Article No: 119
Stepping up to the Habitat challenge
By: Carole McMichael
The Department of Energy's "Building America" program has set up a systems-engineering approach to home construction. The goals are to: produce homes that use 40 to 70 percent less energy; reduce construction time and waste; improve builder productivity; provide opportunities to test out new building materials; and focus on creating energy-saving technologies. The program pursues these goals by forming teams drawn from different segments of the building industry. There are currently five teams, which have worked on 483 projects with different industry partners. Several of these projects have been Habitat for Humanity homes.
"Habitat for Humanity partners with the community," said Dave Daniels, development director for Houston Habitat. "We find financial sponsors and volunteers to help us buy building materials and build a house in partnership with a working Houston family who earns between $19,000 and $29,000 combined income a year. At that level, they would not able to qualify for a mortgage. These families, when they are accepted into the program, are evaluated on their willingness to put in 300 hours of sweat equity into their house project and others. That way, they earn the right to purchase that home. We provide a 25- to 30-year loan at no interest.
"In 2001, shortly after the 9-11 disaster, the Houston affiliate of Habitat for Humanity (the largest in the country) decided to approach Building America. First, we went to the Portland Cement Association (PCA), and made a presentation to mobilize the whole concrete housing industry to build a whole bunch of Habitat homes. We already had the lots. Then together, we pitched the idea of building 50 concrete homes, one for each state. It ended up being five concrete homes - three out of ICFs and two using cast-in-place - in the Woodglen residential subdivision on the northeast side of Houston. By next spring, the subdivision will have completed 118 Habitat homes. Currently there are about 30 more to go."
Ron Ward, CEO of Western Forms Inc., a removable aluminum forms company, was involved at the inception of the Habitat team and in building the two cast-in-place concrete homes. In Woodglen, he worked as a coordinator with Keystone Concrete, a large concrete contractor in Houston and Austin and a Western Forms customer, which donated labor and form use.
Ward grew up in the concrete business, which his parents Bill and Dee Ward founded in Kansas City, Mo. when he was just 10 years old. The company, which has pioneered the use of aluminum forming systems in concrete home construction since the middle 1970s, is coming up on its 50-year anniversary.
"Most of what we have done has been outside the United States, in 42 countries," Ward said, "because in other countries, they prefer concrete homes to wood-frame. In the last 20 years, in Mexico, we have completed about 200,000 cast-in-place homes. In the United States, we've done only 2,000 total; however, recently, because of mold and the rising cost of wood and energy, things are looking more exciting for concrete.
"Currently, (after masonry) ICF systems are the most common choice, but, according to PCA, the fastest growing segment in concrete residential construction is the removable form system and precast."
The preference for ICFs over cast-in-place has grown primarily in the custom market because builders have been hesitant to make the investment in forms for individual projects. In the last two or three years, owner satisfaction with concrete homes has sparked enough market interest to attract builders, who are in the business of building whole developments on a speculative basis.
"They are looking for the most cost-effective way to build these structures," Ward said. "Removable forms deliver the most low-cost structure because they use an assembly line approach compared to building by hand. If you could see an aerial view of a 20-home project, you would see one area being cleared for a slab, then another with a slab being prepped, then another poured, then reinforcement added, forms being set and forms being removed. Doing things this way, they can produce more housing structures than with any other approach."
Ward noted that the company's effort to continuously refine and improve their product and assembly technique translates into the speed that makes removable forms the most cost-effective system for projects of a suitable size. Suitable size, according to Ward, is 100 or more units — the builder category best suited would be production builders whose projects are speculation driven rather than owner driven.
The process begins
Cast-in-place requires quite a bit of preplanning. Ward has a fairly good-sized engineering department that makes the form layout drawings, which indicate where everything goes and how the crew is to assemble the forms. Another part of preplanning is determining the optimum bill of materials. Typically, the builders and developers come to Ward with however many floor plans for models they want for their project. They request one set of forms that can be used for all the models. Ward does layout drawings, putting together a selection of forms that will allow them to do any one of the units, some with repetitive use of pieces, so there won't be a waste of capital equipment. Because it is the expectation of the builders that they are going to produce a structure a day, preplanning also includes an estimate of man-hours to get the structure completed according to that schedule.
"Working as part of a team of developers, builders and subcontractors, we get involved to an extraordinary degree before a project beginning, sometimes as much as six months, Ward said. "Above 100 units is where removable forms have their biggest advantage. When we get in those types of projects, all the work connected with cost, time of completion and sequencing of trades is extraordinarily important because whatever savings can be achieved on a per-unit basis gets multiplied by the number of units."
Western Forms offers a modular, handset aluminum forming system that configures to any type or size structure. A standard panel in the United States is 36 inches by 96 inches. A full metric panel is 90 centimeters by 240 centimeters. Because of the moldability of concrete, it allows builders a variety of shapes, textures and stains. For example; on the Woodglen houses, they used Monotex forms to create the look of brick. It was molded off of a popular brick used in the Houston area, then stained after the forms were stripped and the walls cured. Form liners can be developed to accommodate particular architectural designs. Western Forms provides a complete system, including window and door molds, and forms for floors, ceilings, canopies, parapets, exterior decks and extended decks.
The forms, which are sold rather than rented, should last through 2,000 uses or 10 years at 50 uses per year. Because the forms are aluminum (about 80 pounds per panel), they are lighter and larger than steel forms, requiring fewer panels and less total time in the assembly process - the advantage of speed. There is also an advantage over concrete block construction in doing a monolithic pour for the entire shell. There are no seams or cold joints to leak energy out or noise in.
Western Forms offers different configurations for insulation, which is key to the high R-value in concrete systems. They market a product called Comfort Wall, with polystyrene on the inside face or on the exterior face or on both - in essence, creating an insulated concrete form. Or they put the insulation between two concrete walls, sandwich fashion.
"All the Houston projects used sandwich wall," Ward said. "We set forms, then set the insulation. Protruding fiber- glass connectors cut the face of the form on both sides, holding insulation in the middle of the wall."
The Habitat project in the Woodglen subdivision used the same 1,200-square-foot floor plan that Habitat uses all the time. First, Keystone poured a monolithic slab. The next stage was to set up forms, using reinforcing dowels set in the slab. The panels, which have attached hardware built on the form were set and locked together, and walered to straighten any misalignment.
Electrical conduit was installed with the reinforced steel, so the wire could be pulled through the conduit later. An opening was also left for the plumbing connection. Then, the walls were poured. The forms were removed the next day after eight to 12 hours. A full cure took 18 to 20 days. The interior walls, where the plumbing was installed, were built of wood frame. A drywall compound was applied directly onto the concrete for the interior finish. Once the shell was ready for the roof, conventional wood trusses were used.
"In tornado and hurricane country," Ward said, "people are more likely to build a safe room with a concrete ceiling and then add a typical wood frame roof. In basement country, the basement usually doubles as the safe room. We do have deck forms developed whereby we can monolithically pour the complete envelope."
"The size of the crew," Ward said, "depends on how many men it takes to complete a structure in the desired time frame. That comes out to be the number of men in each one of the specialized segments of the assembly line. Typically, the wall crew would be from eight to 16 men to complete that portion of the structure every day. The number of crew for slab prep and pouring could be another 15 to 20. The idea is to line up the structure-building crews to lead the way and then line up the rest of the trades to follow through in such a way as to complete what they do at the same rate - a house a day.
"We take training requirements very seriously. We typically go onsite when training begins and stay with the new crew a week or two or however long it takes for them to become efficient and get into the daily cycle. It is more training intensive than other systems. There is a lot at stake for these developers, so it is important that they get trained.
For that reason, we have seasoned veteran people with 15 to 20 years experience to make sure they and their supervisors are highly trained."
For builders who inquire about removable forms as a way to build concrete homes, Ward has some key questions: how many units is he going to build and what is the cost objective that he has not been able to meet with another system?
"If we could meet his cost objective," Ward said, "we would take him to visit some sites of developers who have the same goals for the production rate, time sequence and cost; and let them create a builder-to-builder conversation. Our best marketing is to developers where cost and time are the primary parameters.
"In Kansas City, the concrete home business is small but growing. We have about 200 concrete homes in the area. That is only 2 percent of the Kansas City market, but we are working on programs to change that. The beautiful thing is the exposure and successful feedback from the people who live in a concrete home. It's hard to find someone who doesn't love it."