Basements have become the home's lower level
By: Carole McMichael
Currently, builders don't talk about basements. The "basement" of yesterday has become the "lower level" of today because buyers expect to get every last possible square inch of functional living space our of their home investment.
In light of this trend, Concrete Homes is doing a series to showcase some of the basement-building options that fit this concept. Part 1 will cover E-Maxx Systems, Superior Wall Systems, Insul-Deck Systems and Cemen-Tech's material handling.
Tammy Williams, marketing manager for E-Maxx, said its system was developed as an alternative to insulating concrete forms, and is still a very new concept that meets in the middle between ICFs and poured-in-place.
E-Maxx gets dimensions from the builder in linear feet, the height and type and size of the foundation. They do a layout and make the E-Panels, E-Studs and E-Corners. Then, they are delivered to the jobsite and installed by the poured wall contractor. (It can't be used with masonry.) The system provides the EPS insulation, EPS studs and corners. The contractors use their preferred aluminum or steel-ply forms.
"With E-Maxx," Williams said, "the insulation can be on the interior or exterior, or both. Typically, people have chosen to put their insulation just on the interior. In the basement, when back-filled gravel covers the wall, exterior insulation would be wasted. You would be spending money on insulation and studs that you are not using. It all depends on the R-value you want or what the code requires. The heating costs are actually lower in the lower level, because it maintains a constant temperature being underground. When the concrete forms are removed, you have studs imbedded on the interior surface, so nobody has to do interior wood-framing."
The system is installed at the same time the crew installs the removable forms for the pour; so there is no extra process.
According to Williams, the product has sparked so much interest with poured-in-place contractors because they can do the same thing as an ICF does for anywhere from a half to a third of the cost and add only an hour to an hour and a half to the job.
Superior Walls offers a different option for building foundations. Superior manufactures precast, reinforced concrete insulated panels to custom wall dimensions. Besides the concrete face shell and Dow insulation, the wall system includes concrete studs that create "smart cavities" that allow space for added insulation.
"The walls are delivered on a flat bed truck," said Aaron Schoeneberger, Superior Walls' marketing director, "and set in place with a crane. The corners are saddle bolted together, and the panels are sealed with a urethane sealer (that forms a flexible expansion joint). The footers are built into the system so there is no traditional poured footer; rather, the wall system rides on clean crushed stone."
The wall system and the first-floor decking is poured before the lower level slab is poured. (Flat work is subcontracted.) Because that makes a box, you have significant structural integrity. Once the concrete is cured, the interior is ready to be finished because either wood nailers or galvanized furring strips are already attached to the wall. There are also pre-engineered holes formed in the studs for plumbing and wiring.
The walls can be installed at the rate of 200 linear foot in a half a day or less, saving on labor. All product is installed by Superior Walls-certified installers, so contractors don't have to train a crew in a new system. Regional distributors, who manufacture the systems, either own or hire the trucks and cranes, relieving the contractor of having to handle that operation. Because the system is precast, builders can avoid complications from pouring onsite in too cold a temperature and expect a consistently true and plumb product.
Another advantage, according to Schoeneberger, is the great flexibility in design. For example, it is easy to handle load-bearing variations at the time of manufacturing by adding studs. The cost is comparable to poured in place market.
Like E-Maxx, Superior Walls can be used in building the entire concrete house, not just the basement
Insul-Deck has a strong presence in Europe in commercial construction, according to Mike Napier, engineer at Insul-Deck LLC, but has focused on the residential market for joisted concrete floors and roofs in the United States. It is a stay-in-place ICF, molded with metal inserts and pre-cut to order so there is no waste. Builders can request specific insulation and beam depth. R-value ranges from R-10 to R-25.
Design flexibility is one of Insul-Decks' advantages. Custom projects frequently incorporate long spans of floor and ceiling for loft-style openness. The forms can span 30 feet without modification. With greater depth of the concrete beam, the form can reach clear spans up to 40 feet.
"Insul-Deck forms are not structural, so shoring must be set up. Once the shoring is in place, the panels, which slip together with tongue and groove connection, are laid on top of it. Although the forms come custom cut, there might be a little bit of field trimming required, especially for some angled walls. After the panels are laid down, rebar is added. Then, the concrete is poured."
Unlike most ICF systems, Insul-Deck is designed to let builders pour all four walls and the first floor in one continuous pour. So, in effect, Insul-Deck creates a concrete envelope or box. Using the Insul-Deck ceiling/floor as a platform, the crew has a nice big working area for the pour. The pouring is done in 2-foot lifts until it gets up to the deck and then the deck is filled in.
The concrete envelope is an advantage in cold weather climes because it closes in the work space. For homes planning to include radiant floor heating, it provides a concrete barrier that keeps the heat from going downward into the room below. The concrete box also makes the home far safer. Although many builders appreciate the protection concrete offers against many natural disasters, they often stop short of using concrete roofs, leaving the homeowner at least partially vulnerable.
Napier said another advantage to using these system is that it offers quick lead time — about seven to 10 days from the time the order is received to shipping out the forms.
Whether a builder chooses forms manufactured in advance, ICFs or cast-in-place, at some point, the concrete will be poured.
"Cemen Tech makes volumetric mixers that store the raw ingredients for concrete in different bins until it is ready for use," said Josh Watters, national sales manager for Cemen-Tech. "The materials are proportioned and measured volumetrically and carried via conveyor belt to the end of the unit where there is a mixing auger. The auger mixes all the ingredients at the job site and pours it out as fresh cement. It is a homogenizing auger, which has some breaks in it. Where the breaks are, we put mixing paddles. It is spinning about 800 rpm, doing a better mixing job than a drum truck that is basically flipping the load over and over.
"The advantage of a volumetric approach is that it fits the actual work schedule," Watters said. If the ready-mixed truck shows up and the builder's forms are not in place, every minute the concrete sits in a drum truck, the concrete gets weaker. As soon as you add water to cement, it starts the dehydration process. Agitation keeps it from setting up, but the water makes it weaker. If you add more water, it gets even weaker. There are municipalities that have strict regulations. If concrete for home building work sits for more than 45 minutes, the truck must return to the factory and get fresh at added expense. Using a volumetric mixer avoids this problem."
According to Watters, another advantage of this type mixer is that the builder can tell the mixer operator on the job site what psi he wants. Most builders use 3,000 psi. In columns, or areas that need great strength, a builder may use 4,000 or 5,000 psi. They can go as high as a seven and a half bag mix. This is particularly useful to contractors who do the foundations, floors, ceilings, roof and walls.
"On a particular job," Watters said, "there may be different formulas mixed. The mix design can be changed in 20 seconds simply by altering the proportions, using changing gates. The mixer has a 99 plus-percent accuracy rate.
"We can add color, mesh fiber or accelerants to make it cure faster and increase the strength. We can add air entrainment — physically adding air helps it handle the frost-and-thaw cycle. If concrete doesn't have air it will crack and become structurally unsound. We can also add plasticizers that make the concrete more workable. That is important to workers doing flat work."
Carole McMichael is a freelance writer based in Hewitt, Texas, and a former editor of Concrete Homes magazine.