Q&A: When do smoke alarms need to be hardwired?

The following question was recently asked on the Structure Tech Facebook Page:

"Can you give a short version of current fire detecting code? I'm doing reno and it's really complicated to understand if you have to install wired in ones or not."

That's a great question. Smoke alarms are required in part by Minnesota Statute 299F.362, which references the Minnesota State Fire code. Click the following link for information about Minnesota State Fire Code requirements for smoke alarms. I'm no expert when it comes to the state fire code, so I'm not going to try to explain all that. I can, however, discuss what the state building code says, because the requirements for smoke alarms change when work is being done to a house, and that's where the building code comes in.

To start, smoke alarms are covered by section R314 of the Minnesota State Building Code. Section R314.3.1 says that when alterations, repairs, or additions are done to a property that require a permit, the dwelling unit must be equipped with smoke alarms as though it were a new dwelling. This includes the installation or replacement of windows or doors, but specifically excludes work that only involves the exterior surfaces of buildings, such as roof or siding replacement, the addition of an open porch or deck, or chimney repairs. This also excludes plumbing, electrical, and mechanical system.

New dwellings must have smoke alarms installed in each sleeping room, outside of each sleeping area in the immediate vicinity, and on each story of the home, but not including crawl spaces and uninhabitable attics. These smoke alarms must be hardwired and interconnected, so that if one smoke alarm goes off, they all go off. The idea is that if a smoke alarm in a remote area of the home starts sounding off, it will still alert the occupants.

So back to the original question. If work is being performed in an existing dwelling that requires a permit, and such work triggers the requirement to bring the smoke alarms up to today's standards for a new dwelling, the new smoke alarms must meet the requirements listed above. They must be installed in each sleeping room, outside the sleeping rooms, on every story, and they must be hardwired and interconnected. There is an exception to this rule, however, that says you don't need to tear your walls and ceilings apart just to meet this requirement. The exact code language says this, under section R314.4, Exception 2:

Hard wiring of smoke alarms in existing areas shall not be required where the alterations or repairs do not result in the removal of interior wall or ceiling finishes exposing the structure, unless there is an attic, crawl space or basement available which could provide access for hard wiring without the removal of interior finishes.

There is similar language saying that smoke alarms don't need to be interconnected if you need to tear walls and ceilings apart. In this case, independant battery operated smoke alarms will suffice. It would still be wise to install wireless interconnected smoke alarms in this case. Yes, they cost more money, but the whole idea is to prevent people from dying in a fire. When it comes to life safety devices, I think this should be an easy call to make; get interconnected smoke alarms. I blogged about those in this post from 2014: http://structuretech1.com/2014/03/four-important-smoke-alarm-safety-tips/#getwireless

Oh, and one more thing. While photoelectric smoke alarms aren't required in Minnesota (yet…), I urge everyone to put them in their home. Ohio recently became the fifth state to require photoelectric smoke alarms; see the news story here. If you're not sure what type you have in your own home, you probably don't have photoelectric. Even if you rent, go buy some battery operated photoelectric smoke alarms and install them. It's not a big investment, they're easy to install, and they could save your life.

Here are a few posts that I've written about photoelectric smoke alarms:

Author: Reuben SaltzmanStructure Tech Home Inspections

Twitter  Facebook  LinkedIn  YouTube  Google+  RSS Feed

Written By

Reuben is a second-generation home inspector with a passion for his work. He grew up remodeling homes and learning about carpentry since he was old enough to hold a hammer. Reuben grew up thinking he was going to be a school teacher because he enjoyed teaching others so much. In a sense, that’s a lot of what home inspections are about, so Reuben truly does what he loves. Sharlene has worked with Structure Tech since 2000 and Reuben has been contributing to her blog since 2008.

Subscribe to Our Newsletter for Market Updates & Mid-Century Modern Listings

Our weekly HomesMSP Update includes current local market information and a curated list of mid-century modern properties for sale, plus posts from an inspector, a lender, a stager, info about neighborhoods, life in the Twin Cities… even recipes!


Blog Categories


Sharon and John Hensrud

About Us

The HomesMSP Team is committed to meeting you where you are and listening… really listening to understand you so we can use our extensive knowledge of the market and local neighborhoods to give you personalized service.