Has anyone ever heard of a post or other timber checking so dramatically that it became a structural hazard, or of one actually busting in half, or houses falling down....or is this mostly an aesthetic issue?

I know that I have culled many a timber that probably would have brought down a frame had it been used, but those are obvious and I couldn't imagine how anyone would have let one like those get by.

I have also seen many old frames with very large checks. I tend to believe that most timbers withhold their structural integrity once checked and dry in the frame.

Thoughts?

TG,
We had to replace a 10"x16" timber spanning 25 feet and supporting 12 feet of second floor because of severe spiral grain checking. The beam was a bit undersized for the load, but I don't think it would have failed if it had been straight-grained. The timber had a boxed heart, and if it was green enough to have no surface checks when it delivered from the mill, I could see how the spiral grain could have been over looked.
Regards, Chris

Freshly cut green wood is often endgrain sealed with Anchor seal, though I haven't yet heard of timber framers doing it to timbers cut for a frame. If you end grain sealed when you cut timbers, wouldn't it reduce checking? Isn't that desireable? It will dry slower. Will that cause problems with finish items installed then? Endgrain sealing on a frame that wasn't going to be put up right away would seem like it could be beneficial, no?

We use anchor seal on all end grain we cut, even inside mortises. It also helps at raising time, as the tenons are "greased". You're right about not getting it on the finished surfaces, as it will inhibit the finish from soaking in. CB.

I think I read somewhere on the forestry forums. Something like 75% of the moisture loss from a timber goes out the end grain.....

Anchor seal mitigates that loss by plugging the end grain to slow down moisture loss....


Good question TG...I'm interested to see what the response are to that question....

Spiral checking on green wood can be detected if you know what you're looking for (mind you, I only know soft woods, so can't speak for all species).

The checking created by lack of end seal hasn't seemed to be, in my experience, a source of structural concern, though I would never cut a frame without using it. My rule is to end seal any exposed end grain 1" and over, sloped tenons, and inside mortises.
Land Ark makes a nice product, though expensive....

No, my thoughts are those checks that were a topic of discussion on another thread recently (I'm too lazy to link to it, computer bogging down and I think you all know which one I'm talking about) where the guy's post was checked to the center of an 8x8...I saw that and wasn't so concerned; I've seen some fine, strong timbers with such checking (I was more concerned about the girt not snugged up to the housing)
So that got me thinking about this topic. We hear a lot about unsightly checking and how to avoid it (proper drying, kerfing the backsides, end seal..) but I honest to God have never heard of an actual structural failure due to extreme checking.

Spiral checking aside - that goes into the category of things to cull before the frame is cut.

Just plain old big fat check running down the length of the timber to the heart.
That's what I'm after.

I thought about posting this in the engineering forum, but wanted to see what the general consensus might be.

Duuhhh....the other thread I was referring to is Post Checking...right below this one...

I'll second or third watching out for spiral checking. I've seen a few barn timbers with spiral checking that most definitely ruined the timber.
How does TG see spiral checking in a green timber??
Spiral grain can often be seen easily in the bark of the tree...

Hhmmm...How does she see it?

Well, to be honest, it really depends on how green 'green' is.
By the time a timber gets to me it has usually been felled and sawn for a few days, if not weeks. And depending on the weather it may have already started to dry some.
Thus it gives me a bit of an advantage when I go over my timbers.

Spiral grain can be detected in the tree before being sawn, but that is different from spiral check. A timber with spiral grain wouldn't even make it to the saw.

Spiral check happens mostly in straight grained timbers, and can depend on such factors as speed of growth (varying yearly growth can cause a timber to dry in some funky ways, fighting against itself), or how the timber has been sawn.

I don't know exactly how I do it...I just know wood.
The Culling Queen.
The Timber Goddess.

But I'm sure I miss some, as well (*disclaimer*)

The check follows the grain, spiral grain causes spiral checks, straight grain checks straight. The "cleavage plane" if you want to call it that, is along the rays or resin ducts in the wood. Those are the cross grain cells that transport from bark to heart and are a natural weak spot. you can follow grain direction in softwood by watching the direction of those ducts or in hardwood by following the "chicken scratches' of the rays.
Just thought, lumber graders have a small pocket tool, a pick, that follows the grain and shows spiral. Should we try to source them?

There used to be a shear value assumption in the NDS for a checked timber and increases for unchecked material. That was changed a couple of ewditions ago, well they had also blown the math.

Never seen a timber check through although I've seen lumber do it. A timber typically checks to the heart.