The average time it takes to build an ADU (Accessory Dwelling Unit) is 6 to 12 months, depending on factors like permitting, design choices, construction type, and local regulations. At Stonehearth Remodeling, we guide homeowners through each phase, ensuring a streamlined and efficient process from concept to completion.
Understanding What Affects the ADU Timeline
Not all ADUs are the same. The overall timeline depends on multiple factors including the type of ADU, site conditions, permit processing times, and construction complexity. Understanding these variables can help set realistic expectations and prevent delays. To learn the difference between an ADU vs. addition check out this article.
Type of ADU
ADUs can take different forms each with its own timeline:
- Detached ADUs (standalone backyard units) generally take longer due to additional foundation and utility work.
- Attached ADUs (connected to the main home) can be faster but may involve structural modifications.
- Garage conversions are typically quicker because they use existing framing.
- Basement ADUs fall somewhere in between, depending on the condition of the existing space.
Local Permitting and Zoning
One of the most time-consuming parts of building an ADU is the permitting phase. In many areas, zoning laws and building codes can create delays. Some municipalities offer pre-approved plans to reduce this timeline, but in others, obtaining permits may take 3–6 months or more. To learn more about building an ADU on a Minneapolis property click here.
At Stonehearth Remodeling, our team is experienced in navigating local zoning and permitting requirements in Minnesota. We can often shorten the permitting timeline significantly by preparing comprehensive plans and maintaining strong relationships with local officials.
Custom vs. Pre-Designed Plans
Custom-designed ADUs offer flexibility and unique features but can take longer to plan and approve. Pre-designed or modular ADUs are usually faster, as plans are already engineered and approved.
Phase-by-Phase Timeline of ADU Construction
Let’s break down the timeline to show what’s involved in each phase of the ADU building process.
1. Planning and Design (1–3 Months)
This is where your vision takes shape. During this phase, you’ll meet with designers and contractors to discuss your goals, budget, and style preferences. Key activities include:
- Site analysis
- Initial drawings
- Budget estimates
- Design revisions
- Engineering assessments (as needed)
2. Permitting and Approvals (2–6 Months)
Once your design is finalized, we submit the plans to your local building department. The time to receive approval varies widely:
- Simple garage conversions: 2–3 months
- New detached builds: 4–6 months
- Historic or complex sites: 6+ months
Delays in this phase are often outside your contractor’s control, but we help by submitting complete, code-compliant documents to avoid resubmittals and rejections.
3. Site Preparation and Foundation (2–4 Weeks)
After permits are issued, we prepare the site. This may include:
- Demolition (if required)
- Grading and excavation
- Pouring the foundation or footings
For garage conversions or basement ADUs, site work may be minimal, saving time. For detached ADUs, this step is more involved.
4. Framing and Exterior Construction (4–8 Weeks)
Once the foundation is ready, framing begins. This includes:
- Framing walls and roof
- Installing windows and doors
- Exterior siding and roofing
This is a visible and exciting phase—your ADU starts to take shape quickly.
5. Interior Construction and Utilities (6–10 Weeks)
This phase includes:
- Plumbing, electrical, and HVAC rough-ins
- Insulation and drywall
- Flooring, cabinetry, and finishes
- Painting and trim work
Utility connections, especially to sewer and water lines, can extend this phase depending on site conditions and city requirements.
6. Final Inspections and Occupancy (1–2 Weeks)
Before you can legally use your ADU, city inspectors must sign off on the work. Stonehearth Remodeling coordinates all inspections to ensure a smooth finish:
- Electrical and plumbing inspections
- Final structural inspection
- Certificate of occupancy
Once approved, your ADU is ready to use for guests, tenants, or family members.
How Stonehearth Remodeling Helps You Build Faster
With years of remodeling and construction experience, Stonehearth Remodeling brings a collaborative and streamlined approach to building ADUs. We take pride in delivering high-quality ADUs that meet your needs while sticking to the timeline.
Ready to Build Your ADU?
At Stonehearth Remodeling, we specialize in custom ADUs that blend seamlessly with your home and lifestyle. Whether you want a rental unit, guest house, or multigenerational space, our team is ready to guide you through every step.
Contact Stonehearth Remodeling today to schedule a free consultation and learn how we can make your ADU vision a reality.
