ESFR and CMSA Placement and Clearance Rules: EN 12845-2 Clause 5.1.3

Source: EN 12845-2:2024, Clauses 5.1.3 and 5.2 (EN p. 8-16), with TS EN 12845+A2:2026 Clause 12 (EN p. 70-78) for comparison.

ESFR and CMSA placement is read from a different place than the CMDA (density and area) logic. EN 12845-2 gathers sprinkler spacing, the vertical distance below the ceiling and the clearance to storage in Clause 5.1.3, and the building limits (slope, skylights, vents, air movement) in Clause 5.2. All the values below come from those two clauses.

Clauses 5.1.3.2 and 5.1.3.3: spacing and area per sprinkler

The 12 m² exception for CMSA applies only to STC1 storage and only where the ceiling is in one of three conditions: unobstructed and non-combustible; obstructed and non-combustible; or unobstructed and combustible.

Clause 5.1.3.4 (obstruction exception): the maximum linear spacing of a sprinkler in any direction may be extended by up to 0.3 m solely to prevent installed objects from unacceptably obstructing the discharge. This allows the maximum area to rise to 10.2 m². It may be applied more than once, but on each occasion the adjacent spacing shall conform to 5.1.3.2 or 5.1.3.3. The standard states explicitly that this is an exception and shall not be applied as a normal design method.

Clause 5.1.3.1: the linear distance between sprinklers is measured along the slope of the ceiling, not as seen in plan from the floor.

Clause 5.1.3.5: vertical distance from the ceiling to the sprinkler

The vertical distance is measured perpendicular to the floor, between the thermal element of the sprinkler and the uppermost part of the ceiling. As an exception, for corrugated metal roof decking up to 75 mm deep the distance to the deflector is measured from the underside of the flange; in other cases the measurement is taken from the top of the flange (5.1.3.5.1).

Clause 5.1.3.5.2: sprinklers under unobstructed or obstructed construction are installed so that the deflector is at least 100 mm below the ceiling. The maximum vertical distance is in accordance with Table 2.

Table 2: maximum permitted vertical distance of the sprinkler thermal element below the ceiling (mm), EN p. 10

As can be seen, Table 2 does not distinguish by ceiling material (concrete, suspended ceiling, profiled sheet) but by k-factor and by whether the ceiling is obstructed or unobstructed.

Definition of an unobstructed ceiling (5.1.3.5.3): a flat ceiling such as a suspended ceiling; all solid structural members being equal to or less than 100 mm in depth; all solid ceiling structural members being 4.3 m or more apart; or, where the members are deeper than 100 mm, the minimum distance between them being 3.7 m where the ceiling height is up to 9.0 m and 3.0 m where it exceeds 9.0 m. In all other cases the ceiling is considered obstructed. A solid ceiling structural member is a member whose cross sectional area in the vertical plane is less than 70 % open.

Channel pockets in an obstructed ceiling (5.1.3.5.4): ESFR sprinklers are installed in every channel pocket formed by the obstructed construction; the exception is where the solid structural members descend no more than 300 mm below the ceiling and the sprinklers are positioned below those members. For CMSA sprinklers with a standard response element the exception threshold rises to 600 mm and the deflector is positioned between 25 mm and 150 mm below the non-combustible solid structural member; where the member descends more than 300 mm below the ceiling, the resulting channel pockets shall not exceed an area of 28 m² and a horizontal width of 0.9 m. Separate limits are given for combustible members and for descents between 300 mm and 525 mm (EN p. 11-12).

Clauses 5.1.3.6 and 5.1.3.7: orientation and clearance

• 5.1.3.6: sprinklers are preferably installed with the deflector parallel to the floor; where the slope does not exceed 10 degrees they may also be installed parallel to the ceiling.
• 5.1.3.7: a clear space of at least 1 m is maintained between the ceiling sprinkler deflectors and the top of the storage.

Clause 6.1 (EN p. 33) repeats the same requirement and adds: clearances greater than 4 m require no correction to the design parameters. In addition, all flue spaces shall be not less than 150 mm; in STC3 and STC4.3 the distance between loading aisles shall not exceed 6 m; and loading aisles are at least 1.2 m wide unless the design table calls for a greater minimum.

For comparison, on the EN 12845 side (Clause 12.1.2, EN p. 70): below the deflector of roof and ceiling sprinklers a clear space of at least 0.3 m is maintained for flat spray sprinklers in LH and OH, 0.5 m in all other cases, and 1.0 m in HHP and HHS.

Clause 5.2: building limits

• 5.2.1 Ceiling slope: maximum slope 10 degrees (17.6 %). If exceeded, three options: (1) a flat, continuous horizontal suspended ceiling over the affected area and two rows of sprinklers beyond it in each direction (designed in accordance with 5.2.2, with the space above it sprinkler protected and sprinklers installed below it according to the relevant hazard class); (2) in areas with rack storage only, in-rack sprinklers in accordance with 6.6.2.1 plus an additional in-rack level at the top of the storage, at the same spacing as the longitudinal sprinklers and including face sprinklers; (3) designing the system in accordance with EN 12845.
• 5.2.2 Ceiling strength: ceilings, lower ceilings and suspended ceilings (including solid barriers) are securely fixed and shall be able to withstand a vertical upward thrust of 140 N/m².
• 5.2.3 Skylights: they shall withstand 300 °C for at least 5 minutes. Skylights with a volume measured above the level of the normal ceiling greater than 1 m³ are sprinkler protected; no protection is required where the distance from the level of the normal ceiling to the top of the skylight does not exceed 0.3 m or where there is a tightly fitting frame and glazing in line with the roof or ceiling. The clause gives no area limit.
• 5.2.4 Heat and smoke vents: in ESFR or CMSA installations only manual smoke or heat vents are used; drop-out type heat vents shall not be fitted. Where national legislation requires automatic vents, it is ensured that the venting system does not impair the sprinkler system and one of three solutions is applied: corresponding sprinklers are placed directly below the vent opening at a maximum linear spacing of 1.2 m and no more than 0.6 m from the edge of the vent; or the vents are provided with standard response actuating elements with a nominal rating of 141 °C or higher; or the automatic smoke vents are actuated individually.
• 5.2.6.1 Horizontal air flow: ventilation equipment is arranged so that the air velocity at any sprinkler at ceiling level does not exceed 1.5 m/s, or it is automatically shut down upon early detection of a fire.
• 5.2.7 Solid mezzanines: quick response or ESFR sprinklers are installed beneath solid mezzanines that have combustible construction or a combustible occupancy below them. As an exception, standard response sprinklers may be used where a row of sprinklers is placed no more than 0.6 m from the edge of the mezzanine and all storage below it stays within the limits of those perimeter sprinklers, or where there is a smoke curtain around the mezzanine.

In-rack placement

In the modular ESFR in-rack arrangement of EN 12845-2 (Clause 6.6.2.2.4, EN p. 45) the minimum and maximum horizontal distance between in-rack sprinklers is 0.7 m and 1.4 m (except as shown in the relevant figures). The maximum horizontal distance of the face sprinklers from the face of the storage rack, or from the outer edge of a pallet load overhanging into the aisle, is 450 mm.

In the vertical arrangement (6.6.2.2.5, EN p. 47): the maximum vertical distance between in-rack sprinkler levels is 9.1 m for HHS4 and HHS5 and 12.2 m for classes up to HHS3. A vertical clearance of at least 150 mm is provided between the top of the storage and the deflector.

On the EN 12845 side, for intermediate level sprinklers (Clause 12.5, EN p. 78): the maximum vertical distance from the floor to the lowest intermediate level and between levels is 3.50 m or two rack tiers, whichever is the smaller; 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. The longitudinal flue space between goods placed back to back is at least 0.15 m and the transverse flue space between goods placed side by side is at least 0.1 m; the clearance between the deflector and the top of the storage shall not be less than 0.10 m for flat spray sprinklers and 0.15 m for others.

Concealed spaces

EN 12845 Clause 5.4 (EN p. 30): where the height of roof and floor concealed spaces exceeds 0.8 m, those spaces are sprinkler protected. Where it does not exceed 0.8 m, they are protected only if they contain combustible material or are constructed of combustible material. Protection in a concealed space is designed to LH where the main hazard class is LH and to OH1 in all other cases.

Frequently Asked Questions

What are the ESFR sprinkler spacing and the area per sprinkler?

EN 12845-2:2024 Clause 5.1.3.2 (EN p. 8): the minimum distance between two sprinklers is 2.4 m. The maximum spacing between two adjacent sprinklers is 3.7 m where the ceiling height does not exceed 9.1 m and 3.1 m where it does. The maximum area per sprinkler is 9.3 m² and the minimum area is 6 m². The distance to a wall shall not be more than 50 % of the maximum permitted distance between sprinklers. Clause 5.1.3.4 allows the linear spacing to be extended by up to 0.3 m in each direction solely to avoid an obstruction, which raises the area to 10.2 m²; this is an exception and shall not be applied as a normal design method.

How far below the ceiling may the thermal element of a sprinkler be?

Clause 5.1.3.5.2 (EN p. 9) requires the deflector to be at least 100 mm below the ceiling; the maximum vertical distance is given in Table 2 (EN p. 10). Table 2 gives the maximum vertical distance of the thermal element below the ceiling by k-factor: for ESFR, 325 mm for K200, K240 and K400 and 425 mm for K320, K360 and K480. For CMSA under an obstructed ceiling, 325 mm for K160, K240, K280 and K360; under an unobstructed ceiling, 225 mm for K160 and K240 and 325 mm for K280 and K360.

How much clearance is required between the top of storage and the sprinklers?

Clause 5.1.3.7 (EN p. 12): a clear space of at least 1 m is maintained between the ceiling sprinkler deflectors and the top of the storage. Clause 6.1 (EN p. 33) repeats the same requirement: unless otherwise stated, a clearance of at least 1 m is required from the sprinkler deflector to the top of the stored goods, and clearances greater than 4 m require no correction to the design parameters. For comparison, EN 12845 Clause 12.1.2 (EN p. 70) requires for CMDA sprinklers a clear space of 0.3 m for flat spray sprinklers in LH and OH, 0.5 m in other cases and 1.0 m in HHP and HHS.

What is the maximum ceiling slope for ESFR and CMSA?

Clause 5.2.1 (EN p. 12): the maximum ceiling slope shall not exceed 10 degrees (17.6 %). Where the slope exceeds that value one of three options is applied: a flat and continuous horizontal suspended ceiling is built over the affected area and two rows of sprinklers beyond it in each direction (the space above the ceiling is also sprinkler protected and sprinklers are installed below it according to the relevant hazard class); in areas with rack storage only, in-rack sprinklers in accordance with Clause 6.6.2.1 plus an additional in-rack level at the top of the storage; or the system is designed in accordance with EN 12845.

Is there an area limit for skylights?

Clause 5.2.3 (EN p. 13) gives no area limit for skylights. The criteria are: the skylight shall be able to withstand a temperature of 300 °C for at least 5 minutes; skylights with a volume measured above the level of the normal ceiling greater than 1 m³ are sprinkler protected; no protection is required where the distance from the level of the normal ceiling to the top of the skylight does not exceed 0.3 m or where there is a tightly fitting frame and glazing in line with the roof or ceiling.

Is there a minimum distance to a wall?

No. Clauses 5.1.3.2 and 5.1.3.3 (EN p. 8) set only an upper limit for the distance to a wall: 50 % of the maximum permitted sprinkler spacing. There is no provision for a minimum distance to a wall in the text of EN 12845-2:2024.

References

• EN 12845-2:2024 Clause 5.1.3.1, 5.1.3.2, 5.1.3.3, 5.1.3.4 (EN p. 8)
• EN 12845-2:2024 Clause 5.1.3.5.1, 5.1.3.5.2 (EN p. 9)
• EN 12845-2:2024 Table 2, Clause 5.1.3.5.3, 5.1.3.5.4 (EN p. 10-11)
• EN 12845-2:2024 Clause 5.1.3.6, 5.1.3.7, 5.1.3.8, 5.2.1, 5.2.2 (EN p. 12)
• EN 12845-2:2024 Clause 5.2.3 (EN p. 13)
• EN 12845-2:2024 Clause 5.2.4 (EN p. 16)
• EN 12845-2:2024 Clause 5.2.6.1 (EN p. 18)
• EN 12845-2:2024 Clause 5.2.7 (EN p. 20)
• EN 12845-2:2024 Clause 6.1 (EN p. 33)
• EN 12845-2:2024 Clause 6.6.2.2.4 (EN p. 45), 6.6.2.2.5 (EN p. 47)
• TS EN 12845+A2:2026 Clause 5.4 (EN p. 30)
• TS EN 12845+A2:2026 Clause 12.1.2, Table 19 (EN p. 70)
• TS EN 12845+A2:2026 Clause 12.5.1, 12.5.2, 12.5.3 (EN p. 78)

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