First a little history… I’m bulding a house which the second floor spans 20′. The plans called for double #1 2×12, 16″ OC with double rows of cross bridging (2×2). They sent #2 2×12, which were installed. The size differantial in the #2 is causing me to furr the ceiling down with 1×4 & shims to get a level playing surface for the GWB. Any place I put a 4′ level on the bottom of the joists, i could rock the level a 1/4″ or more on the low spots.
The questions are… Is #1 stonger than #2 if spieces is the same? Also is Canadian spruce, #1 grade stronger than #2 hem-fir? By stronger I mean better able to support the load with minimal deflection. Is #1 more constisant in dimension?
Replies
#1 lumber has higher design values than #2 in all species of lumber.
I don't think the grade has anything to do with the final dimension tolerances.
IMHO, 2X12s should never clear span 20'. If there's anything you can do to change this, I would suggest doing it now before the house is closed up.
No 1 should have little if any knots and usually very little warpage. This could help on spanning because they will be less likely to split.
If there was ever a case for web joists this would be it in my opionion.
ANDYSZ2WHY DO I HAVE TO EXPLAIN TO FRIENDS AND FAMILY THAT BEING A SOLE PROPRIETOR IS A REAL JOB?
REMODELER/PUNCHOUT SPECIALIST
The biggest difference between #1 and #2 framing lumber is the size and amount of knots and defects. None of the lumber yards I've ever worked with separate their common framing lumber like they do with pine boards. Truss manufacturers will specify grades in the various members of a truss but ordering a stack of all #1, 2" x 12" from the lumber yard would require a special order.
Lumber is not perfectly straight regardless of the grade. Standard procedure for carpenters is to sight the pieces and place the crowns up. If your floor was framed with crowns up and now you are seeing a sag, the lumber can't support it's own weight. 20' is a long span for 2" x 12" at 16" OC. That is the spacing and size for a 16' span. 12" OC would be the minimum for a 20' span. Although this may carry the weight, the deflection can be more than desired. Many will opt for a TJI or floor truss system in long span applications.
Putting a small level on a joist isn't going to tell you anything, other than there may be an un-straight section on the board. Most good carpenters will not use badly warped framing. The bowed or warped pieces get set aside and cut up for shorter pieces, if possible. I'd guess, the framers didn't pay any attention to the lumber and just put it up, some crowns up, some down. Chances are, you will have problems with bad corners, uneven framing at openings and studs that cause a bow in your walls. I think, if you sighted down the top of individual joists, you would find some up and some down. You could simply pull the nails and flip the down crowns, up. I would change the OC spacing to 12".
Spruce, hemlock and fir fall under the same grading rules. Most of the framing lumber these days is spruce. The #1 designation generally means there are only a few pin knots. The grading rules are very specific about the size and number of knots. A knot free board is considered stronger since there is a limited number defects that may cause failure under load. #1 is the same size as #2 or #4.
Beat it to fit / Paint it to match
Thank to all for your wisdom. All mentioned 2x12 @ 16 OC was to much span. All joists are doubled and a couple are 4 wide and one is 5 wide! This is a Canadian kit home purchased by the owners with a complete design. I also questioned the span and should have posted the question sooner. Now the roof is on, the in floor heat, plumbing and electrical is complete and the drywall is stocked, so adding of flipping is not an easy option. The framers did a good job, but as most monday morning quarterbacks, i can see where improvments could have been made. I also prefer TJI or BCI or floor trusses, but when the engineer says it will work, i guess i get an education and the homeowner gets a substandard house. The floor makes the ceiling of a 20x24 living room, so a beam or post is not an option. I think that if the kit specified #1 and they sent #2, they the kit folks have some MAJOR adjustments to make. Thanks again to all.
If that isn't the ideal use for TJI's, I don't know what is. 11-1/4" TJI's at 16" OC should easily span 20'. That's what should have been speced.
At the very least, you should get the kit company to put it in writing that #2 is OK and they accept liability for the change.
The best way to deal with crowned joist stock is to set them up side by side, get them all crowned upward, and sort them from straightest to crownedest. Put the straight ones at the ends of the room, working gradually to the highest crowns in the middle.
-- J.S.
stik.... the only way i've seen framing lumber sold is like this
"#2 or better"....... in that lift i would get a percentage of # 1 and most would be #2
if i wanted only #1, i would have to go to the lumber yard and cull the lift ( if they would let me , which they probably would if i had a special problem )
other than that i would design my project to accomodate what is available..... looking in the IRC 2000 code for floor framing... 40 psf, 10 lb. Dead Load
if i go down the column looking for 20' span,
i find 2x12 S-P-F, #1 & #2
both spanning the same @ 12" OC....20'7"
all of the tables show the same thing.... same rated spans for #2 as for #1 in both DF & S-P-F
in Hem-Fir & Southern Pine they have different values for #1 & #2.
so in some species, the design rating is the same for #1 & #2, in other species it is slightly differentMike Smith Rhode Island : Design / Build / Repair / Restore
Mike, what is the SPF code mean? I wish i would have been in on the design, as i would have used TJI's. Thanks for the info, John
S-P-F is a species stamp.. it means Spruce-Pine-Fir.. and they don't care ,they consider them the same as far as strength goes
most of it around here will actually be Spruce
DF means Doug. Fir, which will usually rate the highest in terms of the span tables
Mike Smith Rhode Island : Design / Build / Repair / Restore
not to brag Mike, but locally , we have ONE yard that stocks #1 framing lumber. I have to drive 25 minutes or so to get it--------but it's worth the drive.
SYP, 2x12--------12 feet long---MAYBE a single knot in the whole piece the size of my little finger nail( smaller than a dime)---maybe not even that.
also----had been buying redwood 2x4 for another project from another yard over several years---noticed they were having ever increasing amounts of sap wood and the grain was no longer vertical--as it originally was just a couple years ago
checked out the yard with the #1 framing lumber------------who told me they were no longer carrying redwood for the same reason----but they DID have clear, absolutely vertical grained cedar, 18 feet long 2x6. I still have some of it i am saving for my own projects--------- gotta say, I didn't feel entirely worthy to cut or mill it at first.
please don't tell me what enviornmental nightmares may have occured to bring this stuff to market--- I preferr to remain willfully ignorant,LOL
Best wishes, All, Stephen
your concern reminds me of my very first job on my license about 34 yrs agoa guest house / garage combo with 20 foot span
then there was a construction grade stamp that would have been a bit superior to 2 & better
construction grade 2 X 12, 12" OC, blocked every 8' / I was thinking it was 22' feet but after reading Mike's span readout maybe it was only 20'all sheathed & roofed, helper digging wastelines & I'm off to pick up 14" exposed sidewall shingles
couple hrs later I'm coming down the driveway & they are loading the 47th piece of sheetrock through a dormer right in the middle of that span!
very little sleep that night & my only salvation was the hangers were on it first thing in morning
my heart just about stops to this daywith the doubling you have nothing to worry about
Thanks for your input. We also have GWB stocked against the end wall. I would assume that doubled joists @ 16" is the same or better than 8" oc.
It sounds like the carpenters didn't put all the crowns up when they framed the joists in. But that may not be your only problem, It is a long span, probably maxing out general spects. Manufactured floor trusses or at least west coast fir should have been uses on 12" centers. You need to get some decking down and go jump around up there and see if you get significant bounce, which you don't want. If you feel that you need to beef it up a little to get rid of the bounce, then go ahead and add another 2x12 as a sister and put in solid blocking every 4'. that should stiffen it up. Of course I don't know what is going to go on upstairs. but if you get a lot of people up there some day for some reason you could have some problems with excessive deflection.
Ohio vs. Michigan??
Oh sorry, carry on.