Sidewall Sprinklers: EN 12845 Clause 12.2, Table 20 and Clause 14.2.3

Source: TS EN 12845+A2:2026 (EN 12845:2015+A2:2026), Clauses 12.1.2, 12.2, 12.3, 12.4.1, 12.4.3, 14.2.1, 14.2.3 and Tables 20, 37a.

The sidewall sprinkler has no clause of its own in EN 12845; it is regulated from two places. The layout and the area of coverage are in Clause 12.2 with Table 20, and the restrictions on use are in Clause 14.2.3. This article brings the two together and uses only the figures given by the standard.

Which clauses apply

Clause 12.2 (TSE p.73 / EN p.70): the maximum area of coverage per sprinkler shall be determined in accordance with Table 19 for sprinklers other than sidewall, and in accordance with Table 20 for sidewall sprinklers.

Clause 14.2.1 (TSE p.106-107 / EN p.103-104): sprinklers shall be used in accordance with Table 37a for the various hazard classes and as specified in 14.2.2 to 14.2.4. The restrictions concerning sidewall sprinklers are in Clause 14.2.3.

Table 20: the layout rules

Table 20 (TSE p.74 / EN p.71) contains rows for only two hazard classes, because Clause 14.2.3 prohibits general use in HH.

The four notes to the table are as binding as the table itself:

• NOTE 1: One or more additional rows of roof or ceiling sprinklers are required.
• NOTE 2: This value may be increased to 3.7 m provided that the fire resistance of the ceiling is not less than 120 min.
• NOTE 3: The sprinkler deflectors shall be positioned between 0.1 m and 0.15 m below the ceiling and between 0.05 m and 0.15 m horizontally from the wall.
• NOTE 4: The ceiling shall be free of obstructions within a square extending 1.0 m along the wall on each side of the sprinkler and 1.8 m perpendicular to the wall.

Clause 14.2.3: three prohibitions and one condition

Clause 14.2.3 (TSE p.107 / EN p.104) is short and clear. Sidewall sprinklers shall not be installed:

• in HH installations, except for the protection of corridors, cable ducts and columns;
• in OH storage areas;
• above suspended ceilings.

And one positive condition: sidewall sprinklers may be installed only under flat ceilings.

This last sentence should be read together with Clause 12.4.3 (TSE p.75 / EN p.72): sprinklers shall be installed with their deflectors parallel to the slope of the roof or ceiling; where the slope is greater than 30° to the horizontal, a row of sprinklers shall be fixed at the ridge, or radially not more than 0.75 m from the ridge. For sidewall sprinklers the "flat ceilings only" condition closes off this flexibility.

The K-factor: Table 37a

Table 37a (TSE p.107 / EN p.104) lists sidewall among the types permitted in two classes:

The sidewall type is not listed in the HHP, HHS and HHS in-rack rows, which is consistent with the HH prohibition of Clause 14.2.3.

Distance to the wall and to adjacent sprinklers

Clause 12.4.1 (TSE p.75 / EN p.72): the maximum distance from walls and partitions to sprinklers shall be the smallest of the following values:

• 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 insulating material),
• half of the maximum distance given in Tables 19 and 20.

Where Table 20 is used, the last item produces 4.6/2 = 2.3 m in LH and 3.4/2 = 1.7 m in OH (or 3.7/2 = 1.85 m where NOTE 2 is applied); the smallest of these and the other values is then selected.

Clause 12.3 (TSE p.75 / EN p.72): sprinklers shall not be installed at intervals of less than 2 m. The exceptions are: where arrangements are made to prevent adjacent sprinklers from wetting each other (using baffles of approximately 200 mm × 150 mm or intervening constructional features), intermediate sprinklers in racks (12.5.3), and escalators and stair wells (12.4.11).

Clause 12.1.2 (TSE p.73 / EN p.70): in LH and OH a clear space of 0.3 m below the deflector shall be maintained for flat spray sprinklers and 0.5 m in all other cases.

A corridor example: how the figures tie together

The calculation below is only the arithmetic of the figures in Table 20 itself; there is no such example in the standard.

Take an LH corridor 24.0 m long and 2.0 m wide, to be protected with a single row of sidewall sprinklers (since w = 2.0 m ≤ 3.7 m, Table 20 permits a single row).

• Since a maximum of 2.3 m may be left at each end, the distance between the first and the last sprinkler is at least 24.0 - (2 × 2.3) = 19.4 m.
• Since the maximum distance between sprinklers is 4.6 m, for n sprinklers (n - 1) × 4.6 ≥ 19.4 must hold, which gives n - 1 ≥ 4.22, that is n = 6 sprinklers.
• With 6 sprinklers over 24.0 m, 4.0 m of wall falls to each sprinkler; at a width of 2.0 m this is 8.0 m² and does not exceed the 17.0 m² limit of Table 20.

If 5 sprinklers were chosen, 4 intervals × 4.6 m = 18.4 m would be covered, and dividing the remaining 5.6 m between the two ends would give an end distance of 2.8 m, exceeding the 2.3 m limit of Table 20.

Sidewall sprinklers in the spares stock

The spare parts provision of Clause 20.1 (TSE p.122 / EN p.119) carries one detail: where installations include high temperature sprinklers, sidewall or other variants of the sprinkler pattern, or multiple controls, a sufficient number of spares of these shall also be kept. After spares have been used, the stock shall be replenished without delay.

Frequently Asked Questions

Where may sidewall sprinklers not be used?

Clause 14.2.3 (TSE p.107 / EN p.104) lists three prohibitions: sidewall sprinklers shall not be installed in HH installations (except for the protection of corridors, cable ducts and columns), in OH storage areas, or above suspended ceilings. In addition they may be installed only under flat ceilings.

What is the maximum area of coverage per sidewall sprinkler?

Table 20 (Clause 12.2, TSE p.74 / EN p.71): 17.0 m2 per sprinkler for LH and 9.0 m2 for OH. The maximum distance between sprinklers along the wall is 4.6 m in LH and 3.4 m in OH; the maximum distance from a sprinkler to the end of the wall is 2.3 m in LH and 1.8 m in OH.

Can the 3.4 m limit along the wall be increased in OH?

Table 20 NOTE 2: this distance may be increased to 3.7 m provided that the fire resistance of the ceiling is not less than 120 min.

Where is the deflector of a sidewall sprinkler positioned?

Table 20 NOTE 3: the sprinkler deflectors shall be positioned between 0.1 m and 0.15 m below the ceiling and between 0.05 m and 0.15 m horizontally from the wall.

Above what room width are two rows of sidewall sprinklers required?

Table 20: where the room width w does not exceed 3.7 m, a single row is sufficient. For 3.7 < w of 7.4 m, two rows are required; where the room length exceeds 9.2 m in LH or 6.8 m in OH, the layout shall be staggered. Where w exceeds 7.4 m, two rows are again used and, under NOTE 1, one or more additional rows of roof or ceiling sprinklers are required.

References

• TS EN 12845+A2:2026 Clauses 12.1.2, 12.2, Table 19 (TSE p.73 / EN p.70)
• TS EN 12845+A2:2026 Table 20 and NOTES 1-4 (TSE p.74 / EN p.71)
• TS EN 12845+A2:2026 Clauses 12.3, 12.4.1, 12.4.3 (TSE p.75 / EN p.72)
• TS EN 12845+A2:2026 Clause 12.5.3 (TSE p.81 / EN p.78), Clause 12.4.11 (TSE p.80 / EN p.77)
• TS EN 12845+A2:2026 Clause 14.2.1 (TSE p.106-107 / EN p.103-104)
• TS EN 12845+A2:2026 Table 37a, Clauses 14.2.2, 14.2.3 (TSE p.107 / EN p.104)
• TS EN 12845+A2:2026 Clause 20.1 (TSE p.122 / EN p.119)

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