This winter I’ve been having a ball (and saving TONS of money) refashioning adult-sized sweaters into dresses for my daughter. (See the tutorials at Smashed Peas and Carrots, Get Your Craft On, or Make It and Love It.) Now that we’ve created enough sweater dresses, I’m moving on to t-shirt dresses.
One limiting factor has been the size of the neck hole. Because I’m just taking in the shirt (or sweater) at the sides and the armholes, the neck retains the original adult size. If the neck hole is too big, it looks kind of silly on my little girl. Well, not so little. “Mama, I’m only 6 but I feel like a teenager.” Yikes. But I digress…
Anyway, yesterday the shirt that would be absolutely perfect as a dress for her had a neck that was too big. My first thought was to pass on the project, but then I realized that a quick snip and a short seam on each shoulder would solve the problem. Here’s how I did it:
1. First, I cut the sleeves off of the shirt (or sweater). 
2. Then, I cut along each shoulder seam from the armhole to the neck. The serged seam allowance was bulky and in the way, so I cut that off as well. (It’s shown still attached in this photo, but I snipped it off right afterwards.) 
3. I pinned the shirt front to the back at the shoulders, right sides together. Most necks are shaped so that the bulk of the hole is oriented toward the front. This is where I needed to take in the neck, so I offset it so that the top of the back shoulder pieces (shown as the top layer in the photo) were about 1/2 inch below the fronts. 
When you pin the shoulders together, make sure that the neck edges align at the place where your seam will be sewn. In the picture below, I show where my stitching line would be. See how the neck binding on the front and back pieces meets at that imaginary line? That will create a smooth line between the two pieces.
4. This is the shoulder sewn back together. The edges meet up nicely.
I have been trying to figure out how to do this for years ! thank you! I’m guessing you could add the sleeve back on by sewing a new seam lenghwise on the sleeve so where it attaches to the armhole will fit?
Whenever I refashion as shirt, I end up cutting off the sleeves. I cut new armholes that fit me (or my daughter) better, and then recut the sleeves to match. When I take in the neckline, I do it after I’ve cut off the sleeves, but before I cut the new armhole. Then it’s just business as usual setting in the sleeve.
I wanted to decrease the depth of the ‘scoop’ on my tee shirt. I was thinking of making a loose running stitch and pulling the thread slightly, to make the neckline the way I’d like. I’ll give my idea a try before trying the cut and re-sew technique (which is a lot more work). I have several tee shirts that I want to fix necklines. [In case you’re wondering why I don’t want a deep neckline, I had open heart surgery and the scar shows unless the neckline is high enough. I am self conscious about it.]
This sounds like a very good idea. I just wish the instructions were more clear. It seems a bit confusing. Is there any way you could add better details?