A fire sprinkler system is designed in a sequence: gather the building and water-supply data, classify the hazard, choose the design approach, then lay out sprinklers and piping to the standard's spacing rules.
Hydraulic calculations prove the layout, and the shop drawings go to the authority having jurisdiction (AHJ) for approval.
NFPA 13's current edition is 2025, but the edition your AHJ enforces decides what a specific project must show.
What information does a designer need before starting?
A design starts with inputs, not drawings: what the building will be used for, how it is constructed, ceiling heights and roof slopes, and the water supply available to the site.
The reviewed paperwork shows what those inputs amount to.
North Carolina's State Construction Office requires construction documents for the state projects it administers to include a sprinkler design data summary listing the hazard classification, design area, design density, hose allowance and water supply information.
Those items are a practical map of the whole process: classify the hazard, size the demand with a design area and density, then check the water supply against it.
Who makes those calls is drawn jurisdiction by jurisdiction.
Florida's statute (section 633.102, 2026 Florida Statutes) separates system design concepts prepared by the design professional from system layout, which it describes as typically prepared by the contractor.
North Carolina's guidance gives the design engineer of record the hazard evaluation, the design documents, the review of shop drawings and submittals, and the monitoring of installation and acceptance on the projects it administers.
If you are aiming at this desk rather than planning a project, the fire sprinkler designer career guide covers the role and how to become a fire sprinkler designer.
Step 1: water supply and flow test data
The water supply constrains the demand a layout can place on it, so flow test data comes before geometry.
North Carolina's State Construction Office requires water flow and pressure test data within 12 months on the state projects it administers, using a two-hydrant test — a pressure hydrant and a flow hydrant — as indicated in NFPA 13.
NFPA 291, current at 2025 per NFPA's document pages, gives guidance on fire flow tests and hydrant marking.
Freshness rules come from the reviewer.
George Mason University's building official requires a water flow test conducted no more than 12 months before working plan submittal, with the data adjusted for seasonal and daily pressure fluctuations.
Owner criteria can be tighter: the DoD's archived UFC 3-600-01 (2016, Change 6) advised that calculations be based on a waterflow test performed no more than 6 months before submission.
That is DoD criteria, not an NFPA 13 rule.
Because the limits differ by reviewer, confirm the flow-test requirements for your project with the plan reviewer before you order the test.
Step 2: hazard/commodity classification
With the water picture in hand, the designer classifies what the building holds.
Hazard classification is one of the items in North Carolina's required design data summary, and everything downstream keys off it.
Under NFPA 13's density/area approach, each occupancy hazard classification pairs a design density with a design area.
The values live in the standard's Table 19.2.3.1.1 in the 2025 edition.
This page does not restate that table.
Our research verified the table's number and a few of its values from NFPA's public TIA documents, not the full table, and the edition your reviewer enforces governs.
Owner criteria differ.
On DoD projects, the department's archived 2016 criteria set wet-system design points for ceiling heights up to 30 ft.
Light hazard is 0.1 gpm/sq ft over 1,500 sq ft, ordinary hazard 0.2 over 2,500 sq ft and extra hazard 0.3 over 2,500 sq ft.
Hose demands are 250 gpm for 60 minutes for light and ordinary hazard, and 500 gpm for 90 minutes for extra hazard.
Those are DoD criteria, not the NFPA 13 table values.
Storage occupancies add their own classification work, and our research pass did not verify the commodity-class details, so designers take those from the adopted edition and their employer's design procedures.
Step 3: choose system type and design approach
The standard comes first, because it decides the design method.
NFPA describes NFPA 13 as addressing sprinkler system design approaches, system installation and component options.
Alongside it, NFPA publishes two residential design standards.
NFPA describes NFPA 13D as a residential standard for one- and two-family dwellings and manufactured homes, intended to provide an affordable system while maintaining a high level of life safety.
NFPA describes NFPA 13R as a residential design standard for low-rise residential occupancies (multi-family dwellings).
Within the chosen standard, the designer selects the system type and the design approach, then fixes the design area and any adjustments to it.
NFPA 13 includes a design-area reduction for quick-response sprinklers; the DoD's archived 2016 criteria did not permit it on DoD projects and separately required a 30% design-area increase where ceilings slope more than 2 in 12.
Adjustments can stack.
TIA 25-4 to the 2025 edition, effective December 22, 2025, says that where multiple design-area adjustments apply, they are compounded based on the area of operation originally selected from Table 19.2.3.1.1.
Ceiling height can drive the approach.
TIA 25-5 added Table 19.2.3.2.5 for ceilings over 30 ft — for example, Ordinary Hazard Group 2 at 30–40 ft with standard-coverage quick-response K-11.2 sprinklers needs a minimum density of 0.37 gpm/sq ft with no design-area increase.
Where the supply falls short, a fire pump enters the design: NFPA 20 provides requirements for the selection and installation of fire pumps to deliver adequate and reliable water supplies.
Standpipe and pressure questions follow the pump.
North Carolina's office notes that NFPA 14 requires 100 psi at the top of Class I standpipes.
It also notes that the pump-fed 100 psig figure at the top of remote standpipes applies only to high-rise buildings, and that non-high-rise buildings may use manual wet standpipes supplied by the fire department pumper.
The same office requires accounting for city pressure plus pump churn above 175 psig with suitably rated components or a suitably located PRV with relief valve.
Step 4: lay out sprinklers and piping to spacing rules
Layout is the geometry step, and Florida's statute defines it precisely: the layout of risers, cross mains, branch lines and sprinkler heads, sizing of pipe, hanger locations and hydraulic calculations.
The spacing rules that govern that geometry sit in the standard: how far apart sprinklers can be placed, how much area each one can cover, clearances to walls, and how obstructions are handled.
This page does not restate those numbers.
NFPA 13's spacing and coverage figures were not verified from a public primary source in our research, so designers take them from the adopted edition's tables and the data for the specific sprinklers they are laying out.
Device choice narrows as ceilings rise.
Under TIA 25-5, sprinklers with a nominal K-factor below K-11.2 are not permitted in Ordinary Hazard Group 2 and higher occupancies where the ceiling is higher than 30 ft, and sidewall sprinklers are not permitted in Ordinary Hazard Group 1 and higher above 30 ft.
Owner criteria can narrow it further: the DoD's archived 2016 criteria did not permit extended coverage sprinklers except at loading docks and, with the DFPE's written approval, in historic structures and unique spaces — DoD criteria, not NFPA rules.
Step 5: hydraulic calculations
Hydraulic calculations are the proof step: they show the water supply can deliver the selected design at the most demanding part of the system.
One reviewer's guidance makes the focus explicit: George Mason University requires hydraulic calculations for the most demanding area, including hose demand carried back to the water source, plus seismic protection details and calculations where the building's seismic design category requires them.
The margin between demand and supply is reviewer policy, and it varies.
North Carolina state projects require calculations based on 10 psi less static pressure, 10 psi less residual pressure and 10% less residual flow than measured; Owatonna, Minnesota requires a minimum 5 psi safety factor at maximum system flow.
Owner criteria add their own inputs.
The DoD's archived 2016 UFC required hydraulic calculations to include a minimum 12 psi pressure drop for a reduced-pressure backflow assembly and 8 psi for a double check, and permitted a C-factor of 120 where nitrogen is used in dry or preaction systems.
The department's May 2026 change summary for the rewritten UFC goes further.
Per that summary, the rewritten UFC limits maximum system demand to 140% of rated fire pump capacity, requires on-site fire water storage of 120% of Fire Water Demand, and mandates nitrogen instead of compressed air in dry pipe systems.
Designers run these calculations in sprinkler-specific software; platforms the vendors publish include AutoSPRINK from M.E.P.CAD, HydraCAD from Hydratec, which runs on Autodesk AutoCAD, and SprinkCAD from Johnson Controls.
Career context, not design guidance
Step 6: shop drawings, submittal and AHJ approval
When the layout and calculations close, the designer assembles the submittal: shop drawings, hydraulic calculation sheets and a design data summary.
What a package should show is reviewer-specific: North Carolina's required summary — hazard classification, design area, design density, hose allowance and water supply information — is one reviewer's list.
Who may prepare and seal those drawings is set jurisdiction by jurisdiction, and the differences are real.
In Florida, a certified Contractor I or II may design new fire protection systems of 49 or fewer sprinklers, and certain alterations up to 249 sprinklers with no change of occupancy, water demand or increased hazard.
Florida's Contractor I, II or IV may design NFPA 13D systems regardless of sprinkler count, while larger designs need an engineer.
Florida's statute also says contractor-developed plans may not be required by a local permitting authority to be sealed by a registered professional engineer.
On North Carolina state projects, shop drawings must be prepared by a licensed fire sprinkler contractor with a minimum NICET III certification or by a licensed Professional Engineer, with the bid documents' preliminary design sealed by the NC-registered design engineer of record.
George Mason University's building official requires sprinkler working drawings to be prepared and signed by a Virginia Registered Design Professional or a NICET Level III or IV certified designer — and NICET designers may not apply a stamp.
Philadelphia's NFPA 13 plan review checklist requires a professional engineer's seal on construction documents and on hydraulic calculations, with the work done by a licensed FSS contractor.
Federal work carries its own rule: per the DoD's May 2026 change summary, the rewritten UFC 3-600-01 requires NICET Level III/IV certification for fire suppression shop drawings on DoD projects.
These are the rules of individual review authorities, not a national list.
NICET describes its WBSL Level III as for technicians who can work independently to produce complete plans for typical and standard systems for approval.
Confirm who may prepare and seal drawings
Which standards govern design (NFPA 13, 13R, 13D, 14, 20, 24)?
NFPA 13, Standard for the Installation of Sprinkler Systems, anchors this list, and the 2025 edition is current per NFPA's document information page.
The 2019 reorganisation moved design approaches to Chapter 19 and plans and calculations to Chapter 27; the December 2025 TIAs confirm Chapter 19 still holds the design-approaches role in the 2025 edition.
The density/area design table is Table 19.2.3.1.1 in the 2025 edition.
The residential standards carry their own editions and audiences: NFPA's document pages list NFPA 13D at 2025 for one- and two-family dwellings and manufactured homes, and NFPA 13R at 2025 for low-rise residential occupancies.
NFPA 14, current at 2024, covers standpipes — North Carolina's office notes its 100 psi requirement at the top of Class I standpipes — and NFPA 20, current at 2025, provides the fire pump requirements.
NFPA 291, current at 2025, gives the fire flow test guidance behind step 1 — the DoD's criteria, for one, direct waterflow tests to it.
NFPA 24 also sits in the designer's standards list; our research pass did not verify its current edition or scope, so check NFPA's document information pages for the edition your reviewer enforces.
Which edition applies is a separate question from which edition is newest.
The Owatonna, Minnesota fire department, for example, reviews sprinkler plans to NFPA 13 (2016) and NFPA 13R (2013).
NICET's exams sit on their own editions: the WBSL Level III Hydraulics exam lists NFPA 13 (2022), NFPA 14 (2019), NFPA 20 (2022), NFPA 291 (2022) and Brock's Fire Protection Hydraulics and Water Supply Analysis (3rd edition) among its references.
Career information, not licensing, legal, code, inspection, engineering or safety advice. Confirm the edition and design requirements that apply to your project with the AHJ, and certification requirements with NICET.