Plano | Cottages and Duplexes

Plano Backyard Cottages and Duplexes: Sizes, Districts and Permits

Plano has two ways to put a second home on a residential lot. A backyard cottage, the City's name for an accessory dwelling unit (ADU), is a small detached home behind a house, allowed in most residential districts. A duplex, one building with two homes, is allowed in a smaller set of districts. This page gives the size, parking and permit rules for each, from the Zoning Ordinance and the City's fee schedules. The Plano overview has the summary.

What a Backyard Cottage Is

Sec. 8.200 defines a backyard cottage as "a detached dwelling unit subordinate to and located on the same lot as a Single-Family Residence (Detached) dwelling unit." Plano added the rules in 2019 (Ordinance No. 2019-2-10) and amended them in 2023 (Ordinance No. 2023-8-15). The City's fact sheet lists other names for the same thing: "ADU/accessory dwelling unit, carriage home, second unit, granny flat, in-law suite." It adds that a cottage "must contain a kitchen, bathroom, and sleeping area."

The residential use table marks the backyard cottage "P" in 14 districts: SF-20, SF-9, SF-7, SF-6, UR, PH, SF-A, 2F, GR, MF-1, MF-2, MF-3, MH and RCD. The A and ED districts have no "P" in that row. The nonresidential use table also lists it in the UMU and BG districts. Because the cottage must sit with a detached house, it fits lots that already hold one.

Backyard Cottage Rules

Source: Plano Zoning Ordinance, Sec. 15.1800 and the Sec. 16.700 parking schedule.

The size cap works two ways at once. The rule in Sec. 15.1800.2E is "1,100 square feet or 50% of the gross habitable floor area of the main dwelling unit, whichever is more restrictive." Behind a 1,600 square foot house, the cottage may have 800 square feet. Behind a 2,400 square foot house, the 1,100 cap applies. The cottage must also fit inside the district's total lot coverage, which is 45 percent in SF-9, SF-7 and SF-6 and 25 percent plus 10 percent for accessory buildings in SF-20. Lot coverage is the share of the lot under buildings.

"Behind the main dwelling unit" points to Sec. 13.500.2P, which says detached accessory buildings "shall be located behind the main building." The fact sheet shows two site layouts, one marked "in compliance" and one marked "does not qualify." The general accessory building rules in Sec. 13.900 also apply where they fit: carports and detached buildings other than garages must stay at least 3 feet from side and rear lot lines, and a detached building in a required rear or side yard may not exceed 10 feet in height.

The Covenant, Occupancy and Renting

Sec. 15.1800.4 requires the permit applicant to give the City a covenant "suitable for recording with the county," stating that the cottage cannot be sold apart from the main home. A covenant is a promise recorded in the land records that binds later owners. It must require owners to tell a buyer about the limit, and to "remove the backyard cottage and restore the site to a single-family dwelling" if the covenant is broken. Proof of recording comes before the building permit.

The Building Inspections permit handout, revised July 12, 2022, lists two papers: an "Affidavit confirming occupancy according to Zoning Ordinance, Section 15.1800.4.A" and a covenant under "Section 15.1800.4.B." The current code has only one item in Sec. 15.1800.4, the covenant, labeled 4.A. The history table shows Ordinance No. 2023-8-15, adopted August 28, 2023, amended the backyard cottage rules, after the handout's revision date. The adopted code controls, so the current text sets no occupancy affidavit.

The documents also differ on renting. The City's fact sheet lists "Additional Revenue: Property owners may benefit from extra income generated by renting out the BYC, or living in the BYC and renting out the main home." Sec. 13.900.1A of the code says that in a residential district "an accessory building may not be used for commercial purposes... and may not be rented." The code does not say whether a backyard cottage, which it defines as a dwelling unit, falls under that accessory building rule. Ask the Planning Department in writing before you plan on rent.

Short-term rentals have their own rule. Sec. 15.2300.8 treats the cottage and the main home as "a single residence," and the two "cannot be rented as two separate Short-term Rental uses."

Permit Fees for a Cottage

The Building Inspections fee schedule adopted by Ordinance No. 2025-11-4 has one line for "Residential (Addition, Alteration, Backyard Cottage)":

• building permit: $0.48 per square foot, with a $40 minimum fee;
• plan review: $45;
• electrical, plumbing and mechanical, where they apply: $0.01 per square foot each, with a $45 minimum each.

By VanPlex arithmetic, a 600 square foot cottage with all three trades pays $288 for the building permit, $45 for plan review and $135 for the trades, $468 in all. The City's park fee, $5,691 for each new single-family home under Sec. 16-266, does not apply: Sec. 16-264 says the park fee article does not apply "to permits required for backyard cottages or accessory uses." The Residential Permits page on the City site still links an older Building Inspections fee schedule, adopted by Ordinance No. 2020-3-6; Ordinance No. 2025-11-4 repealed that ordinance "in its entirety."

Duplexes: Which Districts and What Rules

Plano's code calls a duplex a two-family dwelling: "a detached building having separate accommodations for and occupied by not more than 2 households." The use table permits it in SF-A, 2F, GR, MF-1, MF-2, MF-3, MH and RCD. The three districts written around duplexes compare as follows.

Source: Plano Zoning Ordinance, Sec. 9.1100, Sec. 9.1200 and Sec. 9.1700.5.

2F. The district "is intended to encourage single-family ownership by permitting the division of a 2F lot along the common wall of the 2 residential units of a duplex." Lots may be platted in pairs, with "only one dwelling unit per lot," and no single house on one of a pair. A lot not platted in pairs may be split once into two parcels by a licensed surveyor's description, if the duplex building permit was issued after June 3, 1983. All utilities must be separate "such that each unit is individually metered," and each unit needs a 2-car garage that may not be closed in. A 2F lot may also be built under the SF-7 house standards instead.

GR. This district serves the Douglass Community near downtown Plano. Its special rules require a covered front porch of at least 40 square feet per unit, horizontal siding of wood, cement board, aluminum or vinyl, or brick (no exterior plaster or stone), a gabled or hipped roof sloped at least 6:12, and fences over 40 inches set back 10 feet from the front of the home. GR sets parking at 1 space per home, half the 2 spaces the 2F and RCD duplex rules require.

RCD. The RCD duplex is "a detached building having separate accommodations for and occupied by not more than two households," with the two homes "side-by-side or one on top of another," and each home must have an entrance on the ground floor. The 2 parking spaces for each home must sit behind the front building line.

Other Ways to Add a Home

• Estate lots (ED). Sec. 9.300 allows accessory dwelling units "for use by family members." Each lot needs "a minimum of one acre per dwelling unit or accessory dwelling unit," the unit must have at least 500 square feet, sit behind the main home, get site plan approval, and may not be sold separately.
• Retail land. Under Sec. 15.1900.1C, a Retail (R) tract of at least 5 acres that touches a residential district and lies outside the R-ECA area may be developed as PH, 2F or SF-A lots, if it leaves any commercial remainder of at least 2 acres.
• MF land. Under Sec. 15.1900.1D, MF-1, MF-2 and MF-3 land outside the R-ECA area may be developed as SF-6, PH, 2F or SF-A lots.

Two caps apply to every lot with a house or duplex. Sec. 13.100.1 allows "only one main building for single-family or two-family use" on a lot, so a second duplex on the same lot needs a different district. A household is limited to "not more than 4 adult unrelated individuals," plus minor children.

Building permit fees for a new duplex, under Ordinance No. 2025-11-4, are $0.48 per square foot plus a $90 plan review fee and a $150 plumbing certificate. A new house pays $0.48 per square foot, an $80 plan review fee and a $75 plumbing certificate.

Where to Go Next

Related on VanPlex: the Plano overview, ADUs in Texas and how Texas zoning works.

Frequently Asked Questions

Official sources (checked October 2026)