Every dimensional figure below names the jurisdiction it belongs to and the section it came from. “An ADU can be 750 square feet” is false in most of the towns we cover, so we do not say it. For your own address, run the finder.
In most of the Front Range jurisdictions we cover, an accessory dwelling unit is allowed by right on a lot with a single detached home — meaning it goes through a building permit rather than a discretionary hearing. Colorado's HB24-1152 (codified at C.R.S. §29-35-401 and following) required many jurisdictions to allow them.
It is decided by your zoning district, though, not by your town as a whole — two houses a few streets apart can get different answers. Enter your address and we will tell you what your district allows, with the code section it comes from.
Not necessarily, and this is worth checking rather than assuming. For jurisdictions that fall under HB24-1152, state law limits how far a local plan or covenant can restrict an accessory dwelling unit. A recorded PUD or HOA prohibition that predates the statute may not be the last word.
When we can tell that your parcel sits in one of those jurisdictions, the finder says so on your result. We are not attorneys and this is not legal advice — but it is a question worth putting to one before you accept a no.
Almost certainly not, and if you were told otherwise a while ago, the rule has changed.
Owner-occupancy used to be a common condition — you had to live in either the house or the ADU. Colorado's HB24-1152 bars a subject jurisdiction from imposing that requirement (C.R.S. §29-35-403), and towns have been removing it. Longmont is a good example: its current Land Development Code contains no owner-occupancy requirement for an ADU at all, and the City's July 2025 ADU Guide reflects the change.
One thing that is easy to confuse with it: some towns still require owner occupancy to rent out individual ROOMS in a house. That is a different rule and it does not govern an ADU.
A few places still carry older at-application language that may have been superseded. Where that is the case we say so on your result rather than resolving it for you.
Yes. Enter the address anyway — we will tell you what we can and cannot answer for it rather than guessing, which is the whole point. If we do not hold a jurisdiction's adopted code, we would rather say so than give you a neighboring town's rules and let you find out at the counter.
And the tool is not the only thing we have. We can look a jurisdiction up ourselves — we have a licensed architect on staff — so if the finder cannot answer for your address yet, ask us.
It depends on the town, and very often on the house you already have. Longmont, for example, allows an ADU of 500 to 800 square feet regardless of the size of your house. It may be larger than 800 only if it stays within 50% of the finished, above-ground floor area of the main house — a finished basement does not count toward that — and a basement ADU inside the house has no size limit at all (LDC §15.02.080.E.3.b).
That wording matters more than it looks. The 800 is a by-right figure, not a ceiling — a larger house earns a larger ADU. A 3,000 square foot home in Longmont supports a 1,500 square foot unit, not 800.
Elsewhere the shape is different: Louisville caps a detached ADU at 800 square feet; Frederick sets a minimum of 500 and a maximum of the greater of 800 or 50% of the principal building, not to exceed 1,000. And under state law a subject jurisdiction must allow an ADU of somewhere between 500 and 750 square feet (C.R.S. §29-35-402(18)(b)).
In some places yes — and it can be the limit that actually governs. Longmont caps the total floor area of all accessory structures at 75% of the principal structure's total floor area (LDC §15.04.040.B.1.d). Your garage, your shed and your new ADU all draw on the same allowance.
Worth working through, because it can bind before the ADU size rule does. On an 1,800 square foot house the size rule would allow a 900 square foot ADU, but the accessory allowance is 1,350 square feet in total — so an existing 600 square foot garage leaves only 750.
Note that Longmont's version is measured in floor area, not footprint. A garage with a loft counts for more than its outline on an aerial photo suggests, which is why we ask you rather than measuring it for you. Larimer County has a similar rule shaped differently — 10% of the lot's net area, measured as ground-floor area (Land Use Code §3.4.3).
Frequently the answer is: no taller than your own house. Longmont provides that a detached ADU may not exceed the height of the principal structure (LDC §15.02.080), and separately that accessory structures in residential districts shall not be taller than the principal structure (§15.04.040.B.1.f). Superior uses the lower of the house or 32 feet. Louisville caps a detached unit at 25 feet outright, while Frederick allows the same maximum height the district permits for a principal building.
Be careful reading a height figure from any source, including ours, without checking how that town measures it. Longmont measures from the average finished grade at the center of all walls to the top of the highest part of the building; Louisville averages natural grade at the highest and lowest corners of the structure. The same "25 feet" describes two different buildings.
This is a cost question before it is a permission one. Building close is usually allowed; it is what building close requires that surprises people — rated exterior walls, limits on windows and openings, and in some places automatic fire sprinklers.
Frederick is the clearest example we hold: an automatic sprinkler system is required where the fire separation distance is 5 feet or less, or 10 feet or less where two dwellings sit on the same lot (Frederick Municipal Code §18-3-20(o), amending IRC R309.2). That is a real ADU trigger and it is scoped by distance, not by size — a small unit sited close pulls it in just as a large one does.
The triggering distance is set locally, so we show your jurisdiction's where we hold it and tell you plainly when we do not.
Usually smaller. Most codes treat a detached ADU as an accessory structure, which carries its own — generally more generous — setback schedule.
State law puts a floor under this for subject jurisdictions: the side setback for an ADU may not be larger than the side setback required for the primary dwelling in the same district (C.R.S. §29-35-402(18)(c)), and the rear may not be larger than the greater of the district's accessory rear setback or five feet (§29-35-402(18)(d)).
Plan on starting around $450 per square foot, all in — the smallest studios sit above that, because a small home carries most of the same requirements as a big one. Read that against the right number: most ADU pricing you will find quoted is construction only, so the design, the structural engineering and the permit are still ahead of you when you compare it. Ours are already inside the figure. A small home also carries most of the same requirements as a big one — a kitchen, a bathroom, a foundation, utility connections, a permit — so there is not much economy of scale to bring the per-foot number down.
It is possible to build for less. What is not possible is to build for less than the soft costs plus the hard costs, and the soft costs are the ones that get left out of a headline number: engineering, soils testing, foundation, utility connections, permitting. We would rather you went in clear-eyed than crossed your fingers — which is why our process starts with a real look at your property.
We want to provide full-service, turnkey ADU delivery. That means we work with you to settle on the model and package you want, look at your property, and get you an all-in price — so you are not stuck halfway through, having already paid for design and engineering, seeing a budget for the first time and having to spend more time and money redoing it.
Two things sit outside our price, and we say so up front: your site survey and, where the ground calls for one, a soils report. Both are arranged in your name — see the process section below for why that is better for you. Beyond that, nobody can control what is underground or whether the local building code changes under us. Our goal is to take the stress and the worry out of everything else.
Because a lot of quotes are for part of an ADU, and it is rarely apples to apples.
It varies enormously. Some prices are for the unit alone and exclude the foundation, the site work and the utility connections. Some exclude delivery, the crane and the installation crew. Some leave out soft costs — engineering, permit fees, the local plan set. We have seen prefabricated units advertised without siding, roofing or a foundation in the price at all. None of that is dishonest on its face; it is just a different thing being sold, and the difference lands on you after you have committed.
Here is one you can check for yourself. In Longmont, before a single board is bought, the City's own published fee manual charges a small ADU three fees that have nothing to do with construction: a Recreation Buildings Impact Fee of $826.75 on a unit of 800 square feet or less, a Park Improvement Fee of $3,639.14, and a Storm Drainage Fee of $1,693.53. That is $6,159.42 before anyone pours a footing. ⚠️ And the recreation fee is banded by size: at 801 square feet it rises to $1,334.33, so crossing 800 costs another $507.58 — which is worth knowing, because 800 is also the top of Longmont's by-right ADU size band (a larger unit needs a house big enough that the ADU stays within 50% of its finished, above-ground floor area). If the unit needs its own water and sewer connection — we are confirming whether a detached ADU does — the City's development fees add roughly $12,000 more, plus $0.58 for every square foot of your lot (so a larger lot costs more for the same ADU). All of it is real, and it is the kind of line a headline price tends not to mention.
So when you compare, compare scopes rather than headlines. Ask what is excluded, and what those exclusions cost here.
Yes — and there is a specific version of this we are actively looking for.
Every plan we sell is priced two ways, and which one you get depends on whether it has been built before. The first build of each plan is cost-plus, and the design is free: you pay the real construction costs and nothing for our design work, and we are open about where the costs land. After that first build the plan moves to a fixed price, plus design fees — a number you can hold us to before you start.
So we are looking for the first project of each plan — one (1) Studio, one (1) 1-Bedroom, one (1) 2-Bedroom — and for those we are not quoting a fixed price. We would rather have one of each than three of the same. Each plan teaches us something different, and the sooner all three are proven the sooner everyone gets a fixed price.
Here is what that is worth to you. We give you the design work, including the structural engineering, once we have a signed agreement in place. On a first-of-plan project we do not charge for it — that cost is ours, because what we are buying with it is a proven plan. On every build after the first, design fees are charged alongside the fixed price.
To be clear about the edges: other engineering disciplines are not included, and neither is your survey or a soils report. Those stay in your name for the reasons above. You then build at cost-plus, so you can see exactly where the money goes rather than taking a fixed number on trust.
You also get our full attention and a real say in how that model develops. Once a model's first build is underway, that slot is gone — though as we add models to the range, new ones open. If you like the idea of helping prove something out rather than buying a finished product, ask which models are still open.
That depends on a lot of things and we cannot guarantee a return on investment. But the question is usually bigger than the spreadsheet: what is it worth to have your parents or your kids close by? What is it worth to look after family in a unit on your own property, at the point where they start to need help?
Then there are the real numbers — what a unit like yours actually rents for on the Front Range, and what it does to the value of the property. We have those, by market, on our rental income page: addwell.design/learn/rental-income
That is up to you, and we do not give financial advice. We have relationships with institutions and are happy to make an introduction — and we would suggest talking to more than one lender.
No. An ADU is accessory to the main home and stays on the same property under the same ownership — that is part of the definition, not a policy of ours. You can rent it out; you cannot sell it off.
First we come by to look at your property and go through the design options with you. It is genuinely the fun part. We take measurements and photographs on site, and with your selections we go away briefly and put together a preliminary investment quote.
Before a final number, two things need to be in hand: a site survey and, depending on the jurisdiction and the ground, a soils report. Not every authority requires soils testing — that is decided by the AHJ, the authority having jurisdiction. The survey needs a title report behind it, so we can see whether easements or other encumbrances limit where the unit can go.
These are commissioned in your name, and we will walk you through it — we can recommend people we trust and handle the coordination. Keeping them yours has a real benefit: a survey and a soils report belong to the property, so they stay useful to you whoever you eventually build with. They also sit outside our project price, which keeps the comparison honest.
Once those are in hand we can give you a final budget. We review your selections again, confirm dates and schedule, sign the agreement, and submit drawings for permit. Even pre-approved plans usually still need site plan and building department review — it is faster, not automatic. If the site or the soils call for additional engineering, we discuss that before it becomes a surprise. When the drawings are approved, work starts: site preparation, utilities, foundations, then the build.
Our insurance does not permit us to carry out soils testing ourselves.
For a stick-built unit, expect roughly two to three (2-3) months from start to finish on site. We will get faster the more that we build. Unfortunately, we can't put a guarantee on it — we do not control the weather, the building department, or supply chains.
Yes. The boundary our finder draws is the county assessor's parcel polygon, which is a record, not a survey — the two do not always agree. Real design needs a survey or a plat.
Usually not. HB24-1152 bars a subject jurisdiction from imposing an off-street parking minimum for an ADU (C.R.S. §29-35-403), and the towns we have read most closely have written that into their own rules.
There is a narrow exception, and it takes the same shape in most places: a single space may be required only where your lot has no existing off-street parking AND on-street parking is unavailable. Longmont, for instance, requires no space at all unless the lot has no existing off-street parking and either has no public street frontage, takes access from an alley, or sits where on-street parking is prohibited. Louisville requires one only where on-street parking is prohibited on your block and there is no spare space on the lot.
If you already have a driveway or a garage, you are almost certainly fine.
We do — the drawings, the submittal and the permit fees.
From the adopted code itself. Every figure we publish is transcribed from a jurisdiction's own ordinance or land use code and carries the section number it came from, so you can check it rather than trust us. Your parcel boundary and zoning district come from the county's own GIS records.
Where we have not read a jurisdiction's rule on something, we say we have not read it. We would rather leave a gap than fill it with a neighboring town's answer.
Every figure carries the date we read it, and we watch the source pages for changes. Codes do change — a town can adopt a new land use code and shift several answers at once — so treat anything here as a first pass and re-check before you commit to a design.
Quite a lot, and it matters. We show what the jurisdiction publishes about your property. We cannot see easements, utility or drainage locations, private covenants, HOA restrictions, or anything else recorded against your title — and any one of those can further limit what you can build. A full title report is what tells you the encumbrances on a property.
The lot boundary we draw is the county assessor's parcel polygon. It is not a survey, and the two do not always agree. Confirm corners and dimensions against a plat or survey before relying on any measurement.
No. It is first-pass feasibility — what the published rules appear to allow on your property. It is not for final design or permit submission, and it is never a statement that a permit will be issued.
Yes. Enter an address, see what your district allows, draw your lot and place a unit on it. You can download the summary and keep it, or send it to a designer or contractor.
The figures above name their towns because the answer changes street by street. The finder reads your parcel and your zoning district and tells you what your own code allows.
Draft v7 · 27 August 2026. First-pass feasibility, not an approval, and not legal advice.
Keep exploring
ADU rules by city
Cited, city-by-city ADU rules across the Front Range.
How the finder works
What to type, what you get back, and what it deliberately will not tell you.
Rental income potential
Rent, resale value, and what a permitted second unit adds to your property.
ADUs for family
Aging parents, multigenerational living, childcare.
How to finance an ADU
HELOC, construction loans, and CHFA options.
Process & timeline
What to expect from contract to move-in.
Floor plans & pricing
Five plans, three finish grades, five architectural styles.
About Addwell
Who we are and how we build.