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Re: Engineer needed in Riverside California (Engineer Liability)

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"
In this situation where the City of Riverside is only concerned of the gravity load, what is the liability of the engineer involved if something  happened to the structure?  How do you avoid the seismic liability in this  case?
 
ASQuilala Jr., P.E."

There is no question that ultimately the responsibility and potential liability is with the engineer who is stamping off the plans. In this case, the city paved the way for the owner to ignore the effects of the lateral load on the structure, but this is at the discretion of the engineer. Personally, I no longer take roof reports because of this issue and I would agree with what you are implying. The only issue that I can argue with is that in most cases a two story light framed home is designed for the worst case condition - that is usually wind loading rather than seismic (unless this is a very large home and deep diaphragm). If the home is goverened by wind, then there may be less chance that even doubling the weight of the roof materials will change the condition. It should be looked at regardless. My concern in this home is that the roof is stacked lumber and not trusses. I would doubt that the 2x6 rafters are capable of taking the load of heavy tile and 3/8" plywood pl
aced over the 1x skipped sheathing (the typical way it is finished here).

These are conventionally constructed homes at the time they were built. The fact is that I stopped doing roof reports because almost no one will consider upgrading the lateral system of their home when putting on heavier roofing materials. Because of this, I don't want the liability. In this case, I don't think the existing roof will carry the new load as the joists are 2x6's (spacing not known) and I suspect that they are braced back to interior walls that may or may not be bearing but are typical of carpenter trusses at the time. The local building departments are not expecting the lateral load system to be upgraded - but they are not taking the liability. It's a no win situation unless you have a client that is willing to go with a light weight tile and this is still twice the weight the original cedar shake.

Dennis
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Dennis S. Wish, PE
California Professional Engineer
Structural Engineering Consultant
http://wish92253.blogspot.com/ (Photo Blog)
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