EN 12845 Storage Configurations: ST1 to ST6 (Clause 6.3.2 and Table 2)

In TS EN 12845+A2:2026 the sprinkler design for a warehouse comes out of the intersection of three inputs: the category of the goods (Category I to IV), the storage height and the storage configuration (ST1 to ST6). This article gives the configuration definitions (Clause 6.3.2), their limits (Table 2), the height/density matching for ceiling-only protection (Table 4), the in-rack sprinkler assumptions (Clause 7.2.3.3) and the positioning of intermediate sprinklers (Clause 12.5), each with its source. Source: TS EN 12845+A2:2026, Clauses 6.3, 7.2 and 12.5.

Clause 6.3.2: Definitions of ST1 to ST6

The standard classifies the storage configuration as follows (TS p.36 / EN p.33):

The same clause adds a note: for each storage method there are specific limitations to storage heights depending on the type and design of sprinkler systems (see 7.2). Typical examples are given in Figure 3 (TS p.38 / EN p.35).

Clause 6.3.1 (TS p.36 / EN p.33) sets the general frame: the overall fire hazard of stored goods is a function of the combustibility of the stored materials, including their packaging, and of the storage configuration. To determine the required design criteria, the procedure shown in Figure 2 shall be followed.

The three conditions for storage in an OH class

Storage does not always have to be HHS. Clause 6.2.3 (TS p.34 / EN p.31) permits storage in occupancies classified as OH, but under three conditions:

• a) The protection throughout the room shall be designed to at least OH3;
• b) The maximum storage heights shown in Table 1 shall not be exceeded;
• c) The maximum storage area of a single block shall not exceed 50 m², with a clearance of at least 2.4 m around the block.

Where the area is classified as OH4, or where conditions b) or c) cannot be met, the storage in the area shall be treated as HHS (see 6.2.4.2).

Table 1: Maximum storage heights for OH3 protection (TS p.35 / EN p.32)

The table has two footnotes:

• a) Where the storage heights exceed the values in the table, HHS protection is used (see 6.2.4.2 and 7.2).
• b) ST6 storage is limited to gondola shelving of 1.2 m total width with a solid central barrier extending from the base to the top of the gondola. All other ST6 storage requires protection to HHS (see 7.2).

The gondola exception is therefore not in the text of Clause 6.2.3 but in footnote b to Table 1.

Table 2: Limits per configuration

Clause 6.3.2 (TS p.36 / EN p.33): "In order for sprinkler protection to be effective, the limitations and protection requirements of Table 2 shall be met."

Table 2 (TS p.37 / EN p.34):

Footnotes to Table 2 (TS p.37 / EN p.34):

• a Not applicable.
• b Intermediate level in-rack sprinkler protection is recommended.
• c The method of protection is limited to risks where the ceiling sprinklers are less than 4 m above the top level of the stored goods. Where the ceiling sprinklers are more than 4 m above the top level of the goods, intermediate level in-rack sprinklers shall be used.
• d Intermediate level in-rack sprinkler protection is assumed to be hydraulically in operation in three racks (see 7.2.3.3).
• e Assumed to be in operation in two racks.
• f Assumed to be in operation in one rack.
• g Assumed to be in operation in one or two racks.
• h Where it is not possible to install intermediate sprinklers in ST6 storage, longitudinal and transverse full height barriers shall be fitted longitudinally within each shelf. Full height barriers shall be constructed to EN 13501-1 Euroclass A1, A2 or a national equivalent.

Ceiling protection: Table 4

Clause 7.2.2.2 (TS p.39 / EN p.36): Table 4 specifies, by category, the appropriate design density and area of operation and the maximum permitted storage height for various storage types with roof or ceiling protection only. Where the storage heights exceed the limit, intermediate level in-rack sprinklers shall be provided in accordance with 7.2.3.

Table 4 (TS p.41 / EN p.38), maximum permitted storage height (m):

ST1 free standing or block stacking

ST2 post pallets in single rows and ST4 palletized racks

ST3 post pallets in multiple rows and ST5/ST6 solid or slatted shelves

The note to Table 4: dry and alternate systems should be avoided in High Hazard storage, particularly with the more combustible products (higher categories) and with high storage. Where it is nevertheless necessary to install a dry or alternate system, the area of operation shall be increased by 25 %.

Clause 7.2.2.1 (TS p.39 / EN p.36): for buildings exceeding 12 m, the authorities shall be consulted.

Excessive clearance

Clause 7.2.2.3 (TS p.39-40 / EN p.36-37): the values in Table 4 shall be used to determine the clearance. Where the clearance, that is the distance between the storage height and the ceiling sprinkler deflector, exceeds 4 m, one of the following options shall be applied:

• Option 1: the density is increased by 2.5 mm/min for the first excess metre. For each further excess metre the water density is increased by 1 mm/min. A K-factor of at least K115 shall be used.
• Option 2: intermediate level in-rack sprinklers shall be provided in accordance with 7.2.3.

Intermediate level in-rack sprinklers

Clause 7.2.3.1 (TS p.40 / EN p.37): where more than 50 intermediate level sprinklers are installed in racks, they shall not be supplied from the same control valve set as the roof or ceiling sprinklers.

Clause 7.2.3.2 (TS p.40 / EN p.37): the design density for the roof or ceiling sprinklers shall be at least 7.5 mm/min over an area of operation of 260 m². Where goods are stored above the highest level of intermediate protection, the design criteria for the roof or ceiling sprinklers shall be taken from Table 5 (TS p.42 / EN p.39).

Clause 7.2.3.3 (TS p.40 / EN p.37): for the purpose of hydraulic calculation, 3 sprinklers shall be assumed to operate simultaneously at the hydraulically most remote position at each in-rack sprinkler level, up to a maximum of three levels. According to the width of the rack aisles:

NOTE: it is not necessary to assume that more than three rows of sprinklers in the vertical plane and more than three in the horizontal plane operate simultaneously.

Clause 7.2.3.4 (TS p.40 / EN p.37): in-rack sprinklers and the associated ceiling sprinklers shall always be fully calculated (see 13.1). NOTE: the minimum pressure at any operating sprinkler is 2.0 bar (see 13.4.4).

This is consistent with the list of mandatory full calculations in Clause 13.1 (TS p.85 / EN p.82): full calculations shall always be used for layouts with intermediate level HHS sprinklers and for gridded or looped layouts.

Positioning of intermediate sprinklers: Clause 12.5

Clause 12.5.1 General (TS p.81 / EN p.78): sprinklers protecting double row racks shall be installed in the longitudinal flue spaces, preferably at the intersection with a transverse flue. It shall be ensured that water from sprinklers operating at intermediate levels can penetrate the stored goods. The distance between goods placed back to back in a rack (the longitudinal flue space) shall be at least 0.15 m, with pallet stops fitted where necessary. The distance between goods placed side by side (the transverse flue space) shall be at least 0.1 m. The clearance between the sprinkler deflectors and the top of the storage shall be not less than 0.10 m for flat spray sprinklers and 0.15 m for other sprinklers.

Clause 12.5.2 (TS p.81 / EN p.78): the vertical distance from the floor to the lowest intermediate level, and between levels, shall not exceed 3.50 m or two tiers, whichever is the less. Unless all roof or ceiling sprinklers are less than 4 m above the top of the storage, an intermediate level shall be installed above the highest level of the storage. In no case shall the highest intermediate sprinkler level be installed more than one tier below the top of the storage.

Clause 12.5.3 (TS p.81 / EN p.78):

• For Category I or II goods: where possible, sprinklers shall be installed in the longitudinal flue at the intersection with every second transverse flue, staggered relative to the row above. 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: sprinklers shall be installed in the longitudinal flue at the intersection with every transverse flue. The horizontal distance shall not exceed 1.9 m and the product of the horizontal and vertical distances shall not exceed 4.9 m².

Clause 12.5.4 (TS p.83 / EN p.80): the number of rows of sprinklers per level is determined by the total rack width. Where racks are placed back to back, the total width is calculated by adding the width of each rack and the distance between them. One row of sprinklers per level shall be installed for each 3.2 m of rack width; wherever possible they shall be installed in the flue spaces.

Clause 12.5.5 HHS intermediate sprinklers in racks without shelves (TS p.83 / EN p.80): for palletized rack storage and multiple row drive-through storage (type ST4 in Figure 3 and Table 4), intermediate sprinklers shall be installed as follows:

• a) single row racks no wider than 3.2 m shall be protected by single rows of sprinklers fitted at the tier levels shown in Figures 13 and 14;
• b) double row racks no wider than 3.2 m shall be protected by sprinklers centrally in the longitudinal flue space, at the ends of the stack and at the tier levels in Figures 13 and 14;
• c) double or multiple row racks wider than 3.2 m but no wider than 6.4 m shall be protected by two rows of sprinklers installed at no more than 3.2 m spacing. Each row shall be the same distance from the nearest rack edge. At each level the sprinklers in each line shall be located in the same set of transverse flues.

The same clause adds: where any shelf or structural steel can significantly obstruct the water distribution of a sprinkler, an additional sprinkler shall be provided to give water distribution to the area screened from water.

Intermediate sprinklers in ST5 and ST6: above the shelf

Clause 12.5.6 (TS p.84 / EN p.81): where intermediate sprinklers are required, they shall be installed above each shelf (including the top shelf if the roof or ceiling sprinklers are more than 4 m above the goods or water access to the goods is restricted), and located as shown in Table 21 and Figure 15. The vertical distance between rows shall not exceed 3.5 m.

Single rows of sprinklers shall be central above the shelves. Double rows shall be positioned so that each row is the same distance from the nearest shelf edge. The distance from the end of the shelf parallel to the range pipe lines to the nearest sprinkler shall be half the sprinkler spacing along the range lines or 1.4 m, whichever is the less (TS p.85 / EN p.82).

Table 21 (TS p.85 / EN p.82)

Configurations the standard does not cover

The term "mobile rack" does not appear in the text of TS EN 12845+A2:2026; there is no separate class, limit or "special consideration" note for that configuration. In the same way there is no provision giving a typical height range for drive-in storage. The configurations the standard classifies are the six types in Clause 6.3.2; Clause 12.5.5 mentions "multiple row drive-through storage" only in the context of ST4.

Field note

Footnotes d, e, f and g to Table 2 and Clause 7.2.3.3 give the same information from two places: as the aisle narrows, the number of racks entering the hydraulic calculation rises. This shows that aisle width is not only a layout decision but a direct water demand parameter; when the rack arrangement changes, the hydraulic calculation has to be redone. Clause 20.3.2.2 requires that change to be caught in the quarterly routine. (This paragraph is engineering commentary.)

Frequently Asked Questions

What are ST1 to ST6 and how are they defined?

TS EN 12845+A2:2026 Clause 6.3.2 (TS p.36 / EN p.33): ST1 free standing or block stacking; ST2 post pallets in single rows, with aisles not less than 2.4 m wide; ST3 post pallets in multiple (including double) rows; ST4 palletized rack (beam pallet racking); ST5 solid or slatted shelves 1 m or less wide; ST6 solid or slatted shelves over 1 m and no more than 6 m wide.

What block area and perimeter clearance apply to storage in an OH class?

Clause 6.2.3 (TS p.34 / EN p.31) permits storage in OH areas under three conditions: the protection throughout the room shall be designed to at least OH3; the maximum storage heights in Table 1 shall not be exceeded; and the maximum storage area of a single block shall not exceed 50 m², with a clearance of at least 2.4 m around the block. Where the area is classified as OH4, or where b) or c) cannot be met, the storage is treated as HHS.

What are the HH block area limits in Table 2?

TS EN 12845+A2:2026 Table 2 (TS p.37 / EN p.34): ST1 HH 150 m² with 2.4 m perimeter clearance; ST2 HH unlimited, aisles 2.4 m or greater; ST3 HH 150 m² and 2.4 m; ST4 HH unlimited (the in-rack assumptions vary with aisle width); ST5 HH 150 m² with aisles less than 1.2 m where there is no in-rack protection, and unlimited with in-rack protection and aisles 1.2 m or greater; ST6 HH only with in-rack protection, 150 m², aisle 1.2 m and perimeter clearance 2.4 m.

How many racks are assumed to be hydraulically in operation for in-rack sprinklers?

Clause 7.2.3.3 (TS p.40 / EN p.37): for the purpose of hydraulic calculation, 3 sprinklers shall be assumed to operate simultaneously at the most unfavourable position at each in-rack sprinkler level, up to a maximum of three levels. Where the rack aisles are 2.4 m or wider, only one rack is assumed to be in operation; where they are less than 2.4 m but 1.2 m or more, two racks; and where they are less than 1.2 m, three racks.

Are intermediate sprinklers placed below or above the shelf?

Above. Clause 12.5.6 (TS p.84 / EN p.81): where intermediate sprinklers are required in type ST5 and ST6 solid or slatted shelves, they shall be installed above each shelf (including the top shelf if the roof or ceiling sprinklers are more than 4 m above the goods or water access to the goods is restricted), and located as shown in Table 21 and Figure 15. The vertical distance between rows shall not exceed 3.5 m.

References

• TS EN 12845+A2:2026 Clause 6.2.3 Ordinary Hazard (TS p.34 / EN p.31)
• TS EN 12845+A2:2026 Table 1 and its footnotes, Clause 6.2.4 (TS p.35 / EN p.32)
• TS EN 12845+A2:2026 Clauses 6.3.1 and 6.3.2 Storage configuration (TS p.36 / EN p.33)
• TS EN 12845+A2:2026 Table 2 and footnotes a to h (TS p.37 / EN p.34)
• TS EN 12845+A2:2026 Figure 3, Clause 7.1 (TS p.38 / EN p.35)
• TS EN 12845+A2:2026 Table 3, Clauses 7.2.1, 7.2.2.1, 7.2.2.2, 7.2.2.3 (TS p.39 / EN p.36)
• TS EN 12845+A2:2026 Clause 7.2.2.3 Options 1 and 2, 7.2.3.1 to 7.2.3.4 (TS p.40 / EN p.37)
• TS EN 12845+A2:2026 Table 4 (TS p.41 / EN p.38)
• TS EN 12845+A2:2026 Table 5 (TS p.42 / EN p.39)
• TS EN 12845+A2:2026 Clauses 12.5.1, 12.5.2, 12.5.3 (TS p.81 / EN p.78)
• TS EN 12845+A2:2026 Clauses 12.5.4, 12.5.5 (TS p.83 / EN p.80)
• TS EN 12845+A2:2026 Clause 12.5.6 (TS p.84 / EN p.81)
• TS EN 12845+A2:2026 Table 21, Clause 13.1 (TS p.85 / EN p.82)
• TS EN 12845+A2:2026 Clause 13.4.4 (TS p.105 / EN p.102)
• TS EN 12845+A2:2026 Clause 20.3.2.2 Review of the hazard (TS p.123 / EN p.120)

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