AITA for snapping at my brother?

I (F33) have been working for weeks on a big home improvement... thing. It's involved hauling furniture, hanging drywall, a lot of intensive cleaning, etc. Exhausting. The main reason is that my parents needed a bedroom on the ground floor, and they have that now. My little reward, though, was that their old bedroom could be turned into an office for me. I'm a (very *modestly* successful!) writer, and I currently work at the kitchen table, or as I like to call it, the "Please walk up and interrupt me all you want" zone.

I boomeranged back home like a lot of millenials in the early 2010s, but I kinda can't leave at this point. Dad is disabled, mom works horrible hours and is not young herself, and my much younger sibling still in high school needs, well, parenting. I cook, shop, handle medical stuff, etc. My brother (30M) also lives at home, and, well, I'm not sure why? He does things around the house, but they're either outdoor work he likes (he's a very good gardener), or random big projects that come up sporadically, not day to day stuff. Otherwise you pretty much never see him.

WRT this project, it was most of the way done when my brother announced he wanted to move into our parents' old room. It's a little bigger than his. I didn't really care, since I could just use his old room instead, but I did ask that he make sure it was done *quickly.* He tends to just kinda let things go. For months. Our dad's old car, which he got for free after dad couldn't drive anymore, has sat unfixed for a year, for example.

Anyway, lo and behold, he spent a very few hours over the weekend hauling the stuff he needed to be comfortable and has left the rest since.

Now right now he's working full time. I'm a teacher and I'm off for the summer or I wouldn't have been able to hang drywall and such so efficiently. But he interjected himself into a mostly finished project and jammed a monkey wrench in to grind it to a standstill with his kinda random request. This morning I offered to carry the rest of his stuff to his new room during the day so he could sort through it at his leisure. He told me (kinda testily) that he had it. Here's where I did snap a bit to point out that no, he didn't have it, nothing had moved since Sunday and he blew off most of the weekend. The rest of the conversation demonstrated that he never listened to a word I said about the project, didn't see why he should hurry, but because I was being so unreasonable he'd finish what he'd said he would do. (That will supposedly happen tonight. My hopes are... not high.)

Why I think IMBTA: I worked long and hard on a home improvement project and I was supposed to get my own little workspace out at the end. I snapped at my brother for what felt to me like blowing off his small part of the job, which he turned up to late without Starbucks so to speak, but my time at the moment is more flexible than his.