Sizing beam to carry second story floor
Michael Mastin
long. The first floor walls are to be 10 feet tall. My roof will be a 12/12
pitch to give me maximum usable area on my second story.
I know that I will need a beam that will run the entire 48 feet length for
my second story floor too. I plan to have a support at 13.5 feet, one at 27
feet and then I wanted to have a clear span in the final bay(my woodshop)
which will be a 30 foot by 21 foot. So my question is how large of a beam
will I need to carry my second story floor across these spans? I was
considering using a steel I-beam, but a glulam sounds more to what I would
prefer(provided that the glulam will not cost a fortune!). If anyone could
provide me with some solid information about the proposed beam size, I would
really appreciate that. I will be using 2x12x16 to span from the walls to
this beam too.
Best regards,
Mike
Craig Simpson
story gargage. They used glulam floor joists 16" o.c. with a doubled
central beam (2x12) running perp. to the joists. Here is a site with some
technical data:
http://www.gp.com/build/englumber/ibeam.html
I think I figured that with my 24 ft. span without the central joist it
should be able to withstand 80 lb./foot live and dead combined. The beam
probably adds to that number a little I would bet. I can feel a little
deflection if I get upstairs and jump around but I will mitigate that soon
with another vertical beam.
Craig
Larry Caldwell
Figure out what you are going to put up there. If you are going to use
it for storage, you might figure 100 psf dead load. Point loading
matters too. Where are you going to put stuff? Some slate pool tables
will weigh in at over 1000 lbs.
Dead load is more important that live load. Wood is subject to fiber
creep if it is loaded for long periods of time. Exceeding the dead load
limit can cause structural failure. Exceeding the design live load may
give you a bouncier floor than you like, but it's not likely to fail.
Standard live load for a house is 40 psf. As you can see, every time you
put your foot down you exceed the design live load on one square foot,
but nobody ever worries about it.
Once you have your load figured out, take it to your beam salesman and he
will sell you the beam that you need. Be aware that supporting a glu-lam
in the middle does not necessarily strengthen it. A middle support
changes the tension and compression distribution in the member, and many
glu-lams are built with different grades of wood depending on the
expected support points as well as loading. You can avoid this
consideration by buying three shorter glu-lams instead of one long one.
They will be easier to ship, easier to set, and probably cheaper since
you can get away with smaller beams on the shorter spans.
If head height is important you can header your 2x12 joists into the side
of the glu-lam with joist hangers. This will gain you another foot of
height under the beam.
Don't forget the mid-span blocking (or bridging) for the 2x12's.
-- Larry
Wes Gardner
The span tables/data that we use are from Louisiana-Pacific (there are
others of course) Here is their # 800-999-9105. These tables should
answer your questions, you may be able to obtain them from a local
lumber yard (probably NOT Home Despot...a real lumber yard...) For
example, if you want to use a 16" deep LPI joist and you want to limit
your deflection to L/360 you should use an 16" LPI 56 which will span
32'11"...if you want to increase your delflection (or acutally decrease
- it'll be stiffe) you can then only span 29'9"....these are placed 16"
o.c. this all assumes 40 psf LL and 15 psf DL. if you wanna place
those joists 12" o.c., you can "reach out" to 36'-3".... with deflection
criteria at L/360. So, according to these tables, you could clear span
the entire building (across the 30' dimension)...is it cost effective,
your call, don't know how much in the way the columns on the first floor
would be....
We usually consider a lawyer's office with a good (heavy) library to
need 100 lbs. psf LL - that's a heap of weight, or maybe you're going to
store engine blocks up there :-)....
My suggestion, go get the tables and do a couple of structural layouts
combining LVL, LPI and steel....you can price the stuff by-the-foot and
get a ballpark....
Wes
Wes Gardner
imposed on the structure, in other words, you and everything you put in
there like pool tables, engine blocks, feather pillows, you pick, but
regardless, this is live load, that's why in a commercial building, we
have to design to 100 lbs. psf of LIVE load to accommodate things like
attorney's libraries if that is part of the design criteria.... Dead
load is the structure itself (and the MEP, etc.)
Just for clarification...
Wes
Wes Gardner
swinging and swaying to UB40 are considered LIVE LOAD and will certainly
tear the deck down if not adequately compensated for... in our area,
this is up to 60 lbs psf.
Please do the math properly, we don't need any needless injuries
Wes
John Milton
of the beam.
Half the load of the floor will be carried by the beam, the other half by
the walls of the building, so the beam must carry 15 square feet of floor
per foot of length. The standard loading for residential floors is 40 lbs
per square foot live load + 10 dead load for a total of 50 so the load on
the beam is 50 X 15 = 750 lbs per lineal foot. To carry that across 21
feet span would require 3 pieces of 1-3/4" X 16" thick parallam bolted
together to make a 5-1/4 X 16 (rated for a total of 783 lbs per foot)
You could use a 2 piece beam rather than a 3 piece for the first 2 bays,
across a 14' span(rounded up) the rating would be 1408 lbs per foot for
the 2 together.
Last time I bought such a thing the 16" ones were about $10 per foot, all
together you will need 117' so say $1200 for the lot. Note these are
Canadian $ prices. That would be about $50 American right????? :<
Michael
Mastin (m...@intur.net) wrote:
: I am building a two-story garage woodshop that will be 30 feet wide by 48 feet
: long. The first floor walls are to be 10 feet tall. My roof will be a 12/12
: pitch to give me maximum usable area on my second story.
: I know that I will need a beam that will run the entire 48 feet length for
: my second story floor too. I plan to have a support at 13.5 feet, one at 27
: feet and then I wanted to have a clear span in the final bay(my woodshop)
: which will be a 30 foot by 21 foot. So my question is how large of a beam
: will I need to carry my second story floor across these spans? I was
: considering using a steel I-beam, but a glulam sounds more to what I would
: prefer(provided that the glulam will not cost a fortune!). If anyone could
: provide me with some solid information about the proposed beam size, I would
: really appreciate that. I will be using 2x12x16 to span from the walls to
: this beam too.
: Best regards,
: Mike
Michael Mastin
jmgno14...@frontiernet.net says...
>
> BTW, why do you want 10 foot side walls? Are you going to park
> a semi-rig inside one of the bays?
Matt,
The 10' side walls are to increase the ceiling height which will allow
me to handle plywood and long lumber in my wood shop easier. My truck
with raised camper shell on it is really tall too.
> Also, at 12 / 12 pitch, with a seven foot ceiling in the second floor, you
> will still have over 16 foot long tie stringers in you roof. Maybe you
> should check out having prefab roof trusses made with a short
> side wall height as well. This would widen the usable space in the
> second floor if done properly, and still probably cost less than
> a conventional rafter and cross tie framing. Say a side wall of 3 feet,
> combined with a truss framed with a four foot minimum clearance for
> as wide a space as possible. You may be able to add another 6 to
> 8 feet of width to the second floor room.
>
> Matt
>
Matt
Michael Mastin <m...@intur.net> wrote in article
<8b63tn$90v$1...@tilde.csc.ti.com>...
> I am building a two-story garage woodshop that will be 30 feet wide by 48
feet
> long. The first floor walls are to be 10 feet tall. My roof will be a
12/12
> pitch to give me maximum usable area on my second story.
>
I agree with some of the other postings that you should consider
engineered lumber for your floor joists instead of 2x12s. You can
easily clear span 30 feet with engineered lumber, and done properly,
you can get a much stronger second floor in the deal.
BTW, why do you want 10 foot side walls? Are you going to park
a semi-rig inside one of the bays?
Also, at 12 / 12 pitch, with a seven foot ceiling in the second floor, you
HOUSE
Glue lam was 21" deep and the I beam only 8". A 20' glue lam. was
over $300.00 with no colums .$240.00 bought 40' of I beam .so
gave me the colums as well.
Consider going an extra two feet on your walls and using a
steel truss.
If I ever build another house I'll use a ten ft. basement
and steel truss floor joists. OPEN SPACE and room to put plumbing
and duct work.
At the cost of wood today check out steel.
Terry
* Sent from RemarQ http://www.remarq.com The Internet's Discussion Network *
The fastest and easiest way to search and participate in Usenet - Free!