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wayne wayne is offline
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Default Floor Joist Beam Spans

You will need to have it engineered and they will tell you what you
need to do. In order to get a permit you will need plans and the plans
will need tom have an engineers stamp on them! If it is not required
you should still get it done or at least approved by a PE.

That said on This old house they had a span they needed to raise the
ceiling on. They cut the joists from 12 to 10" and bolted steel plate
cut to size they also had sag and used the edge of the steel to judge
when the floor was level using floor jacks to jack the ceiling. I
would think with the steel plates on both sides of 2x12's you should be
fine. But the snow load will also have an effect as well as the roof
pitch!
I had a barn built with a 60' clear span. it had 2 with beams bolted
together.

Engineered trusses should take care of it for you

More than you ever wanted to know

http://www.alpeng.com/wood_truss_info.html

W

James wrote:



I plan to build a small garage, 20 feet by 30 feet. I want to be
able to span the 20 foot width, so that I don't have to use interior
posts.

At first, I was doubtful this could be done, and I have seen comments
in these groups that this is not really feasible. Yet, I have
closely inspected one of the yard sheds (with loft) at Home Depot,
that is 16 feet wide, using 2 x 10 beams on 12 inch centers.
It is a yard shed, with a small loft. I went up into the loft area
to see what "bounce" the floor had, and it is quite solid, with just
a small hint of a bounce (I weigh 215 lbs). So, I have concluded
that spanning 16 feet with 2 X 10's is easy, as I have seen it.

But, I know that going from 16 ft to 20 ft wide is 4 feet more
of span and is 25 % more of a span. I am a novice, but I try to
find answers for myself first. Somehow, I got a span table for
Southern Pine lumber. The title of the chart is

Maximum Spans: Souther Pine joists and rafters .

This is the full name.


The chart also says: 40 lbs psf live load/ 10 lbs psf dead
load/ 240 deflection / cd = 1.15

I plan to use the loft only for very light storage, but these "load"
figures seem very low to me. But, once again, I have "felt" what a
16 ft span using 2 x 10's feels like, and it seems very sturdy
to me.




From the chart, it appears that a # 2 visually graded (is that
what you "usually" find in lumber yards and the big box stores??)
2 X 10 beam on 12 inch centers will span 19 ft, 11 inches.


A 2 x 12 beam on 16 inch centers will span 20 ft, 2
inches.

-----------------------

Questions: First, am I on the right track ? Does the chart seem
to apply to my needs and plans? I could email the chart (pdf
format) to anyone who wanted to look, I don't think I should post an
attachment here on a news group.

Is #2 visually graded, the most common lumber found in lumber yards ?

Which would be better, 2 x 10 on 12 inch centers or 2 x
12 on 16 inch centers ?? It seems that the latter may be a bit
cheaper, but price isn't the primary concern.


What happens if you use a 2 X 12 beam, but put them on 24 inch
centers instead of 16 inch?? Do you simply get more deflection, and
less load capacity ?

I know I could use an engineered beam, but I don't want that.

Thanks for any tips, experience, and advice !!!!

--James--