by Richard Connolly
Boston Globe Correspondent
With each new crack, with each new split, with each new sticking door or inexplicable snapping sound in the night, your heart sinks. After years of denial, you can no longer ignore the obvious: not only is your heart sinking, your house is, too.
Aside from a fire, a structural defect in the construction of a house can be a homeowner’s worst nightmare. In its present condition, the house cannot be sold, and living there may become dangerous as the problem worsens.
The cost of rectifying such a problem can send a chill down your spine. One Massachusetts couple heard figures that ranged from prohibitive to confiscatory to solve a collapsing foundation built seventeen years ago on filled land.
A contractor suggested lifting the tri-level home with its finished basement, breezeway, and garage off their foundations, demolishing them, excavating to undisturbed soil, then starting all over again.
The basement in-law apartment and family room with an extra bedroom would still have to be refinished. Only minor work would be required to correct any misalignments caused by the original settling.
Unfortunately, the homeowners would have to live in a trailer located somewhere on site. They never asked the contractor.
Another thought 20 or more structural columns, or mini-piles, could be driven into the ground to underpin the foundation and bear its weight but at $2,100 each, including labor, material, and engineering fees for a total of $42,200.
In addition to stabilizing the settling, the apartment would be unaffected. However, more work and money would still be required for the family room, bedroom, breezeway, garage, and any realignments. The homeowners wondered where it would all end.
A more conventional solution – to build a foundation under the foundation – proposed by a structural engineer had all the advantages of the mini-piles, would have cost no less than $40,000. In any case, major equity in the house would be lost.
Realignments would be billed on a time and material basis. This end phase of the project included: adjusting several interior and all exterior doors or sliders, replacing exterior trim, a brick front veneer, and asphalt roof shingles, rehanging gutters and downspouts, resetting some interior trim, patching cracks in plaster, and reworking kitchen cabinets.
On the very eve when this work was about to begin, the homeowners agreed to consider and commit to another scheme that seemed to have all the benefits of the initial three proposals but none of their disadvantages.
Another structural engineer designed a plan whereby the support and realignment issues would be resolved simultaneously at a very substantial savings by installing nine helical piers at a cost of $9,600, including labor and material, and an additional $1,050 for engineering fees.
A helical pier is a varying length, 1 1/2” x 1 1/2”, hot dipped, galvanized steel, solid column with a helix attached to its end. The helix is a device that looks like an auger and – when turned hydraulically – allows the entire shaft to be bored into the ground.
The helix itself varies in diameter, from 8” to 14”, depending upon soil density. The design called for an 8” helix with a 7’ shaft and 5’ extensions that would allow boring to 50’. By increasing the size and number of helixes, a depth of several hundred feet can be achieved.
A second device is bolted to the foundation to cradle the shaft, secure it in place, and control bending. In raising the foundation, another mechanical part, a foundation bracket, is required at the top of the pier. The bracket consists of a T, an L, and some bolts.
The stationery T – bar slides over the shaft of the pier and is connected by two, 3/4” galvy bolts to the L – shaped device that was slips under the foundation in the manner of a tire jack to transfer the load to the column and, ultimately, the helix at the bottom.
The foundation is raised by hydraulically tightening the connecting bolts on top of the T – bar, thereby drawing the L – bracket to the T in an action similar to the closing of a vise.
For safety purposes, a helical pier is engineered to a factor of two, or approximately 25,000 lbs. Each carried a load of approximately 12,000 lbs.
Much unrelated preparatory work had to be done before the columns could be installed.
Because the center beam of the house was virtually unsupported, special footings reaching seven feet deep were dug, reinforced, and poured. The cracked, 4” cement slab in the family room and bedroom was removed.
To address the sagging in the center of the house, micro laminated beams with special brackets were installed to cradle the main beam. This arrangement eliminated a lally column in the middle of the family room and transferred the weight off the main beam to the micros.
Since the breezeway and garage were originally built on a 12” concrete slab that failed, support for those structures was required. After a week’s worth of work, the slab was finally cut up, broken up, and hauled away.
Two foot footings, four feet deep were dug every six feet around the rear and right side of the garage. In the center of the footings, adjustable lally columns were installed before concrete pouring to support the garage and later help in its leveling. Between the lally column footings, 1’ x 2’, reinforced steel footings were poured.
A foundation was installed under the front wall of the garage and three sides of the breezeway. No forms were used. After excavation, six truckloads of immense boulders were hauled out.
A major crack in the cement foundation was injected with a special epoxy, which made that section stronger and eliminated the need for two more piers.
Once all the preparatory work was completed, the installation of the piers began. An air compressor with a special hydraulic fitting bored the columns into the earth until they hit ledge or solid ground, as indicated by a pressure meter. The average depth was 12’.
At a rear door opening, two piers were installed, one on each side, to allow for an even raising while preventing cracking of that section of foundation.
The pier phase of the work took somewhat longer than originally anticipated because the columns had to worm their way around the boulders that were used as fill.
As soon as the piers were in place – four in front and back and one on a critical corner – and secured to the foundation, the real excitement began. The workers attached a hydraulic jack to the foundation bracket, pumped a few times, and slowly raised the foundation!
The gage on the jack on the critical corner read 21,000 lbs., but not because the house and its foundation weighed that much at that pier. In part, the difference was due to the friction of the earth against the foundation and the suction caused by the raising itself.
The workers raced from column to column, raising and adjusting until the entire foundation was perfectly level. Simultaneously, a second crew inside the basement raised the micro laminated beam until it, too, was level. The garage was attended to with everything else.
The checking and rechecking with transits seemed endless. Everyone was having fun despite the awesome responsibility and deadly seriousness of the work itself.
As the house, breezeway, and garage were finally leveled, the spirits of the homeowners soared. A wide crack in the living room ceiling disappeared, the space between the cabinet counter and the back wall was gone, the front and rear doors shut easily, gutters flowed, the chimney rejoined the house, and cracks in the brick front were no longer noticeable.
Fill inside the basement was added and compacted, masonry support walls built, slabs poured, columns placed under the micros, corrective carpentry completed, and a temporary driveway installed.
For this couple, their house had become their home again. Sleepless nights turned into calm repose. The nightmare was over – and under budget.