Casing a Half-Round Archway

Trimming an opening with no jamb is a pesky problem. October 3, 2009

I just drywalled four different size archways. The customer would like to have some hardwood put up on the facing of the archways (not underneath). Anyone have any suggestions? How can I do this myself?

Forum Responses
(WOODnetWORK Forum)
From contributor K:
It makes no sense to apply a casing to an opening and not have a jamb installed in the opening. Aside from that, it's an involved process to make a simple flat casing for a curved opening not to mention a casing with a face profile. The best thing to do is sub it out to a company that specializes in this kind of product.

From the original questioner:
Thanks for the information, I think I will sub it out.

From contributor B:
The primary problem of trying to apply trim to a plaster or drywall opening is that the curve of the opening is not going to be a "perfect" curve. It will typically weave in and out to an extent that is not very visible to the eye, but will become very visible when you are trying to maintain a 1/4" reveal between the casing and the opening edge.

There are only two options, use a true radius (for a half round for example) casing and let the reveal vary (I've seen templates that easily move up to 1/2"), or make the casing match the edge of the opening, which will usually make for a not very pleasing to view moulding. Best is to make both the jambs and matching casing. This will shrink the opening somewhat unless the drywall jambs faces are removed.