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Convert Duplex to Triplex sprinkler requirements
October 12, 2017
1:19 pm
New Member
Forum Posts: 2
Member Since:
June 19, 2015
Print Post Post #1

If you have three dwellings on the same lot then you are switching from a duplex to a triplex does indeed put you in the 2012 IBC. The code will require a sprinkler system in the whole building as required in section 903.2.8 but there are also exceptions to certain rooms not having to be sprinkled as noted in section 903. which may help you but it also has to approved by the Authority having Jurisdiction (AHJ). The code does permit the use of 13R sprinkler systems which is a cheaper system (903.3.1.2). Your jurisdiction may have local ordinances or State Amendments that contradict this. One option may be that if the garage is detached you could add a property line between it and the duplex that way you may not be a triplex. If the garage was an addition to the side of the house with no upstairs you may be able to put a property line between the garage and the rest of the house. I have always thought it as funny how everyone will put a sprinkler system in their yard which is basically the same thing as the one in the house except it is upside down. When this first started I heard it will flood the house (now residential will run for about 5 minutes and stop and only the effected heads will go off) I then heard that the heads are too ugly sticking out of the ceiling but now flush mount heads are on the market. This also should lower your insurance premiums as an added bonus.  You know the old line "It takes money to make money". You just have to weigh out the options to see if it will be worth it.  Good luck. 

August 29, 2017
11:52 pm
New Member
Forum Posts: 1
Member Since:
August 29, 2017
Print Post Post #2

I own a duplex in Idaho which follows the 2012 IRC/IBC. The home was built in 1960, it is not up to 2012 code but it meets the local "Life Safety" ordinance. I want to convert the garage to a small studio apartment. The city tells me this makes it a Triplex. Duplex falls under IRC but Triplex falls under IBC. Because IBC requires sprinklers in all Group-R, they want me to add sprinklers to the existing duplex as well as the new garage studio apartment.

I'd like to avoid adding sprinklers if necessary. I'm also nervous about what other expensive repairs will be required by changing from IRC to IBC.

Does the city's assessment seem correct or is there a section/clause I can point out to get them to change their minds?

If I'm not modifying the existing structure it seems like I shouldn't need to bring it up to code. It seems like only the new construction should need to match current code.

Also, is there a way to classify the garage as something other than a Triplex so that the entire structure can still fall under IRC?


Thanks for the advice.