How Many Piers Does My Foundation Need?
Estimate the pier count from the affected length and spacing, then multiply by your price per pier to get a planning total for underpinning a settled foundation.
Calculator
A 120 ft affected run at 6.0 ft spacing needs 20 piers ≈ $28,000.00 at $1,400.00/pier. Spacing is a labeled planning band — a structural engineer sets the real pier count and load.
When a foundation settles, the fix is usually to transfer its weight onto piers driven down to stable soil or bedrock — push piers hammered by the building's own weight, or helical piers turned in like giant screws. The single biggest driver of the bill is the number of piers, and that comes from how long the settling run is and how far apart the piers are placed. This tool turns those two measurements into a count, then multiplies by the installed price you were quoted.
Think of it as a way to read an underpinning proposal, not to design one. Enter the length that is actually moving — one corner, one wall — rather than the whole house, choose a spacing from the typical planning band, and put in your contractor's per-pier price. You get a defensible ballpark you can hold up against the bid.
Formula
The count is the affected length divided by the spacing, always rounded up to a whole pier, and the cost follows from your price:
piers = ceil(affected_length ÷ spacing)\ntotal = piers × price_per_pier + engineering/permit
Rounding up matters: a 120 ft run at 6 ft spacing is exactly 20 piers, but a 121 ft run still needs 21, because you cannot install a fractional pier. The spacing you pick is a labeled planning band — an engineer sizes the real spacing to your soil and loads, so treat the count as an estimate to question the bid with, not a design.
Worked example
A house has settled along one 120 ft wall. Your engineer suggests planning around 6 ft spacing, and your contractor quoted $1,400 per installed pier:
- Piers = ceil(120 ÷ 6) = 20 piers
- Piers cost = 20 × $1,400 = $28,000
- Engineering / permit line: as quoted (add it in)
So the underpinning itself lands near $28,000 before the soil report, design and permit. Widen the spacing to 8 ft and the count drops to 15 piers and $21,000 — which is exactly why the spacing is an engineer's call, not a place to shop for a lower number.
Push piers, helical piers and what the price includes
Push (resistance) piers use the weight of the house to drive steel sections to a firm stratum; they suit heavier structures. Helical piers are screwed in and can carry lighter loads or be installed where there is little structural weight to push against, such as a porch or a stoop. Both are priced per pier installed, but "installed" can mean different things: some quotes include excavation, brackets and backfill, others break those out. Read the proposal before you compare per-pier prices between contractors.
The pier count from this calculator is a planning figure. The real number, the pier type, the depth and whether the crew attempts to lift the foundation back toward level or simply stabilize it where it sits are engineering decisions that depend on a soil investigation. A licensed structural or geotechnical engineer should assess the movement and specify the repair; underpinning is structural work that needs a permit and inspection. Put the engineer's fee, the soil report and the permit in the engineering / permit line so your total is honest.
Two more cost movers: depth (piers priced by the section, so deep stable soil means more steel) and access (interior piers under a finished basement slab, or work hemmed in by landscaping, cost more than an open exterior run). Neither is knowable from measurements alone, which is another reason the output is a starting point for the conversation, not the final bid.