I’m looking at a book,”U.S. Span Book for Major Lumber Species.”When looking at the tables for floor joists and rafters-
1. What is the difference between psf dead and psf live
2. What is the normal standard for floors.
3. In the midwest with snow, what would be the norm for a rafter???
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Replies
PSF live - # per sq ft live load - live load is movable stuff - people, furnature, etc
PSF dead load is - the weight of the material used to construct the building - lumber, flooring, shingles, etc.
Normal standard for floors - depends - deck floor - attic floor, primary living area - sleeping room - lots of choices. And they differ per code from state to state.
Can't tell you about snow loads - only seen snow on TV ;-)
Edited 9/27/2004 10:32 pm ET by DIRISHINME
You don't figure loads on a single rafter. You figure them on the whole assembly. it is calculated in SQUARE feet. You read the tables differently if you are framing at 12", 16", 19.2", 24" OC
Live loads are defined by your local building dept. For instance, When I lived in Grand County, CO the normal live load required for smnow was 40#/ Sq Ft but it went up to 70# in parts of the county and the Forest service required 110# in the park, depending on elevation and nearness to the continental divide.
Some states allow as little as 15# and others only 25#. I think a good overall for northern states to shoot for is 40 - 50#
live looad on a roof includes wind loads also. Live is anything temporary.
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Live is anything temporary
Very profound, pippin...What the HECK was I thinking?
Did I say that?
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:-)Yes, you did.I wonder if it's true.Metaphysically, I mean; I agree with your definition as it pertains to structural loading.What the HECK was I thinking?
You might want to try this out instead -
http://www.cwc.ca/design/tools/calcs/SpanCalc_2002/
it is an online calculator.
But make sure you know what you are doing, or you can hurt sombody.
Dead load for a floor or roof assembly will generally be about 15# ( it has to be able to start out supporting it's own weight, or like some of us, it'll get joint disease)
A live load design for some rooms will normally be 40, but there are rooms where you want 50-55 where tjhere will be heavy equipmnet or activity.
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Thank you, only browsing- always wondered what the live and dead term ment.