Our sewing studio is in our lower level (daylight basement). We were flooded in 2007 during a 100 year flood, replaced footing drains, reinstalled laminate flooring (Pergo) and again had serious water intrusion in 2012 from neighbor's water main break. Instead of laminate we went with vinyl planking. Easy to install (use the click kind for basements, garages), comes in many colors, if you do have water intrusion it can be removed, dried off and reinstalled since it is 100% waterproof. I concur that footing drains are needed and a permit will be necessary for electrical. Be sure and check with you insurance agent regarding coverage since the garage will have changed purposes and you want to make sure your machine(s) are insured against theft, fire etc.

This is my humble opinion with your new SR, and might I add, congrats!

First off, good insulation is a must! And, when you paint, I recommend selecting a really light color or neutral paint.

Like some of the others recommended, I would do away with an overhead door and install a regular door, and possibly some windows. If you already have an entryway door, you may not want another one, though, just windows to allow a lot of natural light, plus being able to look out!

I would think about installing a ductless mini split system for heat and air. Go with the largest one possible. It is extremely efficient and works great. My BFF in TX got one for her SR upstairs in the attic (not much insulation), but she undersized it when she figured what she 'thought' she needed. It works great, but does not cool as well at the very end of the long room because of lack of insulation. There are a lot of different brands available, so I recommend reading up on them for comparison. And - many of them may have rebates through your electric company as well as federal and state. That is certainly worth looking into.

As for flooring, especially if you are worried that water may seep in, I would not go with any type of wood flooring. I would go with ceramic or porcelain tile. I love the new plank type ceramic/porcelain tile. You can get it in a wood look if you prefer, and you actually cannot tell that it isn't wood until you run your hand across it. Tile is cooler in the summer to your feet as well. And, it is not that hard to lay tile yourself. I've done it many times.

As for electrical, if you can have a dedicated panel, that would be great! My take is to have those baseboard electrical strips installed, as many as you can around the room as well as other outlets. I hate having to run electrical outlet strips that have those annoying cords everywhere.

And lighting, you cannot get too much lighting IMHO. I recommend LED bulbs or fixtures. My GF has a track system in her SR that is like a box (all around the room) and an X in the center as well. She can move her bulbs around, or add more to it. It is sure worth looking into....

Good luck!

https://www.goductless.com/Mitsubish..._yYBoC2_zw_wcB

I have two of these particular units; one is I my sewing room; the other in 15 x 30 addition I had added a few years ago. I really do like them. Great choice; and when my house unit died me I had two large units installed in the house. SUPER quiet. I never hear them kick on and off.

I don't know if you have thought about this or not, but, how about just taking out the garage door and making it into a regular sewing building (aka sewing shed). You would have to rebuild the wall, but, might be easier to insulate and sheet rock, than trying to figure out what to do with the door. That or just insulate and sheet rock over the garage door, in case you or someone else would ever want to make it back into a garage again.
Whatever you decide to do, Good luck and let us know how it all turns out.

How about putting some French Doors in the garage door opening. You could add some extra panels to the sides and that could give you lots of natural light. I also agree with a heat/ac ductless unit!!! First things first, get working on that drainage asap. Don't put any money into it until you have the drainage perfect. Just my 2cents. Love all the ideas here, good luck on you new adventure!!!

You can just cut a hole for an a/c unit.

Maybe replace the garage door with one with windows? I know down in the south there's roller screen doors too. That would be amazing to me during good weather. Almost like a screen porch.

I have a mini split a/c unit if my den. We have a large house and the den is a SW exposure at the far end of the a/c duct so cooling it in 100 degree summer was always a problem. The mini split works great. I'm not sure if they make one with heating, but my husband has a gas wall heater in the garage. It keeps one bay of the uninsulated garage warm in the winter. As far as the water goes, that can be a real problem. We've fought (or at least the DH has) water seeping into the garage for 15 years now. He finally lowered the back yard and made tiers so hopefully we won't have any more problems. I'd definitely go with the flooring that can be take out and dried and re-installed. It sounds like you might have a chronic problem. Also make sure your power strips are mounted high on the wall so they don't get wet. Wall mounting them makes it easier to plug and unplug your machines anyway.

For the water problem, does the garage have rain gutters? We lived in a house where water leaked into the basement. It had no rain gutters. DH installed rain gutters with a long pipe directing water away from the house. Problem solved.

My question before you do anything with that outside room is - could you remove a wall between two rooms inside the house and have it be large enough?

I had a detached space (20x20 , finished and had a window unit for cooling) and it sounds like a dream but you're out there by yourself, and it's hot or it's cold. I sewed much less than I do inside the house.

Fixing the drainage will help with the water problem, but keep in mind that high humidity levels can be just as much a problem as standing water. Make sure that who ever is helping you transform the space understands that a sewing studio with fabric and thread storage needs to be more consistently conditioned than a garage woodworking shop where the HVAC system may only be run when there is someone actively using the space.

Rob