http://www.ehow.com/how_7485788_calculate-floor-load-capacity.html
Hello; the web address above is a site about calculating load capacities of floor joists. They use a formula for the strength of abeam: maximum load in pounds = FBd^2 /9L.
The width of the woodjoist in inches is B (1.5 inches forstandard 2 by dimensional lumber.)
The depth in inches is d (7.25 in for a standard 2x8.)(9.25 in for a2x10)
The distance (span) in feet is L (Unsupported distance)
F is something called the fiber stress when wood bends. It varies with the type of wood, but graded lumber will be at least a 1,000 number, some are higher.
They use an example of 2x10 floor joists with a span of 14 feet on 16 inch centers and come up with 1,019 pd for each joist. They figure the area supported by each joistas 18.7 sq ft. They get 54.5 pd per square foot of floor area. I think this includes the weight of the flooring and anything else that is supported by the joists.
I looked at some other sites (Addresses listed below) and found a discussion of static loads and live loads. Two sites describe how to measure the deflection of flooring due to weight loads.
http://www.johnbridge.com/vbulletin/deflecto.pl
http://www.awc.org/calculators/span/calc/timbercalcstyle.asp?species=Douglas+Fir-South&size=2x8&grade=Select+Structural&member=Floor+Joists&deflectionlimit=L%2F480&spacing=16&wet=No&incised=No&liveload=80&snowload=-1&deadload=10&submit=Calculate+Maximum+Horizontal+Span
I found these sites interesting but hard to pin down for ageneral rule of thumb. Too many variables involved; Type of wood, condition of wood, dimensional lumber or engineered truss, age of wood and on and on.
http://www.eng-tips.com/viewthread.cfm?qid=62845&page=10
I am tired of searching for now. But a rough estimate of 54.5 pounds per sq ft is what I will use for the time being as I have these floor joists in my house.
Hello; the web address above is a site about calculating load capacities of floor joists. They use a formula for the strength of abeam: maximum load in pounds = FBd^2 /9L.
The width of the woodjoist in inches is B (1.5 inches forstandard 2 by dimensional lumber.)
The depth in inches is d (7.25 in for a standard 2x8.)(9.25 in for a2x10)
The distance (span) in feet is L (Unsupported distance)
F is something called the fiber stress when wood bends. It varies with the type of wood, but graded lumber will be at least a 1,000 number, some are higher.
They use an example of 2x10 floor joists with a span of 14 feet on 16 inch centers and come up with 1,019 pd for each joist. They figure the area supported by each joistas 18.7 sq ft. They get 54.5 pd per square foot of floor area. I think this includes the weight of the flooring and anything else that is supported by the joists.
I looked at some other sites (Addresses listed below) and found a discussion of static loads and live loads. Two sites describe how to measure the deflection of flooring due to weight loads.
http://www.johnbridge.com/vbulletin/deflecto.pl
http://www.awc.org/calculators/span/calc/timbercalcstyle.asp?species=Douglas+Fir-South&size=2x8&grade=Select+Structural&member=Floor+Joists&deflectionlimit=L%2F480&spacing=16&wet=No&incised=No&liveload=80&snowload=-1&deadload=10&submit=Calculate+Maximum+Horizontal+Span
I found these sites interesting but hard to pin down for ageneral rule of thumb. Too many variables involved; Type of wood, condition of wood, dimensional lumber or engineered truss, age of wood and on and on.
http://www.eng-tips.com/viewthread.cfm?qid=62845&page=10
I am tired of searching for now. But a rough estimate of 54.5 pounds per sq ft is what I will use for the time being as I have these floor joists in my house.
