Vertical grain fir is cupping after re-sawing

[scott vroom]

I bought some 1" re-sawn VGF from my local supplier last month. It had just been re-sawn from 8/4 by their supplier. I stickered the lumber in my shop for a month, today I started breaking the 12 footers down to size and noticed the cupping. The dry face (original 8/4 outside face) is convex and the re-sawn face is concave. I took numerous moisture readings and there's a 3-4% moisture difference in the 2 faces. I'm guessing the cupping is from the moisture imbalance. I can joint the concave face flat but it's still 3-4% wetter than the outside face and I'm concerned that it will just re-cup. The boards are for oversize 6' tall 20" wide raised panel cabinet doors and I suspect the problem will cause the doors to go out of flat as the lumber reaches moisture equilibrium. I'm calling my supplier tomorrow, seems to me he should be responsible for selling me poorly processed lumber.

[Mel Fulks]

That is pretty standard for resawing. If you will be planing it ,remove most of the wood from the
convex side.

[scott vroom]

That is pretty standard for resawing. If you will be planing it ,remove most of the wood from the
convex side.

I face planed a couple of boards, they're flat but there is still a 3-4% moisture difference in the faces. Seems to me the cupping will continue to occur until moisture equilibrium has been attained between the faces. Am I missing something?

[Peter Kelly]

I can imagine that stuff wasn’t exactly cheap, even in Oregon. Would be damned upsetting to have it cupping like that, not what’s supposed to happen with vertical grain material.

[Tom Trees]

I'd clamp it to the bench with another plank on top, and leave it for a good while if you can.
Give the boards a chance to equalise.
Happens with my reclaimed iroko which is in the workshop for years, can wind or cup a lot when resawn, and thats with narrow boards, say 3" wide...
Never noticed them cup as bad after unclampng them after for a day or two, compared to some boards straight off the saw.
Tom

[Mel Fulks]

I might let it sit for a day or two ,IF time allows. Besides moisture difference there is just plain stress in the material.

[scott vroom]

It was re-sawn a month ago and has been stickered in my shop the past 4 weeks. I don't think giving it a few more days will have any affect. This is for a customer and i'm up against time. First thing in the morning I'll be on the phone with my supplier letting him know I'n not OK with $7.88/bf for cupped VG lumber. Whether he can replace it tomorrow is another story...we don't see much VGF around these parts. I may just have to use the lumber and hope the big doors remain flat. I suppose it's possible the wood is done cupping. I've never worked with VGF...it's like silk on my machines, and the grain is striking.

[Joe Calhoon]

I use a lot of VG fir and that is pretty typical. 2 problems - this material usually has a higher MC and in the rough VGF is usually on the thinner side than most hardwoods. After facing and planing I sometimes find it is difficult to get 1 3/4 thick out of 8/4 and 3/4 out of 4/4. Not always but usually. One of my suppliers has 5/4. I usually buy that if I need finish thickness more than 3/4.

[Jim Becker]

When you stacked it in your shop, was it stickered for air flow on both sides? If not, stack it again with stickers and wait for the MC to balance between the two faces. Most of it should flatten out. Further processing it now with that imbalance will just result in more of what you have now.

[scott vroom]

Joe, the problem I'm describing may be different than what you're used to. The fir I bought was kiln dried at 8/4 and then freshly re-sawn to 4/4 just before I picked it up, leaving one dry and one wet face. I can't imagine being an acceptable practice for a supplier that claims their lumber is kiln dried.

[John TenEyck]

Exactly what Jim said. If you flatten it now it will cup again when it finally reaches equilibrium. Worse, if you flatten it and put it in the doors they are likely to split or warp the door. Just wait, they will flatten out. If you can't wait your only option is to get new stock - with a uniform MC.

Something is very strange for the MC to be 3% higher on one side than the other after a month. It must have been sopping wet inside when it was resawn. Your supplier should be responsible for making this right.

John

[Jim Becker]

Scott, I reseed a bunch of the leftover 8/4 VG D-fir from a project a year or so ago to use for other purposes. It also required some time to equalize MC. The same is true of other species that I"ve done the same with. It's normal for there to be some MC imbalance after resawing thick stock.

[Joe Calhoon]

Joe, the problem I'm describing may be different than what you're used to. The fir I bought was kiln dried at 8/4 and then freshly re-sawn to 4/4 just before I picked it up, leaving one dry and one wet face. I can't imagine being an acceptable practice for a supplier that claims their lumber is kiln dried.

Scott, did you check the MC? All the VG I buy is KD but moisture can be anywhere from 10 to 12% and higher. And if the boards have pitch it’s hard to get a accurate reading depending on what kind of meter you use. Typically resawed 8/4 will cup. It probably will not flatten out on its own but I would definitely wait a few days and dry stack before facing and planing. If it resaws to 15/16 you can probably get 3/4 out of it. 7/8” or less 3/4 will be difficult.

ok just re read your first post. You checked with a meter. For 6’ doors that will be difficult. Fir usually stays pretty flat after machining if the MC is balanced. 5/4 would be a better choice if available

[Kevin Jenness]

"Kiln dried" can cover a lot of sins. Typical construction lumber is kiln dried to about 19%. I have found that Doug Fir is typically not dried to the same level as hardwoods sold for cabinet work.

Good luck with getting the material replaced by your supplier. They may shine you on unless you have a long-standing relationship- that happened to me years ago when I purchased an large batch of fir from a "reputable", new to me vendor. They told me their other customers had no problems building doors with 18-19% MC wood, and I was basically stuck with it. I wound up taking the material to a local kiln. It's a good reminder to deploy the moisture meter before accepting a batch of lumber.

[scott vroom]

Talked to my supplier this morning, he'll replace all the cupped lumber with KD 4/4 (or 5/4 for no up charge if he can't get 4/4)...none of it re-sawn.

[scott vroom]

Scott, did you check the MC? All the VG I buy is KD but moisture can be anywhere from 10 to 12% and higher. And if the boards have pitch it’s hard to get a accurate reading depending on what kind of meter you use. Typically resawed 8/4 will cup. It probably will not flatten out on its own but I would definitely wait a few days and dry stack before facing and planing. If it resaws to 15/16 you can probably get 3/4 out of it. 7/8” or less 3/4 will be difficult.

ok just re read your first post. You checked with a meter. For 6’ doors that will be difficult. Fir usually stays pretty flat after machining if the MC is balanced. 5/4 would be a better choice if available


Joe, I was hoping to get 13/16 out of the true 1" lumber. I'm wondering if I shouldn't just upsize to 5/4 and make the doors 7/8.

For typical kitchen cab doors, I mill rails and stiles to 3/4 x 2-3/8. For these 6' doors I'm planning 2-3/4 stiles and 3" rails including a middle rail. I've done some research but haven't found much info on rail/stile dimensioning for oversized doors. Do you have any thoughts on this? I'm planning on 3 hinges per door, Blum clip top with the adjustable cam plates. I figure I can adjust out most minor flatness issues.

[David Kumm]

I prefer thicker frames on fir. It is lighter anyway and to me the extra heft seems to fit the wood. My experience is that reclaimed old growth is much more stable but also slivers more. New growth needs extra time in the kiln, especially for 8/4. If I have lead time I ask when the next kiln charge is part way through so the fir can be put in to finish the drying. Fir seems to hold moisture inside longer than other species but I'm no scientist so I either buy fir that doesn't need resawing or put it in the kiln. Dave

[Jim Becker]

Talked to my supplier this morning, he'll replace all the cupped lumber with KD 4/4 (or 5/4 for no up charge if he can't get 4/4)...none of it re-sawn.
Good supplier!

[Joe Calhoon]

Scott, 5/4 is the best way to do this. You will be much happier.

[Joe Jensen]

Until the moisture stabilizes it will move.

[Robert Engel]

Don't plane it!! The moisture differential needs to equilibrate or they will continue cupping.

I have pretty decent luck putting them in stickers with the insides facing up & clamp them in battens or parallel clamps & leave them alone for a week.

Your supplier is amazing they had no obligation to replace it.

[scott vroom]

The boards were flat when I bought them. They cupped when I stickered them, unclamped, in my shop for a month. Next time I'll try clamping, but I'm surprised that works...I would think the the stress built up from the wet side drying would remain in the wood and after unclamping that cupping would still occur.

Yes, my supplier is doing me a big favor. I've been a regular customer for years, but don't do anywhere near commercial volume He knows my projects are paying jobs and probably feels sorry for me :o. Not only did he agree to take the cupped wood back, he's brought in a unit of KD 5/4 (not re-sawn) and giving it to me at the 4/4 price.

[scott vroom]

Here's a photo of the 2 cabinets with VGF doors/drawer fronts. Installers had just finished setting themt, GC will add the trim pieces, knobs & pulls in a few days. The 7/8" thick doors turned out near perfect flat which was a relief. Finished with 4 coats Arm-R-Seal, the first 2 coats were sponged up by the fir. Personally I would have preferred a 5th coat but the customer wanted minimal film buildup.

The VGF was soft and easy to mill, the only issue I had was with edge splintering...it drove me nuts.

Thanks again for the helpful advice.

[Jim Becker]

Those look REALLY good, Scott!

[Mark Gibney]

Very nice work, and I have great affection for doug fir. But yes it is splintery. The edge is so fragile.

[Scott T Smith]

Scott, very nice work - I'm glad that things worked out in the long run.

Your problem was almost certainly related to the wood MC%

99% of 8/4 fir is dried for structural purposes, so it is only dried to 18%, give or take. Frequently the shell of the lumber is dried below the targeted MC% in order to help wick moisture from the core, and then the shell is rehydrated during the conditioning process. If the lumber is not conditioned then it is not uncommon for the shell to be 10% while the core is 19% (structural lumber)

What probably happened is that the surface of the lumber was a much lower MC% than the core, and when it was resawn the newly exposed face from the core started losing moisture and shrinking.

This is not as much of problem with properly dried hardwood lumber, because it is dried below 10%MC. It is not uncommon with structural lumber.