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03/19/2021

The Complicated Math of Foundation Repair Dumbed Down

As it turns out, math is pretty damn important. I mean, mathematics put us on the moon, numbers are the language of computers, and Rain Man used his savant cerebral cortex to win cash money for his brother.

Even simple math – algebra, in particular, axb = c type of stuff, is critical in the real world. Here at Dalinghaus Construction Inc., we use math every day. When it comes to contractors working on your home’s foundation, you want to know they can utilize basic middle school math correctly.

One would hope so, but idiots exist, and the foundation repair contractor field is full of space cadets.

For example, have you ever been told, maybe on a foundation repair job site or at a bar by some guy slurring into his beer, we always reach 10,000 PSI during Push Pier and Helical Pier installation?

Meaning – when we install Push or Helical Piers, the gauges on the hydraulic ram head and hydraulic motor both read 10,000 PSI.  

This guy that reeks of Mike’s Hard Lemonade wants you to be very impressed. Your home is in good hands and safe within the almighty power of the great 10,000 PSI.

If you were to ask this guy why 10,000 PSI he’d shrug and say, cuz that’s what my gauge goes to

So what? What do these numbers even mean? What does it have to do with foundation settlement?   

The truth is, 10,000 Pounds per square inch means nothing by itself. A total of zip. Nada. Zilch. It’s just a reading on a gauge measuring hydraulic pressure.  

The problem is: this poor idiot at the bar is confusing 10,000 PSI with Loading Value.

Loading value is the actual weight/load/force exerted on the push and helical piers during installation. Loading Value is calculated with the equation:

PSI x the Effective Area of the Ram/Drive Cylinder/Jack = Loading Value  

Yes, PSI is part of the equation for determining Loading Value, but it is not Loading Value.  Just like how in the equation  Length x Breadth = Area, length does not equal area.

So, this article is going to explain the great myth and misconception of PSI in the Foundation Repair field. It will focus on:  

  1. Why Loading Value is Important: Capacity  
  2. How to Determine Loading Value

PSI Gauge Pier Install (Dalinghaus)

Why Loading Value is Important: Capacity  

As mentioned above, PSI helps us determine loading value for Push Pier and Helical Pier installations.

Loading value is best described as the weight/load/force exerted on the Push or Helical piers for installation.  

Loading Value is important because it mirrors or exceeds what the endgame load of the home will exert on the piers.

It’s imperative to determine the loading value because Push Piers and Helical Piers have a maximum load-bearing capacity (the maximum weight they can hold):

Push Piers – 68,000 pounds 

Helical Piers – 74,000 pounds

Remedial Brackets – 40, 000 pounds

In other words, these steel pipes need to be strong enough to withstand the force thrust upon them.

Strength (capacity) must be greater than weight (load/loading value).

Note – these are maximum numbers, but in the construction biz we always go by a safety factor rule of 2:1. Meaning the working capacity of these piers is the maximum load-bearing capacity divided by 2.

Working Capacity  

Push Piers – 34,000 pounds 

Helical Piers – 37,000 pounds

Remedial Brackets – 20,000 pounds

Note – because both the Push Piers and Helical Piers are attached to the remedial bracket, both of these automatically are reduced to only bearing a maximum working capacity load of 20,000 pounds.

In reality, most Push Piers and Helical Piers are holding up an average of 10,200 pounds per pier location. For example.

A single-story home weighs approximately – 1000 lbs per linear foot. 

A second-story house weighs approximately – 1,800 lbs per linear foot.

So, if we space the piers 6 feet apart, which we do, then those piers are carrying that amount of load.

6 feet x 1000 lbs = 6000 lbs load requirement 

6 feet x 1800 lbs = 14,400 lbs load requirement 

Both well below the 20,000 lbs safety factor of the remedial bracket, which actually has a maximum load capacity of 40,000 lbs! In other words, after a pier installation, your house is secure!  

So, determining loading value helps ensure that we are driving our Push Piers and Helical Piers to deep, load-bearing soil that is strong enough to sustain the load of the home (which is spread out amongst the total number of piers) for a lift/stabilization.    

Again, PSI is one of the factors that help us determine Loading Value – it is not the loading value itself.

How to Determine Loading Value

The equation for Loading Value is: 

PSI x the Effective Area of the Ram/Drive Cylinder/Jack = Loading Value

The equation broken down:

PSI – Pounds of Pressure Per Square Inch   

Effective Area – the diameter of the cylinder calculated in square inches (*note – the diameter determines the volume of the hydraulic fluid – more volume equals more pressure)    

Loading Value – the actual installation weight/load/force exerted on the push and helical piers  

Here is an example of how Loading Value is Calculated:

PSI – 10,000 pounds per square inch

Effective Area – 5.94 Sqin

10,000 PSI x 5.94 = 59,400 pounds per square inch Loading Value.

We always ensure that our loading value is greater than the actual load that will be exerted on each pier.

We take meticulous notes of each pier depth and loading value in Pier Logs.

 

Brian’s Magic School Bus 

There, we just finished a wonderful field trip through the world of numbers. Now you know the maximum load-bearing capacity and working capacity of Push and Helical Piers. 

You understand that the capacity of these piers is ALWAYS greater than the load put on them. 

And you understand how we calculate loading value: 

PSI x the Effective Area of the Ram/Drive Cylinder/Jack = Loading Value  

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