vast size of this home is hard to grasp. The 18-wheel semi trucks that made deliveries look like toys next to the steel I-beams and ICF walls.”

The home used 16,500 sq. ft. of forms for exterior walls, plus another 2,000 for interior and 450 landscaping uses. ICFs were even used for one of the fountain pool stems in the formal dining room.

In addition to the ICFs, the design takes advantage of a number of other technologies to stay cool. “One of the most sustainable design elements of a home in the southwest is to go underground to take advantage of the naturally cooler ground temperatures, and this home has maximized that benefit with more than 11,000 sq. ft. underground,” says Fetters.

When the steel lintel over the front entry was craned into place 28 feet above the floor, it was a perfect fit.

Above ground, the vast walls of windows have high density self-tinting glass, which are tied to automated window coverings. This provides protection from the hot Arizona sun and adds to the security of the home as well. High efficiency air conditioning chiller units ensure the home remains comfortable year-round.

Lighting is provided by what Fetters calls a “very sophisticated automated LED lighting system.”

He continues, “This home has numerous outstanding architectural features, but what catches the eyes the most is the radius walls and curves.” Of the ICF walls, 415 linear feet were radiused, compared to 575 linear feet of straight walls.

The floor plan shows five complete circles—some which rise more than 30 feet from basement to roof line—as well as a number of circular pools and fountains, all tied to a massive oval.

“The 72-foot oval in the main part of the house made the other circles look small and easy,” says Fetters. “The ICF radius walls on this part reached 28 feet tall without any intermediate floors.” The west section of this oval is interrupted by several huge concrete pilasters and a wall of glass. He says it was “a breathtaking moment” when the steel beams were craned into place to connect the three elements. The embeds were dead on. A perfect fit.

To break up the mass of a home this size, the architect used a number of different roof lines, adding ICF parapets to some sections. This created more than 21 different wall heights for the Castle Rock crew. “These multiple heights were so complex,” Fetters says. “It took a lot of math to get everything perfect. The overall complexity of the tall radius walls and the multitude of elevation changes make this home the most difficult we have ever completed.”

The scale of the home is immense. The semi truck at left is dwarfed by the size of the ICF walls.

The curves continue inside the home with staircases, china cabinets, and floor-to-ceiling glass.

He continues, “Another item that made this a very complex job was the use of multiple ICF core sizes and brands.” The deep foundations required a 12-inch core, which meant using a different brand of ICF for those sections. (BuildBlock now offers a 12-inch core.) In other areas, 8- and 6-inch cores were used. The thicker walls were needed to support the precast post-tensioned floors used throughout the house. Decks were cantilevered, cast-in-place concrete.

Building radius walls capable of withstanding the concrete head pressure generated in 12″ and 8″ core walls required what Fetters calls “old school ICF craftsmanship.” “With these homes, you cannot afford to be off your game,” he says.

Other complexities include the large number of door and window openings, and the “intense double mat of rebar” that had to be placed into the forms and integrated with the heavy mats of floor rebar that the cantilevered decking required.

Fetters says the hardest part was the initial layout. “We used a digital CTX Total Station device to dial in our walls,” he says

Then came the difficult job of stacking and bracing the forms. “Radius walls take attention to detail to pull off, but when they complete a full perfect circle, it takes a lot of craftsmanship and lots of adjustable bracing techniques,” he says. “We used more than the usual amount of strongbacks and bender board.” He reports that the Giraffe bracing was easy to work with, and allowed for easy access to the top of the wall so the inspectors could safely inspect rebar placement and observe the pour.

One ironic challenge on a project of this magnitude was a lack of space; for storage, for bracing, and for all the different trades. The storage issue was resolved by switching to a just-in-time system where ICF material was brought to the jobsite just before it was needed.

The subcontractor issue was trickier. “There were so many trades working at the same time,” says Fetters. “This can put the brakes on stacking production rate. We had meetings every morning to coordinate with the trades to help alleviate conflicts. The meetings brought everyone together as a team and the respect from each company was evident.”

In several areas, the foam was stripped off the wall for architectural reasons. In every case, this revealed perfect consolidation for the third-party consultants hired by the owners and the city inspectors. Fetters says, “Happy inspectors, happy stacking!”

The home is located in one of the most prestigious neighborhoods of Paradise Valley, and there was zero tolerance for construction waste migrating outside the jobsite. “This can be a pretty difficult obstacle with foam bead,” says Fetters. “and with the high winds during the build, we knew we had a challenge on our hands.” They eliminated the use of saws and used hot knifes to make all the cuts.

Situated on a corner lot with heavy traffic, the drive-by onlookers slowed the build somewhat, but that was nothing compared to the foot traffic. “Everyone wanted to know what it was being made out of and had to have ICF information,” says Fetters. “There were so many visitors it came to be an obstacle for the superintendent of the job.”

He admits “it’s a good problem to have,” and says, “We have been chosen for at least four other high profile jobs in the Phoenix area directly from the success on this project.”

He continues, “This house served as a local training tool for inspectors that were new to ICF construction, and has received many accolades from the city officials on how well the house was built, especially how straight and true the walls were.”

In addition to the local publicity, the home received national attention when it was selected to be showcased on the national TV show “Designing Spaces,” which did a full feature on the home and benefits of ICF. “This is a great segment and still continues to bring in leads,” says Fetters. The episode can be viewed online via this magazine’s website, or by searching YouTube.

He concludes, “Its projects like this that brings ICF more to the forefront.”