Beams

[hopm]

Sometimes you just have to make it work. Needed 2 4"x8"x16' hemlock beams and had to get them from one log. Are these going to cause me problems? I tried to center the pith but this was not possible to get 2. Trying to learn a bit and your response is much appreciated.

 

 

[Satamax]

As we say in France, about roofing beams, nail theses on, before they get the chance to give any trouble.  ;D

[Southside]

Well, maybe you will get lucky, but I would expect that top one to bow to the right on you.  Sometimes you can't get what you need from what you have.  If you can live with bow, or nail it up before it moves as suggested, then I suspect it will be fine.  If you had something that needed to dry before final use then the better course would be to saw for quality and find another log.  It can get frustrating when you need to open another log for one piece, but that is better than the alternative and having a completed project fail.  

[thecfarm]

I built 2 buildings out of hemlock. Had no problems with any of it due to warping or twisting. Now that red pine tried to twist on me.

[WDH]

Splitting the pith and leaving all juvenile wood on one side is a recipe for serious bow.  You did good the way you sawed that log given that you had to get two beams by trying to contain the juvenile core mostly in one of the beams. At least you took the right step given what you had to work with.  

[Tom King]

As we say in France, about roofing beams, nail theses on, before they get the chance to give any trouble.  ;D

Here we say, for questions of hesitation:  "Nail it before it rots."

I have no doubt that doesn't always work out for the best, though.

[Don P]

Bow in that sized timber I can usually remove green or dry or choose to accept without frame distortion, so that is not a huge deal to me. Crook is the deal breaker, you are as well centered as possible that way. It also looks like you got away clean on bow from release of growth stress, they look to be flat. Juvenile cells shrink some lengthwise where mature cells do not. As the wood dries the lengthwise shrinkage of the center core of juvenile wood can bow the timbers. If that core is the stronger part of that timber... hemlock grows slow so take a look again. Ahh looking down now at the bottom pic of the pith, the dark ring pretty much identifies the juvenile wood. It isn't a switch, the juvenile to wood transition takes some years but notice the really juvenile wood is not a huge proportion on the wood cross section. 

All that was to say, who knows, you could get lucky with distortion :D.

Morning rant  :D
Distortion structurally is a serviceability issue, not the life safety issue that is job 1. Grade the timbers. The first thing I look at is the end grain to confirm what faces I'm looking at in relation to the heart. Knots are truncated cones starting from a pinpoint at the heart and growing in diameter as a cone across and through the grain, I'm visualizing its proportion of the timber's cross section and location in the section (where is stress in the beam in relation to the "defective" cross grain).  So know where you are in the beam and in relation to the pith, scan for the "limiting defect", the one that will drop the timber to a lower grade. It might be a knot, wane, grain runout!(huge, pay attention) Assess how much the limiting defect compromises the beam. In a joist or rafter I crown the beam up, the concave side will probably contain the limiting defect. Nature is counter to my desires here, the cross grain of the largest knot pulls the wood around it which in turn puts it on the opposite side of the crown. That biggest knot usually wants to be on the bottom, tension edge, of a beam. Is there a strap of sufficient sound straight grain around that defect on the tension face. Then you can decide, if you have the strength, then decide if it is serviceable.