It is no surprise that, with their properties and versatility, helicals would be well-suited to interior work. Conservatively, in 80% of all helical jobs, mobilization, access, or both play a significant role in the decision to use them. In the case of a New England seaside cottage at 1701 Ocean Boulevard, Rye, New Hampshire, as in many such instances, helicals were the only choice. A deep foundation was required and the work needed to be done inside. The owner did not have the option to tear down the building and replace it with a newer, grander structure. The cottage did not conform to the current code and a demo/rebuild would mean a much smaller footprint. However, they could go higher to enhance their ocean views, but that required a beefed-up foundation to support the additional load. Driving piles inside to add another story to an existing structure is nothing new for helical installers.
Amanda Moffat Pottery
TMS Architects has done a lot of work on the water in Rye, New Hampshire, but this situation produced unique circumstances. House raisings and demo/rebuilds were familiar territory. This situation was unfamiliar territory, so they turned to Carpentier Construction, a go-to contractor with whom they had worked in the past on waterfront development projects. Like most of our installers, the geography of the area you work in dictates the nature of helical projects. The geotechnical profile in New Hampshire varies between mountains (rock) to beaches and bogs. Located in the southeast corner of New Hampshire, Carpentier Contractors LLC does a lot of work along both the New Hampshire and Massachusetts coastline.
The geotechnical investigation found unstable soils with low blow counts, a high-water table, and some loose rock as well. The helicals would have to generate enough torque to penetrate and reach a suitable bearing stratum with enough torque to muscle through the debris. This issue ultimately eliminated the hand-held, portable equipment option, as some downward pressure would be needed to penetrate to the 15’ to 20’ depth where the varying loads could be achieved. Portable hand-held equipment is a great option, when necessary, but is slow, more expensive, and creates brutal working conditions as these case histories illustrate.
Norm reached out to Frank D’Angelo for advice. “This job is inside an existing structure. I cannot get a machine in the house. They will have to be put in by hand unless you have a better idea. The floor is slab on grade, so we can bolt the machine down. The loads are pretty light with the exception of the ones in the center of the house. After you digest this, let’s set up a time to talk,” Norm requested.
Due to the rocky soils, Danbro recommended a Toro Dingo walk-behind mounted with a Pro-Dig 6K drivehead, which Norman confirmed could navigate the confines of the building. Our installation network has had success with this size machine in similar residential projects, interior workspace permitting. 330 39th Street, Sea Isle City
The drivehead was ordered from Pro-Dig with expedited shipping. Overhead was limited to 10’ after slab demo and excavation, so Danbro custom-fabricated an attachment for the 8’ boom and shipped it overnight. Speed was of the essence. Other trades were waiting in the wings and could not proceed with their work until the foundation work was completed and summer was quickly approaching. The slab needed to be demolished at pile point locations. 3’ by 3’ holes had to be dug out 2’ below the bottom of the footer. 11 IDEAL 2/78 pipe piles (.203 wall) were installed at nine locations, requiring varying loads of 15K, 20K, 25K and 40K. The 40K load in the center of the home was achieved by installing two piles and tying them together with the pile cap. All eleven piles were installed in three days, allowing the other work to proceed. With the addition of the new foundation, a third story was added to the structure, increasing the size of the residence while maintaining the original footprint. Result: happy owners, happy professionals (who made it all happen for them), including Carpentier Construction who now add the near-impossible to their regular resume of always challenging projects.