Eliminate Roof Life Load due to spansive solar collectors on roof?

[sdcg]

Refer back to old thread179-260442. If large area of existing engineered building roof is being covered with light weight solar collector panesl (@ 4 psf) is is reasonable to perform calculations with using roof live load of zero for this area and replace it with additional dead load from solar panels? Stated further, for a preengineered metal building, is it reasonable to state the building can safely accept additional dead loads from adding roof mounted flat solar panels as long as the weight psf for the solar panels is less than the orignal design roof live load? Thanks.

 

[sdcg]

That's a typo - should be Roof "Live" Load, not "Life" Load

 

[msquared48]

I think that is reasonable for one of the load cases.

However, I would still include the full live load without the solar panels as another load case as they still have to be erected and maintained.


Elements of one or the other will govern in different locations, or they may not based on other combinations.

I assume that you do not have to deal with snow loads?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[sdcg]

The ground snow load in our area is 20psf, with a roof snow load of 12.6 for exposure B.

I guess what I was really asking for was an opinion regarding the example for an an existing pre-engineered building already designed and constructed for DL, LLr, and SL, would any further calculations be needed to conclude the roof's capacity to carry the loads from adding solar panels, as long as the solar panel weight is less than the roof live load used in the original building engineering.

 

[JAE]

I don't think you can simply negate roof live load just because there are solar panels on it.

I understand that there won't necessarily be people walking over these panels, but there still needs to be some level of capacity above the base dead load to ensure a safe roof.

One thought would be to try to sell your idea to the local building official. They would have to approve the idea of having the solar panels "steal" roof live load capacity.