Extremely Low. Foundation underpinning is a specialized structural engineering and construction task that requires licensed professionals, specific equipment, and expert knowledge to ensure safety and code compliance. DIY attempts are highly discouraged and dangerous.
Underpinning directly impacts the structural integrity of the existing building, requiring extensive engineering design, geotechnical analysis, and precise construction techniques to prevent further settlement or damage. It involves working with existing foundations, which presents unique challenges compared to new construction.
Project Guidelines & Rules
Permitting and Professional Design
3 Rules
Plans and specifications for underpinning projects shall be prepared by a registered design professional licensed in the State of Illinois (typically a structural engineer).
2024 IRC R104.1, R106.1.1, R401.1
A permit shall be obtained from your local building department prior to commencement of any work. Submittal documents shall include detailed plans, engineering calculations, and a proposed sequence of work.
2024 IRC R105.1, R106.1
A soils investigation report may be required by the building official or design professional to determine soil bearing capacity, frost susceptibility, and other geotechnical parameters relevant to DuPage County soil conditions.
2024 IRC R401.4
Excavation and Site Preparation
3 Rules
All underground utilities shall be located and clearly marked prior to any excavation. Contact JULIE (Joint Utility Locating Information for Excavators) at 811 before digging.
Industry Best Practice; Local Ordinance
Excavations shall be adequately shored, benched, or sloped to prevent collapse, especially when working adjacent to existing structures or property lines. Worker safety protocols shall be strictly adhered to.
2024 IRC R304.1 (General Safety); OSHA Standards
Protection of existing structures, adjacent properties, and public ways from damage due to excavation or construction activities is mandatory.
2024 IRC R104.1, R104.2
Foundation Underpinning Specifics (Piers)
7 Rules
Piers shall bear on undisturbed soil with adequate bearing capacity, as determined by a registered design professional based on a soils report or presumptive bearing values where applicable.
2024 IRC R401.4, R403.1.1
The bottom of all pier foundations in DuPage County shall extend to a minimum depth of 42 inches (1067 mm) below finished grade to protect against frost heave.
2024 IRC R403.1.4.1 (DuPage County Application)
Piers shall be designed to safely transfer all structural loads from the existing foundation to the bearing stratum without causing settlement or adverse movement to the existing structure.
2024 IRC R403.1.1, R403.1.3
Connections between new piers and the existing foundation shall be positively engaged (e.g., by concrete pour, structural steel, or mechanical fasteners) and designed to transfer both vertical and lateral loads as specified by the engineer.
2024 IRC R403.1.1, R403.1.6
Concrete for piers shall meet minimum compressive strength requirements, typically 2,500 psi (17.2 MPa) at 28 days for foundations, with higher strengths often specified by the registered design professional.
2024 IRC R402.2 (references ACI 318), R402.3
Reinforcement for concrete piers shall be detailed and installed as specified by the registered design professional, conforming to ACI 318 requirements for concrete cover, spacing, and lap splices.
2024 IRC R403.1.3, R404.1.2 (references ACI 318)
Underpinning operations shall be conducted in a specific, engineered sequence to maintain structural stability and prevent damage to the existing structure throughout the process.
2024 IRC R104.1 (General Design Professional Authority)
Drainage and Waterproofing
1 Rules
Where underpinning addresses foundation settlement caused by water intrusion or unstable soil, the design professional may require incorporation of proper subsurface drainage (e.g., drain tile) and/or waterproofing measures.
2024 IRC R405.1, R406.1
Electrical Systems (If Affected)
3 Rules
Any existing electrical conductors, cables, raceways, or equipment disturbed or exposed during underpinning shall be protected from physical damage. Where damage occurs, repairs shall be made in accordance with the NEC.
2023 NEC 300.4
Temporary or permanent disconnection and reconnection of electrical services, feeders, or branch circuits shall comply with NEC requirements and be performed by a qualified electrician.
2023 NEC 110.14, 230.70
Ensure all grounding and bonding systems are maintained or re-established if interrupted during construction.
2023 NEC Article 250
Plumbing Systems (If Affected)
2 Rules
All existing plumbing systems, including water supply, sanitary drainage, storm drainage, and gas lines, shall be protected from damage during construction activities. No plumbing shall be routed through or embedded in new structural elements unless specifically designed and approved.
Illinois Plumbing Code 402.1 (Protection of Piping)
Any necessary disconnection, relocation, or reconnection of plumbing lines shall comply with the Illinois Plumbing Code and be performed by a licensed plumber.
Illinois Plumbing Code 106.1 (Permits), 305.1 (Depth of Building Sewers)
Inspections and Quality Assurance
2 Rules
Required inspections by your local building department, including excavation, footing/pier inspections prior to concrete placement, and special inspections as required by the design professional, shall be scheduled and approved.
2024 IRC R109.1.1, R109.1.3
Final inspection by your local building department is required upon completion of all work to ensure compliance with the approved plans and applicable codes.
2024 IRC R109.1.4
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