CFA Projects of the Year
By: Larry Storer
The actual Griswold house jobsite was 60 feet below street level. A large weight-bearing temporary platform was engineered for the sole purpose to provide craned-in access to the site below.
The Concrete Foundations Association (CFA) has announced the winners of its Projects of the Year competition for 2010. Formerly recognized by the CFA in a single project known as the Basement from Hell, the Projects of the Year are more in tune with the cast-in-place concrete solutions produced by CFA members.
Displayed during the World of Concrete in Las Vegas in January and voted on by industry interests online at the CFA website (cfawalls.org), projects were selected by the industry at-large based on popularity and the established criteria. Projects were submitted in the categories of Single Family Residence less than 2,000 square feet, between 2,000 and 5,000 square feet and greater than 5,000 square feet; Commercial/Multi-Family; Non-wall Structural Element and Above-Grade Concrete Home. Projects in the competition ranged from California to South Carolina and represented some of the top projects ever recorded to the CFA.
The overall grand project for 2010 was the Griswold residence in Laguna Beach, Calif., submitted and built by Jones Custom Crete and Masonry Inc. of San Juan Capistrano, Calif. Entered in the Single-Family 2,000- to 5,000-square-foot category, this project consisted of 310 linear feet of footings and foundation walls enveloping 5,000 total square feet. Footings for the project required 375 cubic yards of concrete and 14.3 tons of steel reinforcement while the foundation walls required 260 cubic yards of concrete and 26.4 tons of steel reinforcement.
We chose this project as our ˜CFA project of the Year submittal due to the intricacy of its location, our creative solutions for equipment access, material delivery, and meeting the location challenge of this jobsite, President Tim Jones (firstname.lastname@example.org) said.
Our first step was to overcome the challenges of delivering heavy equipment, such as LinkBelt HC218 and P&H Omega 60, and material with weight restraints of the narrow streets to the access point above the site. Street closures were required to drive the large cranes to the site and for all other material deliveries as well.
The actual jobsite was 60 feet below street level. A large weight-bearing temporary platform was engineered for the sole purpose to provide craned-in access to the site below.
The footing details call out oversized footings requiring 30-inch by 36-inch grade beams with rebar ranging from No. 6 to No. 10. Grade beam details change at every caisson creating a lapping challenge. The grade beam details are raked and some sections, cantilevered with 40 connections to caissons.
An incredible project, the foundation included a radius wall at 12 feet high with 12 inches to 8 inches of transition and heights varying from 10, 12, 14 and 20 feet, and wall thickness variation from 8 inches to 3 feet.
This is the type of project that would keep anyone on his or her toes, Jones said. Throughout this project, we have successfully met our challenge by providing weight-bearing access, with the temporary platform built for craning in equipment, material and temporary stairways, which were built for safe foot access for jobsite personnel.
The first step was to overcome the challenges of delivering heavy equipment and material with the weight restraints of the narrow streets to the access point above the site, and then work at a jobsite 60 feet below street level. The large weight-bearing temporary platform was engineered for the sole purpose to provide the craned-in access to the site below. All heavy equipment, drill rigs, excavators, etc. were lowered by crane to the site.
In constructing the temporary platform, hillside caissons were necessary for structural support.
Our custom solution was to design the caissons to incorporate the structural integrity of the temporary platform while providing permanent integrity to the structural foundation, Jones said. Due to the limited access and 2:1 slope, the caissons were hand-dug. Tying off and using a 3:1 pulley system with OSHA approved with harnesses, 80-pound jackhammers were used to hand-dig 3-foot by 3-foot slip-form system caissons. A 2:1 pulley system was used to remove the dirt in buckets by hand-over-hand.
This craning system safely lowered heavy equipment " drill rigs, excavators and tractors from our temporary platform. We have also delivered 635 yards of concrete, 81,533 pounds of rebar, forming systems, lumber, etc. We have removed 778 yards of debris and dirt spoils, and hundreds of gallons of underground water.
Located on a beachfront, the underground water table was encountered at 15 feet, which required that water be pumped from the cassions and disposed of offsite. Dirt spoils were craned from the site to the street and removed from the site. The site had gone through hillside repairs for the past 10 years and had never been built on. The owners had to overcome neighbor protests of possible view obstructions and had to obtain building approval from the Coastal Commission.
General Contractor Robert Thomas Carey cited extraordinary performance from everyone in the success of this project, including: Don Zamborelli of Zamborelli Enterprises, the company that set up the critical crane deck and conducted the drilling; James Conrad, architect; Darryoosh Monjezi, structural engineer from Delta Engineering; Brandy Boka, soils engineer with Coastal Geotechnical; and Jim McBride of the Seattle Funding Group.
The project of the year from the Above-Grade Home category was the Doggett House submitted and built by Doggett Concrete Inc. of Charlotte, N.C. This 3,000-square-foot home included a basement, pool house and garage.
The footings required 265 cubic yards of concrete and 3.8 tons of steel reinforcement. Walls throughout totaled an impressive 612 cubic yards of concrete and 4.9 tons of steel reinforcement. The walls were 11 feet tall in the basement and 24 feet for the above-grade portion of the home. Wall thickness ranged from 8 to 24 inches.
This house had the works, Shelly Mony with Doggett Concrete (email@example.com) said.
Originally designed as a 3½-level with a concrete masonry unit (CMU) foundation, the entire house was changed to poured-in-place. It has 24-inch-thick walls to carry an authentic stone boulder veneer 2½ stories to the attic, curved roof ledges, custom window and door openings, freestanding columns to carry masonry fireplaces at three levels, bay windows and multiple floor elevations required intricate planning and forming.
The working drawings were always shown as CMU; we had to plan several phases ahead of ourselves for the framer and other trades installation, accounting for cast-in-place and free-standing steel beams and columns, and internal wall and conduit pipe systems.
In addition to the main house, a pool pavilion and a detached garage also included above-ground poured walls.
Mony said the private community limited the workday hours and construction noise. The site was cleared in sections with major trees limiting equipment and material.
At the same time, the size of the walls required placing concrete in slow lifts timed exactly to eliminate cold joints. Major shoring and bracing was planned to eliminate blow-outs.
The winning entry in the Single-Family, greater than 5,000 square feet category was Montaguna, submitted and built by Ekedal Concrete Inc. of Newport Beach, Calif. This project was astounding in its stats with 1,050 linear feet of footings and walls encompassing 20,000 total square feet.
The footings required 546 cubic yards of concrete and 28 tons of steel reinforcement while the walls contributed another 712 cubic yards of concrete and 55.3 tons of steel reinforcement. Further impressive numbers for this project included wall heights that ranged from 4 feet to 30 feet 9 inches; wall thickness range from 8 to 20 inches; and an 11,000-square-foot deck requiring 227 cubic yards of concrete and an additional 7.9 tons of steel reinforcement.
Ryan Ekedal (firstname.lastname@example.org) said that in this project the majority of the walls were exposed architectural walls. Every sheet break, tie hole and pour break was specified by the architect. Some walls had special bronze bands that had to attach to the form to create borders around steps at the fireplaces. Every interior corner had to be miter cut to prevent plywood edges from showing.
By breaking the job down to its different aspects (shoring, slab and decks, structural walls, architectural walls) we were able to simplify the project to an extent.
The use of special admixtures increased the flowability of the concrete into tight areas.
The walls with window openings and door openings made difficult architectural walls more difficult, Ekedal said. The complex shape of the artisan wall inset did not ease construction.
But by drawing profiles of every wall and sections of the most difficult areas, including the rebar to check clearances, we were able to foresee problems and solve the issues with the architect or engineer prior to construction thus saving construction time and down time.