Cities | Arlington

Arlington Multiplex Rules 2026: Duplexes, Second Units and Small Lots

Arlington zones every lot inside its city limits, so the first question for any project is the lot's district. One document holds the rules: the Unified Development Code (UDC), which combines zoning, design, subdivision and review steps and which the City publishes as a single PDF. In 2025 the City wrote the state laws SB 15 and SB 840 into it, and in 2026 it added form-based zoning downtown. This page gives the main numbers, with the section for each, and links to seven detailed pages.

Arlington Guide Pages

State Law in Arlington, in Brief

Arlington had 394,266 people in the 2020 Census, and Tarrant County, where it sits, had 2,110,640, so Arlington passes the size test in the 2025 laws, by VanPlex count from 2020 Census figures. Arlington has zoning, and it wrote each law into its own code:

• SB 15 became Section 5.5.6, small-lot development on unplatted residential tracts of 5 acres or more, adopted by Ordinance No. 25-059 on August 26, 2025 and in force September 1, 2025.
• SB 840 became Sections 5.12 and 5.13, multi-family and mixed-use homes in non-residential districts, adopted by the same ordinance, with staff-approved development plans under Sections 10.4.5B and 10.4.5C.
• HB 24 reaches Arlington through Section 10.4.2.I, which says the protest rules "are contained in Chapter 211 of the Texas Local Government Code." The City's zoning FAQ page still describes only the older 20 percent rule.

Two parts of Section 5.5.6 do not match the state limits. Its Table 5.5-7 prints a 50-foot interior side setback, where Local Government Code 211.055 bars a side setback over five feet on a small lot, and it requires 35 percent common open space, where the statute bars more than 30 percent. For apartments on commercial land, Table 5.4-1 adds staff and visitor spaces to one space per unit, while Section 218.102 bars requiring "more than one parking space per dwelling unit." The lot size page and the three or more homes page set out each one.

How a Lot Reaches Two, Three or More Homes

Source: Arlington UDC, Tables 3.1-1, 3.1-2 and 3.3-1, Sections 2.2, 2.3, 3.3.6, 4.1.6, 5.4.9, 5.5.6, 5.11 and 5.12, PDF amended by Ordinance No. 25-059; Article 13.

Zoning Districts and the Use Table

Table 2.1-1 lists the residential districts RE, RS-20, RS-15, RS-7.2, RS-5, RM-12, RMF-22, VG and the obsolete MH, thirteen non-residential and mixed-use districts, and seven overlays. The maximum density runs from 1 home per acre in RE to 6 in RS-7.2, 8 in RS-5, 12 in RM-12 and 22 in RMF-22. In the use tables, "P" means "permitted by right," "S" means a specific use permit from the City Council, a blank cell means "prohibited," and "PD" means only through a planned development rezoning.

The result for homes is narrow. Detached houses are allowed in every residential district except RMF-22; duplexes and townhouses only in RM-12 and RMF-22; apartments only in RMF-22 among residential districts. The zoning districts page has the full table, the downtown form-based districts, and the steps to rezone a lot, which cost $1,200 on less than one acre under the fee schedule effective October 1, 2026.

A zone change runs through two public hearings under Section 10.4.2: the Planning and Zoning Commission recommends, and the City Council decides. Notice goes out at least 11 days before each hearing, by mail to owners within 200 feet and on signs posted on the property. If the commission recommends denial, the applicant has 10 business days to ask the Council for a hearing, and the Council may decline, which ends the case. A denied request cannot return for 12 months with the same or a more intense district unless the Council waives the wait.

Second Units and Duplexes

For a house lot, the citywide code's second home is the secondary living unit, which is "only for use by family members or relatives" and "shall not be rented or leased," with no more than one bedroom, one kitchen and one bathroom (Sections 12.3.5.N and 3.3.6.L). It is allowed by right in RE, RS-20, RS-15 and VG, and needs a specific use permit, which means a City Council ordinance, in RS-7.2, RS-5 and RM-12. A garage apartment, which may be rented, is allowed in RM-12 and RMF-22. Downtown, Article 13 allows accessory dwelling units of up to 800 square feet with one parking space.

A duplex needs a lot of 6,000 square feet and 60 feet wide in RM-12 or RMF-22, two parking spaces per unit, and the two-car garage rule. The secondary units and duplexes page covers the details, including how the RM-12 density cap of 12 homes per acre applies to a single 6,000 square foot lot.

Townhouses, Cottages and Apartments

In Arlington's citywide code, three homes in one building count as a multi-family dwelling. The smaller routes are townhouses on 2,900 square foot lots in RM-12 and RMF-22, and cottage communities, which "shall be approved only as Planned Developments in the RM-12 Zoning District" on sites of at least one acre. Apartments in RMF-22 need a multi-family development plan approved by City Council ordinance. On commercial land, the Zoning Administrator approves the plan, and the design rules in Section 5.12 require amenities, covered parking for 80 percent of required spaces, and a building height of at least six stories within 100 feet of a major thoroughfare. Downtown, the Traditional Neighborhood sub-district lists the triplex with 1,500 square feet of lot per home. The three or more homes page covers each route.

Lots, Yards, Height and Parking

The smallest district lot for a house is 5,000 square feet and 50 feet wide in RS-5 and RM-12; RS-7.2 needs 7,200 and 60, and RE needs one acre. A replat must also "conform in width, depth, and area to the predominant pattern established by the existing lots located on the same block" (Section 10.4.17.F). An older platted lot of at least 50 feet and 5,000 square feet can still get a house under Section 11.3.2. Front setbacks are 20 feet on a local street and 40 on an arterial or collector, interior setbacks 5 feet in RS-7.2 and RS-5, and height 40 feet. The lot size page and the parking, setbacks and height page have the tables.

Parking is 2 spaces per house, duplex unit or townhouse under Table 5.4-1, and Section 5.4.9.B.2 requires "an enclosed two-car garage" of at least 390 square feet for those homes unless built before January 31, 1984. Section 5.5.3 also says new houses and duplexes shall be 100 percent masonry. Government Code 3000.002 bars a city from limiting building materials that a national model code approves, so ask the City how it applies the masonry rule.

Trees, the Airport and Historic Areas

A residential development of one acre or more must preserve at least 35 percent of its protected tree inches, with extra credit for Cross Timbers oaks (Section 5.2.3). Unapproved removal costs $600 per caliper inch under the fee schedule. Around Arlington Municipal Airport, the Airport Overlay bars new houses, duplexes and townhouses in zones APO-2 to APO-4. Landmark Preservation Overlay districts need a certificate of appropriateness for exterior changes, and conservation districts can be created by 60 percent of owners under an adopted neighborhood plan. The trees, airport and historic page covers each.

What the Numbers Show

Arlington had 402,134 people on July 1, 2025, by the Census Bureau's Vintage 2025 estimate. The Census Bureau's 2025 permit file shows Arlington reported all 12 months, so the figures below are the City's own reports.

Source: Census Bureau Building Permits Survey, South Region places, 2025 annual.

The Census counts a building by the number of homes it holds, so a fourplex is one building of three to four units. The file gives counts only, with no reasons behind them. Arlington's 51 buildings of three or four units were the most of any city in the table on the more Texas cities page.

Plats, Permits and Fees

Dividing land into two or more parts needs a plat, even when done by deed (Section 6.1.4). A plat counts as filed only when complete, and the City must act on it within 30 days, matching Local Government Code 212.009. A minor plat of four or fewer lots on an existing street is approved by staff for $600 plus $45 per acre, and every plat carries a non-refundable $150 fee, under the fee schedule effective October 1, 2026.

The Impact Fees chapter sets $828.13 for water and $418.00 for sewer per 5/8-inch meter equivalent, and $253.00 or $312.50 per vehicle mile for roads, collected with the building permit. Park fees run $1,532 to $1,806 per unit by district. A home over 2,000 square feet pays a permit fee of $1,375 plus $0.40 per square foot and a plan review fee of 35 percent of that. The plats, permits and fees page has the full lists.

Where to Go Next

Related on VanPlex: the how Texas zoning works page, ADUs in Texas and the Texas multiplex guide overview.

Frequently Asked Questions

Official sources (checked October 2026)