Hi all,

I'm in contract on a house in Concord, CA and would like to convert the 2 car garage to an ADU. I've seen estimates of the cost to do this ranging from $30K up to $150K and beyond. Does anyone have a good way to get a better understanding of what the true cost will be? I've contacted a few contractors and am hoping to get some bids from them, but even so, I'm not sure I'll know what a "reasonable" bid is. Not looking to do anything fancy, just B quality.

The garage already has water hookups but I'm not sure about where the sewer line is yet...

Any suggestions?

@Jonathan Schwerin you may want to hire an architect to come up with a set of plans that you are happy with. Makes bidding and permitting far simpler and gives you a more predictable outcome.

Have a plan drawn up and speak to some contractors. I believe they could give you a rough idea BUT make sure you are aware of new energy regulations that mandate solar panels and that PG and E is ok with the location of the power lines. There is no set in stone cost sheet this will require due diligence on your part.

Thanks, that's quite helpful. My dilemma right now is that I need to know how much it's going to cost before closing because if it's over a certain $ threshold then the deal doesn't work anymore.

To your points above, most contractors I've talked to want plans so they can bid on it. I'm going to try and get in touch with some groups that can do everything in-house from architecture to design to construction. We'll see how this goes... stay tuned.