Article No: 91
By: Carole McMichael
Think quality! Think high-end amenities and old European styling! StoneHaven fits the description. It is the latest residential neighborhood within Montreux, a 726-acre gated community development between Reno and Lake Tahoe in Nevada. Besides trails, creeks and a thick forest setting, StoneHaven has close access to a Jack Nicklaus Golf Course (holes 3, 4 and 5) and a huge club house. What isn't obvious to the eye, but is definitely a quality benefit, is that each of the homes in StoneHaven is built from insulating concrete forms (ICFs).
Jim Smrt, owner of Lake Crest Homes in Reno, is the builder. He has been using ICFs since 1997.
"There were a number of things that sold us on concrete," Smrt said. "At the time, lumber prices were spiking up, and just the overall lack of its quality. Also, we were trying to fill a niche. No one else in this area was building homes from ICFs. The big thing that sold us, however, was the response after we built one. The owners just raved about the efficiency, the quietness. Concrete is just a far superior product. I built my own home from ICFs about a year ago. It is unbelievable how it holds the heat or cooling, considering that it might be 25 degrees in the winter and 95 degrees in summer.
"The ICF we use is Arxx. We started out with another system, but changed because of the technical support we got from the Arxx company. Also important is the scaffolding systems that Arxx forms have in place. Not having that was one of the biggest fallbacks for other ICFs that we looked at. Most of our walls are 12 feet minimum, so the workers need to get on scaffolding. Another good thing about Arxx, is that you can cut the foam out in arch designs and stucco it, making it an inexpensive way to get some nice looking details."
Perhaps one the best arguments for using ICFs in this area is that they can stand up to Reno's tough weather. "We have pretty severe codes here," Smrt said. "We have to build to withstand 85 mph winds, seismic 3 earthquakes and then snow loads too, and houses have to withstand all three at the same time. Arxx stands up to that, but the engineering of the whole structure can be a problem.
"When you have big square boxes, normally that helps with shear walls, but these designs have lots of openings and tons of windows, some at the corners. When you have a lot of openings, it is hard to get shear wall transfers in high-wind country; so trusses can present a problem. We had to do some drag trussing, taking some of the efficiencies of one wall and transferring it to another, so the walls would 'calc' out. Wood-frame builders would sheet the outside shear wall with plywood, so it can't move laterally, but it is so much easier to get a good shear wall with concrete. Where shear strength is needed on the interior, we also use concrete."
Typically, wood-frame builders sheet the roof with 3/8-inch plywood, but that is not enough to handle the snow load encountered in StoneHaven, Smrt said. He usually puts on 3/4-inch sheets. The roof itself is done in concrete tile, using a "cold roof" method where the tile is installed 1/4-inch off the roof sheeting to avoid the effects of the freeze and thaw cycle.
The style of fine estates in England in the 1700s served as inspiration for StoneHaven. Architect Gail Ritchie, who chose a central, square box design with a stone veneer exterior. By using the simpler square form with no in's or out's, the development could hit a lower price point. The StoneHaven versions are flanked by wings and a three-car garage, all done in stucco. Each one, set on about a 1-acre lot, has a long driveway and professionally landscaped gardens that help create the look of an Old World village.
The two-story houses range in size from 2,500 square feet to 7,365 square feet. Seven different floor plans offering open designs generally include five bedrooms and six baths, vaulted ceilings with beams and ornamental decorative trusses. Still, the plans vary drastically and are customized further in cooperation with the clients, who want to do their own thing. Of the 17 lots initially available, Smrt has already completed homes on 12 of them. The Cottages and Manors, earlier parts of the Montreux development, served as models for perspective clients.
Preplanning is more critical when building with ICFs because making changes after the pour is difficult and costly. However, Smrt noted that when they got up to speed on the process, there was no real difference on paper between building with stick or ICF. The client and an architect who knows the system meet and work with Smrt's team that offers some "value" engineering to help make decisions on certain choices.
On the job site
"There are various ways to attach Arxx forms to the footing," Smrt said. "Some people pour a footing and go right to Arxx. We prefer to pour the footing and a stem wall, then build the floor. When the floor is all built, we start the forms, so, we are above grade with them. Our reasoning is: when you start below grade, you have to really protect the forms and that makes it more expensive, and it takes longer.
"We use a lot of number five rebar in the concrete at all the corners and around the windows. The rebar is spaced 16 inches on center both ways. At headers, it is 10 inches on center. We use 2-by-6s to inset the windows and install them to the 2 x 6s. If we want the inset on the interior, we can use the regular buck to hold the concrete in and a 2-by-10 as a sub-buck.
"We pour 8-foot of wall at a time. If we went higher, the aggregate would separate, so we go that high and do the rest of the pour the next day. We can pour in any season. Most of the time, we use a standard ICF concrete mix that gives 3,500 psi, but in winter, we use an accelerator in the mix. The pour on a house (about 4,000 square feet of concrete) would take up to two weeks to finish, depending on the complexity of the design."
For plumbing, Smrt blocks out conduit space. The electrical is put in the interior walls or in the ICF foam. Each of the houses is structurally wired, making them what Smrt calls "smart capable" to accommodate future technological upgrades. Some of StoneHaven's houses have elevators and the others have shaft space functioning as closets that could be converted to elevators if desired.
Expandable closed-cell foam is used for insulation to keep the houses tight. To prevent that tightness from negatively affecting indoor air quality, the houses include an air exchanger that pulls in 10 percent fresh air when the heating comes on. After the heating system reaches the desired temperature, the thermal mass of the concrete tends to hold it there.
"For example," Smrt said, "in a house under construction that didn't have the heating system in yet, workers complained that it was colder inside than out. The house was maintaining the cool temperature reached from overnight."
Smrt added that they had not tested the houses for energy efficiency, but think it reduces energy bills by 30 percent to 50 percent of comparably sized stick-built homes. The energy advantages of passive solar are often coupled with ICF building, but in StoneHaven, it would have to be a personal preference by the client. The trees in the heavily wooded lots often block the sun; and all design modifications have to go through the Montreux Design Review Committee, which does not allow the use of solar roof panels.
"We thought these houses were going to be a big market for radiant floor heating," Smrt said," but most of the owners use their homes as a second summer residence and didn't opt for radiant. Generally, if it is a primary house, the owners will put the money in for radiant."
Code and crew
The building inspectors are not very familiar with ICFs, according to Smrt. Instead of the regular inspectors, he works with a registered engineer, who comes out and verifies steel placement, watches the pour, takes the core samples from the concrete mix and checks pipes and wiring. This way, the building department doesn't have to learn anything because it is all outsourced. It adds about $1,000 per house.
The crew experience was more positive. "There was no trouble getting our four framing crews comfortable with the Arxx," Smrt said. "They were excited to do something different. They picked it up really fast, did it very well and enjoyed it. We were hesitant for a while because we thought building with ICFs was going to be so different, but the changeover was really fairly easy.
"Before we started, the crews got certified by Arxx in a two-day training seminar. Also, they all had some previous experience with our concrete contractor. Then, for the first job, we had a tech rep from Arxx through the first pour. It may be more common for crews not to want to change, but we have fairly young guys who weren't set in their ways."
"Why concrete? It is a far superior product. An ICF-built house will last 100 years and needs very little maintenance. At some point, I think ICFs will take over the residential market; after all, there are only so many trees we can keep cutting down. And once it catches on at the tract-housing level, it will take off."