What 30+ ADUs Taught Us About Small-Scale Housing
Accessory Dwelling Units have become one of the most discussed housing types in Colorado.
For F9 Productions, they have also become one of the fastest-growing categories in our project history.
Our master database currently includes more than 30 projects classified primarily as ADUs.
The timing is striking.
The first appears in 2017.
Another appears in 2021, and another in 2023.
Then six in 2024.
In 2025, the floodgates open.
And projects are already represented in the 2026 database.
Something clearly changed.
Homeowners began seeing the unused portions of their properties differently.
Garages became potential homes.
Backyards became potential building sites.
A few hundred square feet became enough space to create rental housing, multigenerational living, guest space, or long-term flexibility.
Designing more than 30 of them has taught us that ADUs may be small buildings, but they are not simple ones.
Lesson 1: An ADU Is Really a Site-Planning Problem
People tend to think about an ADU as a tiny house.
We tend to begin with the lot.
Where can it go?
How does somebody reach it?
Where does the main house look?
Where should the ADU look?
What happens to the backyard?
Where do cars go?
Where are the utilities?
Does the new building create privacy or destroy it?
What happens to outdoor space?
The ADU is only one piece of a larger property.
A technically good floor plan in the wrong location can make both houses worse.
That is why the site plan often matters as much as the unit itself.
Lesson 2: Every Square Foot Has to Work Hard
The Horstman ADU in Longmont includes a remarkably compact 160-square-foot dwelling component with an associated patio.
The McGinn ADU in Arvada is another tiny project at roughly 246 square feet.
At that scale, there is nowhere for bad planning to hide.
A three-foot-wide circulation zone is not just a hallway.
It is a meaningful percentage of the entire building.
A poorly located mechanical closet matters.
An oversized bathroom matters.
A door swing matters.
Storage matters.
Furniture dimensions matter.
Small housing rewards precision, and everything matters.
Lesson 3: The Best New Dwelling Might Already Be Hiding in the Garage
Four of the 30+ primary ADU projects involve existing buildings, with another combining existing and new work.
That is significant.
The East 29th Avenue ADU in Denver converts an attached garage into an ADU with a loft.
The Vebien & Arnold ADU in Broomfield converts an existing detached garage.
The Coatney ADU in Centennial uses an existing garage with an addition.
The Pearson ADU in Longmont incorporates the dwelling into an existing detached garage structure.
Those projects begin with a completely different economic and architectural proposition than ground-up construction.
Instead of asking where to create a new building, the question becomes whether an underused structure can be made dramatically more useful.
Sometimes the best piece of buildable land on the property already has walls around it.
Lesson 4: Going Up Can Be More Valuable Than Going Out
Small lots create pressure on footprint.
That is where vertical design becomes powerful.
The Murphy ADU in Denver uses a two-story configuration with a garage.
The Boone ADU, also in Denver, places living space over a garage.
The East 29th Avenue conversion uses a loft to gain usable area within a constrained envelope.
Verticality comes with its own costs.
Stairs consume space.
Accessibility changes.
Structure becomes more complicated.
But on the right lot, the value of preserving ground-level outdoor space can outweigh those disadvantages.
The smallest building footprint is not always the smallest building.
Lesson 5: The Main House and ADU Need a Relationship
An ADU should be independent.
It should not feel unrelated.
That relationship can be expressed through roof form, materials, proportions, window patterns, or simply the way the buildings occupy the site together.
The Coatney ADU specifically responds to the aesthetics of the existing home.
The Close ADU in Westminster similarly had to consider compatibility with the primary dwelling.
This does not mean copying the main house.
Sometimes contrast is the right move.
The point is that the relationship should be intentional.
Two buildings sharing one lot are already in conversation whether the architect acknowledges it or not.
Lesson 6: Parking and Storage Can Control the Design
An ADU floor plan might be 600 or 800 square feet.
Then the project has to accommodate a garage.
Or replacement parking.
Or storage.
Or a carport.
Suddenly the support spaces rival the dwelling in size.
The Rosewood ADU in Loveland, for example, combines a roughly 1,000-square-foot ADU with a 302-square-foot carport.
Other projects integrate garages directly below or beside the dwelling.
This is a reminder that small-scale housing is not simply about minimizing the living unit.
It is about efficiently organizing everything the property still needs to do.
Lesson 7: ADUs Expose the Difference Between Area and Value
One of the most useful lessons from this collection is that a few hundred square feet can fundamentally change a property.
An ADU may create:
- Housing for an aging parent
- A place for an adult child
- Rental income
- A guest house
- A future downsizing option
- A flexible place to live while the main house changes hands
The Mcintosh ADU in Longmont connects a grandfather with his children’s home, where he can now enjoy the grandchildren.
That is a disproportionate amount of utility created by a relatively small building.
It is one reason ADUs are such an interesting architectural problem.
The objective is not simply to maximize square footage.
It is to maximize what that square footage allows the property to do.
Lesson 8: ADUs Are Becoming Their Own Serious Building Type
Our project history makes this especially clear.
ADUs barely register as an independent project category during the first decade of F9’s archive.
Then they begin appearing repeatedly in:
Longmont.
Denver.
Wheat Ridge.
Arvada.
Lakewood.
Broomfield.
Centennial.
Westminster.
And Loveland.
More than 30 primary ADU projects now span communities across Colorado in the database.
That is no longer an architectural curiosity.
It is a housing type.
And we think the best ADUs will increasingly be treated with the same design seriousness as any other residence.
Not a shed with a kitchen.
Not an afterthought behind the “real” house.
A small piece of architecture with an unusually big job to do.
30+ ADUs Later
We do not think the lesson is that every backyard needs a second dwelling.
The lesson is that homeowners are beginning to think more creatively about the land and buildings they already own.
Sometimes another 500 or 800 square feet can unlock more value than adding twice that amount to the main house.
Sometimes the garage is more useful as housing.
Sometimes independence is more valuable than expansion.
Sometimes the smallest project on the property creates the biggest change in how the property can be used.
More than 30 ADUs have been enough to convince us of one thing:
Small-scale housing deserves serious architecture.