Density Reduction 2

[bob smith]

Looking at a tiny warehouse that has storage at 15' with building height at 20' Class I commodity on double row racks 15' high. If I use NFPA 16.2.1.3.2 (a) and point E it gives me a .29 over 2000 sq ft. And if I use the density reduction on 16.2.1.3.1 I can reduce the density to 60% which I am calculating a .174. Am I ready this right? Also with that low of density I could use k5.6 or k8.0 sprinklers? Just need a little help please. Thank you

 

[UFT12]

I read it the same way and the K5.6 is also appropriate for such density per 12.6.1 (edition 16). However, the question you should probably ask yourself at this point is whether such a reduction is a prudent decision to follow. If in the future the class of commodity or the height of storage changes, your client will not have a valid protection system for the hazard. So unless you are (or your client is) absolutely sure there is not going to be any change of the parameters of the storage application, it should be worthy to reconsider about reductions and densities.

 

[SprinklerDesigner2]

OP, anything below a density of .25 you can use K8.0 heads but would it really be worth it?

But you need to ask yourself is it really worth it?

If the building is 40,000 sq ft with todays construction cost I have no doubt the cost of the building is $50/sq ft on the low side and we're talking $2 million dollars and that is on the low side.

You need to ask yourself this question "Knowing what I know if I owned the building what would I want the design to be?" After spending $2 million dollars do you really think the owner is going to get all excited about saving $2,300 sprinkler in material costs after spending millions on the building? Really?

You need to remember the client will never know what you know about sprinklers and the client is relying on you to take care of him.

If the job were mine here is how I would handle it.

I would work up the cheapest price explaining in my proposal exactly what the design is and what it covers giving some examples.

Next thing I would do is provide some alternates saying "knowing what I know we could design the building for rack storage of Class III commodities to a maximum height of 17'-0" for an additional $x,xxx.xx". Tell the owner exactly what a Class III commodity is giving some examples. Tell the owner you are concerned that if he pays for a Class I commodity if he ever changes, and I can guarantee you that over the next 25 years it will change, the design doesn't fit the hazard and there could be real problems with the AHJ and insurance carriers.

The world changes and when I started designing in the mid 1970's we didn't have anywhere near the amount of plastic products we have today. Back then all the mayonnaise jars were glass but everything today is plastic.

So I would give some examples of what he might consider and by doing so you are letting the decision be totally his.... my guess would be he would go for spending more money because he didn't spend $2 million dollars to end up with a piece of garbage because someone saved a couple bucks.

Treat your customer how you would want to be treated knowing what you know. You are the expert.

And make sure you get a signed owners certificate.

And that is my two cents worth.

 

[TravisMack]

If you stick with the lowered density as permitted, then you could also space sprinklers at 130 sq ft and 15' max spacing in lieu of the 100 sq ft and 12' max spacing with densities over 0.25. If you have bay spaces between ≥25' and ≤30' this would mean 2 lines per bay in lieu of 3. That could be a significant savings to the project. One of the questions though, is that 20' eave or peak height. Not that it will change much, but if the peak is ≥25' then you will have to calculate for a higher storage criteria. You must calculate storage height to be a minimum of 10' below the deck.

Now, that would be taking the absolute lowest bid price possible. It will be very limiting on future use of the building. Depending on owner wants and needs, they may want just the lowest cost today and not worry about costs in the future at this time.

Travis Mack, SET, CWBSP, RME-G, CFPS
MFP Design, a Ferguson Enterprise

http://www.mfpdesign.com