How much does an in-law suite cost?
An in-law suite can cost $5,000 - $100,000+ when converting existing space, and $40,000 - $200,000+ for a new attached addition. Detached ADU-style suites can reach $100,000 - $280,000+ depending on size, kitchen, bath, utilities, and local rules.
The cost changes sharply based on whether the suite is just a bedroom/bath area, a full apartment with kitchen and laundry, or a detached accessory dwelling unit that needs its own foundation and utility connections.
In-law suite cost by setup
Bedroom or sitting-room conversion
$5,000 - $25,000How to tellExisting finished space becomes a private room, office, or accessible sleeping area
The fixFocus on doors, flooring, lighting, closets, privacy, and accessibility upgrades
Basement or garage conversion
$30,000 - $100,000+How to tellYou are using existing square footage but need egress, insulation, bath, HVAC, or code upgrades
The fixVerify ceiling height, moisture, fire separation, parking, egress, and local conversion rules
Attached suite addition
$40,000 - $200,000+How to tellNew bedroom, bath, sitting area, or kitchenette is added to the home's footprint
The fixPrice foundation, framing, roofing, exterior matching, utilities, permits, and finishes
Detached in-law suite or ADU
$100,000 - $280,000+How to tellSeparate structure with its own bath, kitchen, entrance, utilities, and zoning review
The fixCheck ADU rules, setbacks, utility connections, parking, and rental/occupancy limits
Accessibility and aging-in-place upgrades
$2,500 - $25,000+How to tellThe suite needs no-step entry, wider doors, grab bars, curbless shower, ramps, or caregiver access
The fixPlan accessibility before framing and plumbing locations are final
Before planning an in-law suite
- Write down who will use the suite, whether it needs a private entrance, whether cooking is allowed, and whether rental use is part of the plan.
- Check zoning, ADU, occupancy, parking, short-term rental, and HOA rules before you design.
- Decide whether the priority is privacy, accessibility, caregiver proximity, rental income, or future resale flexibility.
- Ask contractors to separate conversion costs, new construction costs, bathroom/kitchen allowances, utility upgrades, permits, and accessibility items.
Unlock the hiring checklist
Use this before you call an addition contractor, so you know what to ask and what to avoid.
Call a pro when…
- The suite adds a bathroom, kitchenette, laundry, private entrance, or new square footage
- You are converting a garage, basement, attic, or detached structure
- Local ADU, zoning, parking, or occupancy rules may apply
- Accessibility needs affect doors, thresholds, bathrooms, stairs, ramps, or shower design
- You need help comparing attached addition, detached ADU, and conversion options
Repair or replace?
Converting existing space can be much cheaper if ceiling height, moisture control, egress, utilities, and code requirements already work. A new addition or detached ADU costs more but can create a more private and flexible suite.
Need a cleaner scope before you call around?
Use the home additions checklist to compare the same work, questions, cleanup, and warranty before choosing a local company.
Related questions
Is an in-law suite the same as an ADU?
Not always. An ADU is usually a legally defined accessory dwelling unit with local rules. An in-law suite can be simpler, such as a bedroom and bath inside the existing home.
Can I add a kitchen to an in-law suite?
Maybe. Some cities treat a kitchen or separate entrance as an ADU trigger. Check zoning and permit rules before planning full cooking facilities.
What is the cheapest way to make an in-law suite?
Use existing finished space, keep plumbing close to current bathrooms or kitchens, avoid new foundation work, and solve accessibility needs with targeted upgrades.