Narrow Lot ADU with Roof Top
Project Overview
Our first accessory dwelling unit in Denver may just be our favorite ADU project. The homeowners wanted a high-functioning accessory dwelling unit that could add flexible living space and long-term value on a tight urban lot. Prenvalley Builders constructed a two-car garage ADU with a studio, one-bedroom apartment, rooftop deck, and solar array, navigating limited site access and overhead power lines throughout the build. What makes this project special is how much livability and performance were achieved within a challenging footprint while maintaining a clean, modern presence.
Project Details
Size: 2,200 sq ft
Location: Sloan Lake, Denver, Colorado
Architectural Design: Prenvalley Builders
Interior Design: NAGY Design Co.
Our Approach
Prenvalley Builders approached this ADU with a strong focus on logistics, sequencing, and build quality, knowing the tight site and surrounding utilities would require careful coordination. By managing access, material staging, and structural execution with precision, the team delivered a high-performing garage ADU without compromising efficiency or craftsmanship.
Project Highlights
Two-car garage ADU with studio and one-bedroom apartment
Built on a narrow lot with complex site logistics
Rooftop deck engineered for heavy-use features
South-facing solar array for improved energy performance
Efficient interior layouts maximizing usable space
Durable exterior materials suited for Denver’s climate
Results
The completed ADU delivers flexible, high-quality living space while adding long-term value to the property. Despite the tight site and logistical challenges, Prenvalley Builders executed a clean, efficient build that performs well and fits seamlessly into its urban Denver setting.
Project Goals
Add flexible living space within a compact urban footprint
Maximize functionality on a narrow Denver lot
Support long-term rental or multi-use living options
Improve overall property value through a high-quality ADU build
Deliver durable, efficient construction suited to Denver’s climate
Common Questions about Accessory Dwelling Units
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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.
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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.
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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.
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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.
