Maybe you saw the New York Times article “In Housing, Big is Back (Not Cou
Concrete examples of why builders should stay involved from start to finish.
|E-mail Ron Jones at firstname.lastname@example.org.
A major milestone in building a home is reached when the concrete is poured. In our part of the country, most homes are built on concrete foundations and slabs on grade. Even homes built over basements or crawl spaces rest on concrete foundations.
Everything that comes later in a building project is predicated on a good foundation. Yet that part of the process is largely taken for granted, perhaps because it has become so standardized. It is also one of the most prescriptive elements. Ready-mixed concrete from batching plants delivered to job sites in trucks designed for one specific purpose has revolutionized how we build homes in this country.
Portland cement, extracted largely from processed limestone, is blended in precise ratios with crushed rock of various dimensions, water, sand and a host of other additives to create a fluid mass that will mold into almost any shape. We pour it into forms, and magically it hardens into the most permanent part of a structure.
Using all that concrete has tradeoffs. Producing cement from limestone is an expensive, consumptive activity. Most cement plants I have seen are huge, noisy, industrial operations. The extraction of the basic stone itself is extremely destructive to the landform, and processing the quarried stone releases tons of carbon dioxide and dust into the atmosphere.
It also could be argued that producing the aggregate stone needed to create concrete is not environmentally desirable because gravel pits chew up large areas of land and create vast amounts of dust and heavy traffic. Greener concrete is achievable to some extent by adding certain fillers to the mix. Fly ash, a waste byproduct from power plants, is one such filler.
On the other hand, durability is one of the most desirable characteristics of a building material or component, and concrete certainly has that. I remember standing on a concrete slab after an accidental fire had consumed a house under construction. If not for the plastic and copper lines beneath the slab, it would have been ready to accept a new frame with little more than a good washing.
Recently, I had two projects that were ready for stages of the concrete phase on the same day. On the first, we scheduled the pouring of slabs for the entire heated area along with many feet of monolithic footings, complicated step-down stem walls and steps throughout the floor plan.
The pour was scheduled to begin at 6:30 a.m. I drove onto the job site at 6:18, just as the huge pumper truck arrived. The operator wanted to set up above the project and pump from an area adjacent to a busy residential street. I preferred the quieter side street on the lower portion of the site, where I could control the activities of the ready-mix trucks and worry less about neighborhood traffic.
It seems that subcontractors aren’t always used to having the general contractor on the job. They tell me that they mostly see the builder drive by in a BMW or sport utility vehicle with a car phone, and that’s about as close as most builders get when concrete is going down.
It took only a minute, and the pump operator set up where I had told him to set up.
Within five minutes, three truckloads of concrete were coming up the road. I met each one, giving directions on where to maneuver and where to stand by, instructions to keep off neighboring properties and vegetation, and directions on where to wash out when each part of the pour was finished. All agreed to comply. As the first driver moved his load into position to deliver the mix from his chute to the pump’s hopper, I saw the fourth truck coming up the road and hurried to meet him before he got around the corner.
Meanwhile, three pickup loads of men on the concrete crew showed up. Some had been on this project in earlier stages as we formed and poured retaining walls and certain parts of the structure that were designed and built in conventional footings and stem walls. They knew where I would, and wouldn’t, let them park and went to that part of the site without having to be reminded.
For the next couple of hours, everyone was engaged in a blur of activity. Little time was lost as each cement truck transferred its load into the pumper, where the operator deftly delivered it to the precise areas where it was needed. Those who place and finish concrete for a living are all business when the "mud" is going down. They realize from experience that errors at that stage of the work are hard to correct.
After the fourth load had been pumped, the pumper truck took off for another site across town, and the crew worked on what had been poured while waiting for two more truckloads that would be chute-poured. It was after 11 a.m. by the time the last yard was poured and all the heavy trucks had cleared out, leaving only the finishers going methodically about their work.
At that point, I headed for the second site. We had a pump and concrete delivery set up for one afternoon and needed to pump several yards to a huge footing as well as conventional stem walls. In addition, a separate crew was scheduled to pump stem walls being built with insulated concrete forms (ICFs), which will be the main building material for the perimeter walls of the house. So we had two types of mix to pump, with two crews, from the same boom.
When I arrived at the site, I could see that the form setters working on the conventional stem walls had a ways to go. They had been on the site for three days and had made progress, but it would be close. Knowing we would be "tailing back" the final load that day and that we could save their portion for last and chute-pour it rather than pump it, I moved on to check the other parts of the job.
A while later, the same pump operator from the morning job arrived and set up, and even some of the same ready-mix drivers delivered loads for this site. Shortly, a surprised-looking group of finishers from the first job showed up and began the process all over again.
As the afternoon wore on, it became more and more apparent that the form setters were cutting it too close. After the first yards of mix were pumped into the huge footing, the second load (a smaller-aggregate, special pump mix) was hosed slowly into the ICFs. The subcontractor in charge of that phase had underestimated the yardage needed for his portion of the pour. We had to order another load of material to finish his part. At least it bought extra time for the form setters.
When we finally completed the middle part of the operation, we began to pump the balance of the material into the wooden forms. By now it was almost 4 p.m., and the men were wearing down. They were pouring too fast, and suddenly a section of a stem wall began to bulge and float, and everything came to a halt as they scrambled to repair and reinforce the forms and force them back into place.
Eventually it was all over. The trucks were gone. The pump had departed. The men had gathered and cleaned their hand tools, and I was left alone on the silent, muddy site. Almost 12 hours after I had arrived at the first job, we were finished with concrete, at least for now.
The people who will live in those two houses don’t know much about concrete. They know whether it lies flat and looks good, and they have lots of questions about cracks. I don’t think they really want to know much beyond that. The men who made all that happen in one day will be off to do the same things tomorrow. I’m glad I won’t have to go with them.
All too soon it will once again be time to do something "concrete."