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.
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.
I would have to agree. You could try exposing the opposite side to the the
elements and see if it evens out, much like flipping deck boards. You could
try it with just one piece first to see if it works. I believe the cupping
is caused by the wood fibers compressing and does not reverse upon drying.
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.
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.
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.
Not just by that....a steaming to provide a uniform moisture level
followed by controlled drying <might> help, but it's a shot in the
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...
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
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.
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
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.
On Sun, 13 Mar 2005 11:55:48 -0600, Lars S
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.
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.
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,
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