This is going to be a little complicated, and if you decide to take this on, you'll need to follow BOTH the instructions that come with your pattern, AND the ones I give you. I've tried to break my instructions down so that you'll know ROUGHLY when to insert my instructions into the pattern instructions, but you'll need to use a lot of your best judgment about how and when switch back and forth between them. It's also a great project, and the end result is so much more fun (and warmer) than a regular sweatshirt.
My stepson has several very warm sweatshirts that are lined with berber fleece. They are wonderfully warm and comfortable. But they are very expensive ($70 ), and usually not very interesting (lined with very plain linings). So for Christmas, I decided to make a lined sweatshirt hoodie for my father-in-law, who is always cold.
Except I couldn't find a single pattern for a lined hoodie.
I took a look at one of the stepkiddo's sweatshirts, and I noticed that the lining is constructed separately from the sweatshirt shell, and only connected in a few places:
1. At the edges: Along the front edge of the hood, along both sides of the front opening at the zipper, and along the bottom hem. And finally, at the edge of the wrists in some manner.
2. It was also attached internally in 3 places: At the collar where the hood joins the jacket, and under each armpit.
So, that's enough to get started. Ready, set GO!!
Buy DOUBLE the fabric that you would normally need. Buy the right amount of sweatshirt fleece, AND buy enough to replicate it entirely from the lining fleece.
PATTERN & SIZING:
I used KS 3028, and found out from the message board and reviews that it's a generously-sized pattern (note: If you use that pattern, the fabric requirements on the envelope are for BOTH the sweatshirt and pants). I knew that since it was going to be 2-layers thick (polar-fleece AND sweatshirting) that it needed to be sized generously.
You'll need to know if your own pattern is generously sized already or not, in order to pick the right size. You might need to size up slightly, to accommodate the thicker/bulkier fabric. If the pattern is big already (as the KS pattern is) you might not need to size up at all. Use your best judgment. I measured a couple of my sweatshirts to get a feel for the difference between my waist and hip size and the circumference of the garment, and I measured the pattern to confirm the printed finished circumference.
Personally, I did go up a size, despite the generous ease of the pattern, because of some specifics of my father-in-law's measurements. His shoulders were at the top end of the medium, but his belly was between a large and an XL. So I made a large (despite his medium shoulders).
You should be able to do this with any sweatshirt pattern, as I believe the concepts should work with any zippered sweatshirt, hooded or unhooded.
Next, I had to decide on an approach. I knew of two:
1. Construct the sweatshirt shell and lining separately, and then sew them together at the hems, zipper and hood. That had the advantage of hiding most seams, and giving it a nice finished look. However, it was going to take longer to make.
2. Sew the lining and shell as one. In other words, put the lining fabric against the shell fabric, so that the lining shows on the wrong side and the shell on the right side. This would go faster, but seams would show (just as they would in a regular sweatshirt). It would be easier in some ways and harder than others (MUST ensure that all layers are caught in the stitching - I'd serge the pieces together first to ensure this).
I decided on approach #1, which is what I'm going to outline here.
CUTTING OUT THE PATTERN:
You'll need to cut the pattern out two full times - once for the lining and once for the shell. (If you are using ribbing for the cuffs and waist, you only need the usual amount of ribbing fabric).
PLANNING TO REDUCE BULK IN HEMS BEFORE SEWING:
I know it's a bit strange talking about hems before you even start sewing, but it's an important consideration, and you need to prepare for it prior to sewing.
A double-layered seam can get pretty bulky, especially in spots where you are folding fabric up, like in hems and such, AND it's even worse if you are going to be folding the fabrics more than once. I decided NOT to do that, to fold up only once, and cover the edge with decorative stitching. This should be fine, as knits won't ravel.
To reduce bulk at the hems, I cut the excess fabric from the lining. The hem allowance according to my pattern was 1", so I cut 1" off the following areas OF THE LINING ONLY: bottom hem, and front edge of hood. You could do it at the cuffs, too, if you are hemming and not attaching separate ribbed cuffs. I chose not to trim back the lining at the cuff hem - and just left those double-layered, to add some extra body and sturdiness there. I don't know yet if it's a mistake. ;-)
If your pattern calls for a different hem allowance, than cut off whatever that amount is, instead.
Note: if you are using ribbing at the cuffs and/or waistband, you should NOT trim back the lining in those areas, and both fabrics should be caught in the seam that attaches the ribbing.
EXTERNAL DETAILS BEFORE MAIN GARMENT CONSTRUCTION:
Depending on the pattern, you may need to install grommets or buttonholes or some other sort of opening for drawstrings. That needs to be done on the shell fabric only.
If you are installing patch pockets, you'll need to decide if you want to line the pocket. If not, follow the directions on your pattern, and attach them just to the shell fabric.
If you ARE lining the pocket, you'll need to decide whether or not to modify the pattern (to reduce bulk, and how to attach it). I eliminated the pocket facing on the lining, so that only the shell flipped down. Normally to attach this kind of pocket, you sew the top edge of pocket while it's flipped upside down, flip it back down, and then top sew everything else. Rather than turning everything under under to attach it, I merely trimmed .25" (the seam allowance) off the top edge of the pocket lining, serged all the other edges together, and after I sewed on the top edge normally, I merely stitched the rest of the pockets seams down without turning anything under. The serging threads show, but that was a deliberate design feature I wanted. It also lies flatter.
Every pattern is going to be different, so the choices I made on my sweatshirt might not be appropriate for yours. You'll need to evaluate your own pattern, think in terms of bulk and design features, and go from there.
CONSTRUCTING THE MAIN GARMENT
Unless your shirt is quite different than mine, once the pockets are attached to the front of the shell, you'll sew the fronts to the back at the shoulder seams. Next, attach the sleeves to the shoulders, and then sew the underarm and side seams in one continuous seam from wrist to waist (or vice versa). Repeat for the other arm. Be careful at the armpit - it's hard to get the seam intersections to line up.
Repeat for the lining.
Any decorative topstitching (like coverstitching, or something similar) to the shoulders, sleeves, or side seams needs to be done BEFORE you put the lining into the sweatshirt. Ditto for any decorative stitching that you choose to do for the lining. You need to do the topstitching independently of the lining because you'll never get the layers of fabric to line up properly. (If you do the other approach and construct the garment with the two layers sewn as one, then it would only need to be done once, and through all layers).
Once you have the two main parts constructed, put the lining inside out inside the right-side-out shell (in other words, wrong sides together).
Install the zipper according to pattern instructions. Pretend the lining and shell are a single fabric. BE VERY, VERY CAREFUL to get the two fabrics perfectly lined up. BOTH fabrics need to be caught when you stitch the zipper into place. It's a pain in the butt to have to fix it if one or the other fabric didn't get caught in the stitching. (Ask me how I know this).
Sew the left and right hood pieces together for both the shell and the lining (constructing them separately). Insert the lining inside out, inside the right-side out shell (wrong sides together). Sew them as one fabric to the shoulders, following the pattern instructions. Remember that the front edge of the shell will stick out 1" farther than the lining.
I covered my neck seam with twill tape to give it a nice finished look. It also helps reduce bulk in that area. To do this, line up the raw edge of the tape with the bodice fabric. The order of the fabrics are like this: Twill tape, bodice, hood. Once sewn, flip the twill tape over the seam, turn under and edge stitch.
Turn hood shell to the inside by 1", and the same for the bottom hem. Hem the bottom, topstitch the zipper and hem the hood. Insert drawstrings, and do any other finishing details. I did a lot of zig-zag satin-stitch top-stitching to reduce bulk, and to cover up (ahem) a few mistakes I made.
I also didn't bother tacking the lining and shell at the armpit the way my stepson's hoodie was done - It didn't seem to need it.
Anyway, it turned out really well. If anyone follows these instructions, and makes their own, I'd love it for you to post photo URLs in the comments below. :-)