Thread: Seismic Strapping

I got called out today for not writing up that a 1998 water heater needed strapping. Was it required then? Coastal South Carolina!

Jim

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When did you do the inspection?
What SOP does your State require?

Some parts of SC are in a significant seismic zone. http://www.wyff4.com/article/usgs-pa...quakes/7009752

If you provide the jurisdiction/zip code I can do a little research for you as I am curious to what the code might say. Here in NE we are very low seismic zone and usually calculates out to Seismic Category A which only requires to design for 1% of vertical dead load as a lateral load.

In Brawley, CA which has a really high seismic zone, I had to design for 76% of vertical dead load as a lateral load. I would expect special strapping would be required there to prevent any movement causing gas line to break or water heater to tip over.

Originally Posted by Paul Douglas

Some parts of SC are in a significant seismic zone. http://www.wyff4.com/article/usgs-pa...quakes/7009752

If you provide the jurisdiction/zip code I can do a little research for you as I am curious to what the code might say. Here in NE we are very low seismic zone and usually calculates out to Seismic Category A which only requires to design for 1% of vertical dead load as a lateral load.

In Brawley, CA which has a really high seismic zone, I had to design for 76% of vertical dead load as a lateral load. I would expect special strapping would be required there to prevent any movement causing gas line to break or water heater to tip over.

Thank you for your reply. The zip code would be 29418. This was also an electric water heater.

Jim

The South Carolina code is here (as are all ICC and ICC based codes): http://codes.iccsafe.org/

With the South Carolina code being specifically here: http://codes.iccsafe.org/South%20Carolina.html#2015

Click on Chapter 3, scroll down to page 36 to find a map of seismic design areas.

The states are outlined with - - - - (long dash lines), each county is shown, you should be able to pick your county out on the map. Looks like you are just to the left of the 50 arc, on the 33 side, which would put you in Seismic Design Category, some of your area may be in Seismic Design Category D0.

If in Seismic Design Category C, I did not find anything requiring water heaters to be strapped; however, in Seismic Design Category D0, there is:
- R301.1.2.2.3 Seismic Design Category D0, D1 and D2.
- - R301.2.2.3.7 Anchorage of water heaters. Water heaters shall be anchored against movement and overturning in accordance with Section M1307.2.

So it would matter which side of the 50 line the house was one, and you should be able to determine that fairly accurately from the map unless the house was right on or next to a line, then a call to the AHJ would let you know what Seismic Design Category they classify themselves in.

Keep in mind that even though nothing is shown as required in Seismic Design Category C, when you go to Section M1307.2 (which is applicable to all buildings, or not, based on what M1307.2 says yeah, the code sets up a trick for your reading pleasure) ... you will find that the M1307.2 says:
- M1307.2 Anchorage of appliances. Appliances designed to be fixed in position shall be fastened or anchored in an approved manner. In Sesimic Design Categories D0, D1, and D2, and in townhouses in Seismic Design Category C, water heaters and thermal storage units shall be anchored or strapped to resist horizontal displacement caused by earthquake motion in accordance with one of the following:
- - (blah, blah, blah)

That means that you are not off scott free in Seismic Design Category C ... but you wouldn't know that unless you read M1307.2.

That would make a cool tricky test question on the ICC exam as most would stop after not finding any requirement in Chapter 3 for Seismic Design Category C and only finding such a requirement for Seismic Design Categories D0, D1, and D2. It would be a "tricky" question, not a "trick" question, there is a difference.

Wow Jerry that is great information. My local jurisdiction is apparently way behind in the times as they still reference the 2006 IBC. I worked on other projects in other Jurisdictions with 2009 and 2012 IBC and if I had to determine seismic loads I would use those codes and the appropriate ASCE 7-??. I was not aware that the 2015 IRC has the simplified chart to directly give you the seismic design category. The other methods are time consuming and I usually used an online program to obtain various variables and obtain the seismic design category. The 2015 chart you reference is for site class D soils and I believe that is a conservative default unless the building official or the contractor identify worse soils.

Now I also feel ignorant as I just looked in the 2006 IRC and it has the same chart. Looks like I was doing it the hard way for residential structures.