So if you have a beam 20ft long the allowable deflection limit is 20ftx12in ft 240 1.
Floor limit l 360.
On center systems these floors often have deflection between the joists exceeding l 360.
Clear span in inches l over a given number.
They are expressed as a fraction.
A floor joist appropriately selected to span 10 feet with an l 360 limit will deflect no more than 120 360 1 3 inches under maximum design loads.
Maximum deflection limits are set by building codes.
A floor joist appropriately selected to span 10 feet with an l 360 limit will deflect no more than 120 360 1 3 inches under maximum design loads.
The l stands for length.
Note it gives the allowable deflection based on a fractional span quantity so a larger denominator will yield less deflection.
See the table below.
Recent research has shown tile to fail under some conditions when the floor is more rigid than l 360.
And since it is small i will leave the source for where it is found here 1.
For example the allowable deflection of a 12ft span floor joist with plaster l 360 is 0 4 12ft divided by 360.
Clear span in inches l over a given number.
They are expressed as a fraction.
For example while joist manufacturers regularly meet the standard l 360 criteria for code construction with 24 o c.
If that same joist had gypsum ceiling l 240 the allowable deflection is 0 6.