Ask anyone to name the building material which best conveys a sense of solidity, and most will say concrete.
Until recent years, however, that impression left off when the foundation or basement walls were poured.
Lately, more and more commercial building and home owners have been ordering up walls that go all the way to the roof line. They’ve seen how concrete can make a big dent in utility bills, provide strength and durability, shut out noise, and contribute to a dry basement.
They have also seen that a concrete home or other building doesn’t have to resemble a cold, gray, concrete fort but can be dressed up as snazzily as any other building.
Of course, the concrete in question is the kind that gets poured into insulating foam forms which stay in place once its cured.
The advantage to a builder goes beyond the fact that he doesn’t have to strip off the forms. “We can pour concrete to -15 degrees F,” says Marc Robinson, whose MDR Construction discovered the joys of building with insulating concrete forms (ICFs) seven years ago.
“Ease of construction is another advantage,” says Robinson. “It doesn’t take a large amount of skilled labor. A three- or-four-man crew can do most ordinary buildings.”
“And the energy efficiency of the building is better than with wood, not because of the R-value but because there is very little air infiltration with concrete.”
Robinson cites studies reporting five to seven air exchanges per hour for wood-frame homes, compared to once per hour with concrete homes.
“You can get a break on your mortgage rates in some areas of as much as a half percent. You can cut your utility bills 50 percent, which adds up quite quickly,” Robinson continues.
Robinson, whose company operates out of the Rochester, New York, suburb of Spencerport, first learned about ICFs in material a manufacturer mailed to him. He didn’t care for the big investment and quota the company required of its dealers. “But I liked the idea, and I found there were many manufacturers of ICFs.”
Today, there are about 45 of them, he notes, including Reward Wall Systems, the one MDR most prefers. But he emphasizes that no single forming system is ideal for every job, and his company has used many others, including a system by TechBLOC and one by Therm-O-Wall. There is another he has studied – by Standard ICF Corporation – which he wants to try soon.
While MDR uses the products of several companies and the assembly of an ICF wall is essentially the same from one company’s product to the next, each has peculiarities that set them apart. Some systems have one-piece corner forms, which eliminate cutting and fitting on the job site, others don’t. “On some projects with lots of corners that you would have to custom cut, you wouldn’t want to use a no-corner form,” says Robinson.
Some have easy-to-use points for fastening drywall and other finish materials, others don’t. “If the building is to have vinyl siding, for example,” Robinson says, “I’ll use Reward Wall.”
Other ICFs are a post-and-beam style in which the concrete in the wall is not the same thickness all the way through. “No system is less strong than the others, but some customers don’t like that idea,” he explains.
Primarily, though, MDR prefers forms that arrive at the job site already assembled, with spreaders or connectors already in place. These devices, usually plastic, bridge the gap between the two sides of the foam form, holding them in place.
The connectors or spreaders and the rebar which is installed inside the forms do most of the work of holding the forms in place during the concrete pour. Exterior wood reinforcements are incidental, believes Robinson. “It’s all in the engineering,” he explains.
Of course the pour is usually made in two stages, one up to about 4-ft. high and finishing to the specified 8- or 10-ft. height when the truck has worked its way around the building to the starting point. By then the concrete poured first has begun to firm up and help support itself.
At least one forming system is designed for a full 10-ft. pour in a single stage, adds Robinson, and it creates a true post-and-beam wall. In this system, the foam extends all the way through the wall at given points. MDR has used the system but finds many customers have difficulty believing it can be strong enough.
Foam thickness is 2-1/2 in. on each side of the finished concrete wall in the Reward Wall system, and Robinson does not add additional insulation.
“I built a funeral home near here, 6,000 sq. ft. slab-on-grade. Two years later I asked the owner about their utility bills. They said it was better than expected; monthly bills $20 in the summer, highest winter bill $175 for forced air gas.”
A home owner can save $300 a year in utility costs even if just the basement is created with ICFs, he contends.
In business 20 years, MDR primarily builds banks, office buildings, churches, and restaurants, preferring commercial work to residential. “It’s a faster pace,” says Robinson. “You’re in, you’re out, there’s not so much hand holding. They know what they want done, and that’s it.”
Commercial projects also bring advantages to ICF construction that residential work doesn’t, he believes. “The higher you go with concrete block, the more expensive it becomes. But with concrete forms, it’s less labor intensive, so you can go up faster and cheaper.” And since ICFs employ the same types of foam insulation used in EIFS finishes, there is one less step in adding an exterior surface.
“And there is no chance for water to penetrate and get behind the foam.”
Robinson expects to experiment soon with a new concrete additive he has heard about. Called Fiber Mesh, it is a reinforcement added to the mix at the ready-mix plant and is said to eliminate the need for rebar. It can be used with any forming system, according to Robinson, and should make construction of wall forms easier, cheaper, and faster, because there will be no need to buy, bend, and install rebar.
If Robinson has one overriding wish, it is for more ICF customers. “I estimate about 15 percent of our business is with ICFs, but we’re working on it.” Part of his marketing effort is to build a Habitat for Humanity home using insulating concrete forms, with the hope of attracting lots of media attention in his region.
“Habitat also likes the energy efficiency part of it,” he says. RB
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