Posted by Brian A [162.158.74.232] on Sunday, November 08, 2020 at 05:34:12 :
In Reply to: A Flatfender basement posted by Steve in FH [108.162.245.165] on Thursday, November 05, 2020 at 21:16:59 :
To figure loads for a beam you need to know the required loads per square foot for any floor and roof areas that will be supported by that beam. If you have a trussed roof, half the weight of the width over the beam will be on it. For example, if your house is 24' wide with a one foot overhang, the area of roof supported will be 8' × 13' × lbs/square foot required by code. The floor load would be calculated in similar manner, with most floors having a support beam so they don't span the entire building. So half the span of the floor joist × the width of the opening × the rated load of the floor will give you the floor load. Then you have to allow for the weight of the materials used in the construction of the area supported by the beam. For example brick walls weigh more than frame walls and tile floors weigh more than carpet. Thus you will be adding roof load plus floor load, plus weight of construction materials to figure the supported weight for your beam. Where I live, due to winter snows, roofs are typically rated for a minimum of 50 lbs/square foot and often higher, plus 10 lbs/square foot for interior ceilings and insulation, for 60+ lbs/square foot of roof load. Floors are typically rated for a minimum of 40 lbs/square foot. This can all be affected by location and local codes, due to anticipated snow, wind or water loads, plus potential for seismic activity or other factors that may be unique to your location. If you do not know these things, it would be very worthwhile to hire someone with the proper training to engineer your beam for you.
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