Hardwood Loose Tenons in Softwood Furniture?

Can hardwood tenons offer greater strength ó and will there be swelling or shrinkage concerns? November 16, 2011

Question
I'm looking for some technical data to help me determine if mixing two wood species is a good idea for exterior doors.

Forum Responses
(Furniture Making Forum)
From contributor Y:
What is the reason for mixing woods? Why would you not just use the same species for rails, stiles, and tenons?



From the original questioner:
These are large, heavy doors with gothic-arched tops, so the hinges will be all low. Therefore, there will be more than typical stress on the joints and I'm concerned about the shear strength of small, softwood tenons in this application. However, I'm also concerned about the different seasonal movement of two wood species tearing the joint apart prematurely.


From contributor C:
I would be concerned about the oils in the teak. If that is your choice I would wipe it down good with acetone and use epoxy as an adhesive. Why not white oak tenons if youíre looking for a harder wood?


From contributor D:
White oak is notorious for bad adhesion with epoxy. Itís something to do with tylosis in the pores inhibiting a good mechanical grip. Red oak or a more porous wood works better with epoxy. Entire boats built with white oak strip planking have delaminated within a couple of years.

As far as mixing woods goes, I don't consider it a problem in an unexposed joint. Really even exposed is not a big deal. We've built several prairie style doors with exposed square pegged pyramid head tenons of differing species for the color contrast. Literally thousands are out there with no problems. Greene and Greene were famous for mixing species in tenons, pretty much all exposed joinery there.



From contributor U:
Not sure about what species of cedar you are using for the door but I would be more concerned about the strength of the cedar itself failing in the joint than the strength of the bond to a hardwood tenon or swelling of the tenon.