Renovate NFPA 13R System Under NFPA 13D?

8/21/2026

I'm working on an existing 3-unit apartment building in Boston with an existing NFPA-13R system, which is being renovated.

Massachusetts allows 3-unit buildings to be designed per NFPA-13D.

Can the renovations be treated as 13D, or does the system need to be kept as 13R?

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11 Comments

Pete H

8/21/2026 06:00:56 am

I'd say stick with 13R.

You don't know what allowances the insurance companies allowed based on the standard protected from the initial architectural set, and they may have had different allowances between 13R and 13D, it's not necessarily just the state restriction.

chad

8/21/2026 07:44:46 am

yes, (assuming its staying 3 units) they can as per MA CMR 527. I don't recall the city's rules amending that. Its permissible to be a 13D, renovations of a 3 unit to a 3 unit does not change the sprinkler requirements.

Peter G

8/21/2026 08:19:37 am

Would they just be calculating the water for two heads versus four?

Glenn Berger

8/21/2026 08:11:11 am

Based upon the limited information provided, you can treat the revised system as NFPA 13D.

Jesse

8/21/2026 08:45:56 am

I can't speak to the local codes, but I personally wouldn't remodel to 13D. While similar, each standard has a different scope.

8/21/2026 08:58:17 am

What is the scope of work for the renovation? If you are maintaining the existing NFPA 13R system designed, I recommend staying with NFPA 13R and not mixing two different standards.

FP Engineer

8/21/2026 11:20:28 am

The interior work is pretty minimal, just relocating a few heads but the contractor is adding dry heads to exterior overhangs that wouldn't be required under 13D. Nothing wrong with that, just curious if it's necessary.

Jack G

8/21/2026 11:17:09 am

It depends on how the building was built. I d suggest reviewing meyer fire cheats heat 13--13r---13d to see if your project qualifies.
First of all in chat 5 of ibc ,if your building was approved with the following modifications:
Height increase
Area increase ( no 13r or 13d)
Egress width ( tables 1000 ish)
Travel distance
Or separated occupancies ( 13 only)
then a 13d system cannot be used
If there were made for rating reductions such as
Separated occupancies (13 only)
Type 5A construction ( 13 only)
Fire partitions ( 13 and 13 r )
For Miscellaneous modifications:
Hazardous materials, high rise mods, atrium, unlimited area buildings, allowable area of openings, vertical separation of openings, residential floor and area draftstopping, ( sprinklers extended into affected areas/ blind spaces), group r-1, r-2 attic draftstopping ( only 13 or 13r if affected areas are protected with sprinklers )
( review tables and sections in 300,400 s, 700 s, 800 s, 900 s 1000 s and don't forget balconies 1400 s.
Above is a run thru off the top of my head,
I would suggest referencing the original architectural code sheet and the new architectural code sheet for the above.
With the limited info I would suggest that 13d system should not be used.
Remember:
How they build it is how ( system type ) you protect it.

chad

8/21/2026 12:23:32 pm

MA allows 13D to apply on up to 3 family R occupancy only structures. Its not about D vs. R. Its D, period.

You got to think of the 10's of thousands of triple deckers in MA. This is a compromise to get more dwelling units sprinklered. Its not ideal but it does do that.

Jack G

8/21/2026 12:39:42 pm

Like I said above. How it was built depends on how its protected.
Beside.......2 units 13r, 1. 13d--- in same pod? I don't think so.
VA construction is 13 system even un MA.
Do your do dilligence or have your FPE do it as he seals the plans.
I don't see what you are saving for a head relocate job.

J Smith

8/21/2026 01:13:04 pm

It’s required to be maintained per the code it was built under unless they are bringing the entire building up to current code.

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Renovate NFPA 13R System Under NFPA 13D?

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