Today, more and more houses are being built on unstable ground, like the ones you learned about in previous chapters. Between expansive and hydro-compactable soils and subsidence, the foundations push and pull creating movement. Each year, thousands of homeowners are faced with evaluating and repairing foundation problems. Fortunately, this means that reliable engineering solutions are available.
What exactly is available and the right solution for your structural problems?
Since the root of structural problems is the soil, the first two solutions have to do with taking the weight off the foundation from unstable soil and placing it on bedrock or other stable soil; these solutions are called thrust pillars and helical pillars.
Push springs are basically long steel shafts that are hydraulically driven into the ground through unstable surface soils until they reach bedrock or other load-bearing strata. Technicians can tell that the piers have reached bedrock by measuring the hydraulic pressure required to drive the piers into the ground to a depth specified by the engineer. The weight of the house is then transferred from the unstable ground to the pillars through pillar supports attached to the base of the house.
Coil springs are similarly driven into the ground using hydraulics, but are spun into the ground like a giant screw. In fact, they are giant bolts that literally hold up a house through the power of resistance. The weight of the house is then transferred to the pillars using the same durable steel supports.
Indications that you need a drilling system:
You have an area of your foundation wall that is experiencing vertical movement, such as subsidence.
Your chimney is not flush with your house.
Your soil conditions can be classified as expansive, sunken, hydrocompactable, or active.
How to install springs in 6 basic steps:
Step 1: Outside, the grass and landscaping around the house is removed and set aside.
Step 2: Soil is removed until the base of the concrete pad is revealed.
Step 3: Heavy-duty, industrial-strength steel foundation pillar anchor brackets are attached to the home’s foundation.
Step 4: Strong steel piers are hydraulically driven into solid bedrock or strata that carry the same load.
Step 5: The weight of the house, anchored to the steel supports, is carefully transferred from the unstable ground to rock-solid pillars.
Step 6: After an engineer’s approval, the soil around the house is replaced and the landscaping can be returned to its original location.
There are several other options that have been used over the ages to solve foundation problems. The older method is to raise the house and replace the foundation and the newer method is to use pillar systems around the entire perimeter of the house or just part of it. Here’s a breakdown of the other methods people have used to solve base problems, from oldest to newest:
Replace Foundation:
Destroys the yard and takes several weeks to complete
There is no guarantee against recurrence of the same problem (expect the same result
Footings are still in the Active Zone
VERY EXPENSIVE-$50,000 MORE
Concrete foundation/extended foundations:
May take weeks/months
The added weight of concrete can make the problem worse.
The structure cannot be lifted
Footings are still in the Active Zone
Concrete docks:
Concrete cylinders can break during installation and CANNOT be recovered due to depth
The cylinders create too much friction on the skin to get through the active zone
May require additional shims in the future
Even if the chock is included in the warranty, damage caused by resettlement and re-excavation is not covered.
Helical columns with square axis:
Originally designed to provide strength to guy wires on electrical towers during high winds.
Not designed to support weight through floors
Square shafts experience bending and bending when the weight of a base rests on them.
Concrete columns with cable reinforcement:
Designed for specific soil conditions not present in Colorado.
The cylinders create too much friction on the skin to get through the active zone
The wiring in the center of the pillar stretches over time, allowing moment after moment in place.
Additional wiring on the outside of the cylinders can increase the surface friction of the cylinder.
Finally, drilling systems:
thrust springs:
Allow the deepest penetration of any type of spring steel.
Allow for the possibility of low-impact interior installations (typically with much less collateral damage than the exterior approach)
Provide a lifetime guarantee, transferable for the first 25 years, that there will be no vertical movement in the spring areas.
Get the job done in most soil conditions for a designed life of over 100 years.
MAY push springs:
Allow for the likelihood of raising a structure to a flatter, more level condition
Allow the ability to close or reduce existing cracks in brick, stucco, plaster, or other interior or exterior finishes.
Allow realignment of glued doors or windows and straightening of sloped chimneys
Thrust springs DO NOT:
Assurance that perfectly flat or level end conditions will be achieved
Provide lateral (horizontal) restraint to a sloped foundation wall
Improve water tightness or lower the moisture level in a foundation
coil springs:
Get the job done in most soil conditions for a designed life of over 100 years.
Allow installation on relatively older, weaker, or lighter foundation types
Allow installation as a pre-construction (or new construction) bearing system in poor soils
Allow for horizontal installation as a “tie down” system to provide resistance against landslide in hillside areas
With some rare exceptions, it requires exterior excavation, with destruction of the surrounding landscape or paving.
Provide a lifetime guarantee, transferable for the first 25 years, that no vertical movement will occur in the spring areas.
MAYO Coil Springs:
Allow for the likelihood of raising a structure to a flatter, more level condition
Allow the ability to close or reduce existing cracks in brick, stucco, plaster, or other interior or exterior finishes.
Allow realignment of glued doors or windows and straightening of sloped chimneys
Coil springs DO NOT:
Assurance that perfectly flat or level end conditions will be achieved
Provide lateral (horizontal) restraint to a sloped foundation wall (unless specifically installed in “tie” mode)
Improve water tightness or lower the moisture level in a foundation