What is an ADU (Accessory Dwelling Unit)?

An ADU (Accessory Dwelling Unit) is a secondary housing unit on a single-family residential lot. Also called a granny flat, backyard cottage, in-law suite, casita, or garage conversion. ADUs can generate rental income of $1,200–$2,500/month and increase property value by $120K–$280K.

Do I need permit-ready plans for an ADU?

Yes — to build an ADU legally, you need permit-ready (PE-stamped) engineering plans accepted by your local building department. QuiPlans provides PE-stamped structural drawings prepared by licensed Professional Engineers in 25 U.S. states, including architectural, structural, and MEP engineering plans.

How long does it take to get permit-ready ADU plans?

QuiPlans delivers PE-stamped permit-ready plans in 10–14 business days. Instant downloadable architectural concept drawings are available immediately after purchase. The complete permit package including site plan, drainage, and grading takes 3–4 weeks.

Which states do QuiPlans engineers work in?

QuiPlans licensed engineers cover 25 U.S. states: FL, TX, GA, NC, VA, MD, SC, TN, OH, MI, PA, NJ, NY, CT, MA, RI, ME, AZ, NV, CO, CA, LA, OK, NM, and DC. We are expanding to additional states.

What's the difference between a concept plan and permit-ready plans?

A concept plan is an architectural drawing set for early planning, contractor quotes, and HOA submissions — it cannot be submitted for a building permit. PE-Stamped permit-ready plans are signed and sealed by a licensed Professional Engineer and include architectural, structural, and MEP drawings — everything your building department needs to issue a permit.

Can I customize an ADU floor plan?

Yes. All 31 QuiPlans floor plans can be customized to your needs — modify bedroom count, bathroom layout, exterior style, square footage, and more. Customization pricing is based on square footage and complexity. Contact us for a custom quote.

How much rental income can an ADU generate?

ADU rental income varies by location and size. A studio ADU typically generates $1,200–$1,800/month. A 1-bedroom ADU generates $1,400–$2,200/month. A 2-bedroom ADU generates $1,800–$2,500/month. In high-demand markets like California, ADUs can generate $2,500–$3,500/month.

Do I need a feasibility study before buying plans?

If you're unsure whether your lot can support an ADU — due to zoning, setbacks, lot coverage, or utility constraints — a $349 feasibility study by a licensed engineer will give you a clear go/no-go answer before you invest in plans. The full $349 is credited toward your permit-ready package if you proceed.

What is a garage conversion ADU?

A garage conversion ADU transforms an existing attached or detached garage into a livable dwelling unit. This is typically the most cost-effective ADU option ($50K–$120K) since the structure already exists. QuiPlans offers garage conversion floor plans and permit-ready engineering for garage conversions in 25 states.

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What Is an ADU?

An Accessory Dwelling Unit (ADU) is a secondary housing unit on a single-family residential lot. Also called granny flats, backyard cottages, or in-law suites. ADUs can be: • Detached (separate structure in backyard) • Attached (addition to main home) • Garage conversions • Basement units They've become legal and encouraged in most U.S. states as a solution to the housing shortage — which means fewer permit barriers than ever before.

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The Income Opportunity

A well-built ADU generates real, recurring income: • Studio (400 sqft): $900–$1,400/month • 1-Bedroom (550 sqft): $1,200–$1,800/month • 2-Bedroom (750 sqft): $1,600–$2,800/month At a typical 5% cap rate on a $68,000 build: → Annual net income: ~$15,000–$24,000 → Payback period: 3–6 years → Then it's pure cash flow Plus your property value increases $100,000–$200,000.

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The Build Process

Building an ADU involves 5 key stages: 1. Design — Choose your floor plan (this is where QuiPlans helps) 2. Engineering — Get PE-stamped structural drawings for permits 3. Permitting — Submit drawings to your city or county 4. Construction — Build with a licensed contractor 5. Certificate of Occupancy — Final inspection and approval The design + engineering phase is where most homeowners waste money or make mistakes. We help you do it right the first time.

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Why Engineering Matters

You cannot legally build from architectural drawings alone. You need PE-stamped (Professional Engineer) structural drawings for: • Building permit applications • Construction loans • Final inspections WITHOUT proper engineering: ❌ Permit denied ❌ Construction stopped mid-build ❌ Fines and liability ❌ Can't get a CO (Certificate of Occupancy) WITH QuiPlans + LSE Engineering: ✅ PE-stamped in 26 states ✅ Ready for permit submission ✅ 7–10 business day delivery

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Concept vs Architectural vs Permit-Ready

There are three levels of plans: CONCEPT (Starter): For planning, HOA approvals, visualizing your space. Not for permits. ARCHITECTURAL (Full Design): Complete architectural drawings for contractor bids, financing, and planning. Not PE-stamped. PERMIT-READY (Best Value): Full architectural + licensed structural engineering + MEP plans. PE-stamped and ready for permit submission. This is what you need to build. Most homeowners start with Concept or Architectural, then upgrade to Permit-Ready when they're ready to pull permits.

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Frequently Asked Questions

How much does it cost to build an ADU?

Typically $40,000–$120,000 depending on size, finishes, and location. Our ROI calculator uses real market data to estimate your specific project.

How long does it take to get a permit?

Permit timelines vary by city: 2–8 weeks in most areas, up to 6 months in slow jurisdictions. Engineering is usually done in 7–10 days.

Do I need to own the land?

Yes. ADUs are built on existing residential lots. You must own or have ownership rights to the property.

Can I build an ADU in any state?

Most states allow ADUs. QuiPlans engineering is available in 26 states. Availability varies by local zoning — our permit system page can help you check.

What's the difference between QuiPlans and hiring an architect?

A local architect typically costs $5,000–$20,000+ and takes months. QuiPlans offers professionally designed plans starting free, with engineering from $997, delivered in days — not months.

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Everything You Need to KnowAbout Building an ADU