A micropile is a small-diameter (5 to 12 inches) drilled and grouted deep foundation element that transfers structural loads through weak soils to competent bearing strata or rock. Engineers specify micropiles for foundation underpinning, seismic retrofit, slope stabilization, and new construction on poor soils, with typical load capacities from 50 to over 500 kips per pile at installed depths from 20 to 150 feet.

Budinger & Associates is a micropile contractor headquartered in Spokane Valley, Washington with a second office in Hayden, Idaho. Founded in 1976, we design and install micropiles across Washington, Idaho, Oregon, and Montana under a single design-build contract that covers subsurface exploration, structural design, installation, and load testing.

Engineers and contractors face foundation challenges that conventional driven or augered piles cannot solve. Limited overhead clearance, vibration-sensitive neighbors, weak surface soils, and seismic retrofit loads all rule out standard piling. Micropiles work in those conditions. The drilling process generates low vibration, the rigs fit through standard doorways, and the grouted bond zone develops capacity in materials too weak for direct bearing. Our team includes licensed geotechnical engineers, certified field technicians, and in-house drilling crews affiliated with the ADSC International Association of Foundation Drilling, so the firm that maps your soil also stamps your foundation drawings and operates the rig on installation day. See related work on our geotechnical construction services page.

Micropile Specifications

Typical ranges for micropiles Budinger designs and installs in the Pacific Northwest. Project-specific values depend on soil conditions, structural loads, and site constraints.

Parameter Typical Range
Pile diameter 5 to 12 inches
Installed depth 20 to 150 feet
Design load capacity 50 to 500+ kips per pile (compression and tension)
Installation rate 3 to 8 piles per rig per working day
Minimum overhead clearance 10 feet for limited-access rigs
Vibration impact Low (suitable adjacent to sensitive structures)
Reinforcement options Steel casing, threaded bar, or hollow bar
Grout strength 4,000 to 6,000 psi typical (project-specific)
Load testing Compression, tension, and proof tests per specification
Service area Washington, Idaho, Oregon, Montana

When You Need Micropiles

Conventional driven piles need overhead clearance, vibration tolerance, and ground that won’t fail under driving impact. Many projects don’t have those conditions. Micropiles do.

Micropiles are the right solution when:

  • An existing building is settling and the foundation needs underpinning without demolition of the structure above
  • The site has limited access, low overhead clearance, or vibration-sensitive neighbors
  • Soil is weak, variable, or includes fill, but competent rock or dense soil exists 20 to 150 feet below grade
  • A seismic retrofit requires added foundation capacity for an existing structure
  • A slope or retaining wall is moving and needs deep anchorage to stabilize

Common applications include foundation underpinning for existing buildings, seismic upgrades for older commercial and institutional structures, foundation support for new construction on poor soils, and slope stabilization where ground movement threatens infrastructure.

How Budinger Designs and Installs Micropiles

Every project starts with site investigation. Our subsurface exploration team drills test borings to characterize soil layers, locate bedrock, and identify groundwater conditions. The data feeds the structural design: pile diameter, depth, casing length, grout mix, and anchorage details.

Cased Micropiles

Steel casing extends through weak or collapsible soils. Below the casing, a grouted bond zone transfers load to competent material. Cased micropiles handle projects where upper soils cannot support an open hole or where seismic conditions require cased ductility.

Drilled Micropiles

Open-hole drilling through stable soils, followed by grouting around a steel reinforcement bar. Faster and lower cost when ground conditions allow.

Rock-Socketed Micropiles

The bond zone extends into bedrock. Used when design loads exceed what overlying soil can support and competent rock is reachable. Common across the basalt formations of eastern Washington and northern Idaho.

Hollow Bar Micropiles

A hollow steel bar functions as both drill string and reinforcement. Grout flushes through the bar during drilling. Effective in caving soils where conventional drilling won’t hold an open hole.

Micropile Load Testing

After installation, Budinger performs load testing per project specifications, including tension, compression, and proof tests. Our reports document capacity, deflection, and acceptance criteria for the engineer of record.

Budinger installs micropiles across the markets that shape Northwest infrastructure:

  • Transportation infrastructure. Bridge abutments, highway retaining walls, and DOT projects across WA, ID, OR, and MT.
  • Commercial and industrial buildings. Warehouse foundations, manufacturing facilities, and tilt-up commercial structures on weak or filled soils.
  • Existing building underpinning. Historic renovations, settlement repair, and seismic upgrades for schools, hospitals, and institutional buildings.
  • Utilities and infrastructure. Pump stations, water treatment facilities, and substation foundations where uneven settlement threatens equipment.
  • Slope and embankment stabilization. Micropile groups arrest slope movement and stabilize failing hillsides above and below infrastructure.

We have delivered micropile projects on tight urban sites, inside occupied buildings, and on remote infrastructure with no overhead crane access. Limited-access drilling is one of our core capabilities.

Why Choose Budinger for Micropiles

50 Years in the Northwest

Budinger has worked in WA, ID, OR, and MT soils since 1976. We know what to expect from glacial till in northern Idaho, Columbia Basin loess, Puget Sound clays, and Spokane Valley gravels. Local soil knowledge shortens design cycles and reduces field surprises.

In-House Drilling Fleet

We own and operate the drill rigs that install our micropiles. No subcontracted scheduling delays. Limited-access rigs work inside buildings and on sites with overhead obstructions.

Design-Build Accountability

A single Budinger contract covers exploration, design, installation, and testing. The engineer who stamps the design works with the technician on the rig. One firm, one schedule, one phone call when something changes in the field.

Local Engineering Staff

Our licensed geotechnical engineers and geologists work out of Spokane Valley and Hayden, not a remote regional office. Project response is in days, not weeks.

Recent micropile and shoring work includes the I-90 SH-41 Interchange Temporary Shoring in Post Falls, ID, and ongoing dam foundation work at Priest Rapids Dam in Grant County, WA.

Micropile FAQ

What is a micropile and how does it work?

A micropile is a small-diameter (5 to 12 inches) drilled and grouted deep foundation element. A drill rig bores a hole through weak surface soils into competent bearing material. Steel reinforcement (a threaded bar, hollow bar, or steel casing) is inserted into the hole, and high-strength grout is pumped under pressure to bond the pile to the surrounding ground. The completed pile transfers structural loads from the building above through weak soils into stable strata or rock.

What are micropiles used for?

Micropiles support new foundations on weak or variable soils, underpin existing buildings during renovation or settlement repair, retrofit older structures for seismic loads, stabilize moving slopes and retaining walls, and provide foundation capacity on sites with limited access or vibration restrictions. Common project types include bridges, warehouses, schools, hospitals, dam embankments, and historic building renovations across the Pacific Northwest.

How are micropiles different from helical piles?

Micropiles are drilled and grouted into the ground. Helical piles are screwed into the ground with a hydraulic motor that turns helical plates welded to a steel shaft. Micropiles handle higher design loads (50 to 500+ kips per pile) and reach deeper into competent bearing strata or bedrock. Helical piles install faster and cost less for light to moderate loads in suitable soils. Budinger installs both and recommends the right option after reviewing project conditions. Compare options on our helical piles page.

How deep do micropiles need to be installed?

Most micropiles install at depths between 20 and 150 feet, depending on where competent bearing strata or rock is located. In the Pacific Northwest, depth varies widely: basalt bedrock is often within 30 feet across parts of eastern Washington, while glacial deposits in northern Idaho and the Spokane River valley can require deeper installation. Subsurface exploration before design determines the required depth.

How much does it cost to install micropiles?

Project cost depends on pile count, pile depth, soil conditions, site access, and load testing requirements. Most commercial micropile projects range from $200 to $500 per linear foot installed, though residential, restricted-access, and rock-socketed projects can fall outside that range. Budinger provides project-specific pricing after reviewing structural requirements and site conditions. Request a proposal for a firm quote.

Can micropiles fix a settling foundation?

Yes. Micropile underpinning transfers building loads from a settling foundation down to competent strata or rock below. Piles install through the existing footing or alongside it, and steel brackets or grouted connections transfer the load from the structure to the new pile. The result is a stabilized foundation that resists further settlement. This approach works on commercial buildings, industrial facilities, schools, and homes.

Can micropiles be installed inside an existing building?

Yes. Compact drill rigs fit through standard 36-inch doorways and operate in basements, mechanical rooms, and occupied facilities. Budinger has installed micropiles inside operating warehouses, historic buildings during renovation, schools while in session, and structures where the existing foundation needed underpinning without demolition of the structure above.

Are micropiles used for seismic retrofits?

Yes. Cased micropiles provide ductility and tension capacity that older spread footings and shallow piles lack. Seismic retrofit micropiles add foundation capacity to existing schools, hospitals, fire stations, and commercial buildings without disturbing the structure above. The retrofit work happens inside or beneath the building, which lets the facility stay operational during construction.

How long does micropile installation take?

A typical micropile installs in 4 to 8 hours from start of drilling to completion of grouting. Most commercial projects complete 3 to 8 piles per rig per working day, depending on soil conditions, pile depth, and casing requirements. Project schedules also account for grout cure time before load testing or load transfer.

Need a Micropile Contractor for Your Northwest Project?

Budinger provides design-build micropile services from exploration through installation and testing. Get pricing and engineering input on your project.

Request a Proposal or call our Spokane Valley office at 509-535-8841 or Hayden at 208-719-9038.