EN 12845 Minimum Distance Between Sprinklers: Clause 12.3 and Its Three Exceptions

Source: TS EN 12845+A2:2026 (EN 12845:2015+A2:2026), Clauses 12.2, 12.3, 12.4 and 12.5.

Discussions of sprinkler layout usually turn on the maximum distances; what actually spoils a project, however, is the minimum distance being exceeded without anyone noticing. Two sprinklers too close together wet each other, cool each other and delay their operation. EN 12845 regulates this in a single clause, Clause 12.3. This article deals with that clause, its three exceptions and the geometric rules around it.

The main rule: Clause 12.3

Clause 12.3 (TSE p.75 / EN p.72) says, in its full text, that sprinklers shall not be installed at intervals of less than 2 m, except in the following cases:

• where arrangements are made to prevent adjacent sprinklers from wetting each other. This may be achieved by using baffles of approximately 200 mm × 150 mm or by making use of intervening constructional features;
• intermediate sprinklers in racks (see 12.5.3);
• escalators and stair wells (see 12.4.11).

This approximate dimension is the only data the standard gives about baffles. There is no requirement in the text of EN 12845 for the mounting level, material, sheet thickness, water tightness or a product certificate.

Exception 1: escalators and stair wells

Clause 12.4.11 is headed "Escalators and stair wells" (TSE p.80 / EN p.77). Lift shafts are not the subject of this clause; they are covered by Clause 5.1.2 b) (enclosed vertical shafts containing no combustible material and constructed as fire resisting separation) and Clause 12.4.12 (vertical shafts and flues).

The provisions of Clause 12.4.11:

• The number of sprinklers around the ceiling opening formed by an escalator, staircase and the like shall be increased.
• Sprinklers shall be no more than 2 m and no less than 1.5 m apart.
• Where the minimum distance of 1.5 m cannot be maintained because of the design of the structure (for example because of beams), a smaller spacing may be used provided that adjacent sprinklers cannot wet each other.
• The horizontal distance between the sprinklers and the opening in the ceiling shall not exceed 0.5 m.
• These sprinklers shall be capable of providing the minimum flow per sprinkler of the remaining ceiling protection.
• For the purposes of the hydraulic calculation, it is sufficient to consider only the sprinklers along the long side of the opening.

Exception 2: in-rack intermediate sprinklers

Clause 12.5.3 (TSE p.81-83 / EN p.78-80) gives in-rack sprinklers their own geometry; the 1.5 m lower limit of Clause 12.4.11 does not apply here.

Clause 12.5.2 limits the vertical pitch: the vertical distance from the floor to the lowest intermediate level and between the levels shall not exceed 3.50 m or the height of two tiers, whichever is the less. An intermediate level shall be installed above the topmost level of the stack; the exception is where all roof/ceiling sprinklers are at a height of less than 4 m above the top of the stack. In no case shall the topmost level of intermediate sprinklers be lower than one tier below the top of the stack.

Clause 12.5.1 binds the flue spaces and the deflector clearance: the distance between goods placed back to back in racks (the longitudinal flue) shall be at least 0.15 m, and the distance between goods placed side by side (the transverse flue) at least 0.1 m. The clearance between the sprinkler deflectors and the top of the stack shall be at least 0.10 m for flat spray sprinklers and at least 0.15 m for other sprinklers.

Clause 12.5.4: the number of rows of sprinklers per level is determined by the total rack width; one row shall be installed for each 3.2 m of rack width and the rows shall be placed in the flue spaces wherever possible. Where racks are back to back, the total width is the sum of the width of each rack and the distance between them.

Exception 3: an arrangement preventing wetting

The third exception is not a dimension but a performance requirement: where adjacent sprinklers are prevented from wetting each other, the spacing may go below 2 m. The standard suggests two ways of doing this: baffles of approximately 200 mm × 150 mm, or intervening constructional features.

Field note: the use of a baffle is an exception, not a design tool. The same solution appears in Clause 12.4.11 as well, in the words "provided that adjacent sprinklers cannot wet each other"; in both places the obligation is to be able to demonstrate that wetting is prevented.

The maximum distances that put pressure on the minimum

The problem of the minimum distance usually arises from the tightening of the maximum distances. Table 19 (Clause 12.2, TSE p.73 / EN p.70), for sprinklers other than sidewall:

For sidewall sprinklers, Table 20 (TSE p.74 / EN p.71) applies: LH 17.0 m², 4.6 m along the wall, 2.3 m to the end of the wall; OH 9.0 m², 3.4 m along the wall (3.7 m where the fire resistance of the ceiling is not less than 120 min), 1.8 m to the end of the wall.

Clause 12.4.1 (TSE p.75 / EN p.72) limits the distance to walls with seven items and requires the smallest to be selected:

• 2.0 m for standard spacing,
• 2.3 m for staggered spacing,
• 1.5 m where the ceiling or roof is open-joisted or the rafters are exposed,
• 1.5 m from the open face of open-faced buildings,
• 1.5 m where the external walls are of combustible material,
• 1.5 m where the external walls are of metal (with or without combustible cladding or insulation),
• half of the maximum distance given in Tables 19 and 20.

Vertical position and obstructions

Clause 12.4.2 (TSE p.75 / EN p.72): sprinklers shall not be installed lower than 0.3 m below the underside of combustible ceilings, or lower than 0.45 m below roofs/ceilings of Euroclass A1 or A2 (or the equivalent in existing national classifications). Where possible the deflector shall be positioned between 0.075 m and 0.15 m below the ceiling or roof; ceiling, flush and recessed sprinklers are excepted. Where the use of the maximum distances of 0.3 m and 0.45 m is unavoidable, the area concerned shall be kept as small as possible.

Clause 12.4.4: the distance from the edge of a canopy to the nearest sprinkler shall not exceed 1.5 m.

Clause 12.4.5: skylights with a volume greater than 1 m³ measured above the normal ceiling level shall be sprinkler protected, except where the distance from the normal ceiling level to the top of the skylight does not exceed 0.3 m, or where there is a close fitting frame and glass at roof/ceiling level.

Clause 12.4.6: sprinklers shall be positioned directly above beams or girders not wider than 0.2 m, at a vertical distance of at least 0.15 m. Where the deflector is above the level of the underside of the beams, one of the following solutions shall be applied: the dimensions of Figures 9 and 10, the spacing requirements of 12.4.7, or placing sprinklers on both sides of the beam as if it were a wall.

Clause 12.4.9: where roof or ceiling sprinklers are installed closer than 0.6 m to one side of a column, another sprinkler shall be installed on the opposite side of the column, within 2 m of the column. This clause is a typical case in which the minimum 2 m rule can be complied with without being broken.

The effect on the calculation

Clause 13.4.1 (TSE p.101 / EN p.98) defines how the area covered by each sprinkler is determined: by centre lines drawn midway between adjacent sprinklers, perpendicular to the line joining the sprinklers, and by the boundary of the protected area or half the distance to the nearest sprinkler, whichever is the greater (Figure 22).

An example shows the effect of the maximum distances on the number of sprinklers in the area of operation. For OH3, Table 3 (TSE p.39 / EN p.36) gives an area of operation of 216 m²; since Table 19 permits a maximum of 12.0 m² per sprinkler in OH, there are at least 216 / 12.0 = 18 sprinklers in the area. Where the sprinkler spacing is tightened, the same 216 m² is covered by more sprinklers and the hydraulic demand rises. This is the arithmetic of the table's own figures.

Frequently Asked Questions

What is the minimum distance between two sprinklers in EN 12845?

Clause 12.3 (TSE p.75 / EN p.72): sprinklers shall not be installed at intervals of less than 2 m. There are three exceptions: where arrangements are made to prevent adjacent sprinklers from wetting each other, intermediate sprinklers in racks (12.5.3), and escalators and stair wells (12.4.11).

What dimension does the standard give for a baffle?

Clause 12.3 gives only a single dimension: adjacent sprinklers may be prevented from wetting each other by using baffles of approximately 200 mm x 150 mm or by making use of intervening constructional features. There is no provision in EN 12845 for the mounting level, material, sheet thickness or certification of the baffle.

What is the spacing at escalators and stair wells?

Clause 12.4.11 (TSE p.80 / EN p.77): sprinklers shall be no more than 2 m and no less than 1.5 m apart. Where the 1.5 m cannot be maintained because of the design of the structure, a smaller spacing may be used provided that adjacent sprinklers cannot wet each other. The horizontal distance between the sprinklers and the opening in the ceiling shall not exceed 0.5 m.

What is the horizontal distance for in-rack intermediate sprinklers?

Clause 12.5.3 (TSE p.81-83 / EN p.78-80): for Category I or II goods the horizontal distance between sprinklers shall not exceed 3.75 m and the product of the horizontal and vertical distances shall not exceed 9.8 m2. For Category III or IV goods the horizontal distance shall not exceed 1.9 m and the product 4.9 m2.

Which tables give the maximum distances?

Table 19 (Clause 12.2, TSE p.73 / EN p.70), for sprinklers other than sidewall: LH 21.0 m2 and 4.6 m; OH 12.0 m2, 4.0 m in standard layout and S 4.6 m, D 4.0 m in staggered layout; HHP and HHS 9.0 m2 and 3.7 m. For sidewall sprinklers Table 20 applies.

References

• TS EN 12845+A2:2026 Clause 5.1.2 (TSE p.32 / EN p.29)
• TS EN 12845+A2:2026 Table 3 (TSE p.39 / EN p.36)
• TS EN 12845+A2:2026 Clause 12.2, Table 19 (TSE p.73 / EN p.70), Table 20 (TSE p.74 / EN p.71)
• TS EN 12845+A2:2026 Clauses 12.3, 12.4.1, 12.4.2, 12.4.4, 12.4.5 (TSE p.75 / EN p.72)
• TS EN 12845+A2:2026 Clause 12.4.6 (TSE p.76 / EN p.73), Clause 12.4.7 (TSE p.77-78 / EN p.74-75)
• TS EN 12845+A2:2026 Clause 12.4.9 (TSE p.79 / EN p.76)
• TS EN 12845+A2:2026 Clauses 12.4.11, 12.4.12 (TSE p.80 / EN p.77)
• TS EN 12845+A2:2026 Clauses 12.5.1, 12.5.2, 12.5.3 (TSE p.81 / EN p.78), continuation of 12.5.3 and 12.5.4 (TSE p.83 / EN p.80)
• TS EN 12845+A2:2026 Clause 13.4.1 (TSE p.101 / EN p.98)

SprinkCalc — Fire Sprinkler Design Across Three Standards

SprinkCalc covers hazard classification, design density and area, K-factor selection, water demand and hydraulic calculations for NFPA 13, FM Global and BS EN 12845 in a single iOS app, and exports a professional PDF report.

Download SprinkCalc on the App Store

MEP Calc — 86+ Engineering Calculators

MEP Calc bundles 86+ engineering modules in one iOS app: 21 fire calculations plus heating, cooling, HVAC, plumbing, steam and natural gas.

Download MEP Calc on the App Store