Beams twisting and cracking

[Crossroads]

I’m heading back to a repeat customer in the morning and when I talked with him this evening he said some of the 8x8 beams that we cut last time were twisted and cracking pretty bad. I didn’t see pictures, am guessing it is the ones on the outside of the stack. They are stickered and stacked at the edge of the field under some shade. Anyway, he’s not complaining, but asking for suggestions to reduce this. Thank you for any input. Some of it was bigger wood, so there is a mix of boxed heart and free of heart. 

[Don P]

Twisting is spiral grain, the twisting will stop when the wood is dry, then it can be resurfaced and should remain relatively straight as long as the moisture content remains stable. 

Checking is normal in large timbers. FOHC is less prone to checking than boxed heart but has an increased chance of bowing. You can reduce checking the same way as in lumber drying, reduce the moisture gradient in the wood, drying slowly. If you notice more checking in the same type of cut on the outside of the stack then it is drying too fast on the outsides of the stack. If it is pretty uniform throughout the pile it is probably just unavoidable natural checking. If the wood is dry before use he can orient the timbers to hide some of it and reject any really objectionable ones.

It sounds more than anything like this is going to be an education visit. Most folks think wood is inert. There are a lot of things going on as wood dries.

[Crossroads]

Thank you Don! I appreciate the information and will pass it along. 

[Ianab]

Take some pictures too, it will help work out what's going on. Often some warping and checking is unavoidable, just the nature of the wood. Other times it can be worsened by sawing patterns or poor drying conditions. 

[K-Guy]

Often some warping and checking is unavoidable, just the nature of the wood. Other times it can be worsened by sawing patterns or poor drying conditions. 

This is very true but also it can be just the way those beams are and nothing can change it. Cracking and splitting are normal in thick beams, how much depends on factors noted above. 

[Crossroads]

Sorry, I didn’t take any pictures. The twisting was actually pretty minimal, but the cracks were pretty bad in a couple of the beams. The major cracks were along pitch seams, so I don’t think much can be done about that, they were the ones with the boxed heart. The free of heart looked good except one on the top had a slight bow. Which we rotated and stacked more on top. Thank you again for the feedback, there is definitely a learning curve to this drying stuff. 

[Ianab]

Boxed heart is almost certain to check in some way, same reason that it's very hard to get "cookies" of wood to dry intact. The different shrinkage rates mean there is going to be a thin slice of pie missing once the wood is fully dry. This doesn't really affect the strength, and the beam is more likely to stay straight.

[Don P]

the cracks were pretty bad in a couple of the beams. The major cracks were along pitch seams, so I don’t think much can be done about that, they were the ones with the boxed heart

In boxed heart the major check will normally follow the path of least resistance, the shortest path from heart to outside face, or a defect. You can also kerf a face down the length of the timber with a skillsaw about 1/4 depth to create that path. Just like scoring concrete it creates a line of weakness for the crack to follow.

In FOHC if the logs are relatively large getting outside the juvenile core helps with that reaction wood bowing, then you are just dealing with growth stress. A friend has a FOHC dougfir timberframe that I haven't noticed any checking in.

[tawilson]

Don, do you think that kerf helps with twisting too?

[Don P]

Nope, twist is spiral grain. As wood dries it pulls to itself, if it is pulling towards spiral grain it is going to twist and in a large timber there is nothing you can do to resist that. If you remill it flat after it is dry AND if the moisture content stays put after that it won't move or move much beyond that. There are limits in each grade for grain runout, slope of grain, it weakens the wood so keep that in mind as well. Cut plenty of extra, don't put yourself in the position of being forced to use wood that you know isn't good for the job. I see it in old work all the time and know what the guys were doing, they were forced into a bad decision by lack of spares. That is experience gained from being in the same boat.

I use culls for dunnage, cribbing, temporary support posts, garden bed edging, etc. I've got a house up on temporary posts right now, one of those has a good 45° twist but it doesn't matter for that use. As we work, those timbers get cut to whatever next shorter length we need until they end up as dunnage or firewood.

[Crossroads]

Luckily we did cut extras. Also, everything we cut was 16’ long and apparently he only needs 10’, so he’ll be able to trim out the best 

[GeneWengert-WoodDoc]

The faster you dry the beams, the worse the cracking.  What is happening is that with fast drying, the outside tries to shrink somewhere around 4%.  The core however has not started to dry much and so is not shrinking.  With slow drying, the shrinkage is less and the so the stress that develops is less.