Detached ADU vs Attached ADU in Driggs — Which One Makes Sense?

In Driggs, a detached ADU runs $290–$525/sf and rents for 30–45% more than an attached unit. An attached ADU saves 15–25% on build cost and permits faster. Detached wins on rental income and resale. Attached wins on speed, cost, and multi-gen use cases. Here’s how to pick.

What’s the difference in Driggs?

A detached ADU is a stand-alone structure — its own foundation, walls, roof, address for guests. An attached ADU shares at least one wall with the main house (garage conversion, basement suite, addition off the back). In Driggs city and unincorporated Teton County Idaho, both are allowed under the accessory dwelling unit ordinance, but they hit different setback rules, different septic reviews, and different STR treatment.

Pros — Detached ADU in Driggs

• Higher rental income. Guests want privacy. A standalone cabin in your backyard rents for $175–$285/night in peak season. An attached unit rents for $110–$180.
• More resale flexibility. Detached ADUs are viewed as separate income assets by appraisers — you get more of the build cost back.
• Cleaner exit. If you sell someday, some buyers subdivide, some rent it out, some use it as a guest house. Detached gives all three options.
• Better for STR. Multiple STR platforms rate detached higher, and cleaning turnover is easier when guests aren’t walking through your mudroom.
• Doesn’t touch your main house. No dust, no disruption during build — you keep living normally.

Cons — Detached ADU

• Costs 15–25% more per square foot. New foundation, new roof system, new mechanical spine, separate utility runs.
• Eats yard. A 20×40 footprint plus setbacks and driveway pull removes 1,200–2,000 sf of usable yard.
• Longer permit review. Full new structure permit vs. addition permit.
• Utility infrastructure. Might need a new water line, dedicated propane, sub-meter — $8k–$22k.

Pros — Attached ADU (Addition, Basement, or Garage Conversion)

• Lower cost. Shared foundation, shared roof, shared mechanicals — typically 15–25% less per square foot.
• Faster permit. 4–8 weeks vs 10–16 weeks for detached in Teton County ID.
• Better for multi-gen. If Grandma’s living in it, being connected is a feature not a bug.
• Doesn’t eat yard. Especially garage conversions — you use footprint that already exists.
• Easier to heat. Shared mechanicals means one system, not two — real savings in Driggs winters.

Cons — Attached ADU

• Lower rental income. STR guests pay less for a unit connected to the owner’s house.
• Sound bleed and privacy. Shared walls need real insulation and design attention, or every conversation crosses.
• Disrupts main house during build. Especially basement conversions — you live through construction.
• Lower appraisal recovery. Attached ADUs typically recover 55–70% of build cost vs 70–85% for detached.

Cost Breakdown — Driggs 2026

Detached ADU, 750 sf:

• Foundation + site: $34,000–$52,000
• Framing + roof: $52,000–$78,000
• Mechanicals: $45,000–$68,000
• Interior finishes: $52,000–$92,000
• Exterior finishes: $40,000–$62,000
• Utilities + septic: $10,000–$38,000
• Permits + design: $9,000–$16,000
• Overhead + contingency: $30,000–$48,000
• Total: $272,000 – $454,000

Attached ADU (addition or basement), 750 sf:

• Site + tie-in: $12,000–$28,000
• Framing + tie-in roof: $32,000–$52,000
• Mechanicals (tie-in): $28,000–$48,000
• Interior finishes: $48,000–$85,000
• Exterior finishes: $22,000–$38,000
• Utilities: $4,000–$12,000
• Permits + design: $6,500–$12,000
• Overhead + contingency: $22,000–$38,000
• Total: $174,500 – $313,000

Garage conversions come in lower still — $135k–$220k typical — because the shell already exists.

Permitting in Driggs

Inside Driggs city limits, ADUs are handled through the city planning office with setback minimums (typically 5′ side, 10′ rear for detached accessory structures) and a max lot coverage rule that catches people on infill lots. Unincorporated Teton County ID applies the accessory dwelling ordinance with different setbacks by zone.

Detached in Driggs: 10–16 weeks permit review. Attached: 4–8 weeks (basement conversion runs at the low end, garage conversion mid, addition at the high end because of exterior wall changes triggering full envelope review).

Future Value — 10-Year Comparison

Rough 10-year math for Driggs:

• Detached ADU, $340k build, $42k/yr gross rent: Net $28k/yr after expenses = $280k over 10 years, plus ~$255k appraisal bump. Total ~$535k on $340k investment.
• Attached ADU, $225k build, $26k/yr gross rent: Net $17k/yr after expenses = $170k over 10 years, plus ~$150k appraisal bump. Total ~$320k on $225k investment.

Detached wins on total return if you’re going to rent. Attached wins on ROI percentage and cash-flow risk if you’re using it for family.

When Each One Makes Sense

Go detached if: STR is your goal, you have lot area, you don’t want a shared wall with a tenant, and resale flexibility matters.

Go attached if: it’s for family, you’re on a tight lot, budget is the constraint, or you’re converting a basement/garage that’s already partially wired.

How SwagerBuilds Handles the Decision

Before we quote either version, we walk your lot, check the septic system, review your zoning, and price both scenarios so you’re not choosing on assumption. Fixed-price contracts. No allowances that shift the number later. JobTread login so you see the same schedule and budget I do. Twenty years in Driggs means we’ve done both dozens of times — we know which sub-crews handle attached tie-ins cleanly and which framers cost too much on small detached foundations.

FAQ

Can I short-term rent an attached ADU in Driggs?

Yes if your zone allows STR generally. Attached vs detached usually doesn’t affect the permit itself.

Does an attached ADU need a separate address?

Not required, but many owners set up a Suite/Unit B designation for USPS and STR listings.

Can I convert my Driggs garage into an ADU?

Yes if the garage meets setback and you don’t fall below required parking. Full insulation upgrade, egress windows, and separate HVAC needed.

Which appraises higher, attached or detached?

Detached typically. Appraisers treat it more like an income asset.

Timeline difference?

Attached: 5–7 months build. Detached: 6–9 months build. Permit adds 4–16 weeks depending on type.

Which One Should You Build?

Send me your Driggs lot and a rough idea of what you’re trying to do. I’ll price both and tell you honestly which one wins on your specific parcel. Start here.

Related: ADU Cost, Permits + ROI in Teton Valley (pillar) · ADU Rental Income in Jackson + Victor · Complete Guide