Helical Piers vs Push Piers for Underpinning

When part of a house starts to sink, the problem is almost always the soil under the footing, not the footing itself. The soil may have been poorly compacted when the house was built, softened by water from a leaking drain or bad grading, shrunk during drought, or simply never been strong enough for the load. Patching the cracks does not change any of that.

Underpinning solves the problem by transferring the weight of the house past the weak soil to something firmer below. In modern residential repair, that usually means steel piers. The two main types are push piers (also called resistance piers) and helical piers. Both work. They are just suited to different situations.

Signs a foundation may need underpinning

Underpinning is a structural repair, so it is worth knowing what typically leads to it:

• Stair-step cracks in block walls, or diagonal cracks in poured walls, wider at one end
• Doors and windows that stick, or gaps opening at the top of frames
• Diagonal drywall cracks from the corners of doors and windows
• Floors sloping toward one side or corner
• Cracks in brick veneer, or brick pulling away from window frames
• A chimney leaning away from the house

One of these alone is not proof of settlement, but several together, especially concentrated in one area, deserve a structural look. If you are not sure what your cracks mean, start with our guide to foundation crack types.

How push piers work

Steel push piers use the weight of the building itself as the reaction force for installation.

1. A small excavation is dug next to the foundation at each pier location, exposing the footing.
2. A steel bracket is fastened to the footing.
3. Sections of steel pipe are driven down through the bracket with a hydraulic ram, one section at a time. The ram pushes against the weight of the structure above it.
4. Driving continues until the pier reaches a load-bearing layer, such as dense soil or bedrock, where it resists further pushing.
5. The load is transferred from the footing to the piers. Depending on the situation, the structure can sometimes be lifted back toward its original level during this step.
6. The excavation is backfilled.

Where push piers fit well:

• Heavier structures: two-storey homes, masonry homes, small multi-unit buildings
• Sites where a firm bearing layer exists at a reachable depth
• Repairs where some lift is wanted and the structure is heavy enough to drive against

Limitations:

• They need enough building weight to drive against. Light structures such as porches, decks, or single-storey additions may not provide enough.
• Because the depth is only known once the pier hits refusal, the final length of each pier is determined during installation.

How helical piers work

Helical piers are steel shafts with one or more helix-shaped plates near the tip, a bit like a giant screw.

1. As with push piers, the footing is exposed at each location.
2. The pier is rotated into the ground with a hydraulic torque motor, so the helix plates pull it down through the soil.
3. Installers monitor torque as they go. Torque correlates with the capacity of the soil, so the pier is advanced until it reaches the torque needed for the design load.
4. A bracket connects the pier to the footing, and the load is transferred.

Where helical piers fit well:

• Lighter structures: porches, decks, single-storey additions, garages, sunrooms
• New construction or new footings, since helical piers do not need building weight to install
• Sites where the bearing layer is deep or where soils are softer, so the plates can develop capacity in the soil itself
• Situations where vibration should be kept low

Limitations:

• Very dense soil, cobbles or rock can make installation difficult.
• The design depends on soil conditions, so local knowledge and sometimes soil testing matter.

Side-by-side comparison

• Installation: push piers are driven hydraulically using the building's weight. Helical piers are screwed in with torque.
• Best for: push piers suit heavier structures. Helical piers suit lighter structures and new footings.
• Capacity check: push pier capacity comes from the driving pressure at refusal. Helical pier capacity is checked against installation torque.
• Lifting: both can be used to try to lift a structure back toward level in the right conditions, but no installer can promise how much a house will recover.
• Disturbance: both need small excavations at each pier location rather than full trenches.

What drives the cost of underpinning

Underpinning is usually one of the larger foundation repairs. The main factors are:

• Number of piers, which depends on the length of wall affected and the load
• Depth to a bearing layer, since deeper piers mean more steel and more time
• Access, both outside and sometimes inside if piers have to be installed from the basement
• Lifting, if the plan includes trying to raise the structure
• Engineering and permits, which many municipalities require for structural foundation work
• Restoration of landscaping, walks, or finished interior areas
• Follow-up repairs, such as sealing cracks once the foundation is stable

Ask that each quote states the number and spacing of piers, the pier type, the expected or minimum depth, and how capacity will be verified. Without those, two quotes are not really comparable.

Questions to ask before you hire

• What is causing the settlement, and will anything else (drainage, grading, plumbing leaks) be addressed?
• Why this pier type for my house?
• How many piers, at what spacing, and how was that determined?
• How will the installer confirm each pier reached adequate capacity?
• Is lifting part of the plan, and what are realistic expectations?
• Is an engineer involved, and is a permit needed?
• What restoration is included?
• What are the warranty terms, in writing, and do they transfer if I sell?

If a wall is bowing inward rather than sinking, that is a different problem with different fixes. See bowing and leaning wall repair on our services pages, along with the underpinning and pier installation summary.

Frequently asked questions

Which is better, helical piers or push piers?

Neither is better across the board. Push piers suit heavier structures, such as two-storey and masonry homes, where the building's weight can be used to drive them down to a firm layer. Helical piers suit lighter structures like porches, additions and garages, as well as new footings, because they are screwed in and do not need building weight to install.

Can underpinning lift a house back to level?

Sometimes. Both push piers and helical piers can be used to try to raise a structure back toward its original level in the right conditions. No installer can promise how much a house will recover, so ask what realistic expectations are before work starts.

How deep do foundation piers go?

They go as deep as needed to reach a load-bearing layer, so the depth varies from site to site. Push piers are driven until they meet refusal on dense soil or bedrock, and helical piers are advanced until installation torque shows they have reached the capacity the design calls for. The final length of each pier is often only known during installation.

Does underpinning need a permit or an engineer?

Many municipalities require engineering and a permit for structural foundation work like underpinning. Ask each contractor whether an engineer is involved and who handles the permit, since both affect the cost and the schedule.

Get a quote

If you are seeing signs of settlement, fill out our quote form with your city, where the cracks or sloping floors are, and how long you have noticed them. A specialist who works in your area will follow up to set up an assessment and give you a written quote. It is free to request, with no obligation.