There are a number of factors which go into determining the cost of helical piles. Some are more obvious than others, but in the end, the chances of getting an accurate estimate will be much more likely when an experienced installer weighs the following criteria.
Geographical location of the job site
One cost factor which you might find a bit surprising is the element of geographic location. In a cost survey conducted by Helical Pile World in 2016, it became apparent that costs for the same kind of helical pile project would have a significant variance based on which part of the country work was done. Generally speaking, the more expensive pricing was in the Northwest and Mid-Atlantic states, while the least expensive cost of helical piles was quoted by companies in the Midwest and Plains states. So, if you have a project where helical piles will be used, the first cost factor will depend on which region of the country your project will be located.
Repair or new construction
The second most important cost factor in this survey is the type of project to be built. Participating companies universally quoted higher prices for remedial projects involving helical piles, as opposed to new construction projects with pile work. In many cases, the new construction was only about half the cost of the repair work.
After these two top factors, the cost elements tend to be closely related to the actual foundation installation work, which involves the piles themselves. We have broken these factors down as follows.
Number of piles
The number of piles needed on a given project is only partially determined by the size and footprint of the structure to be supported. The amount of piles necessary is also greatly influenced by the loading requirements, support requirements, structure type, and building codes applied to the project.
More importantly, because helical piles come in different sizes at different price points, one hundred piles of one size can cost less than fifty of another. The estimating contractor and the project engineers must be highly experienced in being able to determine how many of each size helical pile will need to be used.
Type of piles
The type of helical piles being used can also vary in diameter, shape and style, as well as whether they are being installed with or without grout.
The shape of the piles is either a square shaft or round shafts. Common square piles come in 1.5”, 1.75”, 2”, 2.25” and up. The common pipe piles come in 2 7/8”, 3.5”, 4.5”, 5.5”, 6.5”, 8”, 10”, etc. Typically, the bigger the diameter of the pile shaft, the more costly they will be.
Grouted shafts are a relatively new development in helical piles. As an anchor is being screwed into the soil, a grout column is gravity fed all around the shaft to reduce the likelihood of buckling under high stress. Such a technique is commonly used in soft soils, and has the effect of making the whole column much more rigid, while increasing the load capacity of the foundation itself. Grouted piles do not cost significantly more than un-grouted shaft installations, but can significantly improve performance. In many cases, small grouted square shaft piles actually cost less than un-grouted pipe shaft piles with similar loading capacities.
Once again, the type of pile used is very project specific and the best pricing will be determined by an experience estimator.
Depth of pile installation
The depth of the pile installation will influence the cost of helical piles simply because it takes more time and material to install deeper, more secure foundations. In many cases, anchoring will need to be drilled deep enough to a point where a more competent layer of soil resides. The load-bearing requirements of the project will also affect how deep piles need to be anchored.
For example, a pile going 40′ deep will add more to the material cost of a job than one going only 20′ deep. More pile extensions need to be added to the main shaft in order to achieve the greater depth. Installing longer piles also increases the time that drill crews need to be on-site.
Soil conditions
The design and selection of the piles being used for a specific project is directly affected by the encountered soil conditions. Buckling, liquefaction, density of the bearing layer to be penetrated, and density of the upper fill layers, all play a factor in which pile is chosen and the overall cost of the job.
In short, the soil conditions for a project will play a large part in determining the number, type, size and depth of piles to be used. As explained above, the choice of helical pile has a significant affect on the cost of helical piles material, needed for the project.
Cost of helical piles – The bottom line
Like all construction, estimated bids are subject to unforeseen developments. However, when an experienced contractor/installer/estimator work up an estimate for a specific installation of helical piles, and take into account ALL of the above considerations, you can be confident that the estimate you receive is realistic and accurate. Location, type of job (new construction or repair), the number, type, and depth of pile installations and the type of soil are all important factors. They, in combination, will determine your price and why only an experienced helical pile installer will be able to deliver a reasonably accurate figure for your project.
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