Wood movement and cupped boards

[Lars S]

I recently acquired over a dozen 42"x12"x1-3/4" white oak stair treads from a rennovation site of a 100-year-old greystone. This would be a gloat, except I already spent a day getting them from the construciton site, pulling nails, and cleaning them off. And, the biggest problem, most of them are significantly cupped from being exposed to a few onths of rain and melting snow. The cupping is about 1/2" to 3/4" across the

12" width of most of the treads.

Here's my question. If I sticker the treads for a while (how long?) will the cupping reverse over time? If not, I can easily plane off

1/2" of material and make some very nice, flat 1-1/2" boards (I'm thinking two side tables and a matching coffee table), but I don't want the planks to reverse-cup once I've made a nice table top. I'm a bit impatient, so I would prefer not to wait a year to use the wood.

[George]

Month or two. 1% per week is a reasonable rate for indoors equalization.

Mostly. Some "set" might have taken place which is not reversable.

If not, I can easily plane off

About stair treads - they've got a buttload of sand and stuff ground into the upper surface. If you can get that sanded off, I'm sure your planer will thank you.

[toller]

You are being too optimistic. If they are cupped 1/2", then you have to remove 1/2" from both sides, so you will wind up with 3/4" stock at most. Plus, if you put them in a planer, they may flatten them out prior to cutting, and never get the cupping out. There are work-arounds, but they are not easy; you really need a 12" jointer.

By all means try letting them dry out and see what happens; but your chances are not good. A few months ought to be plenty.

[Lew Hodgett]

Don't have a clue if you will ever get the cupping to reverse.

Maybe some, but probably not much.

A little tip.

After 100 years of service, who knows what has been ground into the surface of those treads.

When it comes time to surface them, go to a commercial drum sanding house.

Save your jointer and planer blades.

It will not only be faster, but less costly in the long run.

Lew

[Joe Tylicki]

[Duane Bozarth]

....

Not just by that....a steaming to provide a uniform moisture level followed by controlled drying help, but it's a shot in the dark...

You'll salvage a lot more nice material if you resaw them down to 6" or so, joint the edges and reglue...if you keep the pieces together and oriented properly you'll probably find it hard to tell where the joints are when done...

Haste makes...what was that again, precisely?

[Lars S]

Thanks for all of the advice. Very helpful. I'll give the boards a few months indoors and then mill them down. The really badly cupped ones I'll split into 6" planks and then edge glue if I need the extra width.

BTW, I should have said that I have an old set of nicked planer blades that I have been saving for just this kind of job (at least for the first few passes). It sometimes pays to never throw anything away.

Lars

[toller]

That is a good suggestion; it will probably also be less work in the long run.

[Phisherman]

First of all congrats on the treads--I wish I had such a find. The cupping probably won't reverse over time if stickered. However, here's a trick that may work:

On a hot sunny day place the cupped boards on the grass on a hot sunny day. Place the boards in the orientation of "n" rather than "u." The warm moisture from the grass will expand the wood fibers and tend to make the boards less cupped. A moist heating pad might work just as well, although it would take longer to do so many boards.

I learned this method from my father who used it to flatten warped doors. It looked like crazy thing to do then left me amazed how well it worked.

You can plane the boards instead, although you will have thinner boards. If your boads are damp, you will need to dry them and become stable before working on them.

[George]

For your edification :

chapter 3.

[George]

That must be one hell of a planer you've got that can flatten the crown on 1

1/2" oak.

[George]

This works as well as it does for the same reason that stickering the pieces which are now saturated one side works. Once the expanded fibers begin to contract again, the wood returns to nearly the same configuration it held prior to the first imbalance.

Once again, good information in Chapter two.

[Lars S]

My mistake. The cup measurement is actually 1/4" to 3/8" across the boards. I said 1/2" because I knew that is about what I needed to plane off to get one of them flat. Ended up with a board that was about 1-1/4" thick when I was done. Looking across the different treads I've got stickered, I imagine that I could get a few for 1-1/2", although others would need to be planed down to an inch.

[Lars S]

Thanks for the reference. I'll keep this handy in the future.

[Walt Cheever]

I've had SOME luck in reversing the process--wetting the concave side to expand the fibers, and aggressively drying the concave side. Reduces the cupping, anyhow. The Furniture Doctor book recommended putting cupped boards concave side down on the lawn for a few days. Let the moisture from the earth hit the concave side and the sun bake the convex side.

Then you've got to sticker/anchor/weight the boards while they dry to equilibrium so they don't jump back as they were. I don't know if that induces some residual stresses that will show up when you use them.

It's a shame to waste all that fine wood, hope something works.

Another thought--is the convex side the bottom (unfinished) side of the tread? Might be a chance of it flattening out when the unfinished side dries to the same moisture content as the finished side.

Walt C

[Lars S]

Walt,

Thanks for the specifics. BTW, is the "Furniture Doctor" book the one by Grotz? I see lots of used copies for sale on Amazon.com for around

45 cents each, and thought it would be worth it (s/h is, of course, much more).

Lars

[Jonah]

True, but you could rip them in half, joint them flat on a 6" machine, glue them back together, then plane them. You could probably salvage

5/4 or better...plenty for coffee table purposes.

[Joe Tylicki]

George, from what I gathered, Chapter 3 related mainly to the movement of wood upon initial drying from its "green" stage. I did not see anything that relates to the instant case, i.e., seasoned lumber exposed to the elements causing repeated wetting and drying of one surface of the board. In this case, as in the case of your typical deck, it does not matter what direction the grain runs, as the cupping will occur in the direction of the exposure to moisture. This is because the fibers on that side of the board have been crushed by the expansion when wet, and upon drying, the surface area is now smaller than it was originally.

Joe

[George]

Hysteresis is what you want to look at. The answer to whether or not it will return to a semblance of its former configuration.