Basement lowering for builders and general contractors, from rowhouses to commercial buildings.
We underpin existing foundations for builders, general contractors and developers (rowhouses, triple-deckers, multifamily and commercial buildings) when a basement is lowered, a neighbor digs deeper, or new loads come on. Pit-and-pour goes in by hand in the engineer's hit-and-miss sequence; micropiles take over where pits cannot reach good bearing. We work under the builder's or GC's contract, never homeowner-direct, and bid the underpinning sub scope only.
Callouts
Select a numbered part below to read what it is and what it does.
Plain-language view of the same typical ranges.
Before anything is dug, the building and its neighbors get a condition survey and monitoring points. The engineer's drawings set the pit widths and number them in a hit-and-miss order, so no two neighboring pits are ever open together.
A pit about 3 to 5 ft wide is hand-dug under the existing footing, down to the bearing the engineer calls for, with timber shoring as the ground needs. The footing spans over the open pit on the supported ground to either side.
The bottom is checked against the design bearing before concrete goes in, typically by the engineer or inspector. Concrete is placed, with dowels or keys to the next pit where the design calls for them, stopping 2 to 3 in. short of the old footing.
Once the concrete has set, stiff non-shrink dry-pack is rammed into the gap so the footing bears tight on the new concrete, with no shrinkage gap left to settle into.
The next pit in the numbered order opens only after the pits beside it are concreted, packed and cured. When the last pit is packed, the GC lowers the floor and pours the new slab.
Pit-and-pour
Most basement lowering under Boston rowhouses and triple-deckers is done with pit-and-pour: the existing wall is carried down, one short pit at a time, to a bearing below the new floor. It needs no rig inside the building, and the sequence is what keeps the wall supported while it happens.
The hit-and-miss sequence
The engineer numbers the pits so no two neighbors are ever open together. A common pattern is three passes: every third pit, then the next set, then the last. Each open pit has concrete or undisturbed ground on both sides, and the footing spans across it.
Pit widths
Typically 3 to 5 ft along the wall, often 4 ft, set by the engineer from the wall load, the footing and the ground. Narrower where the ground is poor or the load is concentrated.
Dry-pack
Concrete stops 2 to 3 in. below the old footing. Once it has set, stiff non-shrink dry-pack is rammed into the gap, so the footing bears tight on new concrete instead of on a shrinkage gap.
Mass or reinforced pits
Mass concrete pits carry the wall load straight down and suit most lowering. Reinforced pits, doweled or keyed to their neighbors, come in when the underpinning also retains soil beside the lowered floor, goes deep, or has to resist sliding and overturning.
Pits or micropiles
Pits are the plain, economical answer when good ground is a few feet below the footing. When it is not, micropiles (pin piles) carry the wall down to till or rock instead.
Works best when
Good bearing is a few feet below the footing, in ground that stands up in a short pit.
Reaches
As deep as a hand-dug pit can safely go, usually a few feet below the old footing.
Water
Above the water table. A pit below it needs pumping, which is a problem in the GCOD.
Access
Hand tools, shoring boards and a way to get concrete in. No rig inside the building.
Pricing
In our price book. See the rates.
Works best when
Bearing is deep, the ground is soft or wet, or the building stands on timber piles.
Reaches
Through fill and clay into glacial till, or a socket in rock.
Water
Drilled and grouted without lowering the water table.
Access
A compact drill and room to set it up. Access is confirmed on a site walk before pricing.
Pricing
Priced per job. Micropiles & pin piles.
The engineer of record makes the call. Where both could work, pits usually cost less; micropiles buy depth, dry drilling and low vibration.
Neighbors and ground
In a rowhouse block, the wall you are lowering is often a party wall carrying half of your neighbor's building. Underpinning it means working under their load as well as yours, so the sequence, the monitoring and the paperwork all have to include them.
Before work starts: their written agreement for access and any work under their side, a condition survey with photos, and monitoring points they have seen. During the work: readings on the engineer's schedule and a clear action level. The guide to excavating next to a neighbor covers notice, access and what to put in writing.
Much of Back Bay, the South End and Boston's other filled land stands on timber piles. They last while they stay under water and rot once the groundwater drops and air reaches them, which is why the city drew the Groundwater Conservation Overlay District (GCOD) around them.
That shapes underpinning two ways. A building on timber piles usually cannot be underpinned with ordinary pits, because its load sits on the piles, not the soil; the fix is engineered, often with micropiles. And pits or pumping that lower groundwater near a neighbor's timber piles are exactly what Article 32 asks a project to rule out. Building below grade in the GCOD explains the rule, and you can check an address against the district map.
Instruments and readings are by others unless our quote includes them; we build the sequence around them.
To price it
Drawings
Ground
Scope
Access
Pit-and-pour is in our published unit price book three ways: by the cubic yard of concrete, per pit, and per foot of wall. Depth below the footing, access, groundwater and obstructions move the number most. The interior dig, the new slab and drainage are usually by others.
The underpinning cost guide walks through what drives the price, and the budget estimator covers the shoring and other scopes that often come with it.
Rev 1 · valid through December 13, 2026
Pit-and-pour underpinning, per CY of concrete
UP-PIT-POUR$4,550 (budget figure)per CY
range $3,550–6,450 · min $8,900
$8,900 (budget figure)each
range $7,000–12,500 · min $8,900
$2,200 (budget figure)per LF
range $1,700–3,100 · min $8,900
Micropiles and pin piles
Where pits cannot reach good bearing
Priced per job
Typical price with the book's low–high range. Low end: open site, repetitive work, good ground, larger quantities. High end: tight access, obstructions, variable ground, small quantities.
† Budget figure. Depends strongly on ground and configuration; confirm with a firm quote.
Budget and bid-day numbers. Send drawings and borings for a firm, line-item quote within 3 business days.
Illustrative tear sheets — example case studies pending verification.
Tell us about the project and we'll put together a detailed quote within 3 days. We generally work with general contractors.
Or email plans to bids@earthsupportcorp.com
