Homes on Solid Footing : Foundations for Hillside Residences Sunk in Bedrock
High up in the hills here, less than a mile from where torrential rains sent homes tumbling from their foundations, work crews are building houses again.
From the precariously pitched lots, there are sweeping vistas of the Pacific and surrounding canyon land, promising both uncommon beauty and privacy.
Yet these amenities come at tremendous risk, witnessed by the extraordinary wreckage of the fallen residences that now litter the Laguna slopes and those teetering near disaster in Anaheim Hills and in San Clemente.
In attempts to preserve their views and peace of mind, new-home builders are sinking hundreds of thousands of dollars into design features that promise to make their hill dwellings virtually impregnable to future storms or natural disasters.
One local contractor, Robert G. McClaire, estimated that the owner of a Laguna home his company is building would spend up to $200,000 on foundation work alone.
The expensive design, comparable to that used in the construction of coastal piers, calls for up to 30 concrete caissons to be anchored into bedrock, some as far as 20 feet below the earth’s surface.
“I’m not intimidated by hillsides,” said McClaire, whose client’s lot looks off the steep face of the canyon and toward the ocean. “The surprise factor is typically higher for running into conditions you can’t foresee. You just have to remember that something created that hillside and caution people not to cut corners that could come back to bite them later.”
Next door, on Pacific Avenue, architect Mark Singer has set a network of foundation footings--at a cost of about $100,000--deep into the rock below so that his client’s million-dollar investment might withstand Mother Nature’s next assault.
“Every footing is in bedrock,” said Singer, whose firm has designed and/or built a number of homes in the same hills. “We want to make sure (the house) doesn’t go anywhere. There is too much liability here.”
Geologists and builders agree that despite the destructive slides of recent days, engineering technology has helped to make hillside living safer over the years. But nothing, they say, is ever a sure bet in the ever-shifting soils of Southern California.
A soil engineer and consultant since the 1950s, Douglas E. Moran of Tustin has studied the dirt from the Hollywood Hills to Anaheim Hills but acknowledges that the science is far from perfect in this region.
Loose topsoil covering a bedrock that, in some areas, can be booby-trapped with deep cracks or fissures susceptible to movement sometimes disguise attractive hilltop lots throughout Orange County.
In those areas, Moran said, varying conditions may warrant a recommendation against any development or a foundation scheme that will overcome potential movement.
“What you are trying to do is survive in a hostile environment,” Moran said. “For the most part, there are more successes than failures. But the failures make the newspapers.”
Moran and others in the soil engineering business said that since at least the 1960s, on most construction projects some efforts have been made to evaluate the site conditions.
“When one (house) goes over, it pains anybody to see the suffering and dollar loss,” Moran said. “It probably happens too often considering the effort put in. Those in our business can’t give you absolute insurance. Sometimes it happens despite the best intentions of capable people.”
On the edge of Pacific Avenue, McClaire said that he and the owner--who preferred not to be named--are confident that the best of intentions have been grounded in rock-solid design.
“The only thing that could knock this down is a major earthquake,” McClaire said, climbing the steep slope. The owner has planned a $2-million, four-story home, complete with heat-sensitive glass for all-day enjoyment of the breathtaking view. Plans also call for an elevator for easy travel inside and a pool to be set in a back yard, which today is part of the steep slope.
McClaire, whose workers must drive past the Laguna wreckage to reach the project site each day, said there have been no second thoughts on the part of the owner or project manager about continuing construction in wake of the damaging slides.
“This house will be anchored properly,” project manager John Peterka said. “His yard may not be there in a bad situation, but the house will be. We were planning for the worst. . . . You shouldn’t be afraid of it as long as you are willing to pay the price.”
Touted by Moran and other soil experts as one of the most stable forms of hillside foundation designs, the use of caissons or piers was found to be the best available support for the 7,000-square-foot home because of the extreme slope of the lot.
During initial excavations, McClaire said small fissures appeared in the bedrock, causing planners to include six additional piers that would more solidly distribute the structure’s weight. The piers, lined with steel mesh, are to be located under the structure’s upward and downward slopes, driven 10 to 20 feet underground. In addition, McClaire said, about $80,000 worth of steel has been planned for foundation and overall structural reinforcement.
On the same block, architect Singer is about three to five months from completing a hillside home for a Newport Beach physicist.
Singer said that because the foundation rests on a less extreme slope, it did not require the use of piers to reach bedrock. The design employed there is called “spread footings,” in which the foundation rests on pads built into the rock.
The Laguna-based architect said his clients have been so comfortable with the foundation design that the events of recent days have not prompted a single question about the home’s storm worthiness.
“The client came in the other day, and he was more interested in who he would pick to put in a wine cellar,” Singer said.
There are, however, factors that can combine to destroy even the best of plans. Singer said it happened to another client’s home last year in San Juan Capistrano when the home he anchored in bedrock had to be demolished because of a landslide.
Singer said the slide that destroyed Paul Filipowicz’s home was caused by a leaky swimming pool on the hilltop above his home.
Singer considers the San Juan Capistrano slide an “isolated” incident and maintains that continued hillside construction should not be threatened by recent events.
“It bothers me that people have lost homes. It clouds people’s confidence in wanting to live in a hillside community,” he said. “But you don’t build an expensive home with fine finishings on a garbage foundation.”
Because of the risk and associated costs, McClaire said there will be some who would never consider moving to the hills, but he hopes there will always be others willing to pay the price.
“It’s all about view, view, view,” McClaire said. “When you are hanging out there living in a house like this you’ve got to be a person who doesn’t get the heebie-jeebies. Personally, I think the biggest nuisance is the drive up here.”
Keeping That Dream House on the Hill
Architects and builders are trying to give hillside homes better protection against mudslides, but at great cost. One method is to bury pilings deep into bedrock. A look at one design for a Laguna Beach home in which foundation costs are estimated at $200,000:
Street
Sidewalk
Driveway
Garage
Elevator shaft
Third floor
Second floor
First floor
Ground floor
Foundation
Natural grade
Pool
Retaining wall
Dirt
Bedrock
Concrete
Pilings: Concrete poured into steel casings
20 feet
15-18 feet
15-18 feet
12 feet
10 feet
Source: Grant Building Co.
Lower slope: A network of 18 pilings will secure the foundation at the lower portion of the property.
Upper slope: The home will be anchored of 12 pilings (three of which are shown here) that will be buried in the bedrock.
