On Jan 11, 4:58*pm, "BETA-32" wrote:
Thanks for doing those calculations etc.
You wrote, "What are you trying to do?" *Here's the story:
I have a contractor doing vinyl siding on the front of a house I own. *The
house has an open 14'x6' overhang over a similar size concrete area which
creates a front porch. *The porch had 3 wrought iron support posts across
the front -- one center, and one on each corner. *The plan was, and is, to
replace the 3 wrought iron support posts with one steel column on each
corner.
After taking off the old vinyl that covered the porch overhang, it turned
out that what was there was 3/4" plywood on top, double (sistered) 6-foot
2x4's (16" on center) running perpendicular to the house out to the main
cross beam, and a main cross beam of I think two 2x4's sistered together or
1 2x6 (I forget which). *The contractor changed the front beam and side end
beams to 2 2x6's sistered together and said he did that because there was
now a 14-foot span in the front. *The result was a span which looked to me
like it may have a very slight sag in the middle, but I wasn't sure.
The building inspector came out to do the framing inspection before it was
covered up by the new vinyl. *The first thing he said is there is a sag in
the middle that he could see right away just driving down the street while
approaching the house. *Then he said he thought it may be "under span" and
measured that the span is 14 feet. *He said he would check whatever
reference chart he had and said that using 2 2x6's is insufficient for a
14-foot span.
I had no reason to doubt the building inspector, and he was very reasonable
about everything and explained how snow on the roof etc. could create
problems. *The reason I posted the question is that the contractor seemed so
confident that he was doing everything up to and exceeding code. *I am
waiting for a call back from the contractor, and there is no question that
he will fix it so the inspector can approve the job. *In the meantime, I
wanted to see if I could find out more information about what should be
there to be correct.
Now, after reading the feedback here, it looks like I need to start over and
have the whole overhang replaced with one that meets all of the codes.
Obviously, all that existing 2x4 stuff doesn't cut it even if the main
14-foot cross beam were made of titanium. *I'm guessing I'll need (and want)
an architect or engineer's seal on the new plans. *The good thing is that
it's not that big of a job and it will be good to have it done correctly.
Thanks again to you and to everyone else for your thoughts and suggestions..
"RicodJour" wrote in message
...
On Jan 11, 4:52 pm, RicodJour wrote:
On Jan 11, 3:19 pm, "BETA-32" wrote:
I have a 14-foot by 6-foot almost flat porch roof, and the porch roof
is
held up by one column one each of the two front corners. *Right now,
across
the front there are two 2"x6" beams sistered together.
Can anyone tell me if that is considered sufficient under current
building
codes, or where I can find some kind of info or load span table saying
what
is needed for this situation?
I am in New Jersey.
I just ran a quick calc with some large assumptions. *I figured Hem-
Fir, No. 1 grade equivalent (older houses were generally built with
better wood), 70 PSF which is definitely higher than you'd experience
(figured 30 PSF live load as it's almost a floor, 10 PSF dead load,
and 30 PSF snow load for a 2 month duration), and it passed in all
respects. *The deflection was a bit high - almost an inch - but since
it's a porch it's unlikely that that would present problems ( it's
still standing, right?). *If the porch roof is used as a deck, the
live load would be higher, but it's unlikely that you're congregating
on the porch roof while there's two feet of snow or more on it.
For your own edification and reference purposes, the Canadian Wood
Council web site has a nifty online span calculator. *It's under the
Design Tools heading, IIRC.
R
Whoops! *Scratch that! *My blood sugar must be running low - the beam
fails and has more than a _three_ inch deflection with the loads I
listed above. *I also just checked the Canadian Wood Council's site,
and they've changed things around since I was there last. *You'd have
to download one of of their demo packages to calculate beams -
probably not worth it.
Here's an online calculator for a simply loaded beam:
http://www.forestryforum.com/members...eamclcNDS2.htm
It's a bit more complicated. *That one shows 3 @ 2x10 is required,
like EXT mentioned, which is adequate for a floor which has more
stringent deflection criteria.
What are you trying to do? *If you're looking to stiffen the beam you
could sister on a 2x10 on either side and bolt them together, or you
could bolt on some steel plate or channel.
Sorry for the hit-send-before-thinking post.
R- Hide quoted text -
- Show quoted text -
As usual in these type questions the answer is:
You have to satisfy the building inpsector. If he insist on something
being way overbuilt...oh well, he won't pass anything less.
I went through the whole thing with my inspector when I "repaired" my
porch roof. That is the way I worded the application and that is the
way the permit was written. I even beefed it up considerably. Time I
was done all that was original was a few 2x4 rafter.
His inspection wouldn't have passed it if it hadn't been grandfathered
by the "repair" bit. He also said that the clerk who issued the
permit would be "counseled".
Bottom line again: What the inspector says, is what happens.
Harry K