Need a little wood insight

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Blog entry by SST posted 01-22-2008 05:59 PM 988 reads 0 times favorited 7 comments Add to Favorites Watch

While this question for the group knowledge base probably is not of any real significance, I figure that someone here has the answer, so, since it’s been bugging me all morning, here goes.
I stopped at a big home improvement lumber type store this morning (that shall remain nameless, but it starts with “M”) and I was walking through the lumber area (no, I didn’t buy any…I didn’t need any “propeller” shaped 2×4’s or “c” shaped 2×2’s) but I noticed something that kind of puzzled me. As I walked through the plywood area, I noticed a significant number of 4×8 sheets of various kinds & thicknesses of plywood that were bowed as much as 4” across the 4’ span.
As I always thought that the “ply” concept and changing grain directions eliminated the warping problem, I”m wondering just how this can be.
Has Menards (oops) figured out a way to defy the laws of physics? Is the time/space continuum in jeopardy? Is Chinese wood just that crappy?
What’s happening, here.
My world no longer makes sense…Have the basic laws of nature been violated? Are old Shopsmith’s not the greatest & coolest tool on the planet? (sorry, had to throw that one in here)
Anyway, does anyone know the answer to all this? (or really care?) -SST

-- Accuracy is not in your power tool, it's in you

7 comments so far

View Paul's profile


660 posts in 4087 days

#1 posted 01-22-2008 06:07 PM

I’m not sure why. But I know it’s frustrating to build a project assuming stability and seeing it warp and rack before your eyes after it’s assembled!

I think it has perhaps gotten wet somewhere along the line (or it was never dry in the first place). The wet layers working against the dry layers. Outer layers drying faster than inner layers, etc.?

-- Paul, Texas

View rpmurphy509's profile


288 posts in 3849 days

#2 posted 01-22-2008 06:13 PM

I agree with Paul, perhaps it was on the top of the stack and it got wet.
The top layer(s) were saturated while the bottom ones were not. When
it dried, it warped and possibly separated the glue between them as well.

-- Still learning everything

View Moron's profile


5032 posts in 3888 days

#3 posted 01-22-2008 06:20 PM

Plywood isnt any different then any other kind of wood. The portion of the sheet that is exposed to air to absorb moisture or loose moisture pending the ambient humidity levels it is surrounded by and with one of the LAWS of Physics, for every action there is an equal and opposite reaction. What you are seeing is exactly that, relatively speaking… the plywood bends. This a rule but not that there arent exceptions

other cause might be incorrectly dried cores, grains that dont balance each other. Also the amount of layers has decreased and the thickness of the layers has increased from 1/16” plus to over an 1/8” sometimes pushing a 1/4”. Its all about profit and loss statements.

In our quest to demand more for less, companies have more and more products that are made off shore and the quality of said products is a crap shoot. We dont want to spend the big bucks on domestic fabricated products but we sure do whine when we see some of junk that fills the shelves of the big borg stores.

One of my brothers hauls logs during the winter down mountains in the interior of British Columbia, the mills have to go further and further to get old growth trees. A single tree can fill his 18 wheeler. The cost goes up and for the most part, the timber is shipped across the big pond, processed and shipped back to us as…..well, some might think junk…...........and the scraps are put on our shelves.

10 years ago, one in ten appliances was made in China, today that number is pretty close to 9 in 10…...nuff said


-- "Good artists borrow, great artists steal”…..Picasso

View Rob McCune's profile

Rob McCune

123 posts in 4093 days

#4 posted 01-22-2008 07:50 PM

This is an instance where a little forethought will prevent a lot of after-thought. Keeping in mind that as wood workers, we are smart enough to only buy the plywood that is flat and dry, we still need to keep in mind that if not properly used, plywood will still bend and warp because it is made with, wait for it, ... WOOD! Everyone here has those plywood shelves in his garage that were just thrown together and are now sagging where there wasn’t enough support. If you don’t buy it straight and force it to stay straight, there is no doubt that it is going to warp. Time mixed with humidity and gravity will make certain of that. That is why we use glue, biscuits, dowels, dado’s and rabbets instead of just shelf supports and brads.

So yes, while the quality of the wood is an important factor in the short term, it is the quality of the work that will tell the tale 60 years down the road. People who are viewing your piece of furniture when it is 60 years old will first look to the craftsmanship put into it before blaming the product used. How many times have we looked at someone elses work and found fault not with the plywood but with the way it was used. “Well he didn’t use any glue” or ” If only he would have put it in a dado.” And even when we find fault with the material it is only a reflection on the craftsman; “He was an idiot for using that type of plywood.”

I was watching an ask this old house episode where Tom Silva was replacing a set of stairs. Instead of using real flashing under the door sill, the person who built it used the bottoms of several cheap aluminum turkey baking pans. I didn’t fault the pan bottoms for not working, I faulted the “idiot” who used them. I think this is turning into a rant but I just wanted to make the comment that the quality of the wood is only half of the issue. The other half is the person who is selecting the plywood. And don’t get me started on big box store lumber. :(

-- Rob McCune

View Partridge's profile


296 posts in 3951 days

#5 posted 01-22-2008 08:14 PM

I could of bin a return. The first buyer could of leaned it open aginst house and it go wet.
they will sell it for roof or subfloor.

-- I get out in the shop when I can

View Moron's profile


5032 posts in 3888 days

#6 posted 01-22-2008 08:37 PM

Ya, good point….............all the bent crap sells for cheap if you ask for a discount.

-- "Good artists borrow, great artists steal”…..Picasso

View SST's profile


790 posts in 4190 days

#7 posted 01-22-2008 09:50 PM

I never thought of asking for a discount. I should have thought about some potential “bent wood” projects and then I’d have just saved myself a ton of bending work. What was I thinking. I should not have of thought of the glass as half empty…I should have thought of the bin as half full of warped wood.
You guys are the best!

-- Accuracy is not in your power tool, it's in you

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