Concrete Foundation Design and Permit Plans: Slabs, Footings, Piers, and Grade Beams
Learn what concrete foundation design includes, when engineered foundation plans may be required, and how slabs, footings, piers, and grade beams support residential, commercial, and light industrial projects.
A Strong Project Starts With a Proper Foundation
Every successful building project starts with a proper foundation. Whether you are building a new home, adding onto an existing structure, constructing an ADU, installing a detached garage, building a shop, or developing a commercial space, the foundation must safely support the structure and transfer loads into the ground.
Concrete foundation design is more than simply pouring a slab. A properly engineered foundation considers building loads, soil conditions, reinforcement, footing sizes, slab thickness, anchor bolts, drainage, construction type, and local permit requirements.
At PEI Engineering, we provide concrete foundation design and permit-ready foundation plans for residential, commercial, and light industrial projects. Our work includes slab-on-grade foundations, thickened slab edges, continuous footings, pad footings, concrete piers, grade beams, and PE-stamped foundation plans when required.
What Is Concrete Foundation Design?
Concrete foundation design is the engineering process used to determine how a building or structure will be supported. The foundation collects loads from walls, columns, posts, roofs, floors, equipment, and lateral forces, then transfers those loads safely to the soil below.
A foundation design may include:
Foundation layout
Slab thickness
Footing sizes
Pier locations and sizes
Grade beam layout
Concrete reinforcement
Anchor bolt requirements
Column base details
Thickened slab edges
Structural notes
Foundation sections and details
PE-stamped drawings when required
The goal is to create a foundation that is safe, practical to build, code-compliant, and coordinated with the structure above.
When Are Engineered Foundation Plans Needed?
Not every small concrete slab requires engineered foundation plans, but many projects do require a Professional Engineer to design or review the foundation. This is especially true when the project includes structural loads, concentrated column loads, unusual site conditions, or city permit requirements.
Engineered foundation plans may be needed for:
New home construction
Home additions
ADUs and guest houses
Detached garages
Shops and workshops
Barndominiums
Metal buildings
Commercial buildings
Warehouses and light industrial structures
Patio covers and pavilions
Equipment pads and generator pads
Retaining wall foundations
Structures on sloped sites
Projects requiring PE-stamped plans for permitting
In many cases, the city, county, architect, contractor, or building owner may request engineered foundation plans before construction can begin.
Slab-on-Grade Foundations
A slab-on-grade foundation is one of the most common foundation systems used for homes, garages, shops, and small commercial buildings. It consists of a concrete slab placed directly over prepared soil or compacted base material.
Slab-on-grade foundations may be used for:
Single-family homes
ADUs
Detached garages
Workshops
Small commercial buildings
Additions
Metal buildings
Storage buildings
A slab-on-grade foundation may include a uniform slab thickness, thickened edges, reinforcement, vapor barrier, anchor bolts, saw-cut control joints, and localized thickened areas where posts or bearing walls occur.
Important design considerations include:
Slab thickness
Concrete reinforcement
Soil support
Load-bearing wall locations
Column or post loads
Anchor bolt spacing
Site drainage
Vapor barrier requirements
Control joints
Concrete strength
A properly designed slab-on-grade foundation helps reduce the risk of cracking, settlement, uneven support, and construction-related problems.
Thickened Edge Slabs
A thickened edge slab is a slab-on-grade foundation where the perimeter of the slab is made deeper and stronger to support exterior walls or structural loads. In many light residential and small accessory building projects, the thickened edge acts as both the slab edge and the footing.
Thickened edge slabs are common for:
Garages
Small homes
ADUs
Additions
Workshops
Storage buildings
Light commercial structures
Metal buildings
Design considerations for thickened edge slabs include edge depth, edge width, reinforcement, anchor bolts, wall loads, soil conditions, and drainage around the slab.
This type of foundation can be practical and cost-effective when the structure is relatively light and the site conditions are suitable.
Continuous Footings
A continuous footing, also called a strip footing, is a long concrete footing that supports a wall or line of loads. Continuous footings are commonly used below foundation walls, exterior walls, interior bearing walls, masonry walls, and stem walls.
Continuous footings may be used for:
Residential foundations
Crawlspace foundations
Basement walls
Stem walls
Masonry walls
Building additions
Commercial buildings
The footing must be sized to spread the building load into the soil safely. The engineer considers the wall load, footing width, footing depth, concrete reinforcement, soil-bearing conditions, and local construction requirements.
Continuous footings are simple in appearance, but they play a critical role in supporting the structure above.
Pad Footings
A pad footing is an isolated concrete footing used to support a single column, post, pier, or concentrated load. Instead of supporting a full wall, a pad footing supports a specific point load.
Pad footings are common for:
Steel columns
Wood posts
Porch columns
Patio cover posts
Interior support posts
Commercial columns
Equipment platforms
Metal building frames
A pad footing may be square, rectangular, or round depending on the project requirements.
The engineer must consider the column load, footing size, concrete thickness, reinforcement, soil-bearing capacity, anchor bolts, and whether the footing must resist uplift or lateral forces.
Pad footings are especially important when a project creates new concentrated loads, such as after removing a load-bearing wall and adding a beam supported by posts.
Concrete Piers
Concrete piers are vertical foundation elements used to transfer loads deeper into the ground or to support elevated structures. Piers can be used where shallow foundations are not practical or where a structure requires discrete support points.
Concrete piers may be used for:
Pier and beam foundations
Decks
Patio covers
Pavilions
Additions
Elevated structures
Sloped sites
Light commercial structures
Foundation retrofit conditions
Pier design may consider pier diameter, pier depth, reinforcement, soil conditions, uplift resistance, lateral resistance, and connection details to the structure above.
For some projects, a geotechnical report may be required to determine soil conditions and recommended pier depths.
Grade Beams
A grade beam is a reinforced concrete beam located at or near ground level. Grade beams are commonly used to connect piers, support walls, or transfer loads between foundation supports.
Grade beams may be used for:
Pier and beam foundations
Sloped lots
Expansive soil conditions
Additions
Commercial foundations
Metal building foundations
Structures with isolated pier supports
A grade beam design may include beam depth, beam width, reinforcement size, stirrups, pier spacing, wall loads, column loads, and connection details.
Grade beams are useful when a foundation needs to transfer loads across spans between piers or provide continuous support for walls above.
Foundation Design for Home Additions
Foundation design for additions can be more complicated than foundation design for a new standalone structure. The new foundation must work with the existing home while supporting the added loads from the new construction.
Home additions may require:
New slab sections
New footings
New foundation walls
Connection details to the existing structure
Expansion or isolation joints
Step footings where grade changes
Drainage coordination
Existing foundation review
For example, a first-floor room addition may require a new slab-on-grade foundation with thickened edges. A second-story addition may require review of the existing foundation and framing to determine whether additional support is needed.
Good foundation design helps reduce differential movement between the existing structure and the new addition.
Foundation Design for ADUs, Garages, and Shops
ADUs, detached garages, shops, and small accessory buildings often require foundation design because they still need to support walls, roofs, equipment, and code-required loads.
Foundation plans for these projects may include:
Slab-on-grade design
Thickened edge details
Footing layout
Anchor bolts
Reinforcement requirements
Utility coordination
Drainage considerations
Structural notes
Even though these structures may be smaller than a primary residence, the foundation still needs to be properly designed and coordinated with the building above.
Foundation Design for Metal Buildings and Barndominiums
Metal buildings, barndominiums, and pre-engineered building systems often require engineered foundations because they can create concentrated reactions at columns or frames.
Foundation design for these projects may include:
Column pad footings
Thickened slab areas
Grade beams
Anchor bolt layouts
Reinforced slabs
Uplift resistance
Lateral load resistance
Coordination with metal building reactions
For metal buildings, the foundation is not only supporting gravity loads. It may also resist wind uplift, lateral forces, and frame reactions. The engineer often needs reaction loads from the metal building supplier before final foundation design can be completed.
Foundation Design for Commercial and Light Industrial Projects
Commercial and light industrial projects often require more detailed foundation coordination because they may involve larger loads, more complex layouts, equipment loads, and additional code review.
Examples include:
Retail buildings
Office buildings
Restaurants
Gas stations
Car washes
Warehouses
Shops
Service facilities
Light industrial buildings
Equipment platforms
These projects may require coordination between structural, civil, architectural, mechanical, electrical, and plumbing systems. The foundation design must account for building layout, column locations, equipment pads, utility routing, drainage, and construction sequencing.
Outdoor Structures and Foundation Design
Outdoor structures can also require engineered foundation plans, especially when they are large, attached to a building, subject to wind loads, or built for permit approval.
Examples include:
Pergolas
Gazebos
Pavilions
Patio covers
Carports
Decks
Outdoor kitchens
Pool equipment pads
Shade structures
These structures may require concrete piers, post footings, thickened slabs, anchor bolts, uplift connections, and lateral bracing.
Even small outdoor structures can become unsafe if they are not properly anchored or supported.
Soil Conditions and Foundation Performance
Foundation design depends heavily on the soil below the structure. Soil must be able to support the loads transferred by the foundation.
Soil-related factors may include:
Soil-bearing capacity
Expansive clay
Fill material
Poor compaction
Groundwater
Slope conditions
Erosion
Drainage patterns
Previous site disturbance
When a geotechnical report is available, the engineer can use the recommended soil parameters to design the foundation. For larger or more complex projects, a geotechnical report may be required by the jurisdiction, owner, or engineer.
For smaller projects, foundation design may rely on code-based assumptions, local experience, and available site information depending on the project requirements.
Drainage and Foundation Design
Drainage is one of the most important factors affecting long-term foundation performance. Poor drainage can cause soil movement, erosion, moisture variation, concrete distress, settlement, and water intrusion.
Foundation design should consider:
Site grading
Roof runoff
Downspouts
Surface drainage
Water ponding near the foundation
Adjacent paving
Drainage swales
Retaining walls
Slope around the building
A foundation may be structurally adequate on paper, but poor drainage can still create long-term performance issues. Proper grading and drainage are important parts of protecting the structure.
What Is Included in a Foundation Plan Set?
A foundation plan set may vary depending on the project, but it commonly includes:
Foundation layout
Slab thickness
Footing sizes
Pier locations
Grade beam details
Reinforcement details
Anchor bolt notes
Concrete strength requirements
Foundation sections
Typical details
Construction notes
Bearing wall or column locations
Coordination with architectural plans
PE stamp and seal when required
A clear foundation plan helps the contractor understand what needs to be built and helps the plan reviewer verify that the design meets applicable requirements.
Permit-Ready Foundation Plans
Permit-ready foundation plans are drawings prepared to support building permit review. These plans are typically coordinated with architectural drawings and include the structural information needed for the foundation work.
Permit-ready plans may be required for:
New construction
Additions
Detached structures
Commercial buildings
Metal buildings
Foundation modifications
Structural repairs
Retaining walls
Outdoor structures
Projects receiving plan review comments
A permit-ready foundation plan should clearly show dimensions, reinforcement, footing sizes, slab details, notes, and sections. The goal is to provide enough information for permitting and construction without unnecessary confusion.
PE-Stamped Foundation Plans
A PE-stamped foundation plan is prepared, reviewed, signed, and sealed by a licensed Professional Engineer. This indicates that the engineer is taking professional responsibility for the design within the defined scope.
PE-stamped foundation plans may be required by:
Building departments
City or county plan reviewers
Architects
Contractors
Owners
Lenders
Commercial landlords
Metal building suppliers
Insurance or code officials
The PE stamp is especially important when the foundation supports structural loads, includes unusual conditions, or must satisfy permitting requirements.
Common Foundation Design Mistakes
Foundation problems often start with incomplete planning or poor coordination. Common mistakes include:
Undersized Footings
If footings are too small, the soil may not be able to support the load properly.
Ignoring Concentrated Loads
Posts, columns, and beams can create point loads that need specific footing support.
Poor Drainage Around the Foundation
Improper grading or water ponding can lead to soil movement and long-term foundation distress.
Missing Reinforcement Details
Concrete needs proper reinforcement placement, spacing, and cover to perform correctly.
Poor Anchor Bolt Coordination
Walls, columns, and metal building frames often require properly located anchor bolts.
Not Coordinating With the Building Layout
Foundation elements must align with bearing walls, posts, columns, beams, openings, and framing above.
Using a Generic Slab Detail for Every Project
Not every project can use the same slab or footing detail. Loads, soil conditions, structure type, and site conditions vary.
Starting Construction Without Permit Approval
Building without approved plans can lead to delays, corrections, demolition, or added cost.
How Foundation Plans Help Contractors
Contractors need clear, practical drawings. A good foundation plan helps answer important field questions before construction starts.
A foundation plan should help the contractor understand:
Where footings go
How deep and wide footings should be
How thick the slab should be
Where reinforcement is required
Where anchor bolts are located
Where piers or grade beams are needed
What concrete strength is required
How the foundation connects to the structure above
What inspections may be required
Clear foundation plans reduce guesswork and help avoid field delays.
How Foundation Plans Help the Permit Process
Permit reviewers need enough information to confirm that the foundation is appropriate for the proposed structure. If foundation information is missing or unclear, the permit may be delayed.
Common plan review comments may request:
Footing sizes
Reinforcement details
Slab thickness
Foundation sections
Anchor bolt spacing
Engineering calculations
PE stamp and seal
Soil information
Retaining wall details
Load-bearing wall support
Having proper foundation plans upfront can make the permit process smoother.
Information Needed to Start Foundation Design
To begin foundation design, it is helpful to provide:
Project address
Property survey or site plan
Architectural floor plans
Building elevations
Structural layout, if available
Soil report, if available
Building type and use
Desired foundation type
Column or wall locations
Metal building reactions, if applicable
Site grading information
Photos of existing conditions for additions
City or county permit requirements
Contractor notes or sketches
For additions, information about the existing foundation is important. For metal buildings, frame reactions from the building supplier are often needed before final foundation design can be completed.
Foundation Design vs. Foundation Assessment
Foundation design and foundation assessment are related, but they are not the same service.
Foundation design is used for new construction, additions, new supports, or new structural work.
Foundation assessment is used when an existing foundation has cracking, settlement, movement, or distress.
If an existing foundation is showing signs of movement, a structural and foundation assessment may be needed first. If repairs or modifications are required, engineered repair details or foundation plans may follow.
This distinction helps ensure the correct service is provided for the actual condition.
Why Engineering Should Be Completed Before Concrete Is Poured
Concrete foundation work is difficult and expensive to change after it is poured. That is why foundation engineering should be completed before construction begins.
Early foundation design can help:
Avoid permit delays
Reduce construction conflicts
Clarify contractor pricing
Coordinate loads and supports
Identify drainage concerns
Avoid undersized footings
Plan anchor bolts correctly
Reduce costly corrections
Improve long-term performance
Good foundation plans provide confidence before construction begins.
PEI Engineering’s Foundation Design Services
PEI Engineering provides foundation design and permit-ready plans for a wide range of projects, including:
Slab-on-grade foundations
Thickened edge slabs
Continuous footings
Pad footings
Concrete piers
Grade beams
Pier and beam foundations
Metal building foundations
Garage and shop foundations
ADU foundations
Addition foundations
Commercial foundations
Light industrial foundations
Outdoor structure foundations
PE-stamped foundation plans
Our team works with homeowners, architects, contractors, builders, developers, and business owners to provide practical foundation design solutions for permitting and construction.
Build on a Foundation Designed With Confidence
Concrete foundation work is one of the most important parts of any construction project. Whether the project is small or large, residential or commercial, simple or complex, the foundation must be designed to support the structure safely and perform over time.
A clear, permit-ready foundation plan helps protect the project from delays, errors, and unnecessary risk.
At PEI Engineering, we provide concrete foundation design, foundation plans, structural details, and PE-stamped engineering documents for projects of many sizes and types.
Need Concrete Foundation Plans?
If you are planning a new build, addition, ADU, garage, shop, metal building, commercial project, or outdoor structure, PEI Engineering can help prepare the foundation plans needed for permitting and construction.
PEI Engineering PLLC
Structural • Civil • MEP • Inspections
Phone: 918-600-8798
Website: www.peiengineering.com
FAQ
Do I need engineered foundation plans for a small building?
It depends on the structure size, use, location, loads, and local permitting requirements. Small accessory structures may not always need engineering, but many garages, shops, ADUs, additions, and metal buildings do.
What is included in a concrete foundation plan?
A foundation plan may include slab thickness, footing sizes, pier locations, grade beam details, reinforcement, anchor bolt notes, concrete strength, sections, and structural details.
Do metal buildings need foundation engineering?
Often, yes. Metal buildings can create concentrated column reactions, wind uplift, and lateral forces that must be resisted by the foundation.
What is the difference between a slab and a footing?
A slab is a flat concrete surface or floor. A footing is a deeper or wider concrete element designed to spread structural loads into the soil.
What is a grade beam?
A grade beam is a reinforced concrete beam that connects piers or supports and helps carry wall or structural loads.
Can PEI Engineering provide PE-stamped foundation plans?
Yes. PEI Engineering can provide PE-stamped foundation plans where required and where the project is located in a state where our engineers are licensed.
Do I need a soil report?
Some projects require a geotechnical or soil report, especially larger buildings, commercial projects, poor soil sites, sloped sites, or projects with special foundation requirements. For smaller projects, requirements vary by jurisdiction and project scope.
Get in touch
Phone
info@peiengineering.com
918-600-8798
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