Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10.
Flat roof snow load formula.
Determine the transient load of the roof.
Asce 7 05 equation 7 1 assumes that the snow load results from multiple events.
Minimum flat roof snow load values.
For example 18 inches would be 1 5 feet.
First figure out how deep the snow is piled up there.
The flat roof snow load is calculated using formula 7 3 1.
Express the result in feet rather than inches.
Lets assume our project is in madison wisconsin and we have already calculated our balanced roof snow load here.
Online snow load calculator for buildings with flat or low slope roofs for balanced snow drift and rain on snow surcharge loadings calculator asce 7 05 for structural engineers construction professionals and building planners.
Dead load psf span calculator for wood joists and rafters available for the iphone.
This is highly regional as weights of snow for example range from 10 to 300 pounds per square foot based on moisture and volume of the snow.
The snow load that is applied to our structure is not the ground snow load but in most cases the flat roof snow load.
As a result equation 7 1 which accounts for loss between events will result in a non conservative value.
Span calculator for wood joists and rafters also available for the android os.
In our case let s assume that our structure has a flat roof roof slope 5.
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.
In regions with relatively low snow load values the load from a single event may result in the peak loading.
The easiest way is to push a yardstick into the snow on the roof selecting an area that looks typical of the overall snow depth.
From our example our ground load and flat roof snow load were found to be 30 psf and 21 psf respectively.
For ground snow loads greater than 20 pounds per square foot the roof load is equal to 70 of the product of the exposure thermal and importance factors the ground snow load and 20 pounds.
If you have any concerns as you are determining your flat roof snow load consult with a structural engineer or roofing specialist.
Provisions on how to calculate the snow drift surcharge for structures can be found in section 7 8 of asce 7 10.
