McKinney | Backyard Cottages and Duplexes
McKinney Backyard Cottages and Duplexes: Where They Are Allowed and How Big They Can Be
McKinney gives an owner two ways to put a second home on a lot. In the house districts the code allows one accessory dwelling unit, a small second home behind the main house that the code also calls a backyard cottage. In two districts it allows a duplex, two homes in one building. Both rules are in Article 2 of the Unified Development Code (UDC), restated on March 3, 2026. The McKinney overview gives the short version.
McKinney second homes in six facts
- An accessory dwelling unit, which the code also calls a backyard cottage, is allowed in R43, R12, R8, R6, R5, R3, TR1.8 and AG. Source: McKinney UDC Table 2-26
- No more than one accessory dwelling unit may be built on a conforming lot, and none on an SB 15 small lot. Source: McKinney UDC Sec. 205G.2.b
- A backyard cottage may not exceed 50 percent of the house's square footage, or 75 percent when the house is 1,200 square feet or less. Source: McKinney UDC Sec. 205G.2.b
- The cottage must have the same owner as the house and may not have a separate electric meter. Source: McKinney UDC Sec. 205G.2.b
- A duplex is permitted by right in TR1.8 and MR, and in MR it needs a lot of 5,000 square feet, 50 feet wide and 100 feet deep. Source: McKinney UDC Table 2-26 and Table 2-10
- A duplex needs 4 parking spaces per lot, and a backyard cottage needs 1 space when the lot does not already have 4. Source: McKinney UDC Table 2-9 (parking)
What the Code Calls a Backyard Cottage
Sec. 205G.2.b defines an accessory dwelling unit (ADU) as "A residential dwelling unit that is subordinate to and detached from the primary dwelling unit but located on the same lot," and adds that it "may also be referred to as a backyard cottage." Subordinate means smaller than and secondary to the main house. The definition has two parts that shape a design: the cottage is detached, so a unit inside the house or joined to it is a different thing, and it sits on the same lot as the house.
Table 2-26 lists the ADU as an accessory use, marked "A," in eight districts: R43, R12, R8, R6, R5, R3, TR1.8 and AG Agriculture. The cells for MR Mixed Residential, MF36 and MHR are blank, and a blank cell means the use is prohibited. Texas has no state law that requires cities to allow ADUs; the ADUs in Texas page compares cities.
The Eight Standards for a Backyard Cottage
Sec. 205G.2.b lists the standards, labeled a to h. The table gives each one, plus the parking and home business rules from other sections.
| Rule | What the code says | Section |
|---|---|---|
| Number | No more than one per conforming lot | Sec. 205G.2.b.I.a |
| Small lots (SB 15) | Not permitted | Sec. 205G.2.b.I.b |
| Size | No more than 50% of the house; 75% if the house is 1,200 sq ft or less | Sec. 205G.2.b.I.c |
| Height and setbacks | Same as the house; behind the front face of the house | Sec. 205G.2.b.I.d |
| Design | Similar style and complementary materials in the Historically Significant Area or with a Significantly Important Building | Sec. 205G.2.b.I.e |
| Ownership | Same owner as the house | Sec. 205G.2.b.I.f |
| Electric meter | No separate meter | Sec. 205G.2.b.I.g |
| Facilities | Its own cooking, sleeping, eating, living and sanitation | Sec. 205G.2.b.I.h |
| Parking | 1 space if at least 4 are not already on site; 1 if at least 3 are not, in the H Overlay | Table 2-9 |
| Home business | Not permitted in the cottage | Sec. 205G.2.h |
Source: McKinney UDC Secs. 205G.2.b and 205G.2.h and Table 2-9, as adopted by Ordinance No. 2026-03-027, March 3, 2026. The ADU text matches the February 2026 copy of the UDC.
One per conforming lot. Standard a ties the count to "any conforming lot as identified in the summary for residential district standards, Table 2-24." That table lists each district's minimum lot area, width and depth, such as 6,000 square feet, 50 feet and 90 feet in R6. Before you plan a cottage on a lot that is smaller than its district's minimums, often an older lot, ask the Planning Department whether it counts as conforming.
Size. Standard c says the ADU "shall not exceed 50 percent of the total square footage of the primary dwelling," and "If the primary dwelling is 1,200 square feet or less, the ADU shall not exceed 75 percent." By VanPlex arithmetic, a 2,400 square foot house allows a cottage of up to 1,200 square feet, a 1,600 square foot house up to 800, and a 1,000 square foot house up to 750. The limit is set only as a share of the house size.
Height and placement. Standard d says the ADU "shall observe the same building height and setbacks as the primary dwelling and shall be set behind the front face of the primary building." A setback is the required distance between a building and a property line. So in R6 the cottage keeps the 10-foot rear and 5-foot side setbacks of the house and may reach the same 35-foot height. These are larger setbacks than a small shed needs, as the section on accessory buildings below shows.
Design. Standard e applies only in the Historically Significant Area, which Article 9 defines as the MTC McKinney Town Center district, the H Historic Overlay, the TMN Overlay, the Main Street Program area and the Historic Neighborhood Improvement Zone, or when the house is a Significantly Important Building, such as one listed on the National Register of Historic Places. There the cottage must be "constructed in a similar or complementary architectural style" with complementary exterior materials.
Ownership, meter and facilities. The ADU "must be under the same ownership as the primary dwelling," "shall not have a separate electric meter," and must contain its own facilities for "cooking, sleeping, eating, living, and sanitation." Under the ownership rule, the cottage and the house cannot belong to different owners.
Parking for a Cottage and a House
Table 2-9 in Sec. 206E.3 sets parking by use. A single-family detached house needs "4 spaces per DU, 2 of which must be enclosed and on-site," where DU means dwelling unit and enclosed means in a garage. Up to 2 of the required spaces may sit in a common area owned by a homeowners' association within 500 feet of the lot. In the H Historic Overlay the house needs 2 spaces.
The ADU row reads: "1 space if at least 4 spaces are not already provided on-site; or H Overlay: 1 space if at least 3 spaces are not already provided on-site." So a lot that already provides 4 spaces adds no space for the cottage, and a lot with only 2 adds 1. Sec. 206E.3.f says a required space may not be used "for any purpose other than parking."
Sheds, Garages and Other Accessory Buildings
A detached accessory building is a building on the same lot as the house and smaller than it, such as a shed or a detached garage (Sec. 205G.2.a). Its setbacks depend on its size, under Table 2-27. None may be built in the front yard, and on a corner lot the street side follows the district setback.
| Detached accessory building | Rear and side setback |
|---|---|
| 100 sq ft or less | 1 ft from rear and side lines |
| 101 to 300 sq ft | 3 ft from rear and side lines |
| 301 to 500 sq ft | 5 ft from rear and side lines |
| Over 500 sq ft, or 2 stories or more | The district setbacks |
Source: McKinney UDC Table 2-27, Standards for Detached Accessory Buildings and Structures.
Table 2-27 also lists limits that separate a shed from a cottage. A detached accessory building "Shall not be rented or leased," may not be used for commercial purposes unless approved as a home occupation, may not sit in an easement, and may not be built before the main house. Its height follows the district. An open structure such as a pergola or gazebo is capped at 12 feet. A detached building used as a home is an accessory dwelling unit under Sec. 205G.2.b, so it must meet the ADU standards, including the 50 percent size limit and the house setbacks.
Running a Business From Home
Sec. 205G.2.h allows a home occupation, "A no-impact home-based business, occupation, or profession conducted within a residential dwelling unit by the resident thereof," as an accessory use in every residential district. It must take place inside the house or inside an enclosed accessory structure, the operator must live in the dwelling, it "shall not have a separate entrance," and it may use no more than one commercial vehicle. Standard d is direct: "Home occupations are not permitted in accessory dwelling units." Table 2-9 asks for no added parking for a home occupation beyond what the dwelling needs.
Duplexes: TR1.8 and MR Only
Sec. 205D.5 defines a duplex as "A single structure designed and constructed with two dwelling units under a single roof for occupancy by two households on a single lot or tract." Table 2-26 marks it "P," permitted by right, in two districts: TR1.8 Townhome Residential and MR Mixed Residential. Every other cell is blank. A townhome pair is different. Two single-family attached homes, each on its own lot and joined by a party wall, are permitted in R3, TR1.8 and MR.
In MR, Table 2-10 gives the duplex its own column: a lot of 5,000 square feet, 50 feet wide and 100 feet deep; a 25-foot front setback, a 25-foot rear setback, 7 feet on each interior side and 15 feet on a street side; a height of 35 feet; and a density of 14.5 dwelling units per acre. Density is the number of homes allowed per acre of land. By VanPlex arithmetic, 14.5 per acre works out to one duplex for every 6,008 square feet of land, since an acre is 43,560 square feet.
In TR1.8, the district table applies to all uses: a lot of 1,800 square feet, 22 feet wide and 75 feet deep, of which two of three must be met, with a 15-foot front setback in Table 2-9 and a cap of 24 dwelling units per acre. By VanPlex arithmetic, a duplex at 24 per acre needs 3,630 square feet of land. The lot size page explains where the TR1.8 table and the summary table differ.
A duplex needs "4 spaces per lot" under Table 2-9. Like a house, it needs no site plan or landscape plan (Sec. 203E.1 and 203E.2), and a subdivision for duplexes needs a setback exhibit with its plat. A replat in an older neighborhood can trigger state notice rules; the plats, permits and fees page covers them.
Best For
- ✓ An R6 or R5 house lot that meets its district minimum, for one backyard cottage behind the house.
- ✓ A small house of 1,200 sq ft or less, where the cottage may reach 75 percent of its size.
- ✓ An MR lot of 5,000 sq ft, 50 ft wide, for a duplex by right.
Usually Fails When
- ✕ The lot is an SB 15 small lot, where a cottage is barred.
- ✕ The plan is a duplex on R43 to R3 land without a rezoning.
- ✕ The cottage would sit in front of the house or inside the house setbacks.
What To Verify Before Spending Money
- → That the lot meets its district minimums in Table 2-24.
- → Whether the lot is in the H Overlay, which needs a certificate of appropriateness.
- → Recorded deed restrictions and HOA rules, which may bar a second home.
Where to Go Next
Related on VanPlex: the McKinney overview, ADUs in Texas, and building codes from duplex to fourplex.
Frequently Asked Questions
Can I build a backyard cottage in McKinney?
How big can a backyard cottage be in McKinney?
Can I rent out a backyard cottage in McKinney?
Does the owner have to live on the lot to build a McKinney backyard cottage?
How much parking does a backyard cottage need in McKinney?
Can I run a business from a backyard cottage in McKinney?
Where are duplexes allowed in McKinney?
What lot does a duplex need in McKinney MR zoning?
Do I need a certificate of appropriateness for a backyard cottage in McKinney?
How close to the property line can a shed go in McKinney?
Official sources (checked October 2026)
Planning a multiplex in McKinney?
VanPlex builds multiplexes in British Columbia, Canada. For a lot in McKinney, our team makes a custom proforma by hand and emails it to you in 24 to 48 hours.
Get a proforma for your address