Architects need to understand the basics of fire sprinkler head spacing and locations since they often lay out ceiling details where this becomes critical. However, the fire protection engineer usually does a basic layout, which is then finalized by the sprinkler system installer. Final sprinkler head locations are developed through a joint effort among the architect, engineer, and contractor.
***WARNING: Fire suppression systems, including sprinklers, MUST be designed by a Professional Engineer. The information contained in this article is general in nature and is to be used as a GUIDELINE for architects. You must have a Professional Engineer design a sprinkler system to address your specific situation and to meet the codes applicable in your jurisdiction. The information in the article is based on NFPA 13, Standard for the Installation of Sprinkler Systems.
Sprinkler Head Location
There are two main criteria for the location of sprinkler heads. First, sprinklers must be located so they are within the hot-gas layer that develops near the ceiling during a fire because activation occurs when the sprinkler head reaches a certain temperature. Second, they must be located so that the water that is discharged from the sprinkler is not disrupted or affected by construction elements such as beams, trusses, or soffits.
The diagram below shows the water distribution for standard pendant and upright sprinkler fixtures (more information about sprinkler head types). It is useful to understand how objects within this distribution area can alter the throw and disrupt the ability of the sprinkler to extinguish a fire. This is a general depiction of sprinkler throw and should not be used to determine sprinkler spacing. Refer to the manufacturer data for specific throw data. Please note, that the throw of a sprinkler should not be used for sprinkler spacing - local codes determine spacing requirements.
According to NFPA 13 (2016) 8.5.6.1, unless certain requirements are met, the distance between the deflector and the top of storage shall be at least 18 inches. Therefore, building owners must ensure that all storage and objects in the room remain 18" below the sprinkler deflector as shown in the image below.
Sprinkler Head Spacing
The table below shows sprinkler spacing requirements based on NFPA 13. This table shall be used only as a tool for architects. Actual design of a sprinkler system MUST be done by a Professional Engineer for each project.
| OCCUPANCY HAZARD | SQUARE FOOT PER HEAD | MAXIMUM SPACING BETWEEN SPRINKLERS |
|---|---|---|
| Light Hazard (Office, Educational, Religious, Institutional, Hospitals, Restaurants, Clubs, Theaters, etc.) | 130-200 SF per head (based on obstructions and flow calcs) | 15 ft |
| Ordinary Hazard (Mills, Manufacturing, Processing, Machine Shops, Repair Garages, Post Offices, Bakeries, Wood Machining and Assembly, Auto Parking, etc.) | 130 SF per head | 15 ft |
| Extra Hazard (Plastic Processing, Chemical Spraying, Metal Extruding, Printing, Varnishing, Painting, etc.) | 90-130 SF per head (based on obstructions and flow calcs) | 12 ft |
Maximum Distance from Wall: half (1/2) of the maximum distance between sprinkler heads.
Minimum Distance Between Sprinklers: typically 6'-0".
Distance from Ceiling: minimum 1", maximum 12" for unobstructed construction. The minimum 1" is typical; however, concealed, recessed, and flush sprinklers may be mounted less than 1" from the ceiling and shall be installed based on their listing.
Extended Coverage Sprinkler Heads
In some circumstances, standard distribution sprinkler heads will not provide enough coverage. In these cases, extended coverage sprinkler heads can be installed to increase the spacing between heads. Extended coverage sprinklers have a water distribution radius of a little over 10 feet, so they can be spaced approximately 20 feet apart.
