Homeowners often look at an unused spare room or part of a basement and wonder if they can turn it into a separate, self-contained living space. Residents living around Boise frequently figure out how to squeeze more function out of their square footage. Whether property owners are thinking about aging parents or want a bit of rental income, building an internal secondary suite—often called a junior unit—is a popular route. Before anyone starts tearing down drywall, it is important to talk about what it actually costs.
Boise ADU Solutions sees homeowners walk into this with all kinds of mismatched expectations. Some think they can slap up a kitchenette for five thousand dollars, while others assume it will cost as much as a whole new house. The truth sits somewhere in the middle. Most internal conversions or smaller attached layouts across Ada County run anywhere from $75,000 to $130,000. If a space requires major structural changes or a brand-new exterior door and bathroom layout, homeowners will lean toward the higher end of that range.
A few major variables drive that final price tag:
- Plumbing layout: Tying into existing drain lines close by saves thousands of dollars. Running a brand-new sewer line clear across a 1970s split-level in the Vista neighborhood gets expensive fast.
- Electrical capacity: Older homes in the North End often still have 100-amp panels that need upgrading to handle a separate subpanel, appliances, and heating loads.
- Kitchenette versus full kitchen: Code requirements for compact cooking facilities are usually simpler and cheaper than full-scale kitchen packages.
- Finishes and egress: Adding proper emergency egress windows to meet Boise building codes requires cutting concrete foundation walls, which adds specialized labor costs.
When a reputable contractor hands you a proper quote, it should not just be a lump sum scribbled on the back of a business card. A solid estimate includes framing, insulation, drywall, flooring, cabinetry, electrical work, plumbing, and HVAC tie-ins. It should also account for architectural drawings and city permit fees through Boise Planning and Development Services. Always check if appliances and light fixtures are part of the deal or if you are expected to buy those separately.
To keep from overpaying, get at least three itemized bids and look closely at the allowances. Unreliable contractors love to lowball line items for cabinets or plumbing fixtures just to win the bid, knowing you will pay out-of-pocket change orders later. Make sure every material tier is spelled out clearly in writing before anyone starts a project.