Canada may be a metric country, but our lumber sizes are exactly the same as yours.
I am curious howver that everyone here says a 2 x 10 is actually 9 1/4" deep. I’ve built 52 homes in my lifetime and the depth of this item has always been 9 1/2 "
See how complicated this gets? I’m talking not about framing lumber, but about one-by S4S planks. (Though, for the matter of that, Wikipedia says that a 2 x 10 is 1 1/2 by 9 1/4. Go figure.)
I worked in a truss plant a couple summers, and 2x10s (and 2x8s) vary by quite a lot, but are very rarely over 9 3/8", and frequently as low as 9 1/8". Keeping a run of trusses all the same shape when your bottom chords vary in width by 1/4" is a pain in the ass.
Just happened to me yesterday at work…received an expensive custom metal part that didn’t fit right, only to find that the supplier had used our final dimensions as pre-manufacture nominal dimensions. Rest assured, they will be rebuilding correct parts for us on their dime.
Living in the engineering world, where we strictly measure and define raw material stock, in true dimensions and clearly label (and standardize) with “nominal”, “tooling excess”, “tolerance +/-”, that the lumber & construction world gets away with nonsense like this is just plain silly.
Even potato chips get this right. Should one feel cheated upon receiving a Doritos bag that is only half-chips and mostly air, there is still a “net weight” value printed on the bag with a “contents may have settled” warning.
Call it anything else, but calling it a “2x4” and relying on wink-wink traditional oral history to know the true sizes is irresponsible.
Actaully, the first time I made bookshelves this way I was using 3/4" A/C and I had no idea it was really 23/32".
A/C is not cabinet grade plywood.
Respectfully, I submit that if you are cutting stock before measuring it, you should leave furniture manufacture to those more experienced.
Routing out a dado, of perhaps 3/8 inch at best, to use as a support for a shelf is poor design. The inside face of your bookshelf is C quality plywood. Why bother? Why not just attach ledgers?
You are going to encounter many situations where your router bit is not the same dimension as the dado required. You just have to work around it. I will be happy to provide suggestions if you have specific problems. There are also many excellent books on the subject. Link.
Not in the good old USA. Anything over 6 inches (nominal) loses 3/4" in width.
He didn’t cut the stock before measuring it. He wasn’t making any cuts in the thickness of it, was he? He relied on the representation that the plywood was 3/4, when it wasn’t. And how the hell is he supposed to get more “experienced,” in your term, except by trying? I’m not sure why you think he should first have to experience that unnecessary, and perhaps costly, “oops!” moment caused by the mismatch between nominal and actual sizes.
Who said anything about a 3/8 dado? Anyway, I don’t see the objection. Why is it poor design, particularly if you don’t like the look of ledgers? The plywood is plenty strong enough to hold at 3/8, unless you’re storing your gold bullion on it.
Not in good old Colorado. a 2x10 is 9 1/2 inches.
I’m not in the ‘business’ but I’ve done quite a bit of building. I’m currently adding a 2 story addition to my house. I’ve never run into boards or greatly verrying widths, and non of this has ever cause me any confusion or difficulty. I’m really kinda stunned.
enipla, I have to say that if people who are actively engaged in building stuff can’t agree among themselves on whether a 2 x 10 is typically 9 1/4 or 9 1/2 wide, then we’ve got a problem, as alleged.
If he is purchasing stock to use to build furniture he needs to take a tape along to insure that he gets what the needs. That’s what the pros do.
- Start at the bottom and work your way up.
- Take a course in carpentry.
- Watch and learn from a professional
- Read a book. Follow the instructions.
Er, that would you.
Now, admittedly, you said nothing about the depth of the cut, but anything over half the dimension of the stock is asking for trouble, especially with a laminate product.
And speaking of laminate stock, it has a great deal of strength across its span, but not so much vertically. As to not liking the look of ledgers, I believe I have already addressed that, but I will do it again. If the inside face of your bookshelf is C grade plywood, It makes no sense to be fussy about less important details. Hell, he could just cut pieces of plywood to the height of the shelves and sandwich them in.
I’ve never seen a bottom chord of an engineered truss larger than a 2 x 4. Are you telling me they use 2 x 10s for the bottom chord of engineered trusses in Saskatchewan ?
In my own defence I should point out that this was 15 years ago; I know better now, and I learned doing a practice cut. Someone gave me a router and I wanted to try it out. As to why use a dado when something else will do, well, I like the look of the dado joint. And as to measuring the stock before buying it, we’re not talking about the difference between 10" and 9-1/4", or 9-1/2", but 23/32 vs 24/32, a difference of 1/32, or .031 inches. Thats a slender margin, even with a decent steel tape.
If the difference caused a problem, then the difference was significant. The reverse is also true. Blaming the problem on the stock material makes no sense. Are you saying that dadoes that are .031 inches larger than the shelf made the project undoable? What was your point, exactly?
I did not mean to denigrate your carpentry skills. I still do not understand why the joints matter in a project that has exposed plywood edges and “C” grade faces.
I am dubious, but I will take you at your word. Nevertheless, whatever the actual size is, it is standardized and consistent enough so as not to hinder building projects.
Exactly.
Sure. You get heavier bottom chords on all kinds of trusses. Spans much over 30’ usually get bumped up to at least a 2x6 bottom chord. Scissors are generally heavier chords than regular trusses of the same span. It’s been a while but I think you’d get a 2x6 bottom chord on a scissor truss at around 28’. But you won’t get up to a 2x10 without some monster span, probably 60’ or so. Didn’t make many of those, though there was a batch of 76’ monos one time - mono truss has single slope on the top chord, with the highest point right at the one end - in that particular case they were installed back to back for a 150’ total span with some monster steel I-beam running down the centre. A hog barn, I believe, though why they didn’t go all steel for that roof is beyond me. But where one sees the very heavy lumber most frequently is on attic trusses - that is, steep pitch (10/12 or 12/12 usually) trusses with webbing only on the extreme sides and top, allowing for useable attic space. In this case the bottom chord doubles as the attic floor joist and has minimal support from the webbing, so it was generally 2x10 if memory serves.
Here are the industry standards for dimensional lumber in Canada. Link.
The 9 1/4" dimension is for the width, not the depth. The depth is 1 1/2".
I think I have the answer to why I have the experience of 9 1/2" lumber and most everyone else discussing this issue has experienced 9 1/4" lumber.
Here on the B.C.coast we use unseasoned Douglas Fir lumber for building. You can’t build with unseasoned wood of any other softwood species without developing problems. The availability of dressed but green lumber is not available everywhere.
According to this B.C. Sawmill’s Website, The actual width of a dressed 2 x 10 is 9 1/2 inches. However if the 2 x 10 is seasoned, the width is reduced to 9 1/4 inches.
Contrapuntal, If you are going to get picky, at least get it right. I chose my terms based on the extremely likely orientation of a 2 x 10 in a wood frame structure. Depth is a vertical dimension only and the width is the smaller of the two horizontal dimensions.
Yes, if I go to a lumber yard I’ll specify a 10 inch width. I just can’t see specifying 2" deep lumber 
What wasn’t right about it? I mean, other than that I was unaware of your somewhat eccentric personal nomenclature? Most folks identify lumber based on the extremely likely orientation of a board when it is laying on a sack.
If a ten foot 2x10 were standing upright, would it be 9 1/4" long? How the heck woukld you describe such a board used as a rafter in a pitched roof? Way too much trigonometry for me. 