How high can an ADU be, particularly in Colorado? Can an ADU be two stories high? There are just so many questions you didn’t think about before you thought of building an ADU. So let’s consider a few aspects before tackling this topic.
First of all, when it comes to the State of Colorado, all ADU information and regulations are on the municipal level, meaning that each city in the great state of Colorado has its own rules on what you can and cannot do with an ADU in your existing municipality.
Commonalities found with ADUs in Colorado
No matter what, most ADUs in Colorado cannot be a DIY project and will require a proper general contractor and building permits that need to take place.
Can an ADU be two stories high?
- The structure must be similar in design to the original and primary structure
- The ADU cannot be larger than the primary structure. If the primary dwelling is two stories high, then your ADU can be two stories high.
- In some cases, you can build a second story as an attached ADU on top of your home.
On the final point, the ADU will need to be an enclosed property. There are some discussions around building out rooftop decks, but those usually fall under different ordinances and guidelines.
Colorado welcomes ADU’s
Keep in mind that Colorado, in general, is pro-ADU and has a lot of help around this area.
So assistance and support are there to ensure that you end up building a legally compliant ADU if you ever do decide to. But it can still be a minefield if you don’t have an experienced builder alongside you.
But, rules and regulations aside, building such an ADU will usually add significant value to your home. So let’s go through some of them in more easily digestible detail.
In 2010, zoning rules were changed in order to accommodate building more ADU’s.
If you’re considering building an ADU within your Denver or Colorado property. For properties in Denver, start by finding out if your property is properly zoned to accommodate an ADU.
Can an ADU be larger than the main house?
This is where a lot of municipalities in Colorado are in agreement. The general rule here is no, an ADU cannot be larger than the main house.
For example, in Golden, CO, the rules are that the maximum size can be only 50% of the total land available –– or 800 square feet whichever is less.
Whereas in Boulder, CO, they have different rules depending on if it will be a detached or attached unit. So in Boulder, the size can be 1/3 of the existing home or 1000 square feet if attached.
If you’re considering a detached home, then it’s capped at 550 square feet. It also needs to be within an existing structure such as a structured backyard office, or a garage unit.
The height is capped at 20 feet (or 25 feet with a specific pitch)
Where can an ADU be placed?
There are three major areas that ADUs can be placed. These are pretty similar across all municipalities, with some minor differences that will be noted by your government official, or just contact us and we’ll be happy to walk you through this process.
Detached unit
A detached ADU usually has a fixed size that it can be on your lot.
It will have a maximum cap and height to your existing structure and must be similar in nature to the aesthetic and design of your primary home.
Additional rules for parking and driveways will need to be handled, and you’re basically building a new home with a new address.
The height is usually capped to the height of the primary structure, so ensure that the primary structure is at least two stories if you want to consider a two-story ADU.
Attached unit
This is a simple extension to your home and is literally connected to it. Here the rules are pretty common that it’s always the lesser of a certain size cap – or 50% of the primary structure.
It can come in the form of being attached on the side or as an additional second story to your home.
Attached basement unit
Some municipalities allow you to build an additional dwelling as a basement unit in your home.
Keep in mind this is usually considered a finished basement, and might not always be a place that can be considered livable, but still goes through the same process as an ADU.
For further information, you can see a beautiful image from the City of Colorado Springs that clearly shows the above three options.
How big a lot do I need to build an ADU?
The short answer here is you need a large property.
There are some municipalities that will allow an ADU with only 5,000 to 6,500 square feet of land, and those can sometimes be in the bigger cities. Always check with your municipalities, or we can do that on your behalf.
Yet there are some places, such as Lakewood, CO that require a minimum lot size of at least 9,000 square feet before even considering getting approval to be able to build an ADU. In Golden there’s a minimum lot size is 7000sqft.
The lot size being bigger won’t remove the ruling of whether you can build your ADU higher than your original structure. Again it needs to be equal to, or smaller, so make sure your primary structure is two stories or higher, or you’ll need to reconsider your plans.
Costs and permissions
Since you’re considering building an ADU, it will be like building a new home …from the ground up.
Especially in the bigger cities such as Denver, you’ll need to connect them to your utilities, set up all the same permits as a new home, and have them pass numerous types of inspections.
A full list straight from the city of Denver will show you what exactly will be needed to begin this journey here.
Costs
When it comes to the actual construction of your home, be prepared to spend between $260,000 and $315,000 on your secondary home in Denver alone.
You can use that as a price benchmark for whichever city you might be considering. But the variables are many, so engage with an experienced contractor who can evaluate your plans against your budget.
Zoning
Another thing to consider before even considering this journey is to always check with your local municipality site and check the zoning rules and regulations.
You need to confirm with the municipal code that the zone you are in even allows an ADU to be built at all.
Not all zoning maps are the same either. For example, Boulder, CO is very specific and updates its PDF regularly to show you exactly where you can build an ADU. On the other end, Denver just has a zoning map showing its sectors and you would need to consult with them if an ADU is allowed to be built based on the zoning.
If you have the permissions and the means to build an ADU, always consider it as it is a true value-added addition to your home, and can turn into passive income in the future.
More help for a two-story ADU
We hope this has provided you with basic knowledge on whether you can consider going ahead with your ADU plans.
We’re ADU planning and building experts, we’ve been building ADUs for many years. Contact us if you need advice on any aspect of building an ADU.
If this information has sealed it for you, and you’re looking for an experienced contractor that can take your ADU project from start to finish, then simply get in touch today. We’ll be happy to help anyone in Colorado to build their dream ADU.