Caribbean curves in ICFs
By: Carole McMichael
Ever wonder what it might be like to move back to the mainland after years of living on a yacht in the Caribbean? Roger Loo and his wife Destiny did just that; but they brought with them an appreciation of living with the outdoors and a love for the beautiful curved shape of the shells they found on the Caribbean beaches and reefs.
To design their new home, the Loos selected Clifford Taylor of Clifford Taylor Architects, PC, located in Colorado Springs, Colo. Taylor has been a project architect for a number homes ("custom palaces") in California and the East Coast, but returned to Southern Colorado in 1989. This area, at the foot of Pike's Peak, was still primarily tuned to building wood-frame homes; so the Loos' project in 1998 was his first opportunity to design for insulating concrete forms (ICFs). Since then, he's done two other residences that were all ICFs, including a horse ranch.
In El Paso County, Colo, at 6,000 feet, the Loos have a five-acre wooded lot. Like the Southwest in general, the climate is semi-arid with a lot of diurnal fluctuation of temperature.
According to Taylor, building systems that create a good thermal mass will help even out Colorado's considerable temperature swings — from 70 degrees in the day to 20 degrees at night. That alone is a very good reason to use ICFs. However, the Loos did not come to Taylor planning on ICFs.
"The Loos' biggest concern was one of geometry," Taylor said. "They had been living in the Caribbean where the outdoors is as much where you live as indoors. They asked for a house without a lot of right angles or straight parallel walls, one that would let the outdoors in. That is one of the things that led us to ICFs. The other was the home's location, south of Colorado Springs. It is in a very beautiful valley called Red Rocks, which has big red sandstone monoliths; unfortunately, it has a major highway with a steep grade running through it. That means there is a lot of truck traffic about 500 yards from the home site. As the 18-wheelers come barreling down, you hear the hammering of the airbrakes and wheel noise. Because of this, the Loos needed something to give them quiet on the outside as well as the inside. Again, the answer was ICFs."
The house is designed as a series of accelerating radii, sort of like a nautilus shell. An outer wall built of ICFs is extended in a continuing curve at full house height beyond the main structure so the noise reducing properties of concrete help protect the large exterior space that is used for entertaining and everyday outdoor living. The design also included some poured retaining walls for the garden and the spa.
Designing a home with curved walls is always trickier than designing one with conventional straight walls. Taylor decided that ICF systems offered the most efficacious material for the design, especially when compared to wood.
"With ICFs, you have to create a seal from block to block, so each one has to be mitered slightly," Taylor said. "The crew cuts the end of each block at an angle. The outer curve has an 81-foot radius. This allows all the blocks in this wall to be cut at the same angle. We designed a jig to make the whole process more efficient. It is, however, always more expensive to build on a curve than on a straight line."
Sterling Penman Sr., a contractor with 50 year's building experience, subcontracted the erection of the ICFs to ESP Building Services, LLC, which uses Reward Walls Systems. Taylor selected Reward Wall after talking with the company's technical rep.
Reward Wall has well-established training and support. It offers a two-day training seminar taught by experienced system builders. Once the contractor is certified, he qualifies for an additional two-day onsite training session. Technical support is available as well. However, the Loo project was the first time the subcontractors themselves had worked with a curved wall design; and the training was geared to building straight walls, so it was a learning experience all around.
The design used three or four different radii as the interior walls moved toward the inner curve; so for each different curved wall, the contractor had to figure out the angle to cut. "We do our own concrete work," Penman said. "I laid the footers - I made up a line to lay it to, so the stacking would start out right. The first row has to be plumb and level to end up plumb and level. This process is much easier when you are working in rectangular layouts with walls that are 30 or 40 feet, but when you have curved walls that run 120 feet, that is a different story.
"It is also more difficult to do the bracing because the blocks have to be cut for a smaller inside. This means more bracing. The subcontractor provided steel removable bracing, but he also had to design some special bracing to accommodate the curved walls."
For the interior walls, Taylor also went against tradition. "We went with ICF interior walls," Taylor said, "because a lot of these walls were an extension of the exterior and we didn't want to shift plans. Also, there is a lot of glass. If we had changed systems when we moved from exterior to interior wall, we would either have to use a very wide stud wall or have a break in the wall. So, to keep the thickness consistent, we used ICFs. The interior walls were straight, but radiating out, creating radial segments that make the rooms wider on one side. We used Reward Wall's eForms exclusively for both exterior and interior walls.
"Stucco, which we used on the exterior, is ideal with anything with curved surfaces, but with curves as gentle as those in the Loo design, other exteriors could have been used. On the interior, we used sheet rock, which bends enough to make it relatively easy to install over such a large radius curve. There were two interior walls that had a lot of plumbing that were done in wood frame because large vents or waste pipes need more space than pressure pipes."
According to Penman, the electrical and plumbing contractors had not worked with ICF construction before. "They had to learn as we went along." Penman said. "I bought a couple of hot knives to cut the foam to run the conduit. A lot of wiring went up to the ceiling, but there were some conduits that were run horizontally. You can run it that way for a short distance, but for the 120-foot outer wall, you would have to have the electrician right there when the ICFs went up, even before the pour, to run it all horizontally.
"Our plumbing and electrical codes are not particularly strict. The inspectors were not uncomfortable with ICF construction, but it was new to them too. They talked to the contractors and had some things done differently, but it didn't take long for the inspectors to understand the system."
Letting the sun shine in
At first, the great expanse of windows — over almost all of the inner curved exterior — would seem to work against the energy benefits of concrete's thermal mass. Taylor pointed out that the home's placement on the site took advantage of passive solar orientation. Because there is an almost unbroken 120-foot wall where there is the least sun (only two small windows), the "energy budget" can afford a lot of glass on the sunny side where it does the most good and where you have the best view, which is also a major priority.
According to Penman, the huge windows required custom made window bucks. "We put the bucks in the openings," Penman said, "and poured to them, reinforcing them on the back side. The bucks actually made a bulkhead where the window was. We left them in so we would have something to nail the windows to. In some cases, we took out the sill, where we had a stone coping beneath the sill; leaving in the side bucks and the header.
"We got the windows from a Canadian firm, which manufactures glass that stands up to the frigid winters up North. The windows had to be custom sized and trucked down to Colorado. That was one of the harder parts of the job because what was supposed to take six weeks took 10 to 12 weeks. But that is the nature of the beast in building, especially when you are going out of the country for product."
The Loos' have a very efficient heating system, which they augment with hydronic radiant floor heating. The floors are concrete slabs, covered by tile and oak strip flooring over the radiant system.
On the outside, there is a retreat-like atmosphere created by a large flagstone terrace and a pavilion set at the end of the curved retaining walls. There are also arbor-style trellises with grapes growing on them, extending off the inner curve of the house. "It feels like a five-star resort," Taylor said.
Both Taylor and Penman, who have teamed up on other Reward Wall projects since completing the Loo house, believe in ICFs.
"Over the long-term or mid-term, an ICF-built house is a better investment of capital," Taylor said. "It would decrease operating costs, moderate the climate inside and create a quieter and healthier house to live in. Because of the three to four hours of fire protection from ICFs, owners get an insurance break. The trade-off to wood frame is paid back in two or three years from energy savings. By its very nature, ICFs yield houses that are better designed, better thought out.
Penman put his evaluation of ICFs in hands-on terms: "If I were going to build myself another house, I would build with ICFs."
Reward Wall eForm
The eForm waffle grid ICF requires 30 percent less concrete than other forms without compromising the integrity or strength of the steel-reinforced concrete wall.
EForm is designed to conform to standard dimensional lumber specifications, to make attaching the roof and interior wall systems easy. Each form is 48 inches long, 16 inches tall, and comes in either 9.25-inch or 11-inch widths. (The Loo home used 9.25-inch width.)
The lap joint design of the eForm allows for secure, quick stacking, while the raised marks of the recessed furring strips allow the builder to position the forms correctly to provide a consistent vertical nailing surface. The lap joint also provides support during placement of the concrete and relieves the builder from the task of cleaning dirt, debris and ice from the joints before use.
The polypropylene ties that hold the forms together provides an open design that allows uniform flow of concrete throughout the inside of the forms. This reduces the chances of voids or weak spots. A "chair" feature facilitates the correct placement of horizontal rebar according to engineering specifications.