I want to make simple floor molding and window trim for a rustic cabin. Will use knotty pine in 1×6 and 1×4 dinensions. The cabin is in the Black Hills of South Dakota, so I would describe the humidity as moderate (certainly more than Tucson, but less than the Gulf Coast!). Will use a nail gun for installation.
Question: Do I need to do any routing on the backs of either the 1×6 or 1×4 pieces to prevent cupping, or for any other reason? If routing needed, what type?
Thanks!
Tucson
Replies
Tucson,
The back of wider molding is relieved slightly not to prevent warping but to make sure that the two outer edges will contact the wall and form a tight fit that will look good. By relieving the back, the molding can bridge over any rough spots on the wall or deal with a bit of cupping and still sit properly.
The relieved area should cover most of the back with just a strip around 3/8" to 1/2" wide being left proud along the two edges. The nailing should go through this area. For the wood you are working with, I would make the relief a full 1/8" deep.
If you have a table saw with a dado set or a molding head that would be the best tool to relieve the back, but the job can be done with a router. With either a saw or a router you will have to take multiple overlapping passes.
Choose the straightest and most knot free, or at least small knotted, boards for the molding stock. Humidity level isn't important by itself, it's the changes in humidity that lead to warpage. If the humidity stays fairly constant throughout the year wood movement will be minor. If some of the year is very dry and other times are damp then the moldings will shrink and expand and possibly cup. The wood should be fully dried out before you start to work with it.
John White
Edited 7/18/2007 10:38 pm ET by JohnWW
Thanks, John. Very helpful.
Best,
Tucson
You're welcome.
John W.
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