Interest in building an ADU, or accessory dwelling unit, keeps rising because homeowners want more flexibility from the homes they already own. An ADU is a smaller, independent living space on the same lot as a single-family home, with room for living, sleeping, cooking, and bathing. An ADU can create space for aging parents, adult children, long-term guests, caregivers, or rental income.
Before you move ahead with plans, it helps to focus on three issues that shape nearly every building project: cost, zoning, and design. When homeowners slow down and answer those questions early, they are more likely to avoid expensive surprises later.
The answer depends on where you live, what kind of ADU you want, and how much site work your property needs. Recent national cost guides estimate that many ADUs fall in the range of about $150 to $300 per square foot, while some projects run higher depending on location, finishes, utility work, and complexity. In-law suite style additions are often estimated at around $100 to $200 per square foot, and conversions can sometimes cost less than detached new construction because part of the structure already exists.
That wide range reflects real-world variation. A garage conversion may be more affordable than a detached backyard cottage that needs a new foundation, roofing, plumbing, and electrical work. Costs can also rise when a lot has grading challenges, limited construction access, or aging infrastructure that must be upgraded to support a second unit.
A strong ADU budget should include more than lumber and finishes. Homeowners often overlook soft costs and site-related expenses, including:
ADU zoning requirements vary from place to place because ADU policy is shaped by a mix of state law and local zoning. U.S. Department of Housing and Urban Development research notes that many state ADU reforms are designed to limit overly restrictive local rules, but cities and counties still control important details through their ordinances and permitting processes.
Before you spend money on drawings, contact your local planning or building department and ask:
The best ADU design ideas are usually practical before they are trendy. In a small footprint, layout matters more than square footage. Open-plan living areas, strong natural light, and built-in storage can make a compact unit feel more comfortable and functional.
Many homeowners also benefit from thinking ahead. Wider doorways, step-free entries, and accessible bathrooms can make an ADU more useful for aging in place or multigenerational living. Energy efficiency matters, too, and can help lower long-term utility costs.
Another design angle worth considering early is salvaged building materials. Reclaimed doors, cabinets, flooring, lighting, sinks, and architectural details can add warmth and individuality to an ADU while helping reduce waste.
This is where our deconstruction services at The ReUse People (TRP) can fit naturally into an ADU project. If your plan involves removing an old garage, detached structure, or worn-out addition before building, TRP offers deconstruction as an alternative to standard demolition.
And if you want your ADU to look distinctive, not cookie-cutter, TRP can help on the design side, too. TRP’s retail warehouse is open to the public and stocks salvaged materials and appliances recovered from deconstruction projects. Shoppers can find quality used materials at lower prices, which can make reclaimed finishes a practical option for homeowners balancing style, sustainability, and budget.
TRP reduces the solid waste stream and changes the way the built environment is renewed by salvaging building materials and distributing them for reuse. Relied on by architects, contractors, building owners, and federal, state, and local governments since 1993, we’ve deconstructed over 4,000 houses and buildings and diverted over 400,000 tons of waste from landfills. Learn more about our commercial and residential deconstruction, explore our salvaged materials for sale, or donate today to support our work!