What does this project typically cost?
There is no single honest price without reviewing the property and defining the scope. These levels explain what changes between a focused project, a complete professional installation, and complex or premium work. They are not interchangeable: compare what is included, not only the final number.
Garage conversion
$80,000–$150,000+Conversion of a suitable existing shell; structural, slab, utility, envelope, fire, and code upgrades vary widely.
Room addition
$300–$500+ per sq. ft.Foundation, structure, roof tie-in, exterior envelope, utilities, and interior finishes integrated with the home.
Detached ADU
$195,000–$390,000+A complete independent dwelling with site work, utilities, foundation, structure, kitchen, bathroom, mechanical systems, and finishes.
Why does the work cost this much?
Professional remodeling includes far more than the finish material visible at the end. Labor, preparation, protection, demolition, disposal, qualified trades, supervision, code compliance, inspections, and restoration all contribute to a durable result.
Small buildings still need complete infrastructure
An ADU needs a kitchen, bathroom, electrical service, water, sewer, heating and cooling, hot water, life-safety systems, and a weather-tight shell. Those fixed systems make a compact unit more expensive per square foot than a larger simple room.
Utility work can change the budget dramatically
Sewer depth and route, water-meter capacity, electrical service, trench length, concrete removal, easements, and access all affect cost. A unit near existing connections is different from one at the rear of a difficult lot.
Design and approvals begin before construction
Surveying, architectural plans, structural engineering, energy calculations, jurisdiction review, revisions, permits, and utility coordination are necessary preconstruction costs. They also establish what can legally be built.
Garage conversions inherit existing conditions
The existing roof and walls may save money, but garage slabs, foundations, ceiling heights, moisture control, fire separation, insulation, windows, and utilities may not meet residential standards. Reusing a shell is economical only when it is suitable.
The main factors that change the final price
- Utility distance and capacity
- Foundation, grading, drainage, and access
- Architectural and engineering complexity
- Kitchen and bathroom specifications
- Fire, energy, impact-fee, and jurisdictional requirements
What a complete professional scope may include
- Foundation and framing
- Roofing, windows, doors, and insulation
- Electrical, plumbing, HVAC, kitchen, and bathroom
- Drywall, flooring, cabinets, paint, and trim
- Permit and inspection coordination
How the project normally moves from idea to completion
Review property, access, intended use, and available plans
Identify design, engineering, utility, and permit requirements
Price and sequence the complete build scope
Construct shell, systems, interiors, and site connections
Coordinate inspections and final completion
The exact sequence may change for permits, engineering, long-lead materials, inspections, occupied-home protection, or discoveries after demolition.
Conditions that may be hidden before work begins
A responsible contractor documents concealed conditions when they become visible and explains the available correction before additional work proceeds. Common discoveries for this type of project include:
- Insufficient sewer slope or electrical capacity
- Garage slab moisture or foundation deficiencies
- Fire-access, setback, tree, or utility conflicts
- Unexpected plan-check revisions and site-work requirements
Approximate 750 sq. ft. detached ADU
$260,000–$330,000+A standard one-bedroom detached unit with design coordination, permits, foundation, framing, roofing, windows, insulation, utilities, HVAC, kitchen, bathroom, drywall, flooring, cabinets, paint, and inspections. Long utility runs, difficult access, premium finishes, and major site work add cost.
This example illustrates scope and cost relationships. It is not an offer, guaranteed price, or substitute for a site inspection and written proposal.How to control cost without sacrificing the work
Place kitchens and bathrooms near practical utility routes
Use a compact rectangular footprint and standard roof geometry
Decide on a complete permit-ready design before requesting construction bids
Commonly 8–16 months including design, approvals, procurement, and construction.
Additions and ADUs require plans, jurisdiction review, permits, energy documentation, and inspections.
Carry at least 10–15%, with added allowance for utilities and site conditions.
Why bids for the same project can be far apart
A labor-only number cannot be compared directly with a complete construction proposal. Before choosing a contractor, confirm demolition, protection, disposal, material quantities, allowances, delivery, taxes, permits, engineering, qualified trade work, inspection corrections, finish restoration, cleanup, overhead, warranty, exclusions, and change-order procedures. A lower number may represent a smaller scope rather than the same project at a better price.
Questions to ask when comparing proposals
- Are labor, materials, delivery, disposal, permits, and trade coordination included?
- Which selections are fixed prices and which are allowances?
- What preparation and protection are included before installation?
- How will concealed damage and owner-requested changes be documented?
- Which wall, floor, exterior, landscape, or paint repairs are included afterward?
- Does the proposal clearly identify exclusions and owner-supplied items?