It will look a heck of a lot better than the two small crown you would have had.

4.5 is usually the minimum you’d want for 9’ ceilings.

assuming you can’t return the current crown and can get additional base then led to this?

what do you mean by small

molding?

These are just opinions at this point but if time and budget allow I would return the current crown get a larger size so that it’s done right

based on the picture I don’t like how that flows from the base to whatever that small molding is I’m assuming that is not the crown

Not sure what is going on unless it’s my phone.

Here is 5 inch crown on a 10 foot ceiling personally I just don’t like heavy trim

I think your trim guy was right. That should look good once caulked and painted.

Actually, your building supply guy was correct, at least with respect to what would be typical for homes with traditional interiors.

Traditional interiors normally feature crown and picture rail for ceiling heights up to 10 ft. with dimensions of each derived from the classical orders. Cornices and heavier treatments are typically reserved for more formal rooms with ceilings at or greater than 11 ft.

Architect Marianne Cusato's book "Get Your House Right" is a good reference for questions about trim and lot's of other stuff, too.

That's a very good book and very useful tool for all those interested in architecture and how to see and think about it.

A 4 1/2" profile on crown would give a drop of 3 1/4" - 3 1/2" which, IMO, would look skimpy with 9' ceilings. What your carpenter did by adding a backer board with a profile is frequently done in our area (and appears to be used frequently elsewhere given the number of photos on Houzz of this treatment). If the size appears to be proportionate when looking at it in person, then the product looks fine once it is caulked and painted. If the total affect still looks small to you, I would stop now, return what you can and go with a larger crown. You can do a search here on Houzz for crown moldings in photos and you can see the finished product.

Here is one that appears to be roughly the size of yours.

Globus Builder · More Info

My basement has 10' ceilings and we used a 6" crown

Hi, Kristie--

Your trim guy made up what would be normally thought of as a two-piece crown. Using base in a corresponding crown profile is a good way to beef up a profile for an appropriate ceiling like (like you've got), and it's also smart because it repeats the top detail from your base molding as the foot of your crown, creating nice symmetry at the top and bottom of your wall profile. It's a time-tested approach that works well in the right application.

Like others have said, this will look 100% better once caulked and painted. Hang in there!

What did you end up going with @Kristie Garner and how does it look?

I'll take a picture. Everything looks wonderful. i enjoyed designing everything and getting ideas from here. we've been in our house a little over a year now.