When it comes to foundation repair work on your home, there are several choices that need to be made. These choices include choosing which piers you will use, whether you need waterproofing or underpinning, or even eccentric vs. concentric piers. You will hear proponents for each different type of foundation repair underpinning system. You will also hear many different opinions as to why some steel push piers are better than other steel push piers. Wading through all of this information is the key to finding the right method and means of repairing your home. Here we will focus on the differences in piering systems, specifically eccentric piers versus concentric piers. First we must define the terms eccentric and concentric. An eccentric piering systems is one who’s pile axis is not in line with its applied load. A concentric pier is a pier bracket and pile who’s axis is in line with the applied load.
For foundation repair applications, helical piers are always eccentric in nature. The helical sections are installed through the bracketing system from the side of the pier. Micropiers are also installed through the bracketing systems from the side of the pier. The major reason for this is the relatively large equipment used to install these types of systems cannot fit below the wall or footing.
Segmented Concrete Piles are installed directly below the footing and then a bracket or platform is installed on top of the pile to transfer the applied load to the pier. Hybrid piers are the latest concept in underpinning products. These pier systems generally use concrete filled steel pier sections installed directly below the footing and then either a steel bracket or concrete block is placed on top to transfer the load to the pier. These hybrid piers are marketed as the best of both worlds, in reality they are compromise of both worlds. They do not provide the full benefits of steel piers and they have the same negatives as the segmented concrete piles.
As noted above, steel push piers can be eccentric or concentric in nature. Each manufacturer generally determines which design best fits their manufacturing and design capabilities and sticks with that style. Only Earth Contact Products has successfully designed and engineered both types of systems for residential use.
What is better, eccentric or concentric? Well that is the $64,000 question. There is no real answer, because both, if designed properly and applied properly, will work well. While an eccentric designed pier requires more engineering and tighter quality control, not only can they work well but some have worked well for over 30 years. This is not to say all eccentric piers have good engineering behind them. Many are manufactured around cost constraints opposed to good engineering. Concentric steel piers are a lower tech solution that has many application advantages over its rival, the eccentric pier. They can be installed with less footing modification, they can be installed in lower headroom areas and they require less installation equipment to use.
Concentric piers are great for crawl spaces due to the fact that a tall drive stand is not needed to drive the pier sections. For eccentric piers to be used in a crawl space you will need either a fairly deep crawl space or you will have to cut through the flooring to make room for the drive stand. Concentric piers are also not affected by deep brick ledges or other obstacles like their competition.
The down side to most concentric piers is in their lifting or stabilization of structures. Most concentric piers do not allow room for anything more than a bottle jack (car jack) for lifting. They are pressured up with the bottle jack and then simple shims are placed between the bracketing system and the footing, the footing is then lowered onto the pier system. Bottle jacks are very undesirable for a couple of reasons. First, the structure is over lifted to allow for the steel shims (similar to segmented concrete piles). Next, with bottle jacks, the installer has no way to measure or control the hydraulic pressure applied to the structure. Most engineers frown on the use of bottle jacks for structural repairs.
There is only one concentric pier available, that uses a hydraulic manifold lifting system and is continuously adjustable, on the market today. The Earth Contact Products Model 200 uses a hydraulic manifold system, the same system used on their eccentric push piers. This system was designed by engineers for engineers to allow for critical infinite adjustability and control in lifting structures. The Model 200 also uses a patented adjusting platform that does not require over lifting or shims. This unique combination has created large demand and acceptance of this particular concentric piering system.
As you can see there are many variables and styles of underpinning pier systems available. So how do you choose the one that is right for your home? This is the easy part. First, hire an engineer and let him help determine your foundation repair needs. Then take your new found knowledge out into the market and wade through the variety of foundation repair contractors and find one that installs a quality piering system that has been designed and engineered to perform on your home. No bottle jacks, no shims, no shallow installation methods, just good engineering and manufacturing by a quality foundation repair company. Now, whether you are in Dallas, Texas, Kansas City, Kansas or Columbus, Ohio get out there and get your home fixed correctly and permanently.