If you want plaster, they are run in place. In that case what you need are knives, not molds, to make the patterns. The knives will be the easy part. Finding the man to run them will be your challange.

And do not even think about the faux plaster foam moldings. You can never get the seams right, and doubtful you could find the correct scale anyway for 22' ceilings.

Wood would be your other option.

Thank you.

"If you want plaster, they are run in place. "

There are also cast plaster that are available.

All you have to do is finish the joints after you fasten the sections up.

Not for the scale we are talking about. Very impractical.

You would be surprised at the scale and detail available in cast plaster molding.

Run in place molding is limited in styles and detailing.

Cast can have extensive detail.

It is all about how much you want to spend.

Thank you very much for the input. I will check into the suggestions.

There are no "limits" to run in place. Any knife can be cut for any shape than anyone can imagine, and then run. For this ceiling, multiple knives will be required.

22" foot ceilings require a very substantial cornice to look appropriate. Doubtful such cornices could be lifted, let alone shipped!

Which, by the way, is likely why they were not installed originally.

There are "rules" or guidelines for cornice proportions relative to ceiling height. Look them up.

It won't look any good to go small. Might as well leave it as is in that case. A 22' ceiling is a grand thing, and deserving of a no less a grand cornice.

"There are no "limits" to run in place. "

Try and do dentil, or other detailing.

There are of course limits on the shape since it must be formed by a straight pass of the knife.

Really big wood crowns are made in two or three pieces (and I mean just for the cyma and cavetto) So a crown wider than the capacity of a single molding machine is achievable.
Casey

Try and 'run' these.

Here is a link that might be useful: Deco Craft Plaster Cornice