I've been browsing PVC window molding for trimming the outside of exterior windows in home centers and online. I also have a few books. But I'm not finding information on how the various pieces/profiles of trim go together to make a window casing, and what the whole assembly looks like when you're done. The windows are aluminum and some site-built wood non-opening windows that just need trim around them. I'm looking for something simple.

. . . from past experience with this kind of siding I would like to be sure the top edge and bottom sill slope outward and have a drip channel.

I'm finding an array of profiles (AZEK Moulding Styles & Sizes - Profiles for AZEK Moulding) and I am thinking I need a "drip cap" at the top (Drip Cap
AZM-197 11/16" x 1 5/8" x 16') and a sloped sill at the bottom (http://Sub Sill Nose AZM-6933 1 17/3...x 1 3/8” x 16’) with simple 1x verticals at the sides. Will this work or am I misunderstanding how these pieces work together? They both have odd design features (like the extension at the back of the sub sill nose) that don't seem meant to install on a flat surface. The drip cap has that bump at the top, not clear why or how it would integrate into flashing . . .

 

Depends on what kind of windows you are trimming. You'd probably rip the lip off the top of the drip cap since that's supposed to go behind clapboard style siding. And on the sill nose you might want #6930 instead. But its hard to say without seeing the specific window being trimmed and knowing whether the top edge of the sill nose needs to be flat for the first 1" or angled the whole way.

 

Thanks. Do you know what the "Sub Sill Nose" is a "nose" for? The name implies it attaches to something else.

I don't think I need 1" flat on the sill but I have no clue really. What would the factors be in deciding if the top edge of the sill needs to be flat for the first 1" or not? I'd like as much drainage as possible and as little water sitting on the sill and/or dripping on the siding under the window as possible, which is why I want protruding trim top and bottom.

BTW, I contacted Aztek and they got nothing, just that part of the fun of working with molding is putting it together creatively . . . unfortunately you have to do this from the 12' lengths at the home center . . .

 

Metal window (or other) with a nailing fin and 1 to 1 1/8" projection... use the 6930. The one you linked to is good when replacing the front subsill nose of a wood sill that has a dado and a step that accepts the 1/4" tongue of the 6933. Those type of wooden sills are kind of 2 piece and the front subsill nose usually rots off first, so it must be a popular item to replace with Azek.

 

Yeah, I'm looking at that 6930 and it's starting to make some sense. But then there's that projection at the back . . . purpose? It seems fairly substantial so I can see nailing it to the siding (T1-11 as always) over the window gap with finish nails, but on the drip cap (197) I'm not seeing an obvious way to fasten it very securely it's so thin. Could I use the sill at the top also? . . . But it seems like that would look weird. Are you seeing another option for the top piece in that collection? I'm thinking 1x lumber or PVC for the sides.

 

The 6930 has a notch on the bottom back corner so that the siding can fit behind it. But at 2" wide, it might be a little big, judging by the other dimensions you listed. You could use the 6933 and just cut off the tongue in back since you don't need it.

Actually, you could probably make your own sill nose if you have a table saw, (cut a parallelogram the width you want) just use the 5/4 material so that it's 1" thick. Making your own just creates a little more work and some belt sanding. Azek ATM is a full 1 1/4" and it's nice to use for sill noses, but it would be a little more spendy.

If you use the 197 drip cap, you'll also cut off the notch on the top of it, since it sounds like you are applying this on top of your siding just for looks. It would nail down into the top piece of trim, not back into the siding. Again, you could make your own drip cap by cutting an angle off a 1x2 or similar, but you'd have a lot of sanding to do to remove the cut marks from the table saw.

I wouldn't mix PVC with wood trim.

 

I ended up ripping angled top and bottom trim from PT 2x4 material, 1.5" deep, angled downward at top and bottom (i.e., a parallelogram as suggested), and routing a drip edge 3/16" in from the outer bottom edge. Top and bottom (sill) pieces will be the same. I think this will work, altho I'm still pretty aggravated with the molding industry. I'll use 1x on the sides cut at angles to fit the top and bottom.

 

 

You wouldn't usually want to set (for example) a pvc brickmould on top of a wood sill nose because they expand and contract at different rates. The joint where the two dissimilar materials meet would gap open. You can caulk it, but it will be prone to fail. PVC epoxy (like Devcon Trimbonder) is the best thing to use when gluing pvc to pvc joints together so that they don't pop open.

 

Thanks for the tip about Devcon Trimbonder, never heard of it before. According to their literature it can bond PVC to wood.