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Forge & Stone · San Diego
Most people come to us with the same two questions: what will it cost, and will the city let me. Here are our real numbers and our real process — before you give anyone your phone number.
Mid-range detached ADU, turnkey
$270 – $350 / sq ft
Design, permits, construction and finishes included.
$162,000 – $210,000
$200 – $265 per sq ft
That range is ours, not a national average. It does not include city impact fees, which vary by jurisdiction and which we itemize separately so you can see exactly what is ours and what is the city’s.
Run your own numbersSix routes, and the one you can use is usually decided by your lot, not your taste.
From ~$200 / sq ft
The fastest and cheapest path. Existing slab, walls and roof stay. Best when you can live without the garage and the structure is sound.
Up to 500 sq ft
Carved out of the existing house, usually a converted bedroom with its own entrance and kitchenette. Lowest cost of entry, tightest size limit.
~$255 – $330 / sq ft
Shares a wall with the house. Cheaper than detached on foundation and roof, but ties into your existing structure and systems.
$270 – $350 / sq ft
The standard new-build ADU. Full independence, full flexibility, and the cleanest separation if you intend to rent it.
~$295 – $385 / sq ft
For sloped or uneven lots where a flat slab is not practical.
~$230 – $300 / sq ft
Built off-site and set on a foundation we pour. Faster to install, less flexible on layout, and the site work still has to happen.
Four things move the price more than finishes do.
How far the new unit sits from your existing sewer, water and panel. A long trench and a service upgrade can add tens of thousands.
If a truck cannot reach the build area, material moves by hand, and labor hours climb.
A flat lot takes a slab. A sloped one takes engineering.
Existing structure is the single largest saving available to you.
Finishes matter, but they are the part you control at the end. The site is the part you inherit.
Five stages, in order. You will know which one you are in at all times.
We look at your lot, your setbacks and your utilities and tell you what is buildable — including when the answer is “not worth it.”
Drawings that will actually pass plan check, not renderings that look good and get rejected.
We submit and we handle the corrections. San Diego review timelines move; we tell you what we are seeing right now rather than quoting a brochure number.
One crew, one schedule, one point of contact. You get the schedule up front and you hear from us when it changes.
Inspections closed out, and the paperwork you need if you intend to rent it.
Design and permitting is typically the longer half. Construction on a straightforward detached ADU is usually four to seven months once permits are in hand. We give you a real schedule at contract, not before.
Usually yes, and rental income is often the bigger part of the return. We are not the right people to tell you what your house will appraise at — talk to an appraiser. We can tell you what the build costs.
Sometimes. A garage conversion, a simpler roof, a smaller footprint, and finishes chosen for durability over appearance all move the number. We would rather value-engineer with you at the start than surprise you at framing.
We walk your lot before we quote a number. If it is not worth building, we will tell you that too.
Call (619) 949-5296