Working on the design of an addtion to an existing colonial.
The customer wants the addtion to be 16 by 22 feet, 2 floors. 1st floor is wide open family room. 2nd floor is a master bedroom
The existing house is framed with 2×8 floor joists.
I have figured out the framing systems for the roof, 2nd floor ceiling and 1st floor floor. But the 2nd floor floor is a bit of a gotcha.
To keep the floor levels the same it needs to be 2×8 framed. From the Massachusetts code book. Standard SPF2 lumber 12 in O.C. will only do 14′ 11″.
You can’t seem to buy 7.25″ I Joists. My crazy idea of the week is to frame it in 2×8 PT lumber. From what I understand PT here is Mass is basically Southern Pine. Using these tables(Southern Pine No.2) I get a span of 15′ 7″, just enough for this room.
This fact that Southern pine is stronger that KD SPF I have seen confirmed in sizing numbers I have seen done for decks.
Has anyone ever seen it used on the inside of a house???
Replies
you can't get SYP untreated in 2x8 there? Hmmm..get 2x10 and rip em?
The sopping wet treated stuff is (A) not select stuctural (B) gonna crawl all over as it dries out. (c) nor what I want in my house if I had a choice, given the fastner constraints and toxicity being unproven.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
It's interesting that the Mass Code and it's interpretations allow longer spans with PT than with KD.
Don't actually disagree on the thought of not having it in my house but?
I have a copy of BeamChek software, but I a not stuff it can do what you describe.
eg. a floor with a LVL every 3 ft and two 2x8's in between??
It does tell me that Double 2x8's on 1 ft centers works for that span. Kinda of wierd but might be the cheapest way to do it?? Almost a butcher block floor!!
keep reading, it's been yrs. since i did real framing, I was just giving a WAG and opinion.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Even with doubled up 2x8s,you'd better watch out the HVAC and others don't cobble out big notches for ducts/pipes.
I didn't do it....the buck does NOT stop here.
>>
It's interesting that the Mass Code and it's interpretations allow longer spans with PT than with KD.
<<
It's not the fact that it is PT or KD, it's because SYP is stronger than SPF. East cost PT is usually SYP.
All:
I think with many people there is a general misconception about I joists being able to span much further distances than same height dimensional lumber. The advantage to I-joists is that they come in wider(taller) sizes than conventional lumber commonly does.
Matt
Edited 12/26/2004 8:36 am ET by DIRISHINME
No biggie Joe, it was buggin me how 2x8s would match up with 2x10s. As you said, big differance between re-model vs. new. Had a 'fire-job' this summer...a small ranch with full basement. It was simply a brick shell with no wood, period. The only thing left was the non-drilled steel Ibeam running the length of the house.Oh boy.
I didn't do it....the buck does NOT stop here.
And that they are lighter and straighter
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Boise Cascade, and maybe Weyerhaeuser, offer free design sofware for their engineered joists and beams. I doubt 2X8 is going to cut it, but you might develope the option of some paralams or small lam beams interspersed.
There was also a thread a year of so ago about build a shallow floor system that was just an oversided box beam with shallow joists with plywood glued and nailed top and bottom to create a diaphram with great strength.l
And forget the PT. As someone mentioned, it's squirrely and most is course-grained and probably wouldn't have the strength listed in the span tables. (Often, the treating process weakens the inherent strength of the lumber as it's processed. Just for future reference, when using PT in a stuctural application, regardless the species, always opt for the lowest listed values).
How about a 7 1/2" steel I-beam to split your span in half? Or maybe a single/double flinch plate beam?
I didn't do it....the buck does NOT stop here.
Hadn't done the calculation on a steel scenario. Just tried it and it might be the way to go. Two 7" by 3/4" Flitch plates in a flush framed center beam achieve a floor with L/540.
I just hate to pay an engineer $300 just for his fancy stamp in order to use steel. It really is a funny thing that the wood companies give the stamp away but the steel guys don't.
But in the end this may be the way to go. A bit more labor, but even with that and the engineering stamp I bet it will be cheaper than framing the floors in LVL's.
To be honest, if I could find away to get the floor by the BI using conventional lumber barely at a L/360, after inspections I was thinking of adding a 2-4 3/8"x 7 Flitches to stiffen it further for the customer.
I can see a few of use on this site, have finished playing with their new tools and back to surfer the web!!(got a Makita 14.4 impact driver, where has that tool been all my life, 3" deck screws melt thru wood!)
Thanks to all for the ideas.
Thje only way you can span that in 8" depth is with LVLs or sticking a flush beam in there
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Spanning 16' with 2X8s is nuts. I wouldn'r even do it with 2X10s.
You can use 2X12s (or I-joists) and keep them flush at the top edge. It will be well worth losing a bit of height in order to keep from having a bouncy floor.
Break the span in two, run a 6WF12 across the center, bolt the webs full of SPF out a little proud of the flanges, and hanger your 2x8s flush. No problem. Be sure to pack a little column action into your walls at the bearing points of the steel beam.
Nice stiff floor, built one this way as part of a second floor deck, just last year.
Toolin,
I've framed it seems like a million houses and additions with 2x10 doug fir 16' spans with no problems or bouncing what so ever. Some houses we've gone 12' centers some houses we've gone 16' centers an sometimes we've gone 16' centers doubling every other one. This is all specked by Architects or Engineers depending what walls are above just keeping the tops even and cutting down 2" or so off the first floor ceiling height.
Obviously your getting different advice from people but we do it all the time and never had a problem so it can be done without steel or putting beams mid span. If you don't trust the 2x10's then go with 9-1/2" I-joists. Whatever you do forget steel beams mid span just loose the 2" or use 12" I-joists and loose 4" which I think is crazy because a 9-1/2" beam always works around here and I'm no Architect but this is what I've framed plenty of times again with no problems.
Joe Carola
Edited 12/25/2004 9:49 pm ET by Framer
Joe, if you simply cut 2in. off 1st floor studs you will still have that 2in transition in ceiling. When standing in existing house,looking out into addition, there will be two ceiling hgts. A 2x8 and 2x10 'flush on top' as you said. Maybe I'm missing something...
I didn't do it....the buck does NOT stop here.
Your right if the whole existing wall is coming out there will be a 2" drop but he didn't say that. If that's the case he will be putting steel or something else to replace the whole wall he's taking out. If they want all flush ceilings then they either use 2x8's and break the span with some kind of Flush 7-1/2" beam mid span and at the existing house line or use 2x10's and fir down the existing ceilings.There's a lot of different scenarios in remodeling but in his case where he might just be removing a existing window and installing a new dropped header or Archway for a new opening the 2" difference is acceptable for the Architect/GC/Homeowner.The addition I'm working on now the owner decided to take out the whole 22' basement wall and wants a flush ceiling and the Architect came up with a rectangular piece of steel that is 8" in height and 20" in width with 2x10 joist that are going to be hung on ledgers on both sides of the steel because there's also a 2nd story addition coming off the back wall that this steel will be holding up. Homeowner wants FLUSH ceiling so he will get it at his COST.There's a million ways you can do things when it comes to Additions and I know you said somewhere your starting to do additions. It's night and day to compared to new framing.The point in my first post was that I always read guys saying that 16' span is no good for 2x10's when I say that I am no Architect or Engineer I've Framed a lot of house and additions over the years using 2x10's Doug fir @ 16" centers with bridging mid span and we still do it as I described in my first post with no problems and no bouncy floors. Why put girders mid span or steel mid span when you don't need it if you can just double up every other one or go 12" centers. That's my opinion.Joe Carola