Expand Your Home. Add an Attached ADU.
An attached ADU gives you rental income or multi-generational living space without sacrificing your backyard. We design and build additions that blend seamlessly with your existing home.
What Is an Attached ADU?
An attached ADU is a separate living unit that shares one or more walls with your primary home — like an addition or a converted portion of your existing square footage. It has its own entrance, kitchen, bathroom, and living space, but it physically connects to your main house.
Attached ADUs are ideal when you have limited backyard space, when you want to keep a family member close while maintaining privacy, or when a side or rear addition makes more architectural sense than a separate structure.
Attached ADU Options
Side Addition
Built onto the side of your home, typically sharing a common wall. Works well on wider lots with side yard setback clearance. Can be designed to look like it was always part of the original structure.
Rear Addition
Added to the back of your home. Requires a rear setback assessment for your zoning district. Often the best option for lots with sufficient rear yard depth.
Interior Conversion (JADU)
Converting existing interior space — a large bedroom, basement, or bonus room — into a Junior ADU (JADU). Often the least disruptive option, with the lowest construction cost.
Above-Garage Addition
Building living space above an attached garage. Requires structural engineering for the garage floor/ceiling and stair access, but uses otherwise dead space effectively.
Twin Falls Code for Attached ADUs
- →Permitted: Per Title 10-6-10-B, ADUs may be "added to or included within the principal residence." As an Idaho city over 10,000 population, Twin Falls is also covered by SB 1354 (effective July 1, 2026), which requires it to allow at least one ADU per single-family lot.
- →45% Size Rule: The ADU cannot exceed 45% of your primary home's living space. The addition counts toward this calculation.
- →Setbacks still apply: The addition must comply with your zoning district's setback requirements for the principal dwelling — not the more relaxed accessory building setbacks.
- →Design continuity: The addition must be consistent with the existing roof pitch, siding, and windows of the primary residence per Title 10-6-10-B.
- →Shared utilities: Water, sewer, and sanitation must be shared with the primary dwelling. No separate meters per Title 10-6-10-B(vii).
Attached vs. Detached — Which Is Better?
The right answer depends on your lot, your goals, and your budget. Attached ADUs keep your backyard, can be less expensive, and are sometimes easier to permit. Detached ADUs offer more privacy, are generally worth more as a rental, and add more value to the property. We compare both options in your Feasibility Check.
Read the full comparison →How the Attached ADU Process Works
From structural assessment to move-in — one team, every step
Feasibility Assessment
We evaluate your home's structure, available space, and utility systems. We verify zoning, setbacks, and the 45% size limit for your specific lot and district.
Structural + ADU Design
We design the addition and the ADU layout together — making sure the new structure integrates with your home's foundation, framing, and roofline, and meets the design match requirements of Twin Falls code.
Full Permit Package
Attached ADUs require both the Zoning Use Permit and a full building permit package covering structural, electrical, plumbing, and mechanical. We handle every submission.
Construction
Our licensed general contractors and trade teams build the addition and complete the ADU interior. We manage every phase and every inspection through final Certificate of Occupancy.
Add an ADU to Your Existing Home
Start with a free Readiness Call. We'll assess your home's structure, zoning, and setbacks — and tell you what type of attached ADU makes the most sense for your property.