ADU/Guest House Checklist

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Feasibility

Research local ADU regulations

Check zoning laws, ADU ordinances, and building codes in your city/county.

Verify lot requirements

Confirm minimum lot size, coverage limits, and if your property qualifies.

Understand setback requirements

Know how close to property lines you can build. Setbacks vary by wall type.

Check height limit restrictions

ADUs often have height caps of 16-25 feet depending on location and type.

Confirm parking requirements

Some cities require additional parking for ADUs, others have waived this.

Type

Detached vs attached ADU

Decide between freestanding unit or addition. Impacts cost, privacy, utilities.

Garage conversion feasibility

Converting existing garage is often cheapest option if structure is sound.

Prefab vs stick-built decision

Prefab ADUs offer speed and certainty but less customization. Compare carefully.

Determine optimal size

Balance budget, regulations, and needs. Common sizes: 400-800 sq ft.

Define intended use case

Rental income, aging parent, adult child, home office, or guest suite?

Design

Hire ADU-experienced architect

Find designer with local ADU permitting experience. This is critical.

Design for rental or family use

Rentals need efficiency and durability. Family units need connection.

Understand permit strategy

Some cities have expedited ADU permits. Pre-approved plans can save months.

Apply for building permits

Submit complete plans, engineering, site plan. Be patient with review process.

Address fire and life safety codes

ADUs must meet egress, smoke detector, and separation requirements.

Budget

Get realistic cost estimates

Budget $200-400+ per sq ft depending on finishes and location. Get multiple bids.

Explore ADU-specific financing

Cash-out refinance, HELOC, construction loans, or specialty ADU lenders.

Calculate rental income potential

Research local ADU rents. Studio: $1,200-2,500/mo. 1BR: $1,500-3,500/mo.

Factor in ongoing costs

Property tax increase, insurance, utilities, maintenance. Budget 15-25% of rent.

Contractor

Find ADU-experienced contractors

ADU builds have unique challenges. Experience with small spaces matters.

Get detailed bids from 3+ contractors

Compare scope, timeline, payment schedule, and exclusions carefully.

Check references thoroughly

Visit completed projects. Ask about communication, budget, timeline, problems.

Review contract carefully

Include scope, timeline, payment schedule, change orders, warranty, cleanup.

Utilities

Electrical panel capacity assessment

ADU adds 40-100 amps. Main panel may need upgrade ($2,000-8,000).

Assess water/sewer capacity

Verify adequate pressure and sewer capacity. Aging systems may need upgrades.

Plan HVAC approach

Separate system recommended. Options: mini-split, heat pump, or forced air.

Separate vs shared meters

Separate meters cost more upfront but clarify utility responsibility.

Site Work

Site preparation and clearing

Remove vegetation, old structures, and debris. Protect existing landscaping.

Choose foundation type

Slab, crawl space, or pier foundation. Depends on slope, soil, budget.

Utility trenching and connections

Run water, sewer, electric, gas lines from main house or street.

Foundation inspection

Critical inspection before framing. Foundation must be level, properly reinforced.

Structure

Framing and structural work

Wall framing, roof trusses, shear walls. Usually takes 2-4 weeks.

Roofing installation

Roof sheathing, underlayment, and finish roofing. Match main house if visible.

Windows and exterior doors

Energy-efficient windows and secure entry. Affects comfort and utility bills.

Exterior siding and trim

Weather barrier, siding, and trim. Should complement main house aesthetics.

Insulation and air sealing

Proper insulation saves energy long-term. Don't skimp here.

Systems

Rough electrical installation

Wire for outlets, switches, lights, appliances. Plan for future needs.

Rough plumbing installation

Water supply, drains, vents for kitchen and bathroom. Critical to get right.

HVAC installation

Install heating/cooling system. Ductwork if needed. Test thoroughly.

Drywall installation and finishing

Hang, tape, mud, sand, and prime. Takes 1-2 weeks. Creates lots of dust.

Interior paint and finishes

Paint walls/trim, install flooring, baseboards, doors. Biggest visual impact.

Kitchen/Bath

Install compact kitchen

Efficient layout with small-space appliances. 6-10 feet of counter space.

Bathroom installation

Full bath with shower/tub, toilet, vanity. Waterproofing is critical.

Install fixtures and appliances

Faucets, shower, toilet, dishwasher, range, fridge. Test everything thoroughly.

Finish details and hardware

Cabinet hardware, towel bars, toilet paper holder, light fixtures.

Final

Final inspections and certificate of occupancy

Pass all final inspections. Required before anyone can legally occupy the ADU.

Obtain separate address if renting

Separate address makes ADU easier to rent and validates for tenants.

Set up as rental (if applicable)

Document everything

Keep all permits, receipts, warranties, photos. Critical for taxes and future sale.

Stage and photograph ADU

Professional photos help you rent faster and for more money.

Related Projects

Garage Conversion 2-4 months Basement Apartment 2-5 months Home Addition 4-8 months