The hole story
House construction starts with digging out the basement and pouring its concrete walls
April 21, 2002
BY JUDY ROSE
As tall as a "Jurassic Park" dinosaur on tank treads, the excavator dips its long neck to the ground, taps the dirt gently with its top teeth, then slices straight down, cutting a dirt wall so straight you could panel it.
Operator John Wietecha, 41, has been running this single excavator 14 years, and his work has become his art. For 12 years, his digging partner has been Mark Sedlarik, 43, down in the hole pointing to a spot that should be an inch lower.
Though the machine seems to be the size of a brontosaurus, in Wietecha's hands it moves like a graceful giraffe.
"He can scratch my back with it," Sedlarik says.
Few home owners are present when their basement is dug or its concrete walls are poured, but those days of construction are two of the most dramatic and important to the ultimate quality of the house.
If digging the hole is like a duet dance, pouring concrete is ensemble work -- seven cement-splattered workers each carrying out a pivotal assignment.
Before moving to basement basics -- how deep, how thick, how waterproof -- here are vignettes from the home being built by RDK Homes in Van Buren Township for the House Chronicles, the Free Press Sunday Real Estate series documenting the building of a new home. For our previous stories, go online to www.freep.com/realestate/index.htm.
Van Buren vignettes
Pouring a basement costs about 8 percent of the total cost of the house, says RDK designer Brian Kime. In this one, base priced at about $268,000, that's about $21,000. Here are some of the basement issues you will want to know about if you are building a new house:
POURED CONCRETE OR CONCRETE BLOCKS: Poured concrete is most common in metropolitan areas and is usually preferred, because it lacks the mortar joints that connect concrete blocks.
But blocks may be your only choice if your building location is rural. Once ingredients for concrete go into the mixing truck, they have to be poured into forms within 45 minutes. If you live two hours from the nearest concrete source, it can't get to you in time.
BASEMENT HEIGHT: A standard basement today is 8 feet tall, sometimes 7 feet, 10 inches. But many builders now make it higher -- often as an option, sometimes as an included extra.
You might want a taller ceiling if you'd like to finish the basement into living space someday. With a 9-foot height, you can hang a second ceiling to cover floor joists and duct work and still have a pleasant height.
If you're offered a taller ceiling, it may be an 8-foot poured wall with a row of 8-inch concrete block on top. Or the company may use taller forms and offer a 9-foot, all-poured wall.
RDK offered a 9-foot poured basement here for an extra $3,200, but we passed. With ample living space on the main floors, we don't expect to finish the basement.
EXTERIOR SEALANT: This is a must, and some new products are said to be stronger than the traditional coatings.
The old standard was called damp-proofing -- an asphalt spray that became very brittle over time, says Kime. "If and when the concrete cracks, the membrane will crack with it."
RDK uses Tuff-N-Dri, a newer product making fast inroads with Michigan builders. This has a high rubber content and will stretch, not crack, as your concrete shifts. It has an excellent 10-year warranty.
BASEMENT INSULATION: In Michigan's weather, wrapping the outside walls with insulating foam board is desirable, and it was part of the Model Energy Code for this area, developed by the U.S. Department of Energy.
But under pressure from builders, Michigan lawmakers rolled back this requirement, so it's not done here much.
Still, many good products have come into the marketplace, and some builders offer them. One you'll see often is insulating board made of fiberglass by Tuff-N-Dri. Dow has a foamboard product called Perma-bond.
You might see insulation values of R3, R5, even R10.
Why would you want it? Concrete has a very low insulation value of R1.In winter, concrete transfers indoor heat into the cooler soil, and even more so into the cold air where the top of the basement walls are exposed.
A few builders include this basement insulation on their homes. Some offer it as an option. Earlier in the House Chronicles it was a $2,000 option we passed up, and we're regretting that decision. But the basement is done now, and it's too late to change.
We would always give a special look at a builder who included this insulation or even offered it at a reasonable price, if only as an example that the builder stays up with current developments.
QUALITY CONTROL: This should not be your worry; it's up to your contractor and the building inspector, but here is the list they'll follow:
Your concrete walls should be at least 8 inches thick. The footers that support them should be from 8 by 18 inches to 10 by 20 inches, depending on the load they bear. They're probably reinforced with rebar.
At the bottom of the hole, your basement floor should start with 4 inches of the gravel called pea stone. On top of that is poured 4 inches of concrete -- your finished floor. This concrete floor has to come after the basement walls are poured, but not necessarily right away. Once the pea stone covers the soil, workers have a dry base to walk on.
After your concrete cures, you will see shallow cracks. This is normal.
THE TEMPERATURE QUESTION: Concrete doesn't dry, it cures. Curing is a chemical reaction that gives off heat. In cold weather, concrete's water component can freeze, so it doesn't cure well.
Some builders will not pour concrete in very cold weather, but more builders do, adding chemicals -- often calcium chloride -- to adjust for the weather.
If the footers are poured on a cold day, the contractor will cover them with straw to hold heat. But for the tall basement walls there's no practical way to do this. Some contractors will build a plastic tent over concrete work and leave a heater inside.
If timing is no problem for you, the perfect concrete curing weather is 46-66 degrees, says Coleman.
ADDED PLUMBING: This is the only time you can put in plumbing and drains for a future basement bathroom without jackhammering out the concrete floor. If your builder doesn't include it, it's probably worth buying as an option. Here we paid $750.
Contact JUDY ROSE at 313-222-6614 or email@example.com.