How do appraisers handle unpermitted additions and garage conversions?

Unpermitted does not automatically mean worthless

A lot of sellers assume the appraiser will walk into the converted garage, see no permit, and erase the room from existence. That is not the rule.

Fannie Mae's guide says that when an appraiser finds an addition without the required permit, the appraiser must comment on the quality and appearance of the work and its impact, if any, on the market value. Notice the words "if any." The guide does not say zero. It says go find out.

Finding out means asking one question: what do buyers in this neighborhood actually pay for a house like this, with this kind of work? Sometimes the answer is close to full value. Sometimes it is a lot less, because buyers worry about inspections, insurance and the cost of making it legal. Sometimes the answer is that the room is worth about as much as the garage it replaced.

The permit status is a fact. The value of the space is a market question. Mixing up the two is how people end up with numbers that came from feelings.

Why two appraisers can count the same room two different ways

This is one of the areas where appraisers honestly disagree. Here are the common approaches:

• Leave it out of the living area. The space is reported but not counted as gross living area (the finished, heated square footage of the main house). Some appraisers take this view on any unpermitted space.
• Count it at a market-supported value. The space gets whatever value buyers actually show they will pay, which is often less than permitted space.
• Treat it as non-living space. The room gets some value as a bonus room or storage, on its own line, instead of as square footage.

What pushes the call one way or the other is mostly common sense. Does it look like the rest of the house, or does it look like a weekend and a borrowed nail gun? Does it have a permanent heat source? Is it a covered patio, or did it add half again to the size of the house?

One honest limit: an appraiser is not a building inspector or a contractor. I can describe what I see, but I cannot tell you the framing behind the drywall meets code. If the work raises safety questions, the lender may want a professional to look at it.

Garage conversions come with their own questions

A garage conversion raises two issues at once. You gained a room, and you lost a garage. In a lot of California neighborhoods, buyers care about that garage, and the market reaction to losing it has to be measured, not assumed.

Then the appraiser has to decide what the space is. Fannie Mae treats an accessory dwelling unit (ADU) as living space with its own place to live, sleep, cook and use a bathroom. An ADU's area is not added to the main house's square footage. It goes on its own line on the grid, unless it sits inside the main house, above grade, with interior access.

That matches how I work. A detached structure never counts in the main house's square footage. A converted detached garage is valued for what it is, separately. Under Fannie Mae's ADU rule, an attached unit with no interior door into the house goes on its own line too.

If an ADU is not allowed under zoning at all, Fannie Mae still allows the loan in some cases. The appraisal has to say the use does not comply, show the use is typical for the market with at least two comparable sales that have the same kind of non-compliant use, and the lender has to confirm it will not jeopardize an insurance claim. That last part is the lender's job, not yours, but it is a good reason to call your loan officer early.

The best evidence is a sale just like yours, and those are rare

The strongest support for valuing unpermitted space is a comparable sale (comp) that had similar unpermitted work, ideally next to a similar sale that did not. Those side by side sales, called paired sales, show what buyers actually did with their money.

The trouble is that unpermitted work is not always disclosed in the listing. Agents write "bonus room" and hope nobody asks. Finding true matches takes digging: reading remarks, checking permit records and looking at photos.

When recent matches are thin, I look further back. An older sale can still tell you something if it is adjusted to today's market and to the house. Lenders usually want recent sales on the grid, but an older paired sale can still support the size of the adjustment.

What I will not do is pull a number out of the air. "Unpermitted space is worth half" is a rule of thumb, and rules of thumb are just guesses that got popular. The adjustment should come from sales, and the report should show which sales.

What to do if your house has unpermitted work

1. Pull your permit history. Ask your city or county building department what is on file. Sometimes the work was permitted and the county record just never caught up.
2. Call the buyer's or your own loan officer early. Some lenders will not lend on unpermitted space, or have rules about it. Finding out in week three of escrow is the expensive way.
3. Check California's ADU legalization law. Under AB 2533 (Government Code section 66332), a city generally cannot deny a permit to legalize an ADU or junior ADU built before January 1, 2020 for code issues that are not health and safety issues. Ask your city how its process works.
4. Gather the paper. Contractor names, invoices, dates and photos taken during the work. It helps the appraiser describe the quality honestly.
5. Talk to your agent and, if needed, an attorney about disclosure. Unpermitted work that surprises a buyer late tends to cost more than unpermitted work disclosed up front.
6. Consider a pre-listing appraisal. Knowing how the market treats the space before you set a price beats learning it from the buyer's appraisal.

None of this is glamorous. Neither is watching your converted garage get valued like a garage because nobody could prove otherwise.