May 30, 2013
(Picture: Workers use an auger bit to prep the hole for a pull down helical pile under our Pt. Pleasant house.)
2013 -- Point Pleasant, NJ
What do you do when you need to install 30-foot piles under an existing
house? Even after raising the house it is only going to stand about 9 feet
above grade, hardly enough to slip something the height of a telephone pole
underneath. Enter the Helical Pulldown Micropile, made by Hubbell Power Systems.
The concept is pretty simple: A 9-foot section of steel is screwed into the ground under the house. Once it’s set, a second section is attached and screwed in, then a third and so on until you’ve screwed thirty feet of piles into the ground. Engineers have used this technology since the1800s, first for moorings and lighthouses and today for commercial building projects. But going forward there will be lots of residential homes in New Jersey sitting on helical piles, including our house in Point Pleasant.
Our homeowners, Carlos and Maria, have decided to raise their home the maximum amount allowed by zoning, in this case about 9 feet 3 inches and several feet more than the new flood maps require. Better safe than sorry, right? So today our team is setting 50 piles under the raised house using nothing more than a little Bobcat with a drilling attachment.
Why so many piles, I ask? Well, originally the home sat on a concrete block foundation wall that ran the perimeter of the house – about 200 linear feet. That’s plenty of foundation to carry the load of the house. Fifty helical piles that are six inches each in diameter is only 300 inches, a big step down from the 2,400 inches of the old foundation. When I heard the engineer put it that way, 50 piles sounded just right!
Helical piles are more common in commercial construction because they are expensive – they are several times more costly than 30-foot wooden piles hammered into the ground, like the ones we’ll be using in Manasquan. But the helical pile is really the only way people like Carlos and Maria will be able to support their house once it’s raised. There is no room on their lot to move their house out of the way to set the conventional 30-foot piles, and the new building code requires the house to be set on piles instead of a foundation. So for now, they’ll use the same technology that is used to build lighthouses.
Living by the water is great. Building by the water is a whole different story.
(3) CommentsComment on this Blog
Don't they ever hit big rocks and boulders (with either technique)? I would think this method comes with a lot of risk?
Rocks are a common issue with any method of putting support in the ground. The majority of the time (in our experience) we can work around rocks. Once in a while a rock has to be removed but another advantage of helical piles is we can install the pile through the now compromised strata.
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