Uplift Resistance

[Inspector 102]

Having trouble with R802.11, 2003 IRC. Given a ranch home, 28 ft total width of builiding and 12" overhangs, how is the uplift calculated. It should be simple math, but for some reason I am not grasping the formula. Can someone put it into simpler terms?

 

[mtlogcabin]

Re: Uplift Resistance

If engineered trusses are being used the truss drawings will reflect the uplift loads.

If not then (if I have it right its been a long time) lets say you are in a 90 MPH 3 second gust

using Table R802.11 go down the left column till you find 90 go across till you are below the 28 ft roof span you will see -212 continue across to the overhang column you will see -43.22 for a 1 ft overhang add them up and you have -345.22 of uplift ( your overhang load will be muiltiplied by the amount of overhang .5 ft, 1.5 ft, 2.5 ft etc)

Pay attention to the footnotes this Table applys to a "B" exposure only if you are in a "C" or "D" exposure then you need to go to Table R301.2(3)

Lets say your mean roof height is 25 ft and you are exposure "C"

Go down the left column to 25, go across to the "C" column and you will find 1.35

Multiple your original uplift -345.22 X 1.35 and your total uplift will be -466.05