Building an ADU in Glendora. Rules, costs, timeline.

Can I build an ADU in Glendora?

Five things to know before you start

If you read nothing else here, read these. They are the five points that change the most Glendora projects.

How many units your lot can hold

Glendora is a city of about 52,000 people on the San Gabriel Valley foothills, and most of its housing sits on generous single-family parcels. The ordinance treats those lots more cautiously than state law does. GMC § 21.04.040(E)(1) allows one ADU and one junior ADU on a lot in a single-family zone, and separately allows an existing detached accessory structure of any size to be converted.

The Government Code is more generous, and it wins. A city has to allow an ADU created from existing space, plus a junior ADU, plus a newly built detached ADU of up to 800 square feet, in combination on the same lot. That is two ADUs and a JADU alongside the house.

Owner-occupancy

You do not have to live on the property to build or rent an ADU in Glendora. The ordinance imposes no owner-occupancy requirement on an accessory dwelling unit, which is what Gov. Code § 66315 requires of every city in the state.

A junior ADU is the exception, and a narrower one than the code text suggests. GMC § 21.04.040(D)(2)(e) requires the owner to occupy either the house or the JADU, recorded by deed restriction, with no condition attached. AB 1154 narrowed Gov. Code § 66333(b) as of January 1, 2026 so the mandate reaches only a JADU that shares a bathroom with the main house. Give the junior unit its own bathroom and the requirement falls away.

What the City cannot do

Review is ministerial. Glendora checks your drawings against objective standards and issues the permit, or tells you what is deficient. There is no public hearing and no discretionary design review (Gov. Code § 66317). The City may not require you to live on the lot, may not demand replacement parking for a converted garage, and may not use floor area ratio to shrink the unit below the size its own code protects.

What an ADU costs in 2026

An ADU budget has three parts and they behave very differently. The plan fee is fixed and known before you start. Construction is a range that narrows once we see the lot. City fees are modest by comparison, and in Glendora they are tied to construction valuation rather than published as a single ADU line item.

Because Glendora permits detached two-story ADUs at 25 feet and allows 1,200 square feet, the whole lineup is on the table here. Every plan below, single-story and two-story, fits inside the City’s envelope.

The plan fee is fixed — not an estimate, not a range, not a starting point. The build figures in the table are estimates from an independent licensed general contractor for hard construction, and we detail them for your specific lot before you commit. Once your plans are permitted they are yours: build the ADU yourself, bring your own licensed contractor, or build with one of our vetted construction partners.

Development fees

Glendora publishes no flat ADU-specific planning fee, and we will not invent one. Planning application fees and valuation-based building and plan-check fees are set by the City’s adopted fee schedules through the Community Development Department. Ask the Planning Division for a written estimate against your construction valuation before you set a budget. Utility connection charges apply where a separate connection is required.

What it returns

Glendora sits inside the Los Angeles–Long Beach–Glendale HUD Metro Fair Market Rent Area. HUD’s revised FY 2026 Fair Market Rents for that area, published at 91 FR 21301 and effective May 21, 2026, are the benchmark worth anchoring to.

Read those as a floor rather than a forecast. Fair Market Rents average across an entire metro and across housing of every age, most of it far older than anything you would build now. A new, permitted, detached unit generally rents at or above the figure for its bedroom count. What it will actually fetch on your street is a question for a local agent, and worth asking before you commit. Our plans map onto these bands by bedroom count — the Melrose rents as a two-bedroom, the Culver as a three.

The demand side in Glendora is unusually durable. The public schools pull families into long leases, Citrus College and the foothill job corridor keep smaller units occupied, and the San Gabriel Valley’s multigenerational housing culture means many of these units never reach the open market at all. The 25-foot envelope matters here too: a three-bedroom unit reaches a rent band that single-story ADU markets cannot.

The other half of the return is resale. A permitted ADU adds recorded square footage that comps into the sale of the property. An unpermitted conversion does the opposite — it is a disclosure problem and a financing problem, which is why the state built a legalization path for pre-2020 units at Gov. Code § 66311.7.

HUD Fair Market Rents are a federal benchmark for the metro area, not a guarantee of what your unit will rent for. Figures are the FY 2026 Fair Market Rents for the Los Angeles–Long Beach–Glendale HUD Metro FMR Area as revised effective May 21, 2026 (91 FR 21301). Actual performance depends on finish level, lot, access, parking and the rental market when you lease.

When an ADU isn’t the right move

Not every Glendora property is a good candidate, and it is cheaper to learn that now than after you have paid for drawings. Four situations where we would tell you to wait, change type, or not build:

• Your numbers depend on short-term rental income. They will not work. Neither the house nor the ADU may be rented for less than 30 days (GMC § 21.04.040(C)(2)(h)), and state law requires a term longer than 30 days for these units (Gov. Code § 66323(e)). Run the math on a month-to-month tenancy or reconsider the project.
• Your foothill lot is in a fire zone on a narrow street. GMC § 21.04.040(C)(1)(c) does not permit an ADU in a very high fire hazard severity zone where the street does not meet City standards. That is a siting question with a yes or no answer, and it is the first thing to check rather than the last.
• You need to sell the unit as its own condominium. Glendora has not adopted the AB 1033 opt-in that Gov. Code § 66342 requires, and GMC § 21.04.040(C)(2)(g) bars separate conveyance. If a separate exit is central to the plan, this is the wrong city for it today.
• You are planning an SB 9 lot split as well. The City caps the original lot area at four dwelling units either way (GMC § 21.04.040(F)(4)(c)). A split can consume the capacity you were going to spend on an ADU, so choose one route rather than assuming both.

The rules that make Glendora different

Glendora has no Coastal Zone and no AB 1033 separate-sale opt-in. What it does have is a permissive ADU envelope, a young design code adopted in the same ordinance, and a foothill geography that adds one threshold question nothing else on this page can answer for you.

Foothill fire zones and the 36-foot street

Glendora runs north into the San Gabriel Mountains, and the foothill neighborhoods sit inside Cal Fire very high fire hazard severity zones. GMC § 21.04.040(C)(1)(c) does not permit an ADU in one of those zones where the lot is not served by a public or private street meeting City standards. The City’s March 2026 handout supplies the number the code leaves out: the site must be fully mitigated and served by a street at least 36 feet wide, and the condition reaches junior ADUs as well as ADUs.

It is a gate, not a judgment call. The street either measures or it does not, which keeps review ministerial under Gov. Code § 66317 and keeps a qualifying foothill lot on the ordinary 60-day path. Most of Glendora’s single-family lots are unaffected. The point is to read the parcel first, not to assume the worst.

Objective design standards, and the three ways to satisfy them

Ordinance 2095 did two things in November 2025. It carried the ADU section forward, and it adopted a new Chapter 21.15 of objective design standards with a section written specifically for accessory dwelling units at GMC § 21.15.040. The old rule of thumb — make it look like the house — is now one of three named routes.

Every route is objective, which is what keeps the review ministerial. A few standards apply whichever one you take: a top edge treatment of either a 12-inch roof overhang or a decorative molding, a pedestrian walkway connecting the unit to the sidewalk, entrances and parking, and a balcony or deck capped at 400 square feet (GMC § 21.15.040(E)–(G)). One exclusion is worth knowing: Chapter 21.15 does not apply in the Rural Hillside Residential zone or in several of the City’s specific-plan and planned-development areas (§ 21.15.020(B)).

Junior ADUs and the bathroom question

A junior ADU in Glendora is built within the walls of an existing or proposed single-family home, capped at 500 square feet with up to 150 more for a way in and out, and needs at least an efficiency kitchen. It may share the main house’s bathroom or have one of its own (GMC § 21.04.040(D)(2)). That choice now decides whether the owner-occupancy mandate attaches at all.

Multifamily lots

On a lot with an existing multifamily building, GMC § 21.04.040(E)(1)(f) allows conversion of non-livable space — storage rooms, boiler rooms, passageways, attics, basements, garages — into ADUs, up to 25 percent of the existing units, with at least one always allowed where a property holds seven units or fewer. That tracks the state standard.

The detached count is where the ordinance falls behind, and where the City has quietly moved ahead of its own text.

Selling a Glendora ADU separately

GMC § 21.04.040(C)(2)(g) bars conveying an ADU separately from the primary dwelling, and Glendora has not adopted the AB 1033 opt-in that Gov. Code § 66342 requires before a city may allow a condominium sale. That closes the general-purpose exit.

One narrower route survives regardless of local text. Gov. Code § 66341, added by AB 587, lets a qualified nonprofit that built the unit convey it separately to a qualified low- or moderate-income buyer under a recorded tenancy-in-common agreement. It is mandatory statewide and needs no city opt-in. It is a different statute from AB 1033, and the two should never be cited as a range.

SB 9, historic properties, and the four-unit ceiling

Glendora regulates SB 9 in the same code section as ADUs, at GMC § 21.04.040(F), and the interaction matters. The total number of dwelling units within the area of the original single-family lot may not exceed four, whether or not the lot is split (§ 21.04.040(F)(4)(c)). The City’s worked examples make the trade explicit: a lot already carrying a house, an ADU and a JADU leaves a newly created parcel room for a primary dwelling and nothing more.

SB 9 also carries exclusions that ADUs do not. A lot inside the Historic Preservation Overlay Zone, a property on the State Historic Resources Inventory, a designated landmark, a 100-year floodplain parcel or designated protected-species habitat is ineligible for an SB 9 lot split (§ 21.04.040(F)(1)(a)). None of those exclusions appears in the ADU provisions. If you own a historic Glendora property, the ADU route stays open to you where the lot-split route does not.

Recent state-law changes that reach a Glendora lot