This article sets out in detail the CMSA design tables covered by Clause 6.7 of TS EN 12845-2:2025 (EN 12845-2:2024) and the rules for using them. Every row and every figure here is taken verbatim from the text of the standard; the table number and EN page are given as the source.
1. Which standard supplies which part of the design
Table 1 (Clause 4, EN p.7) lists which document each task comes from. In a CMSA project the split is as follows:
| Task | EN 12845:2015+A1:2019 | EN 12845-2:2024 |
|---|---|---|
| Hazard review, identification and classification | Clause 6, Annexes A, B and C | Annex A |
| Hydraulic design criteria | Clause 6 | - |
| Pipe sizing, layout and hydraulic calculation | Clause 13 | - |
| Spacing and location of sprinklers | - | 5.1.3, 5.2 and 5.3 |
| Obstruction to sprinkler discharge pattern | - | 5.3 |
| Water supplies | Clause 8 | 6.4 |
| Type and size of installation | Clause 11 | - |
| Valves, pipework, alarms | Clauses 15, 17, 16 | - |
| Commissioning and initial inspection | Clause 19 | - |
| Maintenance and inspection | Clause 20 | - |
In other words, in CMSA the answer to "how many sprinklers, at what pressure" comes from EN 12845-2, while the answer to "which pipe carries that flow" comes from EN 12845-1.
2. General design rules (Clause 6.1, EN p.33)
- The design shall be based on the design tables in Clause 6; interpolation and extrapolation are not permitted.
- Where more than one single pallet load of a higher category is stored within any 300 m², the design is based on that higher category.
- All flue spaces shall be not less than 150 mm.
- For STC3 and STC4.3, the distance between loading aisles shall be not more than 6 m; loading aisles shall be at least 1.2 m wide unless the design table requires a greater minimum.
- Unless otherwise stated, the HHS3 protection category shall be used for HHS1 and HHS2. Protection for higher categories may be used to protect lower categories.
- A k-factor design at a given ceiling height may be applied to a lower ceiling height provided that no other parameter changes.
- The storage area limitations in Table 2 of EN 12845:2015+A1:2019 do not apply.
- Where conveyors or other automatic handling systems are present, a means shall be provided to stop them on activation of the first sprinkler.
- Unless otherwise required, a clearance of at least 1 m is needed from the sprinkler deflector to the top of the stored goods; clearances of more than 4 m require no correction to the design parameters.
3. Design area shape and water supply duration (Table 6, Clause 6.4, EN p.34)
| Number of ceiling sprinklers | Duration (min) | Design area shape |
|---|---|---|
| 9 | 60 | 3 × 3 |
| 10 | 60 | 3 × 2 + 4 × 1 |
| 12 | 60 | 4 × 3 |
| 15 | 90 | 5 × 3 |
| 16 | 90 | 5 × 3 + 1 × 1 |
| 20 | 120 | 5 × 4 |
| 24 | 120 | 6 × 4 |
| 25 | 120 | 6 × 4 + 1 × 1 |
| 30 | 120 | 7 × 4 + 2 × 1 |
NOTE 1: for in-rack designs, refer to the relevant design clauses. NOTE 2: with a CMSA design the duration for roll paper storage shall be 120 min irrespective of the number of sprinklers. NOTE 3: with a CMSA design the duration for rubber tyre storage shall be 180 min.
In the same clause: where the range pipes contain fewer sprinklers than the stated number, all sprinklers are assumed to operate and the number of range pipes concerned is increased to compensate. A favourable design area is not required and pipe size reduction is not permitted in order to limit the demand of a favourable hydraulic area.
4. STC1 (free-standing/block stacking) designs
Table 15, HHS1/HHS2 (EN p.49) - selected rows
| Storage height (m) | Max. ceiling (m) | k-factor and orientation | Type | Number of sprinklers | Min. pressure (bar) |
|---|---|---|---|---|---|
| 7.6 | 9.1 | 280 pendent | Wet | 15 | 1.1 |
| 7.6 | 9.1 | 360 pendent | Wet | 15 | 0.7 |
| 7.6 | 9.1 | 360 upright | Wet | 12 | 1.4 |
| 7.6 | 10.7 | 160 upright | Wet | 15 | 1.7 |
| 7.6 | 10.7 | 160 upright | Dry | 25 | 1.7 |
| 7.6 | 10.7 | 240 upright | Wet | 15 | 1.0 |
| 7.6 | 10.7 | 240 upright | Dry | 25 | 1.0 |
| 10.7 | 12.2 | 280 pendent | Wet | 15 | 2.1 |
| 10.7 | 12.2 | 360 upright | Dry (25 s water delivery) | 24 | 1.0 |
The wet-dry pairs in this table show that at the same k-factor and pressure a dry system raises the number of sprinklers from 15 to 25.
Table 16, HHS3, HHS4 and HHS5 (EN p.50) - selected rows
| Class | Storage (m) | Max. ceiling (m) | k-factor and orientation | Type | Sprinklers | Pressure (bar) |
|---|---|---|---|---|---|---|
| HHS3 | 6.1 | 9.1 | 160 upright | Wet | 25 | 1.7 |
| HHS3 | 6.1 | 9.1 | 240 upright | Wet | 15 | 1.5 |
| HHS3 | 6.1 | 9.1 | 280 pendent | Wet | 15 | 1.1 |
| HHS3 | 6.1 | 9.1 | 360 pendent | Wet | 15 | 0.7 |
| HHS3 | 7.6 | 9.1 | 360 upright | Wet | 12 | 1.4 |
| HHS3 | 10.7 | 12.2 | 280 pendent | Wet | 15 | 2.1 |
| HHS4 | 5.5 | 7.9 | 160 upright | Wet | 15 | 3.4 |
| HHS4 | 6.1 | 9.1 | 160 upright | Wet | 25 | 1.7 |
| HHS4 | 6.1 | 9.1 | 240 upright | Wet | 15 | 1.5 |
| HHS4 | 7.6 | 9.1 | 240 upright | Wet | 15 | 1.5 |
| HHS5 | 5.5 | 7.9 | 160 upright | Wet | 15 | 3.4 |
| HHS5 | 5.5 | 7.9 | 240 upright | Wet | 15 | 1.5 |
A point to note: for HHS5, Table 16 contains only the 5.5 m storage / 7.9 m ceiling row. Beyond that, HHS5 protection is governed on the ESFR side and by the additional conditions of Clause 5.4.
5. STC4 (palletized racking) designs
Table 17 (EN p.51) is for HHS1/HHS2 with storage ≤7.6 m; Table 18 (EN p.52) for the same classes with storage ≤15.2 m; Table 19 (EN p.53) for HHS3; Table 20 (EN p.54) for HHS4. All four of these tables have a minimum rack aisle width column.
Selected rows:
| Table | Class | Storage (m) | Ceiling (m) | k and orientation | Type | Sprinklers | Pressure (bar) | Min. aisle (m) |
|---|---|---|---|---|---|---|---|---|
| 17 | HHS1/2 | 6.1 | 7.6 | 360 upright | Dry | 20 | 0.5 | 1.2 |
| 17 | HHS1/2 | 6.1 | 9.1 | 240 upright | Wet | 15 | 1.0 | 1.2 |
| 17 | HHS1/2 | 7.6 | 9.1 | 360 upright | Dry | 25 | 0.7 | 1.2 |
| 18 | HHS1/2 | 12.2 | 13.7 | 360 upright | Dry (20 s) | 12 | 3.4 | 1.8 |
| 18 | HHS1/2 | 13.7 | 15.2 | 480 upright | Dry (20 s) | 15 | 3.4 | 2.4 |
| 18 | HHS1/2 | 15.2 | 16.7 | 480 upright | Dry (20 s) | 16 | 3.4 | 2.4 |
| 19 | HHS3 | 6.1 | 9.1 | 160 upright | Wet | 30 | 3.4 | 1.2 |
| 19 | HHS3 | 6.1 | 9.1 | 160 upright | Wet | 20 | 5.2 | 1.2 |
| 19 | HHS3 | 7.6 | 9.1 | 360 pendent | Wet | 15 | 0.7 | 1.2 |
| 20 | HHS4 | 6.1 | 7.6 | 240 upright | Wet | 15 | 1.5 | 1.2 |
| 20 | HHS4 | 7.6 | 10.7 | 240 upright | Wet | 20 ᵃ | 2.4 | 1.2 |
Footnotes:
- a: 1 level of in-rack sprinklers is added at the first level above the mid-level of the rack; that level is designed for 8 sprinklers at 115 l/min.
- b: Applies only to single row and double row racks and where the aisles are not less than 2.4 m.
Table 20 limits its scope with the wording "HHS4 (excluding cartoned expanded plastics)".
6. Special dry pipe designs (Table 21, EN p.55)
This table carries its own water delivery time and system duration columns. Selected rows:
| Class | Storage (m) | Ceiling (m) | Min. aisle (m) | Design | Max. water delivery (s) | System duration (min) |
|---|---|---|---|---|---|---|
| HHS1 | 10.7 | 12.2 | 2.4 | K160 36 @ 3.8 bar or K240 36 @ 1.5 bar | 30 | 120 |
| HHS1 | 10.7 | 12.2 | 1.8 | K360 12 @ 3.5 bar or K480 12 @ 3.5 bar | 20 | 90 |
| HHS1 | 10.7 | 12.2 | 1.2 | K360 24 @ 1.0 bar | 25 | 120 |
| HHS2 | 15.2 | 16.8 | 2.4 | K480 16 @ 3.5 bar | 20 | 120 |
| HHS3 (STC1 and STC2) | 7.6 | 9.1 | 1.2 | K160 30 @ 3.5 / K240 30 @ 1.5 / K360 30 @ 0.7 bar | 60 | 120 |
| HHS4 (STC1 and STC2) | 7.6 | 9.1 | 1.2 | K160 30 @ 3.5 / K240 30 @ 1.5 / K360 30 @ 0.7 bar | 60 | 120 |
| Up to HHS4 (STC1 and STC2) | 6.1 | 7.6 | 1.2 | K160 20 @ 3.5 / K240 20 @ 1.5 / K360 20 @ 0.7 bar | 60 | 120 |
The explanations below the table: for HHS1, goods containing not more than 5% plastics in closed-top solid wooden boxes may be protected; for HHS2, foodstuffs in cartons containing not more than 5% plastics may be protected; STC1 and STC2 cover solid pile, palletized, rack or bin box storage arrangements.
7. Special commodities (Tables 22-25, EN p.57-58)
Table 22, rubber tyres (wet systems only): for tyres on-side or on-tread in STC3, STC4.1 or STC4.2, storage ≤7.6 m / ceiling ≤9.8 m, K160 upright 15 sprinklers @ 5.2 bar or K240 upright 15 sprinklers @ 2.4 bar. Footnote a: the STC3 limitations do not apply to tyres; instead, on portable racks (open bottom) or in banded stacks there shall either be a 100 mm flue around them, or, where they are grouped adjacently in units of 4 pallets in one direction, a 600 mm aisle and a 300 mm flue.
Table 23, heavy roll paper: it has rows for on-end standard/closed array (banded or unbanded) and on-end open array (banded). For storage ≤6.1 m / ceiling ≤9.1 m wet, K160 upright 15 @ 3.4 bar or K240 upright 15 @ 1.5 bar; dry, 25 sprinklers at the same pressures. For storage ≤7.9 m / ceiling ≤18 m wet, K160 15 @ 3.4 bar or K240 15 @ 1.5 bar.
Table 24, medium weight roll paper (on-end, standard or closed array; open array excluded): for ≤6.1 m / ≤9.1 m, wet K160 15 @ 3.4 bar or K240 15 @ 1.5 bar; dry 25 sprinklers at the same pressures.
Table 25, light weight roll paper (on-end, standard or closed array; open array excluded): for ≤6.1 m / ≤9.1 m wet, K160 25 @ 5.2 bar or K240 25 @ 2.4 bar.
In all three paper tables the k-factors are marked upright only.
8. Moving on to the flow calculation
Once the design row has been selected, the flow per head is obtained from Q = K√P (TS EN 12845+A2:2026 Clause 14.3, EN p.104-105); Q in l/min, K the nominal k-factor, P in bar. The ceiling demand is this flow multiplied by the design number of sprinklers, balanced by hydraulic calculation; the calculation method and the pipe diameters are left to Clause 13 of EN 12845:2015+A1:2019 (Table 1, EN p.7). Where there is an in-rack level, the demand of 8 sprinklers × 115 l/min in footnote a is taken into account separately.
In dry systems the water delivery time is a separate verification item: Clause 6.7.1 (EN p.48) gives 40 s with 4 sprinklers operating as the general rule; some rows in Table 18 and Table 21 replace that general rule with values of 20 s, 25 s, 30 s or 60 s.
Field note: The tables contain more than one row for the same commodity and height; the selection consists simply of balancing the table against the pressure-flow curve of the available water supply. A higher k-factor requires a lower pressure but brings larger pipework.
Frequently Asked Questions
How is a CMSA design carried out step by step?
TS EN 12845-2:2025 Table 1 (EN p.7) gives the order of tasks: hazard classification from Annex A, spacing and location from 5.1.3, 5.2 and 5.3, and water supplies from 6.4 in this standard; while the hydraulic design criteria, pipe sizing and hydraulic calculation come from EN 12845:2015+A1:2019. The CMSA design value is read as a single row from Tables 15-21 (general) or Tables 22-25 (special commodities); Clause 6.1 (EN p.33) prohibits interpolation and extrapolation.
What is the water delivery time in a dry pipe CMSA system?
Clause 6.7.1, EN p.48: for a dry CMSA design the water delivery time shall be 40 s with 4 sprinklers operating, unless otherwise stated in the design tables. Some rows in Table 18 and Table 21 carry their own time: 20 s, 25 s, 30 s or 60 s.
How is the shape of the CMSA design area determined?
Table 6, Clause 6.4, EN p.34: 4 × 3 for 12 sprinklers, 5 × 3 for 15, 5 × 3 + 1 × 1 for 16, 5 × 4 for 20, 6 × 4 for 24, 6 × 4 + 1 × 1 for 25 and 7 × 4 + 2 × 1 for 30. Where the range pipes contain fewer sprinklers than the stated number, all of them are assumed to operate and the number of range pipes is increased.
How many minutes is the CMSA duration for rubber tyre and roll paper storage?
Table 6 NOTE 2 and NOTE 3, EN p.34: with a CMSA design the duration shall be 120 min for roll paper storage irrespective of the number of sprinklers, and 180 min for rubber tyre storage.
How is the CMSA flow rate calculated?
TS EN 12845+A2:2026 Clause 14.3, EN p.104-105: Q = K√P; Q is the flow rate in l/min, K the nominal k-factor and P the pressure in bar. The flow per head is obtained from the minimum pressure and the k-factor read from the design table, and multiplying it by the design number of sprinklers gives the ceiling demand.
References
- TS EN 12845-2:2025 (EN 12845-2:2024), Table 1 - allocation of tasks (EN p.7)
- TS EN 12845-2:2025, Clause 6.1 General (EN p.33)
- TS EN 12845-2:2025, Clause 6.4 and Table 6 (EN p.34)
- TS EN 12845-2:2025, Clause 6.7.1 (EN p.48)
- TS EN 12845-2:2025, Table 15 (EN p.49)
- TS EN 12845-2:2025, Table 16 (EN p.50)
- TS EN 12845-2:2025, Table 17 and footnote a (EN p.51)
- TS EN 12845-2:2025, Table 18 (EN p.52)
- TS EN 12845-2:2025, Table 19 and footnotes a, b (EN p.53)
- TS EN 12845-2:2025, Table 20 and footnotes a, b (EN p.54)
- TS EN 12845-2:2025, Table 21 (EN p.55)
- TS EN 12845-2:2025, Clause 6.7.2 (EN p.55-56) and 6.7.3 (EN p.56)
- TS EN 12845-2:2025, Tables 22 and 23 (EN p.57)
- TS EN 12845-2:2025, Tables 24 and 25 (EN p.58)
- TS EN 12845+A2:2026, Clause 14.3 Q = K√P (EN p.104-105)
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Download MEP Calc on the App StoreTS EN 12845+A2:2026 (EN 12845:2015+A2:2026) Fixed firefighting systems — Automatic sprinkler systems — Design, installation and maintenance; TS EN 12845-2:2025 (EN 12845-2:2024) ESFR and CMSA sprinkler systems. Every figure in this article is taken from the published standard text; clause, table and page references are listed under References. General information only, not a substitute for the standard or for a design review.