## First floor framing question

Started by TarMetto, January 13, 2017, 08:51:14 AM

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#### TarMetto

Trying to figure out how to frame the first floor. We have a full perimeter block foundation with 2 rows of 5 piers within the footprint that are 6.6' on center both ways. Piers
are at the same elevation as the perimeter block.
I have attached a pic of what I "think" is correct, but looking for guidance. I'm wondering if I should double the ones that sit atop the piers that all of the other joists attach
to? Pic shows 8" wide piers but they are actually 16" x 16".

#### Don_P

In a crawlspace I'll usually make the piers lower and run those girders under the joists, no hangers.

To size the girder you can look to the prescriptive tables but your spans are off the low end and the configuration is a little different than the tables. Each girder is supporting half of the joist to its left and half of the joist to its right, tributary width is 6.5'. The girder spans 6.5'... 6.5' x 6.5'=42.25 square feet of tributary area supported by the girder. Dead load is assumed to be 10 pounds per square foot (weight of materials)+ Live load is the weight of people and stuff, 40psf. Total design load is 50 psf x 42.25 sf trib area=2112.5 lbs total design load on a girder spanning 6.5'

This is not official, but it is right
http://www.timbertoolbox.com/Calcs/beamcalc.htm
span 78
width 3
depth 7.25
Fb 1000  These 3 entries roughly correspond to #2 SPF or SYP, garden variety framing lumber
E 1.4
Fv 135
Hit "show result"

that was a double 2x8, buy 14 footers and weave the breaks in the 2 plies over the piers.

#### TarMetto

Thanks Don. Is that data good for my situation where the joists will attach to the side of the girders with hangers since the piers are at the same elevation?

I still wonder though, with such short spans, could I use dbl 2x8's for the girders, and full length (joints over piers) sill plates (secure sill to the bottom of the girder in the short span between the piers with timber screws) and have that sill act as a ledger, eliminating the need for joist hangers?

#### Don_P

Yes that will work for either a dropped or flush girder
Never ever.
You can make the girder deeper than the joists and use a 2x2 ledger to rest the joists on, generally frowned upon, the 2x2 rolls off rather than shearing. A 2x4 would make a better ledger