Article No: 96
What do you do with a biology degree? Build cast-in-place houses, of course!
By: Carole McMichael
There are tornado warnings, and the power has gone out. A concrete homeowner goes into a closet to find a flashlight. When he comes out, he finds that the tornado has torn its way across the land only about 500 yards away - and he never heard a thing.
Photo by John Childs
That kind of experience is not surprising to people who live in concrete houses; and hearing about it is starting to get through to people who have lost their home to natural disasters. However, there is still resistance on the part of builders. In the Kansas City, Mo. area where John Childs builds, wood-frame is still king and to many of those builders, trying out concrete means learning a whole new "difficult" system.
Would that be so difficult? Childs, president of Secure Structures Inc. (www.secure-structures.com) based in Raytown, Mo., doesn't think so. He worked for a concrete builder after he got his degree in biology. Yes, biology! But his experience convinced him that he wanted to build concrete homes; and with an offer from Wall Ties & Forms (www.wallties.com) to become a distributor, he formed his own company in 1999 at age 24. Since then, he has built a commercial building for Wall Ties and several custom homes. About eight months ago, he finished a 3,400-square-foot, Southwest-design ranch with a walk-out basement in Lone Jack, Mo.
Childs used Wall Ties' removable aluminum forms for cast-in-place concrete construction. The system offers forms with two-, three- and four-hole options, a variety of ties, blockouts and blockdowns, and hardware and accessories. There are also brick-look forms, super lightweight forms and bracing designed to simplify carrying and using the forms.
According to Childs, the system can add 5 to 10 percent to upfront costs compared to a traditional wood-frame house, but that varies from builder to builder and reflects the complexity of the style. "Whether it's concrete or wood, we are quite competitive," Childs said.
When the Lone Jack clients started shopping for a builder, they were open minded about what system to use, but adamant about certain features. They wanted a concrete deck with columns, which would be pretty much maintenance-free, and also a concrete roof. Child's bid was low enough that they could afford to do both.
From the Beginning
The time spent on upfront preparation depends on how complex the plans are. Clients come with a basic floorplan and ideas of what they want.Then, Childs works with the clients to figure out solutions and come to an agreement. All working blueprints also have to pass the scrutiny of a structural engineer and be stamped before he goes for permits.
"We modified some interior floor plans slightly to fit with the forms," Childs said. "For example, we like to stack bathrooms because it is more efficient to place a sink or something that has to have a vent in that way. Also, we can't run a 2-inch pipe in our walls, so we run our mechanical stuff through wood-frame walls around the bathrooms.
"Before beginning construction, we will do soil testing if it is questionable. Our slabs are designed to work with minimum soil requirements, so we can build on really horrible soil (expansive clay) and the slab will still be okay. If it is placed on really good soil, it will go above and beyond.
"I bring the forms to the site on a 35-foot knuckleboom truck. All the forms just stand up on the back of the truck. Whenever I plan a job, I figure that if I can get a concrete truck onto the site, I can get my truck up there. Some sites can be challenging. If there was a problem, I could try having the bulldozer driver haul the forms up."
The general process for building homes with a basement, using Wall Ties, involves digging the hole for the foundation and pouring the slab on grade, as opposed to pouring footings, and then pouring the floors afterward. Next, Childs puts a water stop around the perimeter of the slab. After that, he sets up exterior wall forms on top of the slab for the basement wall, interior walls and forms for the deck, which is the ceiling.
Four inches of expanded polystyrene is placed on the exterior side of the wall form, rebar is placed 16 to 18 inches on center and four inches of concrete is poured in the interior side of the wall. All this is poured at once. When the concrete is set, the forms are removed and set up for the next floor, which is poured along with the interior walls. There were three major pours for the Lone Jack house. It took about eight days to get to the first pour, using a small crew - usually four men including Childs, instead of a full crew of 10.
Working in Winter
"In winter, I have a small crew," Childs said. "The weather affects the building schedule some, but it is affected more by people's mentality. About October, they start thinking, 'I will wait until spring.' We can work year around as long as we are not pouring concrete on frozen dirt. We poured one house in the dead of winter, doing the slab in the fall, and the shell in January. When we pulled off the forms, it was 15 degrees outside, but felt like 100 degrees inside where we had heaters running. We had blankets on top of the concrete and the foam was in place. You have to remember that when concrete is curing, it gives off tremendous heat.
"I hire mostly young guys for my crew, and train them as I get them. If I get guys with some general construction background, it is easy to train them. They figure it out pretty quickly. The guys who have done foundation work like the speed of it because they are in and out in a day. The only real training for them is in learning to cut foam properly for putting in windows. We pour windows in place. On some, we use window bucks; on some, blockoffs, which are flush plates around the window; and on some, aluminum forms. Sometimes in custom homes, I don't have all the window sizes in aluminum, so I use wood.
"I also train the crew to place the conduit, lights and electrical boxes in the forms, along with the foam insulation. Before we get started with construction, I sit down with the homeowners and we settle where they want the electrical boxes. What most people want is above and beyond what the code requires. I also sit down with the heating and cooling guys, to determine where we need ducts and returns. Once the concrete work is done, I contract out roofing, utilities and heating. From there, it is like a traditional house."
Probably the most challenging design feature in the Lone Jack project was the use of 45-degree angles. "It is not a problem for the forms," Childs said, "but we did some reshuffling to make the best use of space. The interior walls were framed by 2-by-4s, then finished with sheet rock and plaster. Some 20 percent of the interior walls were exposed concrete with a gypsum-based plaster troweled on.
The ceilings, which were also exposed concrete, were plastered as well. The exterior was finished with acrylic stucco applied directly. To do stucco on a wood-frame house involves an extra step with a vapor barrier. We chose the acrylic because it's kind of flexible; whereas real stucco is rigid and cracks a lot. Floor tiles were also laid directly on the exposed concrete. The tile layers like that because they didn't have to put down concrete board first, as they would for a wood-frame house."
As long as there is a variety of bodies controlling building codes, concrete builders will have to deal with a variety of inspection situations. "Although some city code people understand the system," Childs said, "others aren't familiar with it. We would go to plan examiners and there would be no problem, but they were not the ones doing the inspection. Our 'out' on this was to have a third-party engineer come in, which is okay in the Kansas City area. We just call him up and he comes at the time I designate. It is worth it for me to have the inspection on schedule, as opposed to waiting for city inspectors who might not come for two or three days.
"We don't need a slump test every time we pour. We did one when we did our first house; and then a destruct test on a cylinder at seven days and 28 days to see what the psi (pressure per square inch) was. When we changed ready mixed suppliers, the ready mixed people did the tests. Because we use the same mix now, we don't have to retest."
The Energy Advantage
Wall Ties & Forms system puts all the concrete on the interior side of the form. That makes the best use of the thermal mass of concrete. Using the expanded polystyrene foam adds to the benefit because the concrete gets into the cells of the foam and adheres to it. When foam, which has an R-value of about 20, is put directly on a surface that has no air infiltration, that increases the R-value by one half. So, the R-20 would be increased to R-30.
"Some heating and cooling people estimate the R-value at R-45 or R-50," Childs said, "because the formula is based on wood-frame houses that have air infiltration, which concrete doesn't have. We have to educate the homeowners that this system is not like wood. You are not heating the air inside the house, but rather, heating the house (the concrete heat sink). Our foam is on the exterior and we have 18 inches of fiberglass insulation on the attic floor. It is kind of like a thermos. Once you get it to the temperature you want, it takes a lot of energy to change it."
Childs' experience on some of the first homes he built taught him that a cast-in-place house requires an HVAC unit only half the size used in a traditional home. In fact, the houses are so tight, they need to install an air exchanger to bring in fresh air and remove humidity. The exchanger has its own humidistat, so it comes on when the humidity in the house goes above the setting. It uses the fan on the furnace, whether the furnace kicks in or not.
"In the summertime, you have to use some air conditioning, but not as much as in a wood-frame house," Childs said. "It can be 95 degrees outside and 73 degrees inside. The wall stores the coolness and it stays at the temperature it is set at. We did find it was easier to keep the heat level than the coolness level, probably because of the appliances, lights and showers that add heat and humidity to the air inside. Even the same temperature settings feel better. For example, some of our clients lived in an old wood-frame house. They kept the thermostat at 72 degrees in winter. In the new concrete house, they set it at 68 degrees, which they found more comfortable than the 72."
The Builder's ViewChilds took that sharp career turn from biology to building concrete homes with Wall Ties because he can offer energy efficiency, quiet and a much stronger and better house. He noted that a lot of customers look at the extras they can put their money into and trade off the solid, long-term benefits of concrete. For this reason, he found that the best market for concrete homes are people close to retirement who want to build their final house, something that will last and keep the maintenance costs down.