PVC Interior Trim/Extension Jambs

DrMike

After 45ish years of DIY experience, I just discovered this chatroom. Happy to be here.

Don't want to commit heresy but I want to attach PVC jamb extensions to new construction PVC windows (American Craftsman 3000 Series) and then apply PVC interior trim to the extensions. I've done a lot of work with exterior PVC trim but there's no need to attach exterior trim to the window unit - the exterior of the windows already have colonial-style molding fused to the window.

My primary question is - what's the best way to attach the inner edge of the PVC extension jamb to the PVC window? I know the 4 pieces of extension jamb need to be nailed to the wooden studs and/or attached to each other with screws to form an extension "box". But, isn't it necessary to somehow attach the inner edge of the extension jamb to the window?
Should I use PVC cement? Caulk? Nothing at all?
I noticed on these American Craftsman windows there is a groove around the entire inside perimeter of the window unit. Is this groove designed to receive some type of attachment to the PVC extension jamb? If so, it sure would solve the attachment and alignment challenge.

As far as the PVC trim is concerned - do folks use a PVC cement product or caulk to fuse the mitered trim pieces?

Thanks, in advance, for any advice.

Ron6519

I'd just caulk it. I would not fuse the trim to the window.
I would glue the miter joints of the interior molding, though.
Ron

DrMike

Thanks for the recommendation. Is there a particular type of caulk you would recommend? I would want the seam to be as invisible and long-lasting as possible.

Ron6519

If you're going to paint the trim, use an acrylic or latex caulk. If not use a 100% silicone caulk.
Ron

DrMike

Thanks again. Any idea what the groove around the inside perimeter of the vinyl window is for?

Ron6519

It could be an inset for the extension jamb to go into. Andersen windows have this inset for the extension jambs they sell.
A picture would help with the identification.
Ron

DrMike

A picture is attached -The groove/slot is around the very edge of the window and is approximately 1/4" deep:

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Ron6519

Looks to be part of the window design to add a stiffening aspect to the vinyl.
Ron

loneframer

Here's my go to product for PVC trim. I've used medium bodied PVC cement as well.

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It's not that it took him an hour to make 100 bucks, it's that it didn't take you 10 hours to save 100 bucks.

DrMike

Looks like just the right product. Can you purchase it in these small tubes at retailers or do you order it directly from T. Christy Enterprises?

loneframer

It's available at most lumber distributors in this area. Runs about 15 bucks for that tube, which goes further than you'd think. It's also available in caulk tubes for situations that require larger applications. The down side is, the product keeps running after the pressure from the push rod is released.

Christy's is aggressive and any squeeze-out should be wiped away with a rag dampened with Goof Off, or similar product. If left on the surface, it will eat into the finish.

__________________
It's not that it took him an hour to make 100 bucks, it's that it didn't take you 10 hours to save 100 bucks.