How much does it cost to build a custom garage ADU in Denver?

The cost of a custom garage ADU in Denver typically depends on size, site conditions, structural complexity, finishes, and permitting requirements. Most garage ADUs are more complex than standard detached ADUs due to structural loads, stair integration, and utility coordination. Prenvalley Builders provides detailed budgeting early in the process to ensure alignment before construction begins.

Can a garage ADU be used as a long-term rental or guest space?

Yes. Garage ADUs are commonly designed for long-term rental income, guest accommodations, or multi-generational living. With proper planning, they can function as fully independent living spaces with kitchens, bathrooms, and private entrances while maintaining flexibility for future use.

What makes a garage ADU more complex than a standard ADU?

Garage ADUs often require additional structural engineering, fire separation, stair design, and careful space planning to meet code while maintaining comfort. Because the living space sits above the garage, ceiling heights, daylighting, and circulation must be intentionally designed—something Prenvalley specializes in through a design-build approach.

How long does it take to design and build a garage ADU in Denver?

Timelines vary based on permitting, design complexity, and site conditions, but most custom garage ADUs take several months from design through construction. Prenvalley Builders manages the full process—from early planning and permitting through construction—so clients have a clear roadmap and realistic expectations.

Will a custom garage ADU increase property value?

A well-designed and well-built garage ADU can significantly increase property value by adding livable square footage, rental potential, and long-term flexibility. Thoughtful design, durable materials, and high-quality construction are key factors in ensuring the ADU adds lasting value rather than short-term appeal.

Sunnyside ADU + Garage Addition

ADUGarageNew Construction

Feb 18

Written By Phillip Daughton

Custom garage ADU in Denver’s Sunnyside neighborhood featuring a two-car garage, vertical siding, cedar shingle accents, and dormer windows, designed and built by Prenvalley Builders.

Project Overview

This beautiful Sunnyside ADU was completed in the summer of 2024. It features a 2.5 car garage, 2 bedrooms, 1 bathroom, a kitchen/ living area and vaulted ceilings/ dormers that provide a lot of character in and out of the structure.

Project Details

Size: ~1500 sq ft

Location: Denver, Colorado

Architectural Design: Radix Design

Upper-level floor plan of a custom ADU in Denver’s Sunnyside neighborhood showing two bedrooms, a full bathroom, open living and kitchen layout, stacked laundry, and efficient circulation designed by Prenvalley Builders.

Ground-level floor plan of a custom garage ADU in Denver’s Sunnyside neighborhood showing a two-car garage, dedicated ADU entry, stair access, storage, and EV-ready infrastructure designed by Prenvalley Builders.

Our Approach

We approached this project with a focus on efficiency, thoughtful design, and responsible material use. Our design–build process allowed us to refine every detail—from structural framing to material selections—ensuring the ADU performed well in Colorado’s climate while maintaining long-term durability.

Project Highlights

Detached ADU with efficient layout
High-performance insulation & windows
Durable exterior materials for Colorado climate
Energy-efficient HVAC system
Low-waste construction practices
Thoughtful interior finishes
Seamless connection between garage + living space
Designed for both family use & rental income

Framing in progress on a custom garage ADU in Denver’s Sunnyside neighborhood, showing structural walls, second-story layout, and design-build coordination by Prenvalley Builders.

Sheathing and roof assembly in progress on a custom garage ADU in Denver’s Sunnyside neighborhood, showing dormer construction, structural detailing, and envelope preparation by Prenvalley Builders.

Exterior siding installation on a custom garage ADU in Denver’s Sunnyside neighborhood, showing vertical siding, dormer windows, and architectural detailing built by Prenvalley Builders.

Finished exterior of a custom garage ADU in Denver’s Sunnyside neighborhood featuring vertical siding, cedar shingle accents, dormer windows, and a two-car garage built by Prenvalley Builders.

Results

This ADU added significant long-term value to the property while providing flexible living options for the homeowners. The high-performance envelope, durable materials, and thoughtful design ensure comfort, efficient energy use, and lasting durability.

Project Goals

Increase usable square footage
Add long-term rental income potential
Improve energy performance
Blend seamlessly with existing architecture
Support multi-generational living
Modernize functionality

Finished bathroom interior in a custom Denver ADU featuring a skylight, sloped ceiling, modern vanity, brass fixtures, and integrated storage designed and built by Prenvalley Builders.

Open-concept living and kitchen area inside a custom Denver ADU featuring vaulted ceilings, dormer windows, modern cabinetry, and a flexible workspace designed by Prenvalley Builders.

Kitchen interior of a custom Denver ADU featuring vaulted ceilings, a skylight, modern wood cabinetry, island seating, and energy-efficient appliances designed by Prenvalley Builders.

Common Questions about Accessory Dwelling Units

This varies quite a bit throughout Colorado based on your city’s specific zoning guidelines. Our team are experts with zoning rules throughout the state and can provide you with a detailed breakdown of what’s possible.
We usually get asked how much an ADU costs per square foot but this is the hardest metric for an ADU since the cost per square foot parameter can vary drastically based on the size. This is due to the fact that ADUs are small compared to normal homes and the cost per sq. ft. can vary dramatically due to the economy of scale factor. Also, most of the ADUs we build have unfinished garages which complicates that metric even further. We’ve found that ADUs in Denver can vary on average from $250k to $450k based on size, finish level, and site constraints.
As of right now the average ROI ranges from 4 to 7 years until you begin seeing a net positive on your ADU investment which is based short term renting the space over that time. The problem with ADUs in Colorado is that there aren’t many comparables when appraisers are valuing these spaces so they are typically appraised at a lower value than they were built for. As more ADUs are built and sold with their primary homes, these numbers will improve so this ROI is very much temporary. As of now, ADUs are considered a long term investment and are definitely worth the consideration if you’re looking to hold onto your home for the long run.
In our experience thus far, the scale of an ADU hasn’t been proven to be built better or more cost effective in a modular format. The modular ADU on paper seems like a great idea but all of the companies we’ve seen provide them are at a comparable price point if not higher and quality issues can occur due to manufacturing, delivery, and assembly issues. We view ADUs as custom small homes that need to be built with care and craftsmanship which can easily be lost in a mass manufacturing process.

Phillip Daughton

Sunnyside ADU + Garage Addition

Project Overview

Project Details

Our Approach

Project Highlights

Results

Project Goals

Common Questions about Accessory Dwelling Units

How big can I build my ADU?

How much does an ADU cost?

What is the ROI for an ADU?

Is a modular ADU or stick-built ADU better or more cost effective?

Landmark District Two-Story ADU + Garage

Montclair Whole-Home Pop-Top Renovation

Ready to Create More Space, and More Possibility?