If you live in the us our snow load calculator compares the total weight on your roof with the permissible load calculated according to the standards issued by the american society of civil engineers regarding the minimum design loads for buildings and other structures asce7 16.
Sloped roof snow load chart.
If your roof is flat it is more likely to have snow load problems than if it is pitched.
You need to use a snow load formula for flat roofs.
I ignore the slope.
Ground snow load value.
However in my practice i typically use the horizontal run of the roof for both types of load.
For dead loads you are correct.
To do this i use conservative too heavy dead loads and full snow loads regardless of pitch.
P s c s p f.
There are also factors such as deflection elasticity and wood species that come in to play.
Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10.
This rain on snow augmented design load applies only to the balanced load case and need not be used in combination with drift sliding unbalanced or partial loads.
The sloped roof snow load p s shall be obtained by multiplying the flat roof snow load p f by the roof slope factor c s.
For locations where 0 pg 20 psf all roofs with a slope w 50 with w in ft shall have a 5 psf rain on snow surcharge.
It is determined based.
For the design of an actual structure a registered and licensed professional should be consulted as per irc 2012 sec.
Roof snow load is defined as the weight of snow on the roof surface used in design of the building structure ibc 2012.
In our case let s assume that our structure has a flat roof roof slope 5.
The snow load that is applied to our structure is not the ground snow load but in most cases the flat roof snow load.
On multiple factors including.
The flat roof snow load is calculated using formula 7 3 1.
Consult local building codes for snow load capacity and reference the span tables for joists and rafters published by the american wood council awc as a general rule roofs that have a high human occupancy rate should be framed with rafters every 16.
Discount that actual snow loads may exceed them only that the risk of snow load induced failure is reduced to an acceptably low level.
Roofs of steeper pitches will likely.
The minimum roof pitch for shedding snow is around 30 or a 6 12 or 7 12 slope although this is not a definite as the material of your roof the direction of the snow and wind are some factors that can affect whether or not snow will slide as roofs of as little as 10 have been reported to shed snow.
All of the load cases required to fully design an actual structure are not provided by this calculator.
Technically you should use the actual rafter length when adding up the weight of roofing materials.
