How Much Does an ADU Cost in Temecula, CA?
An ADU in the Temecula Valley runs roughly $225,000 for a 499 square foot one bedroom, $290,000 for a 749 square foot two bedroom, $230,000 for a 500 square foot attached ADU, $165,000 for a two car garage conversion, and $105,000 for a junior ADU.
Those totals cover construction, plans, engineering, typical utilities, and standard finishes. They do not cover site costs and fees, which are specific to your property. Below is what sits inside each number and what gets added. License B-842038. Call (951) 551-6165.
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ADU Cost by Size
499 square feet, 1 bedroom, 1 bath
Footprint 16 feet 3 inches by 30 feet 9 inches. Includes construction, plans, engineering, typical utilities, and standard finishes.
749 square feet, 2 bedroom, 2 bath
Footprint 19 feet 4 inches by 38 feet 9 inches. Bedrooms at opposite ends with a great room between them, full size appliances, separate laundry.
500 square feet, attached ADU
Shares one wall with your existing home. Includes construction, plans, engineering, typical utilities, standard finishes, and main house demo work.
Two car garage conversion
Uses your existing garage footprint. Includes construction, plans, engineering, and typical utilities.
Junior ADU, up to 500 sq ft
Created inside your existing walls. Includes construction, plans, engineering, and typical utilities.
ADU Cost Per Square Foot
Estimated costs. Every property is different, so your final price depends on your lot, design, and finish selections. We give you a firm number after a free site visit.
Cost per square foot drops as the unit grows. That surprises people, but the reason is simple. A kitchen, a bathroom, a service connection, a permit, and a roof cost about the same whether the unit is 500 or 1,200 square feet. Spread those fixed costs across more area and the per foot number falls.
The practical consequence: if you are deciding between a 499 and a 749, the extra 250 square feet costs you roughly $260 per foot at the margin, well below the average. A bigger unit is often better value per dollar than the headline number suggests.
What Is Included in Those Ranges
Two components.
Base construction cost
The building itself. Foundation, framing, roof, exterior finish, windows and doors, insulation, drywall, plumbing rough and fixtures, electrical rough and devices, and HVAC.
Standard finish cost
Cabinetry, countertops, trim, flooring, and standard fixtures. Upgrading to premium finishes moves this line, and we show it separately so you can see exactly what a finish decision costs you.
What Is Not Included
This is where most ADU quotes mislead people. These costs are real, they are specific to your property, and no honest contractor can name them before walking your lot.
Site plan of your lot
City permit fees
School fees
Additional engineering consultants
Soils report
Grading plan
Grading and long utility trenching
Retaining walls
HOA fees
New utility connection fees
Why we separate them. A contractor who folds site costs into one headline number is either padding the number to protect themselves or discovering the costs later and hitting you with change orders. We give you the building cost, then price your site after we walk it. You see both.
What Actually Moves Your Price
Five factors, roughly in order of impact.
Site conditions
A flat pad and a sloped pad are different projects. Slope brings a soils report, engineered foundation work, retaining walls, and a drainage plan. On the hillside neighborhoods around Lake Elsinore and Crowne Hill, this is the largest variable in the budget.
Distance from the main house
Every foot between your existing house and the new unit is a foot of trench for water, sewer, and electrical. A unit 20 feet away and one 150 feet away have very different plumbing and electrical numbers. On rock or decomposed granite that trench costs more per foot.
Septic or sewer
On sewer, you connect. On septic, the county reviews whether your existing system handles a second dwelling. If it does not, a leach field expansion or a new system exceeds any finish decision you will make. This is the biggest single variable on Wildomar and Wine Country properties.
Electrical panel capacity
Older homes on 100 or 125 amp service usually need an upgrade to carry a second dwelling. Known cost, quotable, as long as somebody checks the panel before writing a number.
Finish level
The smallest of the five, and the one homeowners think about most. Standard finishes are included in the ranges above. Premium tile, stone counters, and upgraded fixtures move the finish line, not the base.
The Cheaper Routes to a Second Unit
A detached new build is not the only option, and it is the most expensive one.
Garage conversion
The foundation, walls, and roof already exist, which removes the most expensive part of a build. A conversion inside your existing garage footprint also skips the four foot setback requirement, so it works on lots where a detached unit will not fit.
Junior ADU
Up to 500 square feet carved out of your existing house with its own entrance and a small kitchen. No new foundation, no new roof, and the lightest permit path of any option. Junior ADUs require you to live in the main house or the JADU.
Attached ADU
Shares one wall with your existing home, which shortens utility runs and removes one wall from the build. Costs less than detached, delivers less separation.
Costs After the Build
Three ongoing items homeowners rarely budget for. None are dealbreakers. All are better known upfront.
Property tax on the new construction only
California assesses new construction at its added value. Building an ADU does not reassess your existing home. Under Proposition 13, your original assessment stays where it is, and the county adds an assessment for the ADU itself. So the tax increase reflects the unit you built, not your whole property at current market value. Ask the Riverside County Assessor for a figure specific to your project.
Insurance
Adding a dwelling unit changes your coverage needs, particularly if you rent it. Call your carrier before construction starts rather than after. The increase is usually modest and the gap in coverage during construction is the part worth handling early.
Utilities
Whether the ADU runs on your existing meters or gets its own affects both your build cost and your monthly bills. Separate metering costs more upfront and makes billing a tenant far simpler. We walk through this decision with you during design.
How to Compare Two ADU Quotes
If two bids differ by fifty thousand dollars, the gap is almost never the building.
Ask both contractors these four questions. The answers will explain the difference.
- 1
Does this number include a soils report and grading, or are those extra?
- 2
What is the trench distance you have assumed from my main house to the pad?
- 3
Have you checked my electrical panel capacity, and does the number include an upgrade if needed?
- 4
What permit, school, and utility connection fees are excluded?
A contractor who cannot answer those has not walked your property carefully enough to quote it.
What the Rules Allow
Up to 1,200 square feet detached, 500 square feet for a junior ADU.
Four feet from the side and rear property lines for a detached unit.
16 feet standard, up to 18 or 20 feet in some cases.
None required within half a mile of transit, and no replacement parking for a garage conversion.
Not required for standard ADUs permitted after January 1, 2020.
A decision on a complete application within 60 days.
Temecula administers ADUs under Municipal Code Chapter 17.23 through the Building and Safety Division.
What Happens After You Call
An initial phone consultation, then a site visit. We walk your property, note hillsides, slopes, and setbacks, locate your utilities, and look at access and how the unit ties into your outdoor space.
We then go through the cost of each size with you, check whether one of our free floor plans fits your needs, and identify what engineering your site requires and which finishes you want.
With that, we give you a complete estimate. Not a range. A number for your property.
Licensing and Credentials
California general contractor license
B-842038, active and in good standing.
Experience
Spencer has worked in construction since 1990 and has built in the Temecula Valley since 2004. More than 350 completed projects.
Bonded and insured
General liability and workers compensation certificates provided before work starts.
Licensed subcontractors only
Every subcontractor on your job is licensed and insured.
Verify any California contractor license, including ours, through the Contractors State License Board. Check it before you hire anyone.
What Temecula Valley homeowners say
More than 350 completed projects in Southern California and the Temecula Valley, and a five star rating across Google, Yelp and Houzz.
“Everything about our experience with Woollard Construction was amazing!! Spencer was fantastic!! He was punctual, professional and great at communicating where we were in every step of the process. Our ADU is beautiful and we are so happy with how everything turned out.”
“The bid was competitive and very reasonable. Spencer was responsive and accommodating; always ready to answer any questions that came up or think outside the box to keep us on budget. His subcontractors were professional and efficiently organized. The whole process was extremely quick once the permits were in place... just under four months from start to finish.”
Roughly $225,000 for a 499 square foot one bedroom, $290,000 for a 749 square foot two bedroom, $230,000 for a 500 square foot attached ADU, $165,000 for a two car garage conversion, and $105,000 for a junior ADU. Those totals cover construction, plans, engineering, typical utilities, and standard finishes. Site costs and fees are extra.
In the Temecula Valley, roughly $390 to $450 per square foot for detached construction, plans, engineering, typical utilities, and standard finishes. Smaller units cost more per foot because fixed costs spread across less area.
A garage conversion, because the foundation, walls, and roof already exist. A junior ADU inside your existing home is also considerably cheaper than a detached new build.
Site costs. Grading, soils reports, retaining walls, trench distance, septic upgrades, and panel upgrades are property specific and often excluded from a headline number. Ask every contractor exactly what their number excludes.
An ADU adds both rental income and square footage under roof. What it adds to appraised value depends on your neighborhood and the unit quality. Ask a local appraiser for a figure specific to your address rather than trusting a national percentage.
Homeowners here commonly use a HELOC, a cash out refinance, or a renovation loan. We are contractors and not financial advisors, so talk to a lender about which fits your situation.
Plan on roughly 6 to 12 months end to end. Design and engineering take a few weeks, city plan check and permitting several more, and construction itself typically runs four to six months depending on size, site work, and utility connections.
City permit fees, school fees on units over 500 square feet, and utility connection fees are separate from the construction totals above and usually add several thousand dollars. The exact figures depend on your lot, your unit size, and which utilities you connect to, so we price them once we have your site plan.
Yes. Standard ADUs permitted after January 1, 2020 do not require owner occupancy, and long term rental is allowed. Short term rental rules are separate and stricter, so check current city rules before you count on nightly rental income. A junior ADU does require you to live in either the main house or the JADU.
Get a real number for your property.
We walk your lot, check your utilities and site conditions, and give you a complete estimate rather than a range. Call (951) 551-6165 or request a free site visit.