Did I miss something, 2x4 question

[RogerMcAllen]

Now my whole life, I was under the assumtion that a 2x4 was 1.75" by 3.5". This makes sense becacause two the tall way next to each other should be just as wide as one laid the wide way.

I recently joined a research group, and the wanted me to construct a soundproof box. I figured the easiest thing to do was just to build the box like a stud wall, and insulate the inside. I decided to make the box exactly 4' tall to make sheeting it easier. Since I decided to be slick, I just subtracted the height of the top and bottom plate from my stud height, which left me with 44.5". When I finally got my wall together, I noticed that it was .5" short. On the upside, I just told the professor that this was because I planned ahead, since after adding my 1/2 sheeting the box came out the pefect 4'. What's the deal, I know it has not always been this way. Have you ever come across skinny boards?

[loganj]

I've seen 2x4's as much as .25" off in thickness...especially boards from the big chain stores. When I want really good lumber, I always go to the local sawmill and pay a little more. Anytime I do go to Lowes, Home Depot, ect..., I'll spend a half hour picking through the pile to get a few good boards.

[RLG2182]

Standard pine will be .5 inches off. Pressure treaded pine (the green ones) will deviate in size as well. This is due to the original cut that is made with mill blades, and shrinkage after drying time. A 2X4 will generally be 1.5x3.5 give or taka a few mm. These are the measurements I use when I draw my blueprints for anything, and have never been off. (I hug my architecht's ruler every night... lol)

If you make the length cuts yourself, obviously they'll be what you measure them to. But if you need a 2x4 piece that's TRULY 2x4, you'll have to join 2 milled pieces, or merely take the size difference into account with future measurements, and add material to compensate. Redwood and oak are more precise... but then again... who would EVER use oak to make a 2x4??

[jsoong]

I think lumber had shrunk in size over the years .... prob as a way to save the sawmill some money.

In my old house (built 1950), the old 2x4 is 1.75 thick, but 2x4's in the last 10 or more years is 1.5"x3.5", give or take 1/4!

I think the standard measurement for 2x lumber is now 1.5". If I have to make headers to fit the width of a 2x4, I always have to add spacers to make up the difference.

[acronym:495a4ccde6="By the way"]BTW[/acronym:495a4ccde6], hardwood is not much better either. A 1" hardwood board can be 3/4 or 7/8, and 2x hardwood is now showing up as 1.5", even if not dressed. Moral of the story, always measure the wood & make adjustments to plan before building. And for fine furniture, you pretty much need a thickness planner to get boards all the right thickness.

[RandyStacyE]

The easiest way to create a soundproof box is exactly like you were saying (like a stud wall) then instead of using typical insulation, etc... you should use SAND.

Everyone has heard of Winchester (the gun manufacturer). Well they soundproofed the entire Winchester Mansion this way because it is truely 100% sound proof. I recently learned this myself.

[Mazdaman]

first off never buy any construction grade lumber where it is stored indoors. Lumber is kiln dried to have a specific moisture content (approx. 19%) when it is stored indoors it either gains or losses this moisture (depending on building condition) That is why they are always bent, twisted or warped.

no matter what side "stud" you buy they are always half inch less than stated.
2x4 - 1.5x3.5
2x6 1.5x5.5
and so on.
However most plywood should be exactly what is stated
4x8 - 4x8

If your looking for the reason why it's simple. The "stud" started at 2x4 but after sending it through various plainer to get the boards "straight/smooth" on all 4 sides it ends up being half inch smaller.

Construction engineering technology graduate and new home sales rep

[jsoong]

Originally Posted by Mazdaman

However most plywood should be exactly what is stated
4x8 - 4x8

The plywood may be 4x8 in area, but the thickness had shrunk. A 3/4" plywood is now at least 1/16" thinner ... when 10 years ago 3/4" thick means just that.

Just the other day I put up a 2x6 header & guess what, it is only 1.5 x 5.25". ... so I can't even trust the 1/2" less than nominal rule.

[skipm]

Actually if you pay close attention to the plywood you buy the stuff they sell as 3/4" is usually something like 23/32". That is why if you use a 3/4" router but to make a dado the dado is kinda loose. Skip