Fence laws in Boulder, Colorado
What the Boulder municipal code says about fences, one topic at a time, with the section number and a link to the document behind every line. Where Boulder sets no rule of its own, the Colorado rule is shown in its place and marked as such.
Fence laws in Boulder, Colorado, question by question
The short version
- Who pays on the line
- Boulder is one of the few cities in this set that ties the boundary rule to the consent of the neighbor rather than leaving it to private law, and the answer turns on whether the abutting owner agreed, and the grade on each side. The figure is 12 feet, for absolute ceiling on an agreed boundary fence.
- How tall
- Boulder sets one number and applies it to the whole lot, and the answer turns on what the fence encloses and who agreed to it. The figure is 7 feet, for fence anywhere on a lot.
- Permits
- The Boulder fence section names a permit in exactly one place, and the answer turns on whether the fence is electric, conforming, or needs a variance. The figure is 5 feet, for how far inside the line an electric fence sits.
- 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
- Boulder has no spite fence statute. The chapters that were read are listed below. Cities and counties decide this one.
- Measured from what
- Height in Boulder is measured from the finished grade directly beneath the fence to its tallest element, and the answer turns on what the fence sits on. The figure is 42 inches, for guard permitted on a retaining wall.
- Corner lots
- Boulder writes its corner rule as a percentage rather than as a ban, and the answer turns on what the fence meets and how much it blocks. The figure is 30 inches, for bottom of the protected sight band.
- Retaining walls
- Boulder leaves retaining walls to each board of county commissioners, and separately each city and town, which adopt building codes on their own.
- Materials
- Boulder names no permitted material and instead writes one prohibition with narrow exits, and the answer turns on the district, the use and whether a permit is in force. The figure is 8 feet, for height barbed wire has to start at.
- 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 Boulder?
Compare fences on the property line across all 50 states
Boulder answers this, but the answer changes depending on whether the abutting owner agreed, and the grade on each side.
Boulder is one of the few cities in this set that ties the boundary rule to the consent of the neighbor rather than leaving it to private law. No fence, hedge or wall may extend beyond or across a property line unless an agreement with the abutting property owner is obtained. Then the same consent buys height. A fence, wall or hedge on or within three feet of a property line may go up to twelve feet where the abutting property owners are in joint agreement and the height still does not exceed seven feet measured from the highest elevation of grade within three feet of either side of the line. That is the code answering the split level problem directly: on a slope the higher neighbor sets the measurement, and the extra height exists only because the ground fell away. Twelve feet is an absolute ceiling regardless. Separately, no fence or wall may be placed nearer than eighteen inches to a public sidewalk.
A fence, wall, hedge, or any combination thereof located within three feet of each other and located on or within three feet of a property line, may be permitted up to a maximum of twelve feet in height, provided that the abutting property owners are in joint agreement and the height does not exceed seven feet when measured from the highest elevation of grade within three feet of either side of the property line.
The answer turns on whether the abutting owner agreed, and the grade on each side.
- crossing the line
- Only by agreement with the abutting owner.
- both neighbors agreeing
- Up to twelve feet. 12 ft
- a public sidewalk
- Eighteen inches of clearance. 18 in
Also on fences on the property line in Boulder
- 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 Boulder?
Compare fence height across all 50 states
Boulder answers this, but the answer changes depending on what the fence encloses and who agreed to it.
Boulder sets one number and applies it to the whole lot. Seven feet is the maximum for any individual fence, wall or hedge, or any combination of them standing within three feet of each other on the same property. There is no separate front yard figure, which is unusual: nearly every other city in this set cuts the front to three or four feet and Boulder does not, relying on the sight triangle rules instead to keep a corner clear. Four exceptions run higher. Fencing around an athletic facility, tennis courts named, may reach ten feet so long as everything above seven feet is at least fifty percent non-opaque. A fence or wall over seven feet may be approved by the city manager along a major street as part of a comprehensive noise barrier system. A temporary construction fence may be as high as the site needs. And a shared boundary carries its own separate allowance.
A maximum of seven feet in height is permitted for any individual fence, wall, hedge, or any combination thereof located within three feet of each other and located on the same property (see Figure 9-10), except as otherwise permitted by this section.
The answer turns on what the fence encloses and who agreed to it.
- anywhere on the lot
- Seven feet. 7 ft
- a tennis court or athletic facility
- Ten feet, half open above seven. 10 ft
- a noise barrier on a major street
- Over seven feet with city manager approval.
- a construction site
- As high as the site needs.
Also on fence height in Boulder
- 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 Boulder?
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Boulder answers this, but the answer changes depending on whether the fence is electric, conforming, or needs a variance.
The Boulder fence section names a permit in exactly one place. No person shall maintain an electric fence without a fence permit, and the permitted electric fence then has to carry a controller approved by Underwriters Laboratories with an attached label, stay at least five feet inside the periphery of the property, sit interior to a non-electric fence that completely encloses the yard, stay out of any landscaped setback and out of a required sight triangle, and not inhibit access by emergency equipment. Everything else runs through two other channels. A fence is permitted if it meets this section together with the sight triangle rules and the building code in Chapter 10-5. And where it does not, the requirements may be varied by the city manager under the variance and interpretation provisions, with a decision appealable to the Board of Zoning Adjustment.
No person shall maintain an electric fence without a fence permit.
9-9-15(d)(3), with (b) and (f)
The answer turns on whether the fence is electric, conforming, or needs a variance.
- an electric fence
- A fence permit, plus six conditions. 5 ft
- a conforming fence
- This section, the sight triangles and the building code.
- a fence that does not conform
- A variance from the city manager.
- a refusal
- Appealed to the Board of Zoning Adjustment.
Also on permits in Boulder
- 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 Boulder
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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 Boulder 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 Boulder
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Boulder 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 Boulder 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 Boulder
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Boulder answers this, but the answer changes depending on what the fence sits on.
Height in Boulder is measured from the finished grade directly beneath the fence to its tallest element. Two rules then close the gaps that measurement usually leaves. A fence on a berm or mound has to include the height of the berm above natural grade in the overall measurement, so building a mound and putting a seven foot fence on it does not produce a taller screen. And modifying the grade for the purpose of increasing permitted height is prohibited outright: where there is evidence that a change to the grade has occurred, the city manager may consider any information to determine the unaltered ground and then set the limit at what the fence height would have been without the change. The one place the code gives ground back is safety. A fence or guard not over forty-two inches may sit on or within three feet of a retaining wall regardless of the combined height, provided both are on the same property.
No person shall modify the grade for the purpose of increasing the permitted height of a fence, wall, or hedge. If there is evidence that a modification to the grade has occurred which results in lowering or increasing the height measurement, the city manager may consider any information to determine the unaltered grade.
The answer turns on what the fence sits on.
- flat ground
- Finished grade beneath to the tallest element.
- a berm or mound
- The berm counts toward the seven feet.
- a retaining wall
- A forty-two inch guard on top, whatever the total. 42 in
- a raised grade
- Measured as if the ground had not been changed.
Also on how height is measured in Boulder
- 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 Boulder
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Boulder answers this, but the answer changes depending on what the fence meets and how much it blocks.
Boulder writes its corner rule as a percentage rather than as a ban. No structure, fence, landscaping or other object may sit in a sight triangle where it obstructs or obscures sight distance by more than twenty-five percent of the total view in the vertical plane between thirty inches and ninety-six inches above the roadway surface. So a partly open fence can stand in the triangle, which is what the twenty-five percent figure is doing, and anything protruding no more than thirty inches above the roadway is allowed outright. Trees may stay where branches are trimmed clear to ninety-six inches and the mature canopy will not block more than a quarter of the area. The triangles themselves are measured rather than left to a manual. A driveway or alley meeting a street makes a fifteen by fifteen foot triangle, and where a multi-use path runs along the street one leg stretches to ninety-six feet. At a street intersection the X dimension is thirteen feet from the curb line and the Y dimension varies with the speed limit.
No person shall place or maintain any structures, fences, landscaping, or any other objects within any sight triangle area described in subsections (c) through (e) of this section that obstructs or obscures sight distance visibility through such structures, fencing, landscaping, or other objects by more than twenty-five percent of the total view in the vertical plane above the sight triangle area between a height of thirty inches and ninety-six inches above the roadway surface
9-9-7(b), with (c) through (e)
The answer turns on what the fence meets and how much it blocks.
- the protected band
- Thirty to ninety-six inches above the road. 30 in
- a partly open fence
- Up to a quarter of the view. 25%
- a driveway or alley
- Fifteen feet along each leg. 15 ft
- a multi-use path
- Ninety-six feet along the path.
Also on corner visibility in Boulder
- 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 Boulder
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Boulder 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 Boulder 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 Boulder
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Boulder answers this, but the answer changes depending on the district, the use and whether a permit is in force.
Boulder names no permitted material and instead writes one prohibition with narrow exits. No barbed wire or other sharp, pointed or electrically charged fence may be erected or maintained, except in four cases. A temporary construction fence on a site with an active building permit may be topped with barbed wire where the wire starts at least eight feet above the ground and rises no more than two feet above the fence. In the agricultural district barbed or electric wire may be used as an internal fence, not on the periphery, to contain livestock. In the B, IM, IG, IS and P districts a fence set back at least twelve feet from the property line may carry barbed wire on the same eight foot and two foot terms. And an electric fence may protect crops and plantings in the agricultural and three rural residential districts. The wildfire rules reach materials from another direction: a newly built fence of any height inside the Wildland Urban Interface has to meet the Wildland Code.
No barbed wire or other sharp, pointed, or electrically charged fence may be erected or maintained except as follows:
The answer turns on the district, the use and whether a permit is in force.
- a house lot
- No barbed wire and no electric fence.
- an industrial or business lot
- Barbed wire twelve feet back, starting at eight feet. 8 ft
- livestock in the agricultural district
- Internal fences only, never the perimeter.
- the wildfire interface
- The Wildland Code applies to any new fence.
Also on materials in Boulder
- 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 Boulder
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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 Boulder 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 Boulder
- 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
8 documents, of which 2 were published by Boulder itself. Each was read on the date shown.
- Colorado General AssemblyColorado Revised Statutes 2024, Title 35, Article 46, Section 35-46-112
- City of BoulderBoulder Revised Code 1981, Title 9, Chapter 9, Section 9-9-15, Fences and 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
- City of BoulderBoulder Revised Code 1981, Title 9, Chapter 9, Section 9-9-7, Sight Triangles
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 Boulder 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