How can I deal with wood from DIY stores that is crooked and may or may not be dry?

Question

I've been meaning to build a desk for a while now. I made a design with millimeter accuracy, but when I went to the home improvement store, I found that all the beams they had were crooked! Some more than others, but the only non-crooked wood they had was chipboard (particle board in the US), but it didn't come in any shape I needed.

So, back home I did some research on wood. It appears there are several different types, most importantly regularized or unregularized. Basically one is allowed to be crooked, the other isn't. I couldn't find any exact specifications though as to what qualifies as straight (surely, no beam is perfectly straight, right?).

Another important bit I stumbled over is that some regularized wood is not completely dried out: does that mean it could become crooked over time?

Then I looked into straightening the wood, but this doesn't seem to be a very viable option unless you're building a porch or something.

I went back to the store and asked if they had any regularized and dry wood. They didn't know what I was talking about. Just pointed me towards the piles of planks and beams and said it's really good wood!

TL;DR

1. If wood is "regularized" and not dried, could it become crooked over time?
2. How can I tell if wood is completely dry or just sort of dry?
3. If I were to find some unregularized wood that's reasonably straight, would it most likely stay that way?
4. If I were to find a suitable shape of that wood that's made of chipboard, is that a viable option? I've only seen it in cheap furniture, mostly where a chip has broken off from what used to be a screw hole.

Answer 1

It might be a regional issue, but I hadn't heard the term "regularized" in the context of buying lumber. Perhaps that threw off the people at the store, although even if you had asked for S4S (surfaced 4 sides) hardwood lumber, the employees at a home improvement store may or may not have been able to help you.

1. If wood is "regularized" and not dried, could it become crooked over time?

Believe it or not, all the dimensional lumber that you see in the store was straight before it was dried. If you buy green (non-dried) lumber, it will warp as it naturally dries. That said, some cuts of lumber are less prone to warping than others. Plainsawn will show the most warping, especially if taken from small, fast-grown trees. Rift sawn will warp less than plainsawn lumber, and quartersawn lumber will warp the least.

2. How can I tell if wood is completely dry or just sort of dry?

Use a moisture meter to read the moisture content (expressed as a percentage). You'll never get to 0%, but you should wait until the wood has reached its Equilibrium Moisture Content (EMC), the point at which it is neither taking up nor releasing moisture from the air. Ideally you should work the wood when it is at the EMC for the location where it is going to ultimately live once the piece is finished.

3. If I were to find some unregularized wood that's reasonably straight, would it most likely stay that way?

No

4. If I were to find a suitable shape of that wood that's made of chipboard, is that a viable option? I've only seen it in cheap furniture, mostly where a chip has broken off from what used to be a screw hole.

Yes, chipboard (aka particle board) and MDF are considered dimensionally stable and will not warp with changes in humidity. Even high-quality plywood and OSB are more dimensionally stable than solid wood. However, chipboard and MDF have some disadvantages--namely, durability and appearance.

Although the big home improvement stores do sell some hardwood lumber (sometimes wrapped in plastic), it is incredibly expensive and still may not be as flat and straight as you might hope.

Your best bet is to buy lumber from a hardwood dealer or lumber mill that properly dries its lumber, rather than buying from a home center or lumber yard which primarily sells construction lumber. Many lumber mills will surface 2 or 4 sides for you for a small fee, but even then the wood will continue to move with changes in humidity.

Once you have your lumber, there are several techniques you can use to eliminate warp, but the key thing to keep in mind is that you should buy your lumber oversized in order to be able to mill it flat and straight as needed.

Answer 2

Don't know where you are, but in my area, the wood from big box stores is extremely variable. Finding a specialty supplier will probably yield better results.

To answer your questions:

1. Wood that hasn't been dried much will probably twist and turn more than wood that has dried. That said, wood commercially dried will frequently be twisted by the time it ends up in the big box store. Your best bet is to find dry wood that isn't twisted.

2. The proper way to test moisture content is with a moisture meter. If you pick up enough pieces of wood, you'll get a sense of which ones are too heavy to be dry. Even if a kiln dried bit of wood comes out at 12% moisture content, it'll acclimate to whatever storage area it's in. This'll vary according to where you are.

3. I'm not sure how you're using the term "unregularized", so I might not be answering your question. Wood that is dry and straight will generally stay reasonably straight. Exceptions occur... for instance when you cut a plank down its length and previously balanced forces are removed and you get two curvy pieces from one straight piece.

4. "Chips and glue", (I'm assuming you're referring to chipboard/particleboard), comes in different grades (which is to say, higher and lower density), but are mostly crap, as they don't hold fasteners well. You need to think like an Ikea designer to make these work for you. (Not saying it can't be done, but it's extra work.) Chipboard isn't very good at bearing weight. (A long span of it as a desktop would soon sag.) The only good thing about chipboard is that it's fairly stable in terms of flatness.

Other options in sheet goods include MDF (medium density fiberboard), which is really just glorified cardboard. It mostly has the same properties as chipboard, except that it's denser/heavier and a little less prone to warping. As noted, its dust is nasty.

Plywood is generally more substantial than either MDF or particleboard. It'll span further without sagging, compared to the others. Fasteners perpendicular to the face work pretty well; fasteners on the edges don't.

If you told us more about the desk you've planned (drawings, even), you'd get more advice.

Answer 3

I hate to say it, but wood is not usually predictable down to the millimeter, and your design needs to take that into consideration. For example, when making solid wood panels - these can shrink, warp, twist or cup significantly in the first year after they are manufactured, and will continue to shrink for the next 100 or so years. A design that constrains the movement too tightly may just result in the wood splitting.

I think that you're in for a lot of trouble/frustration if you haven't built some allowance for you skill level in cutting the wood accurately, and the characteristics of the wood itself. Even if you get it panel sawed at the box store, you will find that it can vary in width by up to 1/8" across the cut, and they usually only give you a +- 1/8" tolerance on the absolute measure, unless you have a particularly attentive operator.

I'd suggest first revisiting your design to see what allowances you can build into it, and not stretching your skillset too much (at least not on highly visible pieces at first).

Answer 4

I would recommend that you look for a local hardwood merchant. The stock won't be as expensive as in the big-box stores. I also suspect the hardwood is drier, having been stored longer after cutting. Another option is to use what is sometimes referred to as 'torrified' stock. In this case, it really means oven-dried. A hint: Your furniture production will really improve when you acquire the ability to create your own stock, so put a thickness planer (even a cheap one) on your wish list. That will put you in control instead of the wood merchant, and you can buy rough lumber much cheaper and dimension it yourself. Hope this helps.