Friday, September 5, 2014

Why "Refusal" is not a universal term.

I was sitting with a customer today, and we were going over the repair plan that I had offered, and going over different proposals they had gathered as well, when I was asked a very interesting question. "They say they push to refusal too, but they said a much different depth than you." Which led me back to "Refusal is a relative term." What is refusal, why is it not a universal term, and why don't all companies have the same refusal?  Remember, when trying to compare apples to apples, the term "refusal" is not always an apples to apples term.

What is Refusal?

Refusal is defined as being reached in one of three scenarios:
1) The pilings will not press any deeper.
2) The house is "jumping" and certain PSI levels are being met as measured by the drive pressure gauge on the hydraulic ram.
3) The house is experiencing significant distress from the pressing process, and risks significant structural or cosmetic damage from continuing to press.

If you look at #'s 1 and 2, this is the key areas where from company to company, your definition of refusal can change.

Not all companies use the same machines or instillation techniques to install pressed pilings.  The depth of refusal will depend on the strength of the machine.  Here are examples of 4 instillation techniques, and how depth of refusal will be different in each scenario.

1) Companies that install piers by digging below grade, installing 1 large concrete block, and lifting off of that block.

How it works.



Basically, this process is where you dig a hole, place a large concrete block in the ground, and lift off the top of that block.

Why it fails - Because these aren't piers.  These are blocks in the ground.  When the blocks move (which they will, because they are only 2-3 feet deep and still in the active zone) you will have to redo the entire process.


2) Companies that install pressed pilings by pressing with a hydraulic canister jack (usually 22-50 tons)

Why it fails- Because only 1 or 2 cylinders will get in the ground before you meet refusal.  This is not any different than the block in the ground method.  It's deep enough to close cracks, but it will not last.


3) Companies that install pressed pilings  by using a gas driven ram capable of achieving 2,500 - 3,500 PSI.


Why it fails- While this does get piers significantly deeper, it usually does not get them out of the active zone of the soil.  Your piers can still "float" in that active zone, and change with it, or lose pressure and slip deeper.


4) Companies that install pressed pilings by using a hydraulic driven ram capable of achieving 10,000 PSI.


Why it fails- This has the highest success rate, and lowest warranty call rate out of any of the pier instillation techniques.  Companies that use this machine generally have warranty call rates around 2%.  When it fails, usually the piers have lost pressure over time, and you can repress those piers and not have another issue.





Why is Depth Important?

 Depth is important for two reasons.

1) To get out of the active zone of the soil.
2) To get as much friction on the piers as possible.  Pressed pilings rely on friction to hold them in place.  Friction is the force that causes "Refusal", and friction is what stops warranty calls.  The deeper you press a pier, the more friction you are overcoming to gain that depth, which also means the more friction there is in place on that pier column.  More friction = less chance of movement.




How to know which technique they are using.
Ask.  Ask your installer how they are installing, what method they are using, what machines they use etc.  In the end, you are buying a repair for your home.  Make sure you know what you are purchasing.



Thanks for reading,
Brian

Email Me Directly: Brian.Gilchriest@permapier.com
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