OK, now lets talk about the affect of Kiln and Radio Frequency Drying vs. Green as it relates to actual dimensions!
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Hi @medeek
That’s seems like a very useful resource to have. I need to try and find the UK version.
Mike
It was mainly the principle really. It’s the same with quoted size of 50 x 100mm. It’s not actually that size.
I think the issue is, some Timber Merchants list the actual size in Brackets whereas some don’t.
I just don’t see why they can’t just use the finished size and forget using the size which is not the finished size.
I take your point and am not sure myself. I suspect it is because they may not always know exactly what size it will be and don’t want to be caught by someone saying it was listed as 47 x 95 and it actually was only 45 x 93. Better to call it something more standard and acknowledge that it is only a generic dimension. But I admit I’m guessing. Maybe it could be more accurate if all timber were kiln dried and free of further shrinkage (but then if it was exposed to moisture again…). The problem doesn’t occur with steel.
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Now there’s a thought… Build shed using Steel. No bugger will steal anything from it 
I guess it’s just one of those oddities then. When I can eventually get to the Timber Merchants I’ll see if they have a definitive list with sizes, (and prices, as I can use that information in Estimator for Sketchup).
As it happens, I alway prefer to go there and choose the timber in person. I guess it’s because it’s not something I do regularly that I need a reference list to refer to when modelling.
Simple. It started at the saw mill. When you had to cut a 2 inch slab, you set your depth to 2 inches. The actual thickness cut was the 2 inches minus the saw blade cut. It is less than 2 inches but retains its nominal size. Planed strip wood still retains its nominal size but it is reduced even further at the planer.
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Finnish sawmills define their standardized timber sizes as having a 20% moisture content. 100 mm sawn becomes 98 mm as “dimensionally accurate” and 95 mm planed.
I was always told, and this could be 1000% wrong, that the dimension was 1/2" less for “convenience” when laying out the exterior walls of a house. A 2" x 4" stud only measuring 1 1/2" x 3 1/2" turned out to be an even 4" exterior wall once you put a 1/2" gypsum board on the inside of it. Then all of your interior dimensions came out at a convenient whole-inch measurement. Probably had a lot more to do with the lumber industry sneaking an extra 1/2" out of every board, adds up over millions of boards.
The proper answer on the difference between nominal and actual sizing has been given above: the nominal size is (or was) the rough cut size at the mill, before dressing (planing) the board.
It’s not a function of the lumber industry trying to screw unsuspecting carpenters, and as was noted above, hardwoods are still (and mostly) sold rough-sawn by the board foot, with minimal difference between nominal size (in 1/4’s) and actual dimensions.
I also don’t understand the OP’s frustration: anyone who works regularly with lumber quickly figures out nominal/actual sizes and it becomes a total non-issue.
There might be even more of a problem if nominal sizes where dispensed with, due to the natural dimensional variation in batches of green lumber (typically ~1/16). Can you imagine how pissed certain customers would be if they measured their 1-1/2 x 3-1/2 at 1-7/16 x 3-9/16?!
For rough framing these variations aren’t critical, and for fine woodworking rough-sawn lumber is always planed and sawn to finish size/thickness by the woodworker.
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What about the metric system? The Devils work if you ask me.
Only in the sense that it’s a devil of a sight easier, surely?
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Since this is about both trains & timber I’ll bite…
Shay locomotive Wendling ca. 1912|690x493 .
This Shay engine was named, “2 Spot”. These narrow gauge trains were the method used to move logs down from the Cascade mountains to the central mill. I’ll have to re-find the gauge of these trains. The loggers family houses were the width and length of the flatcars on which they were moved to each new “show”.
My mother said that their house up in the “Camps” was 7’-8’ wide so the track gauge might be just over 50".
For anyone worrying about paying for wood you can’t touch; Logs are sold here by the Board Foot Measure, starting in the woods. When you or I buy either logs or S4S ( Surfaced 4 Sides ) 2x4’s we still pay using that old BFM formula.
Our unique Canadian 2x4 is usually planed twice ( ± ⅛" ea. ) on both sides/edges after it’s dry to 18% ±. The missing ½" goes to the drying & planing, no one in the woods or the mill is taking that extra material home in their lunch pail !
As has been mentioned here by others, ordering wood by the quarter, 5/4’s, etc, is the way to get higher quality wood at nearly the same price as HomeDepot offers the dregs.
It’s no big deal. It’s rough sawn lumber sizes. But if you can’t get your head around that just consider it a name of the product you are buying. It’s a “2 by 4”. it’s a “2 by 6” it’s ’ Michael" or a “Bob”. It doesnt have to mean something if you don’t want, it’s a means of identification.
Hello Mike:
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Instead of you telling the mill to custom plane rough sawn 2X or 4X framing lumber for your order, giant softwood mills grow trees, cut logs, saw them to rough full dimensions, stack to air dry then kiln dry then plane the boards to a mostly uniform dimension. This cheap, soft, fast growth spruce and hemlock has to be processed to become usable. You pay based on the board feet of the lumber before milling, so a 2 X 12 X 16 feet long is priced from the mill to the lumberyard based on thirty-two board feet, even after processing to 1-1/2" X 11-1/4" X 16’ (or often, 16’-1" +/-), although the lumberyard may only show unit pricing per piece.
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English speakers generally avoid unnecessary syllables, such as would be required in saying “inch and five eighths by eleven and one quarter” requiring 12 syllables, opting instead to simplify to the three syllable “two by twelve”. “Hava cuppa?” instead of “Would you care for a cup of tea?”.
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When framing lumber came from old growth, dense vertical grain Douglas Fir, which was straight and stable, it was left in its rough state, only air dried and then lathed and plastered during construction which enabled the plasterer to accommodate any small irregularities with lath and plaster. Now very uniform framing is covered with gypsum board and the odd wanky board is cut into blocks or used for bracing, not where gypsum board attaches.
If you ever get to re-use full dimensioned rough sawn lumber from over a hundred years ago, you will be shocked at how substantial and solid it feels compared to modern stud, joist and rafter material.
I know that this convo is related to lumber sizes, etc., but I recently had to remind myself about the differences in Troy versus Avoirdupois weight systems. A Troy ounce of gold (31.103 grams) weighs more than an (Avoirdupois) ounce of feathers (28.349 grams). However, a Troy pound of gold is only 12 Troy ounces (372.2 grams) whereas an Avoirdupois pound of feathers is 16 ounces (453.60 grams).
I assume that the jewelers and precious metals commodities folks like it this way.
That because of the added weight of the chicken.
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The lumber still warps after installing and will be planed in place and have paper shims added to level it before drywall is installed. In the worse cases the stud is cut and another crippled beside it.
Loved this post. Fabulous, interesting and amusing.
Steel sizes are not definitive either. If you look up the actual dimensions of a 152 x 89mm x 16 RSJ, you’ll find the width and depth are actually 152.4mm x 88.7mm.
The difference between nominal and actual dimensions are less than those for timber, but that’s understandable, as steel tolerances and shrinkage/ expansion are presumably much less than those for timber.