Could someone point me to a source that provides diagrams and discussion of spline use - especially with respect to terminating a beam? Thanks.

Splines are discussed in several articles in the Guild Workbook. In particular, Brungraber's "Engineered Tension Joinery". You won't find it in Sobon's "Historic American Timber Joinery", as splines were not used in traditional frames here. They are borrowed from the Japanese tradition. I'll add my own opinion, which is that a splined joint should also be a fully housed joint. CB.

Semi off topic, but I thought Clark might appreciate an FYI

Free tenons are a relativly common scarf typology found in historic framing in this area usually found in plates mid bay, two foot bridles simply butt which recieve a four foot spline

Not at all off topic! I'm no expert on historical joinery -- I was merely repeating what I've read. Happy to learn something new today. Thanks, Will. CB.

i recently bought a ted benson book called "TIMBERFRAME: the art and craft of the post and beam home"
and there are lots of photographs of splines in that book.
BUT there is no discussion or diagrams.
still, i would take a look if you can get ahold of it
-M.

Splines are popular because they overcome the poor tension value in a mortise and tenon joint. The problem of course, being the shearing out of the end of the tenon by the force of the peg when in high tension.

There are many framers that rely heavily on splines to provide both tension and torsion to a joint. A hardwood spline of enough depth will allow you to tie a beam through a post to a beam on the opposite side, it increases the surface area for pegging, and its vertical stiffness will also help resist a beam's potential twisting torque on the joint.

When the spline is used in this way, then posts only need to provide vertical support and hold down capability. As a result the posts dimensions can be diminished due to the simplified joinery.

The reality is that in traditional timber frame joinery there are very few joints that stand up to significant tension. We all know how often we rely on panels and/or steel to hold these trouble spots together. While the use of splines strays from traditional methods, there are occasions where there use will solve a connection where steel may have been the only alternative.

Spline use is a popular solution to the unique loading demands in seismic areas and is popular with nortwestern timber framing companies. But they are popluar all over due to their strength, ease of implementation, and ability to use smaller posts due to joinery design issues. At S.P. Brooks & Co. we rely almost 100% on the use of splines. We pre-insert and glue our splines to our posts, simplifying erection, although complicating the loading of the truck! When tested we have found the glued spline becomes stronger than the wood (similar to steel and welds) and failure occurs in the pine first, but not until the joint has resisted some suprisingly high forces. As it turns out, the softwood shrinking around the dry hardwood spline, saturated in glue not only provides a tremendously strong tenon, but adds significant resistance to racking, working much like a small brace.

In summary, properly designed and implemented spline joinery is an economical alternative to more labor intensive traditional joinery requiring larger diameter posts. They are superior in strength to most tradtional joints and they are a good compromise for a framer that would prefer not to implement the use of steel in his or her frame but is challenged by some high tension loads at a particular connection.

Well put Paul. As an engineer, I never met a brace or spline that I didn't like.

Thanks all for the informative discussion! The use of glue sounds great and is not something I ever would have thought of. I've seen some diagrams of splines used to connect two beams [through a post] but have never seen a diagram where one beam was tied to an end-post. Are guidelines or examples available for such applications?
Thanks again for the thoughtful input!
Mark

Mark, here's some pictures, the second link is specific to your question I think:

http://www.spbrooks.com/join.htm

http://www.spbrooks.com/pic251.htm

A very simple joint that could easily be adapted to be fully housed (with bigger posts of course). Typically on the end post we run the mortise all the way through so that we have the entire thickness of the post through which to peg. We shoulder load carrying timbers and drop the spline low, the intersecting member then is rarely also load carrying, and in tension, so here we use a straight thru shorter spline. Usually the load carrying deeper spline is inserted first then the mortise redrilled and the intersecting spline run through, so that they are doing an over/under deal inside the post. Tight post to spline connection, glued and pegged. Voila!

Amazing! So it seems that the presence of the top spline acts like an oversized peg?