Building in Katy — first find out which Katy your lot is in

Before anything is designed for a lot in Katy, find out which Katy it is in. A Katy mailing address can sit inside the City of Katy, in unincorporated Harris County, in unincorporated Fort Bend County or in Waller County — the area straddles all three counties — and the city limits cover only a small part of what people call Katy. The answer decides who reviews your drawings, whether a zoning ordinance applies at all, and which queue the permit joins.

Most of the region has a jurisdiction question. Katy has it more sharply than anywhere else we work, because the name on the address, the school district, the utility district and the permitting authority can all point in different directions for the same lot.

Three counties and one name

"Katy" is used for a city, a school district, a postal area and a loose region of master-planned subdivisions running west from Houston along Interstate 10. Only the first of those has a building department of its own. The postal area follows mail delivery routes; the school district follows its own boundary; neither tells you anything about who issues a building permit.

So a single drive along one road can take you through four different answers:

• Inside the City of Katy. The city permits the house, applies its own adopted construction codes, and its zoning ordinance governs the lot.
• Unincorporated Harris County. The county permits the house through the Office of the County Engineer. There is no zoning and no county setback.
• Unincorporated Fort Bend County. The county is the authority. A large share of the master-planned sections people describe as Katy sit here or in Harris County rather than inside any city.
• Waller County. The westernmost part of the Katy area, and a third county with its own office and its own procedures.

The practical consequence is that two lots a mile apart, both sold as "Katy", can be governed by a city with zoning and by a county without it. One has a district table that sets the setbacks and the coverage; the other leaves those entirely to the plat and the deed restrictions. Our guide on which city or county permits your lot covers how to tell them apart anywhere in the region.

Is a Katy address inside the City of Katy?

Usually not — the city limits are a small part of the area the name covers. The reliable test is the appraisal district record for the property: it lists every taxing unit the lot pays, and if the City of Katy is not among them the lot is not inside the city.

What changes with each answer

The paperwork changes, but that is the small part. What matters is that the rules the house is designed against change with it.

Inside the City of Katy, the building code is set by the city. Its Ordinance 3116, adopted on 23 October 2023, adopted the 2021 International Building, Residential, Energy Conservation, Existing Building, Fire, Fuel Gas, Mechanical, Plumbing, Property Maintenance and Swimming Pool codes, NFPA 101 (2021) and the 2023 National Electrical Code. The residential and energy codes are the two that shape a house most directly — wall assemblies, insulation, window performance, stairs and guards. On top of the building code sits the city's zoning ordinance, which sets where on the lot the house may go and how much of it may be covered.

In unincorporated Harris County, the county has no zoning and no setback ordinance. The building line comes off the recorded plat, the size and style limits come from the deed restrictions, and the county's own review concentrates on floodplain management, platting and driveway or culvert access. We covered that position in depth in our guide to building in Cypress and unincorporated Harris County, and it applies just the same to the Harris County side of Katy.

In unincorporated Fort Bend or Waller County, the county is again the permitting authority. Texas counties generally have no zoning power, so here too the envelope of the house — how close it sits to each line, how much of the lot it covers, how tall it goes — comes mainly from the plat and the deed restrictions rather than from a district table. We have not yet read either county's residential requirements into our own data, so we do not quote figures for them; the county office is the place to confirm what it reviews, and floodplain review should be expected wherever a lot sits in or near a mapped floodplain.

Do I need a City of Katy permit if I am in its extraterritorial jurisdiction?

Not usually for the house itself. The extraterritorial jurisdiction is the band just outside a city's limits where the city can still regulate how land is subdivided. A lot there can answer to the city for its plat and to the county for its building permit. The building permit follows the city limits; the plat approval can reach further. Confirm both with the offices concerned, using the lot's legal description rather than its street address.

Why we will not quote you Katy's setbacks

Here is the part of this guide we would rather not have to write. For every other city in our guides — Bellaire, West University Place, Sugar Land, Pearland — we publish the residential district table: setbacks, coverage, floor area ratio and height, each figure read from the adopting city's own ordinance with the section and the date recorded. For the City of Katy we do not.

The reason is simple. Katy's zoning ordinance is published through a code-hosting service that required a login when we went to read it in September 2026, and we will not publish a setback, coverage or height figure we have not read from the ordinance itself. That rule exists because the shortcut has already failed once: a search for Katy's residential setbacks returned a neat table that turned out to belong to a different Texas city altogether. A figure like that, repeated on a page about Katy, would be wrong in a way nobody could see.

So, for a lot inside the City of Katy, the district table is something we read with the city at the start of the project, alongside the plat and the deed restrictions — not something we can show you here. That is a real limitation of this guide, and we would rather say so than fill the gap with a number from the wrong city.

Can I build a two-storey house in Katy?

Inside the City of Katy, the height limit comes from the zoning district the lot is in, and we do not quote it until it has been read from the ordinance. Outside the city, in unincorporated Harris, Fort Bend or Waller County, there is no county height table at all — which means the deed restrictions decide. In most master-planned sections they say something about height, storeys or roof form, and they are the document to read first.

Where the envelope really comes from in a master-planned section

Whichever authority issues the permit, most new houses in the Katy area are built in deed-restricted subdivisions, and in those the private rules usually bind harder than the public ones.

Three documents sit on top of each other:

1. The recorded plat draws the lot lines, the building lines, the easements and any reserves. It is public and recorded with the county, and our explainer on what a plat is and why it outranks the ordinance shows how to read one.
2. The deed restrictions run with the land and bind every owner in the section. They typically set minimum house size, masonry or material requirements, roof pitch, garage orientation, fence height and the approval process.
3. The architectural control committee's guidelines, where a committee exists, interpret the restrictions — often in more detail than the restrictions themselves — and the committee's letter is a separate approval from the permit.

The committee is where design decisions tend to be won or lost. A committee that expects a particular style, a percentage of masonry on the front or a roof pitch within a range will review the elevations, not just the site plan. If you are weighing styles for a west-side lot, a piece on Hill Country modern against industrial modern in Fulshear is useful further reading on how those two looks are usually built — then hold either one up against your section's guidelines before falling for it.

Does the HOA approve the house before or after the permit?

We get the committee's read before the drawings are finished and its approval letter before the permit submission, wherever the guidelines allow. A permit can be issued for a house the committee later refuses, and redrawing elevations after permit review is the most expensive order to do it in. The committee approves what the house looks like; the permitting authority approves whether it is built safely and in the right place. You need both.

What is the MUD line on a Katy tax bill?

A municipal utility district — a local government that supplies water, sewer and often drainage to a subdivision, funded by its own tax line. Many Katy-area sections outside the city are served by one. A MUD on the tax record tells you who runs the pipes, and usually that no city is on the record. It does not issue your building permit.

The review queue a Katy lot joins

Once the authority is settled, the calendar follows from it. Our planning ranges carry one row for the City of Katy and Fort Bend County together, and a separate row for unincorporated Harris County. These are the ranges we plan around, not quotes:

The difference is narrower than the difference in rules. For a new house it is about a week at each end of the range, and for additions and remodels the ranges are identical. Fees follow a similar pattern: for a new custom home we plan on $2,000 to $7,500 in Katy and Fort Bend County against $1,500 to $6,000 in unincorporated Harris County, with additions at $1,000 to $3,800 and $900 to $3,500. Floodplain review and association approval sit alongside both, and either can take longer than the permit itself.

We do not carry a separate planning range for Waller County. If your lot is there, the county office is the source for both the review time and the fee. For a quick estimate on any of the others, the permit calculator on our home page uses the same figures.

How long does a building permit take in Katy?

For a new house, plan on 4 to 9 weeks of plan review inside the City of Katy or in Fort Bend County, and 3 to 8 weeks in unincorporated Harris County. Additions run 3 to 7 weeks in both, remodels 2 to 5. The clock depends far more on how complete the submission is — and on whether the committee's letter is already in hand — than on which side of a county line the lot sits.

Sorting out a Katy lot, in order

All of this happens in the first weeks of a project, in what we call programming and site review — typically 2 to 4 weeks before any schematic design begins. The order matters, because each answer changes the next question:

The step people skip is the third one, and it is the one we cannot do for you from this page. A buyer looking at a lot inside the city limits who sizes the house from a neighbour's, or from a subdivision outside the city, is using the wrong rulebook. Read the district table first.

The fifth step is the other one that bites. Floodplain review is listed as a standing requirement for both the Katy and Fort Bend row and unincorporated Harris County in our planning data, and a floor raised to meet a floodplain rule eats into whatever height the deed restrictions allow. If you are planning an addition rather than a new house, the same order applies; on a wide suburban Katy lot, building out rather than up is often the simpler answer, but only once the building lines and the committee's rules confirm there is room to do it. For a new house, our page on new custom homes sets out how the design phases follow on from here.

Official pages

These are the official permitting pages for the authorities a Katy lot most often answers to. The City of Katy's site refuses automated requests, so its links occasionally look broken to software that checks them; they open normally in a browser.