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

What you can build on your lot

Everything in this section is grounded in Glendora Municipal Code § 21.04.040 and the California Government Code it implements, with state-law citations called out where they supply or override the local rule. We won’t re-cite the Glendora section on every line — assume it under each heading unless we tell you otherwise.

Number of ADUs per lot

• Single-family lot. The ordinance frames the allowance as one ADU plus one junior ADU (subsection (E)). State law is more generous, and it controls: Gov. Code § 66323(a)(1)–(2) requires the City to allow a conversion ADU created from existing space, plus a junior ADU, plus a new detached ADU of up to 800 sqft — up to two ADUs and a JADU on one lot. We cover the preemption in the state-law section below.
• Multifamily lot — existing building. Conversion ADUs in non-livable space — at least one, up to 25% of the existing units — plus detached ADUs. Glendora’s text caps detached units at two, but SB 1211 raised the floor to eight detached ADUs on a lot with an existing multifamily building, not to exceed the number of existing units (Gov. Code § 66323(a)(3)–(4)). State law controls.
• Existing accessory structures. A detached accessory structure of any size may be converted to an ADU (subsection (E)) — an old workshop, barn, or oversized garage can become a unit without being held to the new-construction size limits.

Size limits

• Detached or attached ADU: up to 1,200 sqft (subsection (C)(2)(i)) — more generous than the floors state law forces a city to allow.
• Detached ADU built with a JADU: held to 800 sqft, the by-right detached size in Gov. Code § 66323(a)(2).
• The 800-sqft floor is protected. No FAR, front setback, lot-coverage, or open-space rule may shrink an ADU below 800 sqft (Gov. Code § 66321(b)(3)).
• Conversion ADU: no separate square-foot cap when created within existing permitted space; a converted accessory structure may add up to 150 sqft for ingress and egress (Gov. Code § 66323(a)(1)).
• Junior ADU: up to 500 sqft inside the single-family home, plus up to 150 sqft for ingress and egress (subsection (D); Gov. Code § 66313(d)). The minimum size is an efficiency unit under Health & Safety Code § 17958.1.

Setbacks

Side and rear setbacks are 4 feet for a new attached or detached ADU — matching the state-law floor in Gov. Code § 66314(d)(7) — and the front setback follows the underlying zoning district. No setback at all is required for an ADU built within the same footprint as an existing structure, whether a conversion or a replacement (subsection (E)(1)(d)). On a typical Glendora parcel the practical move is to set the unit in the rear yard and let the 4-foot envelope do the work.

Maximum height — the two-story difference

Here is where Glendora stands apart. A detached ADU may reach 25 feet and two stories (subsection (C)(2)(i)) — not the 16-foot, single-story envelope that the state floor in Gov. Code § 66321(b)(4)(A) gives most cities, and that most of Glendora’s San Gabriel Valley neighbors stop at. That makes Glendora a two-story detached-ADU market. Our three two-story Signature Homes — the Fairfax, Venice, and Culver — are detached designs built for roughly a 25-foot envelope, so they permit on Glendora lots. A two-story plan puts a full second bedroom or two upstairs and gives the same livable area back as yard on the ground — the move that turns a tight lot into a real home. Every one of our six single-story models also clears the bar easily, so the choice here is genuinely yours.

Parking

Glendora requires no off-street parking for an ADU — the ordinance recommends one space per dwelling unit but does not require it (subsection (C)(2)(i)). That is more generous than the state framework, which lets a city ask for up to one space per ADU and then waive it in a list of situations (Gov. Code § 66322). A junior ADU never requires parking (Gov. Code § 66334(a)), and when a garage, carport, or covered space is demolished or converted for an ADU, those spaces never have to be replaced (Gov. Code § 66314(d)(11)). For a Glendora homeowner this removes one of the most common design headaches before it starts.

Lot coverage, FAR, and open space

The underlying zone’s floor-area-ratio, lot-coverage, and open-space limits still apply to an ADU, but every one of them is expressly subject to the 800-sqft floor: none may force an ADU below 800 square feet (Gov. Code § 66321(b)(3)). On Glendora’s deeper foothill lots these rarely bind a backyard unit, and where a steeper or tighter parcel comes into play, an 800-sqft unit is still protected.

Owner-occupancy

Glendora does not require the owner to live on the property for an ADU — the ordinance imposes no owner-occupancy requirement on an ADU, matching Gov. Code § 66315, which bars it statewide. The ordinance still requires the owner to occupy either the junior ADU or the primary dwelling for every JADU, recorded by deed restriction (subsection (D)(2)(e)), but that language predates AB 1154. Effective January 1, 2026, AB 1154 amended Gov. Code § 66333(b) so JADU owner-occupancy applies only when the JADU shares sanitation facilities with the primary dwelling. Because Glendora adopted Ordinance 2095 in November 2025, the local text is operatively behind the state rule — a JADU with its own dedicated bathroom carries no owner-occupancy mandate. We cover this in the state-law section below.

Impact fees and utility connections

No development impact fee may be charged on an ADU under 750 sqft, and state law exempts ADUs of 750 sqft or less outright (Gov. Code § 66311.5(c)). Above that threshold, impact fees are charged proportionally to the primary dwelling’s square footage — the ADU’s floor area divided by the primary’s, times the usual fee — not a flat per-unit charge. An ADU generally relies on the primary dwelling’s existing utility connections; where a separate connection is required, the connection and capacity charge are priced to the burden the unit actually adds.

Permitting timeline

ADU and JADU applications are reviewed ministerially — no public hearing, no discretionary design review, no neighbor sign-off (Gov. Code § 66317). The City must approve or deny a complete application within 60 days or it is deemed approved. SB 543 (effective January 1, 2026) adds a written completeness determination within 15 business days (Gov. Code § 66317(a)(2)).

How California state law overrides Glendora

Glendora’s ordinance is generous on size, height, and parking, but on a few points it still reads more narrowly than current state law. Under Gov. Code § 66316 the state standard controls wherever the local text is narrower — here are the places that matters for your plan.

• You can build more than “one ADU plus one JADU.” Subsection (E) describes the single-family allowance as one ADU and one junior ADU. State law requires the City to allow the full stack: a conversion ADU from existing space, plus a junior ADU, plus a new detached ADU of up to 800 sqft — up to two ADUs and a JADU on one single-family lot (Gov. Code § 66323(a)(1)–(2); HCD ADU Handbook, March 2026, pp. 17–18). The narrower local reading is preempted.
• Multifamily lots can hold up to eight detached ADUs. The ordinance caps detached ADUs at two on a multifamily lot. SB 1211 raised the floor to eight detached ADUs on a lot with an existing multifamily building, not to exceed the number of existing units (Gov. Code § 66323(a)(4)). The two-unit cap holds only where the multifamily building is merely proposed.
• Junior-ADU owner-occupancy is narrower than the local text. Subsection (D)(2)(e) requires owner-occupancy for every JADU. AB 1154 amended Gov. Code § 66333(b) effective January 1, 2026 to require it only when the JADU shares a bathroom with the main home. Glendora’s ordinance was adopted weeks before that change, so a JADU with its own dedicated bathroom carries no owner-occupancy mandate.
• The 800-sqft floor beats local coverage and FAR rules. An 800-sqft ADU at 16 feet with 4-foot setbacks must be approved regardless of lot-coverage, floor-area-ratio, or open-space limits (Gov. Code § 66321(b)(3)) — useful certainty on a tighter or steeper foothill parcel.
• No owner-occupancy for an ADU, and no replacement parking. Gov. Code § 66315 bars an ADU owner-occupancy requirement statewide, and Gov. Code § 66314(d)(11) bars requiring replacement parking when a garage is demolished or converted for an ADU. Glendora’s ordinance already reflects both — confirmation, not conflict.

Renting an ADU in the foothills

Plan a Glendora ADU around 30-day-or-longer tenancy. The City bars renting an ADU for any term shorter than 30 days (Glendora Municipal Code § 21.04.040(C)(2)(h)) — the 30-day minimum state law lets a city set (Gov. Code § 66323(e)). Nightly and weekly short-term rental is out; the compliant model is a long-term lease or a furnished mid-term rental — corporate, traveling-medical, or academic tenants.

The benchmark worth anchoring to: HUD’s Fair Market Rents for the Los Angeles–Long Beach–Glendale metro area, revised effective May 21, 2026, put a one-bedroom at $2,328, a two-bedroom at $2,903, and a three-bedroom at $3,681 per month (FY 2026 FMRs, huduser.gov; 91 Fed. Reg. 21301). A newly built ADU with in-unit laundry and a private entrance typically rents at or above those figures — and here a two-story three-bedroom Culver, which Glendora’s height rules make buildable, reaches into the three-bedroom band most single-story ADU markets can’t. Glendora’s drivers are durable: strong, in-demand public schools that pull families into long leases, a deep San Gabriel Valley multigenerational housing culture, and steady demand from Citrus College and the foothill job corridor.

For payback math keyed to your lot and financing assumptions, use the ADU ROI calculator.

Newly constructed ADUs first occupied after February 1, 1995 are generally exempt from California rent-ceiling controls under the Costa-Hawkins Rental Housing Act (Civ. Code § 1954.50 et seq.). The statewide rent-cap framework under AB 1482 (Civ. Code § 1947.12) may still apply depending on the ADU’s structure and ownership — confirm before you lease.

HUD Fair Market Rents are a federal benchmark for the metro area, not a guarantee of what your unit will rent for. Actual performance depends on finish level, lot, access, parking, and the rental market when you lease.