What is Foundation Piering and How Does it Work?

Indications that You Need a Piering System

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Today, more and more homes are being built on unstable soils, such as the ones that you learned about in previous chapters. Between expansive and hydro-compactable soils and subsidence, foundations are pushed and pulled, creating movement. Each year, thousands of homeowners are faced with evaluating and repairing foundation problems. Thankfully, this means that there are reliable, engineered solutions available.

What exactly is available and is it the right solution for your structural problems?

Since the root of structural problems is the soil, the first two solutions deal with taking the foundation’s weight off of unstable soils and placing it on bedrock or other stable soil-these solutions are called push piers and helical piers.

Push Piers are basically long steel shafts that are hydraulically driven into the ground through the unstable surface soils until they reach bed-rock 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 until they meet an engineer specified depth. The home’s weight is then transferred off of the unstable soil and onto the piers through pier brackets attached to the footing of the house.

Helical Piers are similarly driven into the ground using hydraulics, but they are turned into the ground like a giant screw. In fact, they are giant screws that literally hold up a house through resistance power. The home’s weight is then transferred onto the piers using the same durable steel brackets.

Steel pipes

Indications that You Need a Piering System:

You have an area of your foundation wall that is experiencing vertical movement, such as sinking.

Your chimney is not flush with your home.

Your soil conditions can be classified as expansive, subsiding, hydro-compactable, or active.

How Piers are installed in 6 Basic Steps:

Step 1: Outside, sod and landscaping around the homeares removed and set aside.

Step 2: Soil is removed until the footing of the concrete foundation is revealed.

Step 3: Foundation pier anchoring brackets of heavy, industrial-strength steel are attached to the home’s footings.

Step 4: Rugged steel piers are hydraulically driven down to solid bedrock or equal-load bearing strata.

Step 5: The weight of the home, anchored to the steel brackets, is carefully transferred from unstable soil to rock-solid piers.

Step 6: After an engineer’s approval, the soil around the home is replaced and landscaping can be returned to its original location.

There are several other options that have been employed during different eras to resolve foundation problems. The oldest method is to jack up the house and replace the foundation and the newest method is to utilize piering systems either on the entire perimeter of the home, or just one portion. Here’s a breakdown of the other methods that people have used to resolve foundation issues from oldest to most recent:

Replace the Foundation:

Destroys yard and takes several weeks to complete

No warranty against the same problem reoccuring (expect same result

Footings are still in the Active Zone

VERY EXPENSIVE-$50,000 PLUS

Concrete Underpinning/Spread Footings:

Can take weeks/months

Added weight of the concrete can make problem worse

Structure cannot be lifted

Footings are still in the Active Zone

Concrete Piers:

Concrete cylinders can break during installation and CANNOT be retrieved due to depths

Cylinders create too much skin friction to get through the Active Zone

May require additional shims in the future

Even if shimming is included in the warranty, the damage from re-settlement and re-excavation is not covered

Square Shaft Helical Piers:

Originally designed to provide resistance to guy wires on electrical towers during high winds.

Not designed to hold up weight through soils

Square shafts experience bending and folding when a foundation’s weight resting on it.

Concrete Piers with Cable Reinforcement:

Engineered for specific soil conditions that are not present in Colorado.

Cylinders create too much skin friction to get through the Active Zone

Cabling in the center of pier stretches over time, allowing for a moment after piers in place.

Additional cabling on the exterior of cylinders can increase skin friction of cylinder.

Finally, piering systems:

Push Piers WILL:

Allow the deepest penetration of any steel pier type.

Allow for the possibility of low impact interior installations (typically, with far less collateral damage than the exterior approach)

Provide a lifetime warranty, transferable for the first 25 years that vertical movement in the piered areas will not occur

Perform its job in most soil conditions for a designed life in excess of 100 years

Push Piers MAY:

Allow for the likelihood of lifting a structure to a flatter, more level condition

Allow for the possibility of closing or shrinking existing cracks in brick, stucco, sheetrock, or other interior or exterior finishes

Allow for the re-alignment of sticking doors or windows, and the straightening of leaning chimneys

Push Piers WILL NOT:

Guaranty that perfectly flat or level final conditions will be achieved

Provide lateral (horizontal) restraint to a bowing foundation wall

Improve the water tightness or lower the moisture level in a basement

Helical Piers WILL:

Perform its job in most soil conditions for a designed life in excess of 100 years

Allow for installation on relatively older, weaker, or lighter foundation types

Allow for installation as a pre-construction (or new construction) bearing system in poor soils

Allow for a horizontal installation as a “tie-back” system to provide resistance against land creep in hillside areas

With a few rare exceptions, require exterior excavation, with destruction to surrounding landscaping or paving

Provide a lifetime warranty, transferable for the first 25 years, that vertical movement in the piered areas will not occur

Helical Piers MAY:

Allow for the likelihood of lifting a structure to a flatter, more level condition

Allow for the possibility of closing or shrinking existing cracks in brick, stucco, sheetrock, or other interior or exterior finishes

Allow for the re-alignment of sticking doors or windows, and the straightening of leaning chimneys.

Helical Piers WILL NOT:

Guaranty that perfectly flat or level final conditions will be achieved

Provide lateral (horizontal) restraint to a bowing foundation wall (unless specifically installed in “tie-back” mode)

Improve the water tightness or lower the moisture level in a basement

Source by Cassi Henes