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RE: Residential Floor Framing [DUMB]

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> Okay, it's been a few months since I've submitted a
> characteristically "dumb" question, so let me make
> up a little for lost time.

It's only a dumb question if the answer is staring you in the face before
you ask it, and you ask anyway.

> The designer didn't seem to worry about bearing walls
> lining up, either (is that typical these days?) so I'm
> actually supporting walls on the floors themselves,
> and it's kinda hard to see which of them are going to
> be transmitting roof loads-you mean I actually oughta
> finish the roof framing before going to the second
> floor? Do tell!

It's not necessarily typical, but it happens when the "designer" doesn't
know what he/she is doing.  And they get away with it because most
residences never see full design loads.

> Anyway, I'm sort of going at this in my customary
> Attention-Deficit, non-linear fashion, which is kind
> of how I figure out how things go together. The guy
> only gave me exteriors and floor plans, so I've had
> to do a lot of surmisin'.

Is there another way to design???

> Anyway, the builder is adamant that we stick to No. 3
> So. Pine exclusively, which is okay by me, but I've
> got a question about what variable to "hold" and which
> to "vary."

SYP No. 3 is pretty crappy stuff for joists.  Lots of knots and warping, and
the floors will squeak like crazy.

> 1) In the opinion of the group, what is the priority
> among depth, no. of plies, spacing and grade when you
> are specifying sawn lumber floor joists?

I always try to keep a uniform depth, spacing, and grade.  2x10's @ 16" o.c.
appears to be the universally preferred floor system locally.  If I need
extra strength I'll add double joists at 48", 32", or 16" o.c. before going
to tighter spacing.  I have a simple spreadsheet that I print out with each
job that calcs the max span for 4 custom load cases and 6 joist spacing
configurations (singles @ 24" to doubles @ 16").  I'll send it if you want
it.

> 2) How do you allow for different depths, if they vary?
> Is it better to notch ends, build up ends or just stick
> to all the same depth of joist because the relative cost
> is minor compared to the labor involved in notching,
> providing seats, etc?

Try to keep a uniform depth throughout a level.  That way all stud lengths
are the same, and the top plates all line up.  It will (probably) be cheaper
to make all the joists the deepest required and NOT do any custom cutting -
you're begging for over-cuts, massive cracks along the grain, and potential
shear failures.  If you HAVE to have a deeper beam or two in isolated areas
do not notch your beam.  Instead, cut your top plate and have the beam sit
on extra bearing studs, then repair the plate with metal straps.

> 3) What weight to you use for supported partition walls?
> Can you support them without blocking at the location of
> the wall?

I use 8 psf for non-load bearing walls.  Also, I specifically require that a
joist NOT be located directly under the wall to avoid problems with plumbing
and electrical runs.  Load-bearing walls will probably require either an LVL
or steel beam if parallel, and solid blocking with multi-ply joists if
perpendicular.

> Oh, one other thing: Does anyone have any plans-I don't
> care if they are CAD, PDF, anything-that they wouldn't
> mind letting me have/look at? None of the "go-by" plans
> I have from the builder are worth a cr*p, because
> engineers here don't typically-NOTE I DO SAY "TYPICALLY"
> -do a very good job of producing structural framing plans
> for residential. I want to see what some of you guys are
> doing because I have respect for your diligence.

Unfortunately, not for single-family residential and not with sawn joists.
Most of my rare wood projects are large multi-family apartments with
engineered floor joists (plated wood trusses are the current favorite).  The
spreadsheet I mentioned is for "extras" like decks, breezeways, and stair
landings.

---
Jason Kilgore
Leigh & O'Kane, LLC
Kansas City, Missouri



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