When a Building Permit Is Required Under IRC 2024

Quick Answer

Under IRC 2024 Section R105.1, a building permit is required before beginning any work to construct, enlarge, alter, repair, move, demolish, or change the occupancy of a building or structure, or to install or alter any electrical, gas, mechanical, or plumbing system regulated by the code. The rule is broad by design. If you are changing anything structural, mechanical, or electrical in a one- or two-family dwelling, your default assumption should be that a permit is required.

Under IRC 2024, section R105.2 lists specific categories of work that are exempt, but those exemptions are narrower than most homeowners expect, and violating the permit requirement can result in stop-work orders, fines, and mandatory demolition of unpermitted work.

What IRC 2024 Actually Requires

Section R105.1 states that any owner or authorized agent who intends to construct, enlarge, alter, repair, move, demolish, or change the occupancy of a building or structure, or to erect, install, enlarge, alter, repair, remove, convert, or replace any electrical, gas, mechanical, or plumbing system, shall first make application to the building official and obtain the required permit. The language is intentionally expansive. “Alter” includes almost any modification to the existing structure or its systems.

New construction of any size triggers a permit. This includes new homes, additions, garages, sheds, decks, and accessory dwelling units. Alterations that change the use of a space—finishing a basement, converting a garage to living space, or adding a bathroom—require permits for all trades involved: building, electrical, plumbing, and mechanical. Repairing structural damage, whether from storm, fire, or deterioration, requires a building permit because the repair must be inspected to confirm it restores the structure to code-compliant condition.

Section R105.2 lists work exempt from the permit requirement. The IRC 2024 exempt categories include: one-story detached accessory structures used as tool and storage sheds, playhouses, and similar uses if the floor area does not exceed 200 square feet (local amendments frequently reduce this threshold); fences not over 7 feet high; retaining walls not over 4 feet in height measured from the bottom of the footing to the top of the wall, unless supporting a surcharge; water tanks supported directly upon grade if the capacity does not exceed 5,000 gallons; sidewalks and driveways; painting, papering, tiling, carpeting, cabinets, counter tops, and similar finish work; prefabricated swimming pools with a capacity at or under 5,000 gallons; shade cloth structures constructed for nursery or agricultural purposes; swings and other playground equipment; window awnings that do not project more than 54 inches from the exterior wall; and prefab moveable partitions.

Critically, the exempt-work list does not exempt electrical, plumbing, or mechanical work within those categories. Replacing a water heater, adding an outlet, or installing a new HVAC system always requires a permit, even if the structural work associated with the project might be exempt. Permits for mechanical, electrical, and plumbing (MEP) systems are governed by their respective referenced codes—the IRC Chapter 24 for fuel gas, the IRC Chapters 25–32 for plumbing, and the IRC Chapters 14–23 for mechanical—but the permit obligation flows from R105.1.

Why This Rule Exists

Building permits exist because construction work has consequences that extend beyond the person who commissions it. Structural failures injure and kill occupants. Faulty electrical wiring starts fires. Improper gas connections cause explosions. Substandard plumbing contaminates water supplies. The permit and inspection system is the mechanism by which the public interest in safe construction is enforced. Without mandatory permits, there is no point in the process at which a code-trained professional reviews the work against the adopted standard.

Permits also protect property owners financially. Unpermitted work discovered during a home sale typically must be disclosed and can either derail the transaction or require retroactive permitting at the seller’s expense. Insurance companies may deny claims for losses arising from unpermitted work, particularly fire losses from uninspected electrical systems. Lenders financing home purchase or refinance sometimes require confirmation that no open or unpermitted work exists on the property. The short-term savings from skipping a permit can easily be consumed by these downstream costs.

The permit record also benefits future owners and contractors. A permitted addition or remodel leaves a documented record of what was built, what inspections were passed, and what approvals were obtained. That record is invaluable when a future contractor needs to understand the structural design of a home or when a homeowner wants to add to work done by a predecessor.

What the Inspector Checks at Rough and Final

The permit process begins with plan review. For simple projects, plan review may be done over the counter at the same time the permit is issued. For complex projects, plans are submitted, reviewed by plan examiners for code compliance, and approved before the permit is issued. The approved permit documents must be kept on-site and available to the inspector at every inspection.

During construction, the building official schedules inspections at defined stages specified in IRC Section R109. For structural work, those stages include foundation, framing, insulation, and final. For MEP systems, inspections are required before the systems are concealed. The inspector at each stage reviews the work against the approved plans and the applicable code sections, approves or rejects the inspection, and documents the outcome in the permit record.

The final inspection is the last step before a certificate of occupancy is issued. The inspector confirms all prior inspections were approved, all conditions of the permit have been satisfied, and the completed work matches the permitted scope. Work performed beyond the permitted scope—a contractor who added a bathroom not shown on the plans, for example—will be flagged at final inspection and must be permitted and inspected before the CO is issued.

What Contractors Need to Know

One of the most common contractor errors is performing work beyond the permitted scope without pulling a supplemental permit. If the approved plans show one bathroom addition and the owner asks the contractor to also finish the basement, the contractor must obtain a separate permit for the basement work before proceeding. Working beyond the permitted scope is a violation that can result in stop-work orders, fines, and refusal to issue the certificate of occupancy until the additional work is separately permitted and inspected.

Contractors must also understand that the permit is issued to the building owner, but the contractor is responsible for complying with the conditions of the permit during construction. In most jurisdictions, licensed contractors must be identified on the permit application, and the contractor’s license number is associated with the permit record. A contractor whose license is associated with a pattern of permit violations may face disciplinary action by the state licensing board.

Permit fees are typically based on the valuation of the project. Contractors who understate project valuation on permit applications to reduce fees are committing a misrepresentation that can result in permit revocation and liability exposure. Use the actual contracted value or the building official’s published valuation tables, whichever applies in the jurisdiction.

For fast-moving projects, work with the building department to pre-schedule inspections in advance. Many jurisdictions offer online inspection scheduling that allows contractors to book inspection slots several days out. Failing to schedule inspections early enough can cause costly waiting periods between phases when inspectors are in high demand during busy construction seasons.

What Homeowners Get Wrong

The most frequent homeowner mistake is assuming that because work seems minor or cosmetic, no permit is required. Cabinet replacement, new flooring, and painting do not require permits. But adding a new circuit for a kitchen appliance, replacing a water heater, or framing a new partition wall that might affect structural load paths all require permits, even if the homeowner performs the work themselves. In many jurisdictions, homeowners are permitted to pull building, electrical, plumbing, and mechanical permits for their own primary residence. The homeowner exception does not eliminate the inspection requirement—it only waives the requirement to use a licensed contractor for the work.

Homeowners also frequently misunderstand the “like-for-like replacement” assumption. Replacing a failed water heater with an identical water heater of the same type is often assumed to be permit-exempt. Under IRC R105.1, it is not. Water heater replacement is explicitly a mechanical system alteration that requires a permit in most jurisdictions. The permit ensures that the installation is inspected for proper gas connections, venting, seismic strapping (in applicable zones), and temperature-pressure relief valve installation.

A third common error is performing work on a property the homeowner owns as a rental without recognizing that the homeowner permit exemption may not apply to rental properties in their jurisdiction. Many states and cities limit the owner-pull permit to the owner’s primary residence. Rental property work typically requires a licensed contractor.

State and Local Amendments

The 200-square-foot shed exemption in IRC R105.2 is one of the most commonly amended provisions at the local level. Many jurisdictions reduce the exemption to 120 square feet or even eliminate it entirely for properties in historic districts, flood zones, or wildland-urban interface areas. Some jurisdictions also limit the number of exempt accessory structures per lot regardless of size. Never assume the IRC base threshold applies without checking local ordinances.

California’s Residential Code requires permits for retaining walls over 3 feet in height measured from the bottom of the footing rather than the IRC’s 4-foot threshold. California also requires permits for any electrical work beyond simple device replacement, including all water heater replacements. Florida requires permits for reroof work in all jurisdictions, a requirement that goes beyond the IRC’s general permit obligation because roof replacement in hurricane zones has been identified as a critical structural concern.

Some jurisdictions have adopted streamlined permit processes for common projects. Online over-the-counter permits for standard deck construction, water heater replacement, or HVAC equipment replacement are increasingly common and allow homeowners and contractors to obtain permits quickly without a formal plan review. These expedited permits still require inspections—the streamlining is in the permit-issuance process, not the inspection requirement.

When to Hire a Professional

Any project involving structural modifications, new electrical service or subpanels, gas system extensions, or significant plumbing reconfiguration should involve a licensed contractor and a design professional where required by the jurisdiction. Structural work in particular should be reviewed by a licensed structural engineer if the project involves removing walls, adding openings, or changing load paths, even on projects that the owner could technically permit themselves.

Homeowners considering unpermitted work should understand that the consequences extend well beyond the construction phase. Unpermitted work disclosed during a real estate transaction can require retroactive permitting, inspection by a licensed contractor who certifies compliance, and in some cases demolition and reconstruction where work cannot be inspected after the fact because it is already concealed. The cost and disruption of retroactive permitting almost always exceeds the cost of obtaining the permit at the time of construction.

For projects in jurisdictions with complex local amendments—particularly in California, New York, or Florida—consult a local permit expeditor or contractor familiar with the specific jurisdiction’s requirements before beginning design. Local knowledge of the plan review process and inspection scheduling can save significant time and cost on complex residential projects.

Common Violations Found at Inspection

• Electrical work performed without a permit, including new circuits, panel upgrades, and subpanel installations discovered during inspection of adjacent permitted work.
• Water heater replacement completed without a permit, missing required seismic strapping in applicable seismic zones, improper venting, or missing temperature-pressure relief valve.
• Addition or alteration work performed beyond the scope shown on the approved permit drawings, requiring a supplemental permit and inspection before CO can be issued.
• Shed or accessory structure built over the local exemption threshold without a permit, discovered during site inspection or neighbor complaint.
• Deck construction performed without a permit, with undersized footings, incorrect post-to-beam connections, or missing required ledger attachment inspections.
• Garage conversion to living space performed without permits for building, electrical, plumbing, and mechanical systems involved.
• Contractor performing work before the permit is issued and posted on-site, in violation of R105.1’s requirement to obtain the permit before beginning work.
• Homeowner pull permit used for rental property work in a jurisdiction that limits owner-pull permits to primary residences.