Case Study
Elevation for Affordable Housing, Crosby, Texas
Situation
A home under construction through the Harris County (TX) Hurricane Recovery Program was designed for elevation three feet to four feet above grade to help it avoid damage from potential flooding in the hurricane-prone region. This community in suburban Houston is one of many in that area retooling its flood zones and building codes in the wake of devastation from Hurricane Harvey in 2017. This is especially challenging for affordable housing, which must not only meet the code requirements but must do so without incurring steep additional costs. The character of the soil in this community also presented a challenge because it is vulnerable to expansion and contraction (heave) in changing weather conditions.
Scope of Work
Helical piles provide the best solution for achieving the needed elevation and proven resistance to damage from heave. Galveston Piling Company, on the recommendation of Southeast Texas Engineering, installed 23 Cantsink helical piles. The home was built directly on the piles, to address the compressive loads. Few battered piles were included to address the lateral load forces. Cantsink helical piles can be quickly and cost effectively installed to depths below the nine feet to 14 feet of expansive soil where heave occurs. The slender shafts of helical piles perform better than traditional methods using timber or concrete with self-verifying compression and tension loads. Furthermore, the use of helical piles eliminated the vibration impact to neighboring structures typical for driven beams, and reduced the need for removing spoils.
Anchor System
Twenty-three Cantsink 2 7/8-inch OD pipe piles (ICC certified) with galvanized finish were used, totaling more than 600 feet in all. Installation was accomplished using a standard skid steer machine with a minimum torque drive head of 6,000 ft.-lbs. String lines and laser levels can be used to locate the piles for supporting the triple 2×12 beams specified in the engineering plans.
Results
Installation was completed in one day followed immediately by the framing of the floor system. Providing the reliable support of helical piles not only saved time and money on this new construction, it will eliminate concerns over the possibility of future damage from heaving. The number and intensity of hurricanes and tropical storms affecting coastal regions are increasing. Cantsink helical piles can provide cost-effective elevation and support that help avert damage from extreme rain and flooding.
