Twisted timbers

      Determining the cause of twisting in Douglas fir construction timbers. August 10, 2000

I am faced with a very unfortunate situation on about (40) 5-1/2-inch by 5-1/2-inch by 10-foot-long rough-sawn Douglas fir timbers. The problem is that they are badly twisted, and probably not usable for construction. They were to be used in an outside garden pergola.

Here are the particulars:

After getting some good advice and education from this forum a couple of months ago, I found a local mill and ordered about 3000 board feet (BF) of rough-sawn Douglas fir. About one-third of it consists of these 40 square posts, and the rest is 3-inch-by-8-foot and 3-inch-by-12-foot timbers.

I picked up the lumber as soon as it was cut and it looked pretty good. I stacked it with stickers the same day. I covered the ends that faced the sun and covered the top. I made provisions to cover it when it rained. It has been sitting in this stack for about eight weeks, air-drying. I am in Salt Lake City, Utah. The weather here has been very mild, with humidity usually in the 20 to 40 percent range, and temps from 60 to 85 over the last eight weeks.

The last few weeks I have noticed that the 6-by-6 posts looked a bit twisted. Today I pulled some of the posts out to begin cutting and getting ready to construct the pergola. I found that the majority of them are twisted, many quite severely; laying them flat on a concrete slab, the opposite corner will be raised from around 1/2 inch on some to nearly an inch on others. This amount of twist is occurring in the 10 feet of length. Only a handful have minimal twist.

I believe they are basically dry. I don't have access to a moisture meter, but am getting one next week. They do have some checking, but it is not all that bad, and is manageable.

I am really wondering where I went wrong. I did a good job stickering and stacking them and have kept the stack protected from the elements. I don't think it has even gotten rained on once. The east and west sides were exposed to the sun in the morning and evening, but the twisting was no worse on the side boards than the middle ones.

I'm wondering if the cause is the type of cut the mill did. Based on info from this forum before ordering, I asked if they could cut it FOHC (free of heart center) and he told me no, that it really wasn't a big deal. So I let it go. But almost all of the logs are heart center, it looks like each one was cut from a single log and each one shows the center of the tree. I am wondering if this is the problem.

My options are:

1. Try and use the lumber. The problem is that with a 5-1/2-by-5-1/2-inch timber, it is real difficult if not impossible to take out twist in only 10 feet of length.
If I were to have him remill them now that they are dry, could he take the twist out and would it stay out? I would obviously have to accept a smaller post.

2. Take it back to the mill and tell him they are unacceptable. This is probably impossible due to them being custom cut and the mill not having control over the drying.

3. Throw the whole mess out and start over. This would be very costly, as I paid .85 per board foot (BF); I'd be looking at about $1,000 wasted for the 40 timbers. While extremely unpalatable, this may be my only option.

Did I do OK in my drying sequence, or is that the cause of my problem? Is it reasonable and customary to be able to buy 5-1/2-by-5-1/2 timber that is FOHC? The other timbers, the 3-by-12s and 3-by-8s, are mostly FOHC and do exhibit some twist and some cupping, but are not nearly as bad, and are probably usable. It is much easier to take the twist out of a narrower board.

Sorry for the long post, but I am just sick over this problem. Any and all comments are appreciated. I would like to avoid repeating this experience and salvage what I can.

I do not believe that you did anything wrong. Twist is a defect that is common in the heart-center portion of the tree. It is nearly impossible to prevent or even control well in drying. In answer to your specific questions:

1. NOT AN OPTION, as they will continue to dry and will twist a little more. The tendency is in the wood. Twist seems more pronounced in the center portion of a log.

2. In most states, a product sold must perform as it is intended. You may have some legal recourse, but only if you are trying to get $1,000. Small claims court may indeed be an option.

It is unusual in the Rockies to get Douglas fir large enough to produce large timbers and also avoid the heart center region.

I'm sorry to hear of your unfortunate situation. It sounds to me, as well, that you handled the wood perfectly, but were simply the recipient of some poor-quality timbers.

Even if these timbers had been dried using state-of-the-art technology, (RFV Kiln) it is likely that the twisting would have happened anyway.

There is one technique timber framers use that you might be able to employ to salvage the situation.

The idea is to create a smaller, square timber (say, 4-by-4) on the end of each of the 6-by-6 twisted timbers. The corners of the new "timbers" are then joined lengthwise by a chalk line on all four sides. These lines are used to do all of the layout for your joinery. Each intersection is "housed" to the smaller timber section, thereby producing plumb, square joints.

A similar result can be achieved by setting the timbers on a sawhorse, and drawing a plumb and level line across each end (much like the crosshairs in a gun sight), connecting these lines down the length of the timber, and doing your layout from them, rather than the actual side of the twisted timber.

In order to make the twist much less conspicuous, you might also want to consider making the timbers into an octagon shape. (planing off the corners with a power hand plane).

While the timbers will still be twisted, it will be much more difficult to tell.

I understand exactly what you are describing. Unfortunately that technique doesn't appear that it would work with my project, but I'll consider it. I used that technique many years back when I ran a framing crew.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
Heart center 6x6 green cut from small trees is going to twist and develop heart center seasoning check radiating out from the heart. Regarding drying procedures, when to use and when to dry, there are a number of options.

1. Use the timber right away in the green. At least the ends would be held in place in the structure and would have moved less, unlike being free to move around in the drying pile.

2. Have the timber sawn in the late fall or winter months when it is cooler. I bet drying it in 65 - 85 degrees you could hear that heart center timber popping and snapping. You want to air dry lumber in the cooler time of the year and draw the moisture out *slowly* from the center of the timber while at the same time keeping the surface from checking (splitting). Even go to the extent of wetting down the pile for the first couple of weeks to keep the outside of the timbers moist with a fine spray occasionally.

3. Paint the butt ends of the timbers with end-seal or latex paint or bees wax, etc to reduce end split.

4. Keep out of any direct sun, ideally under a shed.

5. Put up on blocks, ideally 12 inches off ground for first layer, then sticker horizontally each layer with min. 1" x 2" stickers. Put horizontal stickers right out to the bitter end of the timbers to reduce end splitting and then every 2 to the other end. Do not set stickers in from the end even 1 inch. The weight of the timbers above will be transfered vertically down to the timbers below and be inclined to hold the butt ends together and resist end splitting. Also, seperate timbers vertically for vertical air movement.

Another option would have been to buy the timbers oversize by about 1" and then after drying you could resaw them on 4 sides to square them up. This is what we do when we kiln dry timbers in a radio frequency (micro-wave) kiln. The moisture is taken out in about 6 days and we get M.C. at the center of a large timber, say 12 x 12", right down to 12 - 14%. But even I use FOHC timbers to get the best results.

Then we resaw 4 sides and run it through a planer the day before we ship it back to the east coast.

Even when we air dry our FOHC Doug fir, it is for 60 - 90 days during the late fall through winter to early spring. This gets MC down to about 19 - 20% then we S4S plane it just before loading the truck.

Your best option at this stage is to resaw the timber down to reduce the twist/crook and even though it is a bit cheaper, try not to buy heart center timber in the future, and you should try to find a source for FOHC timbers.

Comment from contributor B:
I work as a lumber grader in a mill in BC, Canada. In fir the first ten to fifteen years the wood grows in a spiral so it is prone to twisting. We kiln dry wood the size you have. We don't put heart centers in as it is a crap shoot as to how twisted it will be.

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