Garage or basement conversion?

I’m looking to buy a home, and on a limited budget. I’ve seen a number of listings that mention a bonus room, then in person it turns out to be a barely converted garage or basement space. (Often just some paint on the walls, maybe a thin carpet over the concrete floor, but basically not really usable other than for storage.)

I’m wondering if someone can advise on ballpark estimates for converting such a space into a bedroom or office? I know nothing about construction, but it looks like info online suggests about $600 per square foot; is that accurate with current inflation and supply chain issues? This would be for a space that’s attached to the home, not changing the building’s footprint. In Oakland, if that’s important. At a minimum I imagine you’d need to install ducting to connect to the heating system, put in an actual floor, maybe some insulation for the walls, and install or enlarge windows (or maybe a skylight, if it’s a garage with nothing above). No plumbing, I wouldn’t be adding a bathroom or full ADU.

I have some money saved beyond what I need for a down payment, and I’m hoping to figure out if it might be feasible to buy a home with the plan of doing this kind of work. I know costs can vary a lot depending on the specifics of the situation, but any help on figuring out a ballpark amount would be great!

Parent Replies

Parents, want to reply to this question? Sign in to post.

RE: Garage or basement conversion? ()

Yes, costs vary a lot, but remember also your property taxes (which are going to be quite high as a new owner) will increase also. Good luck with your search and project.

RE: Garage or basement conversion? ()

We looked into a garage conversion shortly after buying our home in West Contra Costa in 2013, seeking to make a "bonus room"-slash-office. We found that (at least where we live) the city building code requires a minimum number of covered parking spaces, so we couldn't do anything that would permanently alter the functionality of the garage (add interior walls, remove the big door, etc.) without adding another covered parking space (not an option for us). We did pay contractors to hang drywall and run electrical, which ended up costing us about $15-$20K if memory serves, and my partner uses the room as a workshop and hobby room, but it wouldn't be a space I'd want to hang out in all day. 

I think a lot depends on the building code in the city you're looking in. Might be worth investigating.

RE: Garage or basement conversion? ()

We converted part of our unfinished basement into work space, about 400 square feet, for about $35,000. But it is not connected to the rest of the house; you have to go outside and through the garage to get in. We did it without permits because it is not livable space connected to the house, which reduced the cost. I'm not a contractor but my wild guess is you'd be looking at at least 1.5-2x what we spent if you want it permitted and livable, depending on whether you need to do anything to get full ceiling height, add proper egress/change windows, etc. If you need to add stairs to connect it to the rest of the house, that would be a significant expense and require engineering -- our neighbors were quoted over 100k, but it of course depends on your space. A few things you might want to think about doing:

- Have your realtor find a contractor or engineer who could come look at a house with you either right before you decide to put in an offer, or after you've put in an offer (but only if you have contingencies). Their estimate will be a total ballpark, but they'll at least be able to tell you if it's NOT feasible from the get-go.

- If you have more than 20% down, take out a HELOC after you close and get more cash to put towards your project. If you put 20% down you can take out 9.9%. Or, wait a year or two for your value to go up, then do the HELOC to access that additional equity.

Good luck!