Fence laws in Thornton, Colorado
What the Thornton municipal code says about fences, one topic at a time, with the section number and a link to the document behind every line. Where Thornton sets no rule of its own, the Colorado rule is shown in its place and marked as such.
Fence laws in Thornton, Colorado, question by question
The short version
- Who pays on the line
- Thornton answers the double fence problem directly, and the answer turns on whether a fence already stands on the line. The figure is 5 feet, for separation between two parallel fences.
- How tall
- Thornton states two numbers and then three exceptions, and the answer turns on the yard and what the fence abuts. The figure is 4 feet, for fence in the primary front yard.
- Permits
- Every fence and screen wall over thirty inches above grade in Thornton needs a building permit, which is a low threshold and catches most garden fencing, and the answer turns on the height of the fence and the post material. The figure is 30 inches, for height at which a permit is required.
- Pool barriers
- A fence around a pool open to the public in Colorado stands at least sixty inches high, with gates that close and latch by themselves and a latch at least fifty four inches up. The figure is 60 inches, for minimum fence height around a public swimming pool.
- Spite fences
- Thornton has no spite fence statute. The chapters that were read are listed below. Cities and counties decide this one.
- Measured from what
- Thornton measures the failure of a fence rather than only its height, and the answer turns on whether the fence faces a public way. The figure is 6 inches, for most a fence may lean out of plumb.
- Corner lots
- At a street intersection the Thornton visibility triangle is not a fixed leg but a sight line, and the answer turns on the kind of intersection and the design speed of the road. The figure is 20 feet, for leg of the driveway visibility triangle.
- Retaining walls
- Thornton leaves retaining walls to each board of county commissioners, and separately each city and town, which adopt building codes on their own.
- Materials
- Fences and screen walls in Thornton may be built of the listed materials only, and the list is specified rather than named, and the answer turns on the material and what the fence faces.
- Livestock
- A lawful fence in Colorado is a well built three barbed wire fence on strong posts set about twenty feet apart, good enough to turn back ordinary horses and cattle. The figure is 3 strands, for barbed wires in a lawful fence.
Who owns the fence between two properties in Thornton?
Compare fences on the property line across all 50 states
Thornton answers this, but the answer changes depending on whether a fence already stands on the line.
Thornton answers the double fence problem directly. A person may not build or maintain more than one fence of any type parallel to or generally following a property line unless the fences are immediately abutting, meaning touching for their entire length, or at least five feet apart. So a second fence is either flush against the first or far enough away to be a separate thing. Orientation is settled by construction rather than by direction: a perimeter fence of sixty inches or more has to be two-sided, and where a single-sided fence with exposed framing is built, the framing side has to face the interior yard of the owner who built it. Nothing may sit in a public right-of-way, fences and their columns have to stand at least two feet from trails, and a fence in a floodplain needs a Floodplain Development Permit.
A person shall not construct or maintain more than one fence of any type parallel to or generally following a property line unless the fences are immediately abutting, i.e. touching, for their entire length, or at least five feet apart.
The answer turns on whether a fence already stands on the line.
- a second fence on the same line
- Touching, or five feet apart. 5 ft
- a perimeter fence of sixty inches or more
- Two-sided construction. 60 in
- a single-sided fence
- The framing faces the owner.
- a trail
- Two feet clear. 2 ft
Also on fences on the property line in Thornton
- set in state lawColorado splits the cost of a fence on the line between farm and ranch neighbors. Where farm or grazing land of two or more people touches, each owner builds half of the line fence, and it has to meet the state lawful fence standard. A person who already has a lawful fence on the line is owed half its cash value by the neighbor who moves in next to it. This rule covers farm and grazing land only, not a fence at a house. C.R.S. 35-46-112Colorado · Statute
How tall can a fence be in Thornton?
Compare fence height across all 50 states
Thornton answers this, but the answer changes depending on the yard and what the fence abuts.
Thornton states two numbers and then three exceptions. The maximum height of a fence or screen wall is four feet above grade in the primary front yard and six feet above grade in all other yards, and the code says expressly that the six feet includes wing fences. A fence in a side or rear yard may reach eight feet where it abuts an arterial street, a regional thoroughfare, an interstate or a toll road. A fence screening accessory outdoor storage answers to a different section. And the Director may approve a taller fence or screen wall as an administrative adjustment. One further exception runs the other way and lifts the city out of its own rule: the height restrictions do not apply to city financed or constructed public improvement projects for sound walls or fencing.
Maximum height. The maximum height of fences or screen walls shall be as detailed in Subsections (a)(1) and ( 2) of this section , unless otherwise allowed in Subsection (b) of this section or required elsewhere in this Code: (1) Primary front yard - four feet above grade. (2) All other yards - six feet above grade. This includes wing fences.
The answer turns on the yard and what the fence abuts.
- a primary front yard
- Four feet. 4 ft
- every other yard
- Six feet, wing fences included. 6 ft
- abutting an arterial or highway
- Eight feet at the side or rear. 8 ft
- a city sound wall project
- The height restrictions do not apply.
Also on fence height in Thornton
- no rule, documents checkedColorado sets no limit on how tall a fence at a house can be. The city sets it. The state fence law only describes a lawful fence for farm and grazing land and gives no top height for a fence at a house, and state law gives cities and towns the power over fences on the line. C.R.S. 35-46-101 to 35-46-115Colorado · Statute
Do I need a permit for a fence in Thornton?
Compare permits across all 50 states
Thornton answers this, but the answer changes depending on the height of the fence and the post material.
Every fence and screen wall over thirty inches above grade in Thornton needs a building permit, which is a low threshold and catches most garden fencing. The code then supplies the structural standards a fence between thirty inches and eight feet has to meet, in the kind of detail usually left to a builder. A five to six and a half foot fence needs four by four wood posts, or steel pipe of one and seven-eighths inches with a wall thickness of one hundred and twenty thousandths of an inch. Above six and a half feet the pipe grows to two and three-eighths inches with a thicker wall, and a four by four wood post has to be spaced six feet on center rather than eight. A four by four wood post has to sit in a concrete pier at least ten inches across and two feet deep. Any masonry or concrete fence is reviewed by the city against the building code.
All fences and screen walls over 30 inches in height above grade require a building permit.
The answer turns on the height of the fence and the post material.
- anything over thirty inches
- A building permit. 30 in
- a five to six and a half foot fence
- Four by four posts, eight feet on center. 8 ft
- a wood post
- A ten inch pier, two feet deep. 2 ft
Also on permits in Thornton
- no rule, documents checkedWhether a fence needs a permit in Colorado is a county or city question. The state adopts no building code for houses at all, so there is no statewide permit rule and nothing statewide to be exempt from. State law says a board of county commissioners may adopt a building code, which leaves the choice to each county, and cities and towns get their own power over building rules and over fences on the line. C.R.S. 30-28-201Colorado · Building code
Pool fence requirements in Thornton
Compare pool barriers across all 50 states
Colorado answers this in its own law. The words that do it are quoted below.
A fence around a pool open to the public in Colorado stands at least sixty inches high, with gates that close and latch by themselves and a latch at least fifty four inches up. Section 3.24 of the state swimming pool rule requires the fence so people reach the pool only through controlled ways in, and a building or other structure can do the job of the fence. A stricter local code or ordinance takes the place of this rule.
This one is Colorado law, not Thornton law. All Colorado findings
Every swimming pool in a non-restricted public place shall be fenced to prevent unauthorized access to the pool except through controlled entrances.
60 inminimum fence height around a public swimming pool
Spite fence laws in Thornton
Compare spite fences across all 50 states
Thornton law has no rule about this. The chapters that were read are listed below. Cities and counties decide it instead.
Colorado has no state law about a fence built to annoy a neighbor. The fence law in Title 35 and the property laws in Title 38 have no spite fence rule and no height that turns a fence into one. A limit of that kind comes from a local ordinance.
This one is Colorado law, not Thornton law. All Colorado findings
Documents read before writing that:
- C.R.S. 35-46-101 to 35-46-115Colorado General Assembly
- C.R.S. Title 38Colorado General Assembly
How fence height is measured in Thornton
Compare how height is measured across all 50 states
Thornton answers this, but the answer changes depending on whether the fence faces a public way.
Thornton measures the failure of a fence rather than only its height. Any fence more than thirty inches tall running parallel to a public street, alley, right-of-way, trail easement or trail tract that is out of plumb by more than one inch per foot of height, to a maximum of six inches out of plumb, or that fails the wind load standards of the building code, has to be repaired with similar material, replaced, or removed entirely. A span with a gap from more than one missing or broken picket or chain link that was part of the original design has to be repaired the same way, as does any missing or broken rail or post. The rule expressly does not apply to fences between private property boundaries, so it is about what the public sees. All repairs are at the expense of the owner or occupant of the property the fence stands on.
Any fence that is out of plumb by more than one inch per foot of height, not to exceed six inches out of plumb, or does not meet the wind load standards of the city's Building Code shall be repaired with similar material, replaced, or removed entirely unless the fence is required by the Development Plan.
The answer turns on whether the fence faces a public way.
- a leaning fence on a public street
- An inch per foot, up to six inches. 6 in
- a fence between two private lots
- The rule does not apply.
- a missing picket or rail
- Repaired with similar material.
Also on how height is measured in Thornton
- left to the townColorado has no fence height of its own, so it never says where one would be measured from. Section 31-23-301 lets the city council set the height, number of stories and size of buildings and other structures, and it even covers the height of trees. The state fence law describes a lawful fence by its three barbed wires and its posts about twenty feet apart, and gives no height at all. So the city picks the number and the surface it starts from. C.R.S. 31-23-301(1)Colorado · Zoning code
Fence rules for corner lots in Thornton
Compare corner visibility across all 50 states
Thornton answers this, but the answer changes depending on the kind of intersection and the design speed of the road.
At a street intersection the Thornton visibility triangle is not a fixed leg but a sight line. It is drawn from the point where the adjacent street curb lines meet to points on each curb line created by a sight line projected from the centerline of the nearest oncoming travel lane, starting at the minimum sight distance for a stopped vehicle based on the design speed of the through road and corrected for grade, to a point on the centerline of the nearest oncoming through lane ten feet inside the curb line, with a table of distances. At an alley or a driveway meeting a street the shape is simpler, twenty feet from the intersection along each curb line, dropping to ten feet on a detached single family lot. Nothing between two and a half feet and eight feet above the top of the adjacent curb may be erected, placed or maintained inside a visibility triangle, and the traffic engineer may approve revised sight distance criteria for a special circumstance.
No person shall erect, place, or maintain any structure, berm, plant, or any other item that is between 2.5 feet and eight feet in height, as measured from the top of the adjacent street curb, within a visibility triangle.
The answer turns on the kind of intersection and the design speed of the road.
- a street intersection
- Sized by stopping sight distance.
- an alley or driveway
- Twenty feet, or ten on a house lot. 20 ft
- the protected band
- Two and a half feet to eight feet above the curb. 8 ft
- a special traffic circumstance
- The traffic engineer may revise the criteria.
Also on corner visibility in Thornton
- set in state lawNo Colorado law draws a clear view triangle on a corner lot. Counties and towns write that under Titles 30 and 31. The state once had a general rule against blocking the view along a highway, and the legislature repealed it in 1981. What is left is narrower. Section 43-1-411 refuses a permit for an outdoor advertising sign within five hundred feet of the center of an intersection when it would badly cut the view of traffic on the crossing road or of an oncoming train. That is a sign rule on state highways. C.R.S. 43-1-411Colorado · Traffic code
Retaining wall rules in Thornton
Compare retaining walls across all 50 states
Thornton does not set this. It leaves it to each board of county commissioners, and separately each city and town, which adopt building codes on their own.
Colorado has no state rule for a wall that holds back earth, because it adopts no building code for houses at all. State law says a board of county commissioners may adopt a building code for the parts of the county outside any city or town, and cities and towns get their own separate power over building rules. So there is no state height at which a wall of that kind needs a permit and no state standard for building one. Each county, city and town sets it.
This one is Colorado law, not Thornton law. All Colorado findings
A board of county commissioners is authorized to adopt ordinances and a building code consistent with the uniform building code, 1988 edition, as promulgated by the international conference of building officials and as revised from time to time, in all or part of the county, and not embraced within the limits of any incorporated city or town.
The code hands this to each board of county commissioners, and separately each city and town, which adopt building codes on their own, which is not published in the code itself.
Fence materials allowed in Thornton
Compare materials across all 50 states
Thornton answers this, but the answer changes depending on the material and what the fence faces.
Fences and screen walls in Thornton may be built of the listed materials only, and the list is specified rather than named. Stone, brick, architectural block that is not smooth faced, stucco on masonry, concrete made to look like masonry, decorative metal, wrought iron, hot-dip galvanized chain link, cementitious fiber board, milled wood or wood composite that is treated or naturally decay resistant and construction grade two or better, vinyl or PVC meeting the manufacturer standards, gabion baskets of at least eleven gauge galvanized wire with openings no smaller than four inches, and three rail fencing. Waste materials including debris, junk, rolled plastic, sheet metal and anything not designed for use as a fence are prohibited. Fences next to natural open space, detention ponds, parks and public gathering areas have to be open fences and specifically not chain link, unless the Director approves otherwise.
Gabion baskets with minimum wire gauge of 11 galvanized steel wire with openings no smaller than 4" x 4";
The answer turns on the material and what the fence faces.
- the permitted list
- Thirteen materials, each with a specification.
- junk, rolled plastic or sheet metal
- Prohibited.
- a fence facing open space or a park
- Open, and never chain link.
Also on materials in Thornton
- set in state lawColorado defines a lawful fence as a well built three barbed wire fence on solid posts about twenty feet apart, good enough to turn ordinary horses and cattle, with gates as good as the fence. Any other fence that works as well counts the same. C.R.S. 35-46-101Colorado · Statute
Livestock and boundary fence law in Thornton
Compare agricultural fencing across all 50 states
Colorado answers this in its own law. The words that do it are quoted below.
A lawful fence in Colorado is a well built three barbed wire fence on strong posts set about twenty feet apart, good enough to turn back ordinary horses and cattle. Every gate has to be as good as the fence. Any other fence that works just as well counts the same.
This one is Colorado law, not Thornton law. All Colorado findings
"Lawful fence" is a well-constructed three barbed wire fence with substantial posts set at a distance of approximately twenty feet apart, and sufficient to turn ordinary horses and cattle, with all gates equally as good as the fence, or any other fence of like efficiency.
3 strandsbarbed wires in a lawful fence
Also on agricultural fencing in Thornton
- set in state lawColorado is a fence out state. The landowner who wants livestock kept off builds the fence, not the animal owner. Money for a livestock trespass goes only to a person whose crops were behind a lawful fence at the time, kept in good repair, and whose fence the animals broke through. Without that fence, nothing is owed. C.R.S. 35-46-102Colorado · Statute
Documents behind this page
7 documents, of which 1 was published by Thornton itself. Each was read on the date shown.
- Colorado General AssemblyColorado Revised Statutes 2024, Title 35, Article 46, Section 35-46-112
- City of ThorntonThornton City Code, Chapter 18, Development Code, Article VI, Division 2, Fences and Screen Walls
- Colorado General AssemblyColorado Revised Statutes 2024, Title 31, Article 15, Part 6, Building and Fire Regulations
- Colorado General AssemblyColorado Revised Statutes 2024, Title 30, Article 28, Part 2, Building Codes
- Colorado Department of Public Health and Environment, Water Quality Control DivisionCode of Colorado Regulations, Swimming Pools and Mineral Baths, Section 3.24, effective December 15, 2020
- Colorado General AssemblyColorado Revised Statutes 2024, Title 38, Property, Real and Personal
- Colorado General Assembly, Office of Legislative Legal ServicesColorado Revised Statutes 2024, Title 43, Transportation
What this page does not cover
A city ordinance is not the only rule that reaches a fence. The zoning district a parcel sits in can change the height allowed on it, and so can an overlay district, a recorded easement, a fire hazard severity zone or a coastal zone. A homeowner association can be stricter than the city and nothing in the municipal code will say so. None of those appear here.
The rules above are the ones Thornton publishes, plus the Colorado rules that apply where the city sets none. Fence laws in Colorado has the state layer in full.
This is general information drawn from published government documents. It is not legal advice, ordinances are amended, and the date beside each finding is the date the document was read. How findings are made · What the terms mean