If you are thinking of building a free standing shop don't let the HOA stop you. I built a free standing shop (21'X21') even though it was against HOA rules.
Here's what I did. Before I built it I met with the HOA president and presented him with an approved permit from the city, I asked him very politely for the HOA deviation form. He gave it to me and I filled it out and asked him to put it to vote at the next HOA meeting. I talked to a handful of my neighbors and told them what I was planning on building. I told them it wouldn't look like some crappy shed, but instead would look really good, be landscaped properly, and compliment the house. I got about a half dozen neighbors on my side. (it didn't hurt that I had build a number of projects for each of them, as well as lent them tools.) Anyway at the next HOA meeting I brought 5 other neighbors with me and my plan was voted acceptable. Most HOA meetings have fewer than 3 home owners attending so because I brought 5 with me it was easy to get it approved.
Then what you do is keep a copy of the approved deviation form for yourself (just in case) and ask the HOA president to put a copy in the file for your house. Ta-da! New workshop behind the house.
I later found out I could have more easily short-circuited the process by becoming the HOA president. Nobody ever runs for those positions so if you are willing to take on the role you can do what ever you like for a year and then find some other homeowner to take over.
But seriously just buddy up with the HOA president and get a deviation added to your file. Most HOA presidents are just some lonely joker who wants nothing more than somebody to be his/her friend. Of course there's always the risk that your HOA president is some A-hole rule stickler Nazi. But if that turns out to be the case get yourself voted in at the next annual meeting. Seriously you bring a half dozen home owners with you, you'll get voted in for sure.