Londonderry

Helical piles in Londonderry, New Hampshire

Londonderry is in the southern part of the state, where deep frost and rocky ground shape almost every foundation. Manchester, Nashua, and Concord each use a 48-inch frost depth, according to a compiled frost-depth reference that cites local codes. Helical piles get below frost with compact equipment and resist the uplift that heaves shallow deck posts each spring.

The New Hampshire residential code requires footings to extend below the local frost line and at least 12 inches below undisturbed ground. Ledge and boulders are common, so a test pile helps confirm the helicals will reach design depth.

Helical pile companies serving Londonderry

One company is based in Londonderry.

• Helical Drilling Inc: installs helical piles and micropiles and does ground improvement for commercial projects across New England and the Northeast.

Costs and what to ask

National figures from HomeGuide show installed helical piers at about $2,000 to $4,000 apiece. Rock, depth, and camp access affect New Hampshire pricing, and many deck projects need only a few piers. Read our helical pier cost guide for what a quote should include.

Questions to put to any installer:

• Is the pile layout stamped by an engineer for ledge and till?
• Will the crew log torque at every pile and hand over the log at the end?
• What are the shaft size and helix configuration, and how is the steel protected for the soil?
• Is a permit required through the Londonderry building department, and who handles it? What does the warranty include in writing?

For the wider picture, see our page on New Hampshire helical pile installers.