Can 17-Story Apartment + Garage Have 1 Riser?

7/11/2025

I recently inspected a hotel that was constructed back in the 1970s but was recently converted to an apartment building. The total square feet of the 17-story building is 270,000 square feet.

There is an attached 3-story parking garage that is only partially sprinkler-protected. The main apartment building is fully sprinkler-protected.

Only one incoming riser was noted for the property.

My question is, can one riser feed the entire footprint of both buildings?

There are other vertical pipes noted, but one is labeled as a dry standpipe.

Is the other vertical pipe also considered a riser? Or did I just miss finding all of the main risers?

Trying to piece this together. Thanks in advance.

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4 Comments

Pete H

7/11/2025 08:24:46 am

I'm not addressing the garage because that's a separate building and I don't have the square footage of the attached parking garage, just the 17 story building.

From NFPA 13 (2016 Edition)

8.2 System Protection Area Limitations.
8.2.1. The maximum floor area on any one floor to be protected by sprinklers supplied by one sprinkler system riser or combined system riser shall be as follows:

(1) Light Hazard - 52,000 Sq. Ft.
(2) Ordinary Hazard - 52,000 Sq. Ft
(3) Extra Hazard - Hydraulically Calculated - 40,000 square feet
(4) Storage 0 High Piled storage (as defined in 3.9.1.16) and storage covered by other NFPA standards - 40,000 sq. ft.

-

You have 270,000 square feet in the 17 story building. Is that the total between all floors or the total per floor? If it is the total per floor, you need more than one riser. If each floor is a little under 16,000 square feet, you need a single riser (It can be a combination sprinkler/standpipe, you definitely need standpipe in the 17 story building). And each floor's service must be separated by floor control valve assemblies off the riser. If it is a 270,000 sq ft floor that goes up 17 stories, you need around 6 risers and to separate all floors with floor control valve assemblies.

Either way, I don't think I can fully answer your questions with the information given.

MIKE

7/11/2025 10:27:53 am

thanks! it is 270,000 square feet total, spread through 17 floors. The six risers seems to make sense. Sometimes it seems there are not control shut offs and not all of the risers are monitored. Thats my main concern i am still having problems with.

mike

7/11/2025 10:46:00 am

pete h, i got tx, that makes sense, its per floor.

Dan Wilder

7/11/2025 09:08:15 am

If this is a 25 inspection, sure it could have 1 riser, be partially sprinklered, and have a dry standpipe. The scope of 25 isn't to address the design, just if it operates properly (25-23 1.1.3.1)

Now, should this be noted, absolutely but within a separate document outside of the NFPA 25 inspection report. How deep you go with those recommendations can be scoped within the design review process.

Some good commentary out of 25

"It is not the intent of NFPA 25 to place the burden of a complete system evaluation on the inspector. However, nothing in NFPA 25 prohibits an inspector from informing the owner when design deficiencies are found. In reporting alleged design or installation deficiencies to the owner, the inspector must keep in mind that variations from current installation standards are not necessarily deficiencies and could be compliant with the installation standard or equivalency used for the original installation or variances permitted by the AHJ."

If the "inspection" was a design review or system adequacy to current AHJ codes and standards, these are all good points to address. There would be a lot to review for applicability for a 13 system as to allowances and omissions, standpipe requirements, the addressing the partially sprinklered floors.....all this on top of what the building construction can provide to lessen some sprinkler requirements (construction and ratings)

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Can 17-Story Apartment + Garage Have 1 Riser?

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