How to legalize unpermitted work

Updated October 6, 2026 · 4 min read

Short answer

Apply to the building department for a permit covering the work as it exists, often called an as-built or retroactive permit. An inspector then checks it, which can mean opening walls or ceilings. You correct anything that fails and get a final inspection. Expect extra fees, and expect the work to be judged on code, not appearance.

The steps

1Get the permit history for the address so you know exactly what is and is not on record.
2Have a licensed contractor, architect or engineer assess the work and tell you what is likely to fail.
3Ask the building department what it needs. Many require drawings of the work as built.
4Submit the application and pay the fees.
5Schedule the inspection. Be ready to expose wiring, plumbing or framing that has been covered up.
6Make the corrections the inspector lists.
7Pass the final inspection and keep the paperwork with the house records.

What drives the cost

Three things make up the bill. Costs vary too much by city and by job for an honest average, so get a quote from a contractor who has taken work through this process in your city.

The permit fee, plus a penalty. Many departments charge a multiple of the normal fee for work started without a permit.
Drawings and professional fees.
Corrections, including opening and repairing finished walls. This is usually the largest part and the hardest to know in advance.

Which code applies

It varies. Some departments judge the work against the code in force when it was built, if you can prove the date. Many apply the current code. Ask before you apply, because the answer changes the cost.

When work cannot be legalized

Building code problems can usually be corrected. Zoning problems often cannot: an addition over the setback line, a structure too tall for the lot, an extra dwelling unit where only one is allowed. The options then are a variance, altering the work until it complies, or removing it.

Common questions

Can I ask the building department without reporting myself?

You can ask general questions about the process without giving an address. Once you apply, the property is on record.

How long does it take?

From a few weeks to several months. It depends on the department's review times and how much has to be corrected.

Should the seller or the buyer do it?

Either can. The owner at the time applies. In a sale it is a negotiation: the seller legalizes before closing, or the buyer takes it on in exchange for a lower price.