I have been reading a great deal about the proper post and beam materials to use. It seams that timber that is
quarter sawn is the material of choice. Unfortunalely in
My area South Central Alaska logs large enough to saw a 10"x10" beam in this fashion are very rare. Can I
safely use timbers that are cants with the heart still in them and does this require some added engineering?
I understand the shrinking issue and the checking problem. I believe I would get most of the bound moisture out before assembly and raising. Your thoughts. Thanks.

Have your timbers milled so that the heart/pith of the tree trunk is in the middle of the timber, up and down and left to right, both ends. This is called boxed heart timbers, they are the strongest and easiest to mill.
Good luck with your project.
Jim Rogers

The Japanese often kerf boxheart timbers along their length in their traditional construction. The kerf is located on the side away from view (on top of high timbers and on the back of timbers against the wall.) The kerf creates a weak point for tangential drying stresses. This often forces the tangential drying shrinkage checks to conveniently locate themselves where you want them.
I would recommend that you assemble your frame before the fabricated timbers dry too much. Timbers fixed together in a frame will be somewhat restrained from twisting and bowing while they dry. Good Luck!
What type of timber is availiable near you?

Thanks Christoper I am using White Spruce.
our Sitka Spruce althouth nicer in color grown near the
coast and does not grow very straight. Local sawyers
warn of its instability.
I have used Kurfs in the past with some success on
logs of the white spruce. How wide and deep should
they be as a relation to the timber thickness. i.e. 8"x12"
principle rafter kurfed on the top.
Also do you think it is a sound idea to wax the ends to
reduce checking.
Thanks Sterling

The conventional wisdom is that for White Pine, you want boxed heart, and for Douglas Fir, you want FOHC (free of heart center). Those are the only two species I'm familiar with. CB.

yes i would wax the ends(i'd seal any open end grain) and waxing the joints makes fitting much easier
we have plenty of white spruce here in central ontario
i've always liked working with it
last fall i built a set of mortise and tenon sawhorses for timberframing
white spruce is light and strong and tough to work with hand tools
the only thing i would watch out for is spiral grain, spruce can certainly twist.
-Mark in Ontario.

I would think that a kerf 1/2 the distance between the surface and the heart would provide enough of weak spot to attract the majority of the checking. I can't tell you this from experience though. I wouldn't go deeper than a third of the total member depth. The width can be as thin as you are able to cut. Sealing all of the surfaces will slow drying especially the endgrain. Good Luck

I wonder what impact a kerf has on the sction properties of the timber with respect to its ablity to carry a load. I would think that the kerf would need to be very shallow, perhaps only an inch. I wonder if anyone has any information on this.

A vertical kerf in the top of a beam has little structural effect as long as the beam is braced laterally by flooring or roof sheathing. Obviously fasteners should be driven into one of the two halves of the top surface of the beam and not into the kerf. Kerfs in posts also have little structural impact. As always, each situation should be evaluated independantly.