Investor · Sacramento, CA · Member since 2020 · 64 posts · 17 votes
Would anyone be able to give a quick breakdown of the various costs associated with planning and building an ADU in either your backyard, or as a garage-conversion in California? I'm talking about modest-sized JADUs or ADUs in the 400-600 sq. ft. range.
I've been considering building or converting a garage into these units, for a long-term, buy & hold real estate strategy. But I just wasn't sure where to start, or how to properly save/consider the various costs associated with them.
Contractor · San Diego, CA · Member since 2016 · 88 posts · 100 votes
6y
As a good rule of thumb, figure on $275-325/sqft for all-in ADU project costs…so an 500 sqft 1BR standalone ADU would typically cost around $160K. You can think of costs in two phases… Pre-construction and Construction:
Pre-construction costs: $10-15K
-Design: if using a stock plan, the design work costs about $5K. If going with a full custom plan (e.g. you have a unique lot layout that will require a customized layout)… closer to $10K, including construction drawings, title 24 energy report & electrical layout, permit processing
-Permits: $5K is typically what the total costs to the city will run for an ADU, even with the waived fees
Construction costs: $250/sqft + $10K
-Building costs: typically $250/sf to start, for vertical building only. This is higher than for single family homes, since the cost is spread out over a much smaller footprint (e.g. still a kitchen+bath, but only 1-2 BRs).
-Site work: typically $10K is a good number to start with, which includes preparing the building pad, connecting utilities, plus a small amount of landscape and concrete work.
Other costs (not typically required): Additional structural engineering, Civil engineering, Soils engineering
Also, the cost would be around $75K for a standard garage conversion project of about 400 sqft....$8-10K for plans/design/engineering, $3-5K permits/fees, rest construction costs.
Luis thank you man!! I thought I was taking crazy pills! Isn't the whole point of this community to self start and handle business? Your sqft costs are much more reasonable for an owner builder who is willing to do the work, do the research, save money where you can and spend it where you need to
@Whitney Hill I'm 4 years late to this thread, but it's so illuminating! If you're still around these forums, would love to get your thoughts on one small question related to a standard garage conversion project.
You'd mentioned earlier: "Also, the cost would be around $75K for a standard garage conversion project of about 400 sqft....$8-10K for plans/design/engineering, $3-5K permits/fees, rest construction costs."
My question is: If the detached garage already has water and electricity (100A) set up, how much does the cost go down and from which of the three cost categories (plans, fees, construction)?
Contractor · San Diego, CA · Member since 2016 · 88 posts · 100 votes
2y
@Jay Patel what a fun time capsule experience! Four years ago we were just building our first half a dozen or so ADUs, and now we are up to 128 in progress and completed. With all that experience has come a very solid understanding of costs, and I'm sorry to report that it's all gone up. WAY up. This is mainly for two reasons:
1) Labor & material costs: the California Construction Index has gone up 38% since 2021. What cost $250K to build would be around $350K. While we don't do remodel work (e.g. garage conversions), I've heard from contractors who do that the typical range for all-in costs is ~$100-120K. 2) ADUs are not as wild west: in the early years, we saw inconsistent application of requirements for things like upsizing water meters & lines, soils reports, surveys, electrical panels, stormwater management (all depending on property specifics & jurisdiction). So now there are many, many more additional costs that we have to budget for. If you google "ADU costs San Diego," you should notice (after the paid links ;) ) our very detailed blog that breaks down what to expect into even more cost buckets, as well as dozens of additional costs to look out for.
To your specific question about the detached garage with water & electricity... again, remodels are not my specialty because we just do detached new construction. The requirements are also going to be different for conversions. But I would expect that having water & electricity there could save $10K in sitework/utility costs.