Residential construction in our area is complicated by expansive clay, hilly lots, and variable soils that can make excavating and pouring conventional concrete foundations challenging and expensive. In addition the environmental laws get stricter every day so excavating large quantities of soil need special permits and the material usually has to be hauled away which is costly.
Helical piers or concrete piers work well with almost any soil type, and their strength and integrity are verifiable, unlike that of standard concrete foundation, which can vary in quality and strength.
The engineer determines how many piers are required and locates them on a foundation plan. To properly estimate the depth, number, and size required, it’s usually necessary to have a soil test done or at least have some experience installing piers in the same general area.
As a helical pier is screwed into the ground, the torque generated by the helical blades provides a direct means of determining soil density, stiffness, and strength. Measuring the torque allows you to determine whether the pier can support the required maximum load of 100KIP or 100.000 lb per pier. Even for a small design we will need a minimum of 4 piers which means they can support together 400.000 lb or 180 tons. Even bigger wood houses have only up to 50 tons of weight in total so we easily get a security factor of 3.
The process starts with the installation of a 6-foot lead (the part with blades). It’s driven down to grade, then 6-foot extensions are bolted on as needed. Installing one pier usually takes about 30 minutes to an hour.
Concrete piers work in a similar way but in this case 1 foot wide hole get drilled into the ground according to the pile plan. Then the concrete pile gets cast in place.
Advantages of Helical Piers:
- Torque is a strong verification for capacity
- Secure Foundation system for expansive clay and variable soil conditions
- Eliminate concrete curing and formwork
- Require less time to install
- Can be installed in ground water
- Are easily transported to remote sites
- Minimize disturbance in environmentally sensitive sites
Advantages of Concrete Piers
- Similar to Helical Piers but at a lower cost