ceiling panel joints?

Mine had plastic H trim between the panels. Similar to this:

https://www.njsupply.com/mobile/18X8-White-Divider_p_69476.html

They are called Battens. Your local camper supply can get them, or you can find um on the interweb ( do a search for battens for rv panels), but shipping is $$$. Pretty easy to make them too. Rip down some 1/8" Luan and cover to match.

MWJones wrote:
Lowes, Home Depot, etc. Just white molding, wood or foam.

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Any RV dealer or independent repair/parts shop should have them. I bought a couple previously from a dealer and still have one. They're just some lightweight luan with a wrap on them. You'll probably want the color and texture to match the existing ceiling. I'll give you our leftover one if you drop by... ;)

I recently went to Lowes looking for the same stuff - it's not just a flat piece of trim or tape - it is a T molding. They are also used in soffits to cover the seam where two boards join together. Lowes doesn't stock it.

Are you talking about tape type material or strips made from plastic or wood ?

If it's the tape type you'll need to go to a wallpaper supply to find a replacement. You use heat (iron) & pressure to make the tape stick.

Plastic or wood look in the molding section of a home center.

Lowes, Home Depot, etc. Just white molding, wood or foam.

Big box stores have similar pre finished material in their lumber yards.