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RE: 25% of Live Load added to Lateral

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Considering this is a lateral load, then my read on it (and maybe this is the same as yours but worded differently) is that you add the 25% of the Storage load only to the 4th floor. My interpretation of what you stated is that you would isolate the area of the room and then add 25% of the storage load for this one area distributed uniformly across the 4th floor. This would greatly reduce the lateral load if the roof is a storage closet for example.

The other half of the argument is that the building department would not be able to control a portion of one level but would assume that the entire level could be used for storage if the user expands the area required.


I have a feeling that we are agreeing on this one. I have already made the change and have allowed for a percentage of the storage load to be added into the roof where the attic area is used for storage. I think this should be left to the discretion of the user.


Thanks for getting back to me. I have posted another question that is probably applicable in your area of Michigan but comes into play only in a smaller area of the California – Snow loads per ASCE 7 section Please see this post which asks for clarification.





From: Scott Maxwell [mailto:smaxwell(--nospam--at)]
Sent: Saturday, July 19, 2008 9:55 AM
To: seaint(--nospam--at)
Subject: RE: 25% of Live Load added to Lateral


It is added to the overall seismic mass of the building ONLY for areas that are designated as storage per the code provisions.  Thus, if you have one ROOM on the 4th floor of a 10 story building that is storage, then only for that THAT portion of the live load would you add the 25% to teh seismic mass...all other locations would have zero percent of the live load added to the seismic mass.


At least that is how I read it.





Adrian, MI

-----Original Message-----
From: Dennis Wish [mailto:dennis.wish(--nospam--at)]
Sent: Friday, July 18, 2008 8:07 PM
To: seaint(--nospam--at)
Subject: 25% of Live Load added to Lateral

If one floor in a multi-story building is to be used for light or heavy storage, is the 25% of the floor live load added only to the level that is used for storage or is it added to all floors?


Dennis S. Wish, PE


Dennis S. Wish, PE

California Professional Engineer

C-41250 Exp. 3/31/09

Structural Engineering Consultant

La Quinta, CA 92253