Foundation underpinning methods and settlement repair field guide

What underpinning is, and why the cause comes first

Underpinning strengthens or deepens an existing foundation by carrying its load down to deeper, stronger soil or onto piers. The foundation you have is sitting on soil that can no longer hold it the way it needs to, so you build a new load path that reaches past the weak ground to soil that can. That is the whole job, whether the new path is a hand-dug block of mass concrete under the footing or a steel pier driven 30 ft down.

Three situations call for it. A foundation has settled and is still moving, so you have to stop it and sometimes lift it. You are adding load, a second story or heavy equipment, and the original footing was never sized for it. Or someone is digging a deeper basement or excavation right next door, and the ground that supports your foundation is about to be cut away. The methods range from mass-concrete pits to push piers, helical piers, and micropiles, and the right one depends on the soil, the load, the access, and the cause of the movement.

Here is the part that gets skipped, and it is the one that matters most. You find out why the foundation moved before you decide how to fix it. Pier a foundation that is heaving on expansive clay and you have fought the wrong direction. Diagnosing the cause and engineering the load transfer come before any digging. This guide covers the methods, the diagnosis, the sequence, and the records. Helical piers are one underpinning method and get their own full treatment in the helical pier and screw pile guide. For where footings and deep foundations come from in the first place, see the foundation types and footings guide.

When a foundation actually needs underpinning

Underpinning is not the first answer to every crack, and treating it that way costs the owner money on a problem a downspout would have fixed. It earns its place when one of a short list of triggers is real.

The first is settlement that is structural and ongoing: a corner or a wall has dropped, the cracks are widening season over season, and the foundation can no longer hold its position on the soil it sits on. The second is added load. You are putting a story on top, hanging heavy equipment, or changing the use, and the footing that suited the old load is undersized for the new one. The third is an adjacent deeper excavation. A neighbor digs a basement or a foundation deeper than yours, and the soil that braces and supports your footing is about to be removed. The fourth is a failing footing itself, one that was undersized, poorly built, or bearing on fill that was never compacted.

What ties them together is that the existing load path no longer works and a deeper or stronger one has to replace it. If the footing is sound and the soil is fine and the movement is cosmetic, you are not underpinning. You are fixing drainage, sealing a crack, or watching it. Spending pier money on a stable building is its own kind of failure.

Why is my foundation settling?

A foundation settles when the soil under it loses the ability to hold the load in place, and the cause drives the fix, so you find the cause before you pier anything. Pier the wrong cause and you spend the money and the building still moves.

The usual causes are a short list. Poorly compacted fill keeps consolidating under the weight of the building for years after the slab is poured. Water is the one behind most of it: a leaking line, a downspout dumping at the wall, or grading that runs toward the house saturates and softens the supporting soil or erodes it out from under the footing. Erosion carves voids that a corner then drops into. Expansive clay shrinks in drought and swells in wet, ratcheting the structure up and down with the seasons. Decaying organic soil and consolidating clay settle slowly under sustained load. And sometimes a tree drinks the moisture out of the clay on one side and that side drops.

Each of those wants a different response, and some do not want piers at all. A water cause gets fixed at the water first. An expansive-clay problem is a moisture problem before it is a pier problem. This is exactly the kind of call that belongs to a structural or geotechnical engineer with the soils information, not to a pier salesman with a quota. Treat any settlement on a real structure as undiagnosed until the engineer has named the cause.

Settlement, heave, and reading the crack pattern

Settlement is the building going down because the soil gave way. Heave is the building going up because the soil swelled and pushed. They look similar to a homeowner and they call for opposite fixes, so telling them apart is the first real diagnostic step. Pier a heaving slab and you have anchored the part that was not moving while the swelling clay keeps lifting everything around it.

The crack pattern is the first read, not the final word. Differential settlement, where one part drops more than another, commonly shows as stair-step cracks running through the mortar joints of brick or block, doors and windows racking out of square, and a floor that slopes toward the low corner. Heave tends to show in the middle: a slab that bulges or cracks upward in the center, interior partitions lifting, and doors that suddenly bind at the top or gap at the bottom. Horizontal cracks in a basement wall are a different story again, usually lateral soil pressure rather than vertical movement.

Cracks alone do not close the case. The reliable answer comes from monitoring the movement over time and from levels that map where the floor actually sits, read against the soils information. A structural or geotechnical engineer makes the settlement-versus-heave determination, because the fix forks completely on that single call and a wrong guess wastes the whole repair.

The engineer designs it, not the crew

On any structural underpinning, a licensed structural or geotechnical engineer diagnoses the cause, sets the loads, selects the method, and designs the load transfer. This is not a formality and it is not a place to save a fee. The pier count, the depth, the capacity, the sequence, and the bracket detail come from the engineer working with the soils information, not from a rule of thumb on a truck.

The reason is that everything downstream depends on numbers a crew cannot read off the ground. What does the structure weigh and how does that load come down to each footing. How deep is the competent bearing soil and what will it hold. Is the movement settlement or heave. Is the soil expansive. Get any of those wrong and the repair is wrong in a way that hides until the building moves again. A foundation contractor installs the system and verifies it in the field; the basis of design is the engineer's.

Where the soil is the question, and on settlement it usually is, push for a geotechnical engineer and a soils investigation rather than designing on assumption. The engineer also signs the work the AHJ and the special inspector will check. Build to the stamped design, record what you installed, and flag any field condition that does not match the drawings before you cover it up.

Mass-concrete pit underpinning

Mass-concrete underpinning is the traditional method, and on the right job it is still the right answer. You hand-dig a pit down under the existing footing, to a deeper bearing level the engineer specifies, then fill the pit with concrete so the footing now bears on a new block that reaches the stronger soil. Do it in a controlled sequence along the wall and the footing ends up on a continuous new foundation that is deeper, wider, or both.

It suits shallow situations where firm soil is not far below the footing and access is too tight or too rough for a pier rig. As a practical matter it is limited to roughly 10 ft, about 3 m, below the existing bearing level, because below that the open pits become hard to keep stable and safe. The last step in each pit is the one crews shortcut: dry-packing the gap between the cured concrete and the underside of the footing, ramming a stiff, low-slump mortar into that joint so the load actually transfers. Leave a soft gap there and the footing settles again into the space you left.

Mass concrete is labor and shoring, not specialty equipment, so its cost lives in the digging and the sequence discipline. The depth limit, the bay size, the bearing level, and the dry-pack detail all belong to the engineer. Confirm them against the design before the first pit is open.

Never undermine the whole footing at once

The single rule that keeps mass-concrete and pit work from collapsing the building is sequence: you never excavate under the full footing at one time. You work in short bays, commonly around 3 to 5 ft, about 1 to 1.5 m each, and you alternate them so no two adjacent bays are ever open together. Dig bays 1, 3, and 5, fill and let them cure and dry-pack, then come back for 2, 4, and 6. The trade calls it hit-and-miss or hop-scotch, and it is not optional.

The mechanism is simple and unforgiving. The footing can span a short gap on its own for a little while, carried by the soil and concrete on either side. Open two adjacent bays and you have made that gap too long, the footing has nothing under a stretch it cannot bridge, and it can drop or fail. Crews get impatient waiting on cure and want to open the next bay early. That is exactly how a controlled repair becomes a collapse.

The bay length, the cure time before the next round, and the order all come from the engineer's design for that wall and that load. Temporary support stays in place through the work, and the sequence is followed even when it slows the job. The footing is being asked to hold the building while you remove what holds the footing, a few feet at a time.

Beam-and-base and needle beams

Beam-and-base underpinning is the heavier cousin of the mass-concrete pit. Instead of building a new block directly under the existing footing, you cast a reinforced concrete beam that picks up the wall and carries its load sideways to new bases set on better soil, often on both sides of the wall. The beam does the spanning and the bases do the bearing, which lets you bridge over soft spots the footing cannot sit on directly.

Needle beams are a related move. A needle is a beam threaded through or under the wall, sticking out both sides, that transfers the wall's load onto piers or bases positioned outside the building footprint. You use it when you cannot get a continuous beam under the wall, or when the bearing has to land well clear of the existing footing line.

These methods carry more load and reach more awkward conditions than plain mass concrete, and they cost more in steel, forming, and engineering to match. The beam size, the reinforcement, the base bearing, and the load path are all engineered for the specific wall. This is firmly the engineer's design, not a field adaptation.

What are push piers?

A push pier, also called a resistance pier, is a steel tube driven straight down under the footing by a hydraulic ram that uses the weight of the building itself as the reaction to push against. The crew bolts a load-transfer bracket to the underside of the footing, then drives pier sections through that bracket into the ground until the tube reaches firm strata or refusal. The building's own weight is what forces the pier down, so a pier that can be driven to depth against that weight has been load-tested against the very load it will carry.

That self-testing quality is why push piers are a settlement-repair workhorse on heavier structures. Once the piers are down and confirmed, hydraulic jacks on the brackets can take the load off the bad soil and, where the engineer allows, lift the structure back toward level before the load is locked off onto the piers. The weight then runs from footing to bracket to pier to firm soil, bypassing the soil that failed.

Push piers need two things to work: enough building weight to drive against, and a firm bearing layer within reach. A light structure cannot generate the reaction to push a pier to depth, and there has to be competent strata or rock to land on. Where those hold, the pier capacity, the bracket, the drive pressure, and the lift are designed and verified by the engineer and the manufacturer, not improvised.

Helical piers as an underpinning method

Helical piers, also called screw piles, are steel shafts with helical plates that a machine rotates into the ground until the plates bear in firm soil. They underpin a settling foundation the same way push piers do, through a bracket bolted to the footing, but they get to depth by turning in rather than being pushed, so they do not rely on the building's weight to install.

The thing that sets them apart is that capacity is verified by the installation torque. The harder the soil fights the advancing plates, the more torque it takes to keep turning, and that final torque correlates to the load the finished pier will hold, against the manufacturer's published factor and the engineer's design. That makes them a good fit for lighter structures, for tension and uplift loads that push piers cannot take, and for tight or low-headroom access.

Because helical piers are a full topic of their own, this guide keeps to where they sit among the methods. For how torque proves the capacity, the Kt factor and the ICC-ES report behind it, brackets, tension anchors, corrosion, and the records that make them stand, see the helical pier and screw pile guide. The choice between helical and push piers is the next section.

Push piers vs helical piers: which one?

Push piers and helical piers both underpin a settling foundation by carrying its load to firm soil through a bracket on the footing, and the choice between them comes down to the weight of the structure, the type of load, and what the soil is doing. Neither is universally better. The engineer picks the one the conditions favor.

Push piers need the building's weight to drive against and a firm bearing layer within reach, which makes them the common choice for heavier structures sitting over reachable dense soil or rock, where their drive-against-the-load installation doubles as a capacity check. Helical piers do not need building weight to install, so they win on lighter structures, garages, porches, and additions, on jobs where you need to resist uplift or tension, and in tight or low-headroom spaces a drive rig cannot work. Helical piers also verify capacity by torque as they go in.

The honest version is that both can carry serious load and the lines blur in the middle. A light structure rules out push piers because there is not enough weight to react against; a tension load rules them out because they only work in compression. Beyond those hard limits, the call is the engineer's, balanced against the manufacturer's published capacities for the exact product. The helical pier guide covers the torque-to-capacity side of that decision in depth.

Micropiles for high load, limited access, and rock

A micropile, sometimes called a mini-pile, is a small-diameter drilled-and-grouted pile reinforced with high-strength steel. The crew drills a hole, often right through the existing footing, sets a steel bar or casing, and grouts it into competent soil or rock below. The grout bonds the steel to the ground along the shaft, and the finished pile carries the load down past the weak soil. Diameters typically run under about 12 in, roughly 300 mm, yet the capacity is high, commonly in the range of 50 to 300 tons depending on the design and ground.

Micropiles earn their keep where the other methods run out of road. They drill through almost anything, including the hard rock and boulders that stop driven piers, and there is no real depth ceiling in a normal soil profile. The drilling rigs work in low headroom, down around 6 to 8 ft of clearance, which puts them inside basements and under bridges where nothing larger fits. So the high-load job in a tight basement on rocky ground is the micropile job.

The trade-off is cost and specialty work. Micropiles bring drilling, grout, and a crew that does this for a living, so they sit at the higher end of the methods. The pile capacity, the bond length, the grout, and the reinforcement are engineered and, where required, proven by load test. This is design-and-build territory for the engineer and the specialty contractor, not a field call.

Ground improvement: jet grouting and compaction grouting

Not every settlement problem gets solved by adding piers. Sometimes the better move is to improve the soil itself so it can carry the load it was failing to hold. That is ground improvement, and it sits alongside underpinning as an alternative the engineer weighs against piering.

Compaction grouting, also called low-mobility grouting, injects a stiff, low-slump grout into the ground that expands a bulb and densifies the loose soil around it, tightening up poorly compacted fill or voids without disturbing the structure above much. Jet grouting uses a high-pressure jet to cut and mix grout into the soil in place, building columns of cemented, improved ground that strengthen the bearing or cut off water. Both change the soil rather than bypass it.

Ground improvement competes with piers when the problem is weak or loose soil over a depth, and it can be the cleaner answer where access is hard or where you want to fill voids rather than build a new load path. It is also easy to oversell. Whether you improve the soil or add piers is a design decision that turns on the cause of the movement, the soil profile, and the load, and it belongs to the geotechnical engineer.

Which underpinning method fits the case?

The method follows the cause, the soil, the load, and the access, in that order. There is no default. The engineer matches the system to the conditions, and the table below is how those conditions usually sort out, not a substitute for the design.

Read it as a starting point for the conversation with the engineer. Mass concrete fits shallow firm bearing and tight, rough access where a rig cannot go. Push piers fit settlement on a structure heavy enough to drive against, over firm strata in reach. Helical piers fit lighter loads, tension, and tight access. Micropiles fit high loads, deep or rocky ground, and low headroom. Ground improvement fits weak or loose soil where you would rather strengthen the ground than add piers. The cause of the movement sits over all of it: fix a water or heave cause first, because no method holds against a cause you left running.

Can underpinning lift a foundation back to level?

Underpinning can often lift a settled foundation, but lifting and stabilizing are two different goals with two different risk profiles, and the realistic goal is usually to stabilize, not to chase perfect level. Once the piers are down, hydraulic jacks can raise the structure, and on push piers in particular the lift can recover a meaningful part of what was lost. How much comes back depends on the structure, the cause, and how brittle the finishes are.

The risk lives in the lift. A building that settled slowly has adapted to its dropped position. Force it back up hard and fast and you can crack walls that had healed, break tile and plaster, stress the plumbing, and open new gaps. The aggressive lift that looks good on the level can do more visible damage than the settlement did. Many repairs are stabilized in place, holding the building where it sits so it stops moving, with only as much lift as it tolerates without tearing itself up.

Set the owner's expectation before the jacks come out. Full re-leveling is sometimes achievable and sometimes not, and trying for it is not always the safer choice. The engineer sets the target lift, and the realistic outcome is often a building that has stopped moving and recovered some elevation, not one returned to the day it was built. Tell the owner that plainly. The disappointment comes from a promise of perfect level that the structure was never going to allow.

The load transfer: bracket, engagement, and lock-off

Underpinning only works if the load actually moves from the old failing path onto the new one. That handoff is the load transfer, and it is where a good design becomes a real fix or quietly fails. On pier systems the transfer runs through a steel bracket clamped to the underside of the footing: structure weight goes from footing to bracket to pier to firm soil. On mass concrete it runs through the dry-pack rammed between the new block and the footing.

The bracket has to be engaged, not just present. The pier is driven or screwed to its capacity, the bracket is set against the footing, and then the load is locked off onto the pier so the system carries the building rather than just sitting next to it. On a lift, the jacks raise the structure and the bracket is locked at the new elevation. On a stabilize, the load is transferred at the current position. Either way, an unengaged bracket is a pier doing nothing while the soil keeps moving.

The capacity that gets engaged, the lock-off, and the lift all come off the engineer's design and the manufacturer's bracket details. A pier driven deep but never locked off has not transferred anything. Confirm the engagement and record it, because from the surface a transferred load and an idle pier look the same.

Shoring and temporary support during the work

Underpinning means removing or undercutting the support of a loaded structure, on purpose, while people work beneath it. Temporary support holds the building through that window, and it is a safety item before it is a quality item. Shoring, needling, and props carry the load while the permanent system is built, and the excavation that exposes the footing has to be supported so it does not collapse on the crew.

The hazards stack up in this work. Open excavation under a loaded footing is a cave-in and an undermining risk at the same time. The structure can drop if the sequence or the support fails. Spoil, tools, and the structure itself are overhead and struck-by hazards in a pit someone is standing in. The protective system for the excavation and the temporary support for the structure are both engineered for the depth, the soil, and the load, and they are not the place to improvise.

Treat the temporary works as part of the design, not an afterthought the crew sorts out. For the excavation side of it, the protective system and the entry rules cross into trenching, shoring, and struck-by practice that has its own requirements. Confirm both the structural shoring and the excavation protection against the engineered plan before anyone is under the building.

Fix the water, or it settles again

Water is behind most foundation settlement, so if the cause was water and you pier the building without fixing the water, you have bought time, not a repair. The soil that was softened or eroded by a leaking line, a downspout dumping at the wall, or grading that runs toward the house will keep moving the ground around and below the new work. The piers may hold their points while the slab and the soil between them keep going.

The root-cause fixes are unglamorous and they matter more than the hardware. Get the gutters working and the downspouts discharging well away from the foundation. Grade the ground to fall away from the building. Find and fix the plumbing or drainage leak that was feeding the soil. On expansive clay, stabilizing the moisture is the actual problem, because the swelling and shrinking that lifts and drops the structure is driven by the wet-dry cycle, not by a lack of piers.

This is the step owners and some installers want to skip because it is cheap and boring and does not feel like a foundation repair. It is the repair. A pier system installed over an unaddressed water cause is a callback waiting to happen. Fix the water as part of the scope, not as an upsell after the building moves again.

Monitoring before, during, and after

You verify that the movement actually stopped, and the only way to know is to measure it over time rather than eyeball the cracks. Monitoring runs in three phases: before, to establish what the building is doing and confirm the diagnosis; during, to catch any movement the work itself triggers; and after, to prove the repair did its job and the structure has gone still.

The tools are simple. Crack gauges, the tell-tale type that shows relative movement across a crack in two directions, give a cheap, datable read on whether a crack is alive or healed. A level survey of the floor, repeated on a schedule, maps the elevations and shows whether a corner is still dropping. On sensitive jobs and adjacent-excavation work, the engineer may call for survey points and tighter monitoring with trigger thresholds that stop the work if movement exceeds a set limit.

Monitoring is what turns an opinion into a record. A crack that has not moved in twelve months across a gauge is evidence the cause was addressed; a crack still widening says the cause is still running, no matter how many piers went in. Set the baseline before the work, keep reading after it, and let the data, not the calendar, say the repair held.

Underpinning to protect a neighbor

Not all underpinning fixes a problem you have. Some of it prevents one you are about to cause. When you dig a basement or a foundation deeper than the building next door, you are about to remove the soil that supports your neighbor's footing, and the building code does not let you do that without first underpinning or otherwise protecting that foundation against movement.

This is as much a legal matter as a structural one. The party who excavates generally carries the duty to protect and to make good any damage, and depending on the jurisdiction there are notice requirements to the neighbor before the digging starts. Where party-wall or adjacent-excavation rules apply, the protection, the monitoring, and the procedure for halting work if the neighbor's building moves get written down and agreed before anyone breaks ground. The underpinning has to be installed in a sequence that protects the neighboring structure, not just your own site.

The design and the loads here are firmly the engineer's, and the legal framework is the AHJ's and, where it applies, the surveyor's. Do not start a deeper dig next to an existing building on assumption. The underpinning of the neighbor's foundation is part of your excavation, and the obligation to protect it does not wait for permission you forgot to ask for.

Load testing the piers

Where the design or the AHJ calls for it, piers get load-tested to prove they carry what the engineer says they carry, separate from the installation read. Push piers are tested against the building weight as they drive, and helical piers are verified by installation torque, but a physical load test applies a known load to a pier and measures the deflection, which is the most direct proof of capacity there is.

Whether a test is required, and how many piers get tested, depends on the project, the soil variability, and the AHJ. A site with uncertain or variable soils, a high-consequence structure, or a design that pushes the system near its limits is more likely to need verification testing than a routine repair in well-understood ground. The engineer sets the test program and the acceptance criteria, and the special inspection regime ties it to the code.

The helical pier guide covers torque verification and load testing for screw piles in detail, including how the torque correlation relates to a load test and where a load test confirms it on the actual site. Confirm the testing requirement against the engineer's design and the adopted code before you assume an installation read alone will satisfy the inspector.

Permits, special inspection, and sign-off

Structural underpinning is permitted work, and on most jobs it draws special inspection. The building code treats underpinning and deep foundations as elements that get inspected during installation, not just looked at when they are done, because once the pier is in the ground or the pit is backfilled, the work that mattered is buried.

The 2021 IBC addresses underpinning directly in Chapter 18, requiring that excavation not reduce the support of any foundation without first underpinning or protecting it, and that underpinning be installed in a sequence that protects the structure and the site. Deep-foundation elements, including driven and cast-in-place piles and helical piles, carry special-inspection requirements in Chapter 17, with continuous inspection during helical pile installation that records the equipment, dimensions, depths, and final torque. The exact sections, and which provisions a jurisdiction has adopted or amended, change between code cycles, so confirm them against the edition the AHJ actually enforces.

Pull the permit, build to the stamped design, and give the special inspector what the code wants recorded. The engineer signs off on the design and the field verification, the special inspector witnesses the installation, and the AHJ closes the permit. Skipping the inspection on buried structural work is the kind of shortcut that surfaces at resale or after the next movement, and by then there is nothing left to inspect.

What to document, and tying it to a field tool

Underpinning is buried work, so the record is the only thing left to defend it after backfill. Six months on, when a crack reopens or a buyer's inspector asks what was done, the answer is the file, not the dirt. The diagnosis, the design, and the as-built installation all have to be captured while they are visible.

Keep the chain intact: the engineer's diagnosis of the cause, the stamped design with the method, loads, depths, and sequence, and then the field log of what actually went in. For piers, that means each pier's location, type, depth, final drive pressure or installation torque, bracket engagement, and any lift. For pits, the bay sequence, the bearing level reached, and the dry-pack. Add the monitoring baseline and the follow-up readings, the load-test results where required, and the special-inspection reports. A field tool like FieldOS is where that log lives in the field, geotagged and timestamped per pier or per bay, so the record matches what the inspector witnessed and survives the job.

The discipline pays off twice. The inspector and the engineer get the verification they need to sign, and the owner gets a defensible record that the cause was found, the right method was used, and the load actually transferred. A repair with no record is a repair you cannot prove happened.

Common mistakes

• Piering the building without first diagnosing why it moved, so the wrong cause keeps it moving.
• Undermining the whole footing at once instead of alternating short bays in sequence.
• Lifting too aggressively and cracking walls, tile, and plumbing chasing perfect level.
• Ignoring the water or drainage cause, so the soil keeps moving and it settles again.
• Choosing the wrong method for the soil and load, like push piers on a structure too light to drive against.
• Leaving a soft gap under the footing by skipping the dry-pack, so it settles back into the space.
• Driving piers but never locking the bracket off, so the pier sits idle while the soil moves.
• Designing the repair without a structural or geotechnical engineer and the soils information.

Field checklist

Standards and references

The framework starts with the registered design professional. A structural or geotechnical engineer diagnoses the cause, designs the underpinning, sets the loads and the method, and signs the work, working from a soils investigation where the soil is in question. That design is the basis of the job; the contractor builds and verifies in the field. Hedge the methods, the loads, and the sequence to the engineer on every job, because they turn on numbers only the design and the soils information carry.

The building code framework, commonly the IBC, addresses underpinning in its soils and foundations chapter, requiring that excavation not reduce support of a foundation without first underpinning or protecting it, and that underpinning be installed in a protective sequence. Its special-inspections chapter sets inspection and testing for deep-foundation elements, including continuous inspection during helical pile installation that records depths and final torque. Section numbers and adopted provisions vary by edition and jurisdiction, so confirm them against the edition the AHJ enforces and any local amendments before citing them.

Proprietary pier and pile systems carry their own evaluation. Manufacturers publish capacities, torque correlation factors, and bracket details in ICC-ES evaluation reports backed by testing, and those values, not a rule of thumb, govern the product. Three things hold across every method: diagnose the cause before you pier, sequence the work and engineer the load transfer, and fix the water cause and monitor that the movement stopped. The engineer, the manufacturer, and the AHJ are the authorities behind the rest.

Units and terms

Underpinning carries its own vocabulary, and the same idea can read differently across an engineer's report, a manufacturer sheet, and a permit set. These are the terms that have to be clear before the work starts.

Depths and bay sizes show in feet and meters across sources, capacities in tons or kips, and torque in foot-pounds for helical work. The definitions below are the field meanings; the design values for any specific job come from the engineer and the manufacturer.

Underpinning

Strengthening or deepening an existing foundation by transferring its load to deeper, stronger soil or to piers

Differential settlement

One part of a foundation settling more than another, the movement that cracks and racks a structure

Heave

Upward movement from soil swelling, usually expansive clay taking on moisture, the opposite of settlement

Mass-concrete (pit) underpinning

Hand-dug pits in sequence under a footing, filled with concrete to a deeper bearing level

Push (resistance) pier

A steel pier driven by hydraulic ram using the building's weight as reaction, for settlement repair and lift

Micropile

A small-diameter drilled-and-grouted steel pile for high loads, limited access, or rock

Load transfer

Moving the structure's weight from the old failing path onto the new piers or pit through a bracket or dry-pack

Lift vs stabilize

Raising the structure back toward level versus holding it where it sits so it stops moving

Related tools

Calculators and readiness checks for this work

Compare your options

FAQ

People also ask

• What is a helical pier?
• What is a footing?
• What is the difference between dampproofing and waterproofing?
• What is selective demolition?
• How long do you cure concrete?