EN 12845-2 ESFR/CMSA Design Examples: Sprinkler Selection by Ceiling Height (7–17 m)

This article gives dozens of worked ESFR and CMSA solutions organised by ceiling height — 7.6 m, 9.1–10.7 m, 12.2 m and above 12.2 m — for both non-storage process (FH) and storage (HHS1–HHS5) occupancies, based on the actual design tables of EN 12845-2:2024 (Tables 7 to 21). Every row states the K-factor, the number of operating sprinklers, the minimum operating pressure and the source table. Values are for information; the full text of the standard governs any actual design.

General Rules (Applying to All Tables)

• ESFR is wet pipe only (even a dry pendent ESFR counts as a wet system, Cl. 6.5). CMSA may be wet or dry; dry CMSA uses 141 °C heads on terminal tree pipework, and gridded or looped arrangements are not permitted (Cl. 6.7.2).
• Water supply duration: generally at least 90 minutes; 60 minutes for combined ceiling and in-rack designs; 120 minutes for certain special dry CMSA designs.
• Maximum roof or ceiling slope is 10 degrees; beyond that a flat suspended ceiling, an in-rack combination, or a move to CMDA is required.
• Interpolation and extrapolation are prohibited — intermediate cases are rounded up to the next safe row.
• Special-condition ESFR designs have a minimum design area of 71 m² (9 sprinklers arranged 3 × 3 on adjacent range pipes).

1. Non-Storage Process (FH) — CMDA Required

In FH3 to FH5 ESFR and CMSA are prohibited; only CMDA (density and area, EN 12845-1) may be used. Where ESFR or CMSA is used in FH1 or FH2, it is designed on an HHS1–HHS3 basis (the storage tables below) regardless of the actual commodity category. Process CMDA criteria:

2. Storage (HHS) — Ceiling Around 7.6 m (Storage Around 6.1 m)

ESFR options

CMSA alternatives

3. Storage (HHS) — Ceiling Around 9.1 to 10.7 m

ESFR options

CMSA alternatives (STC1 block and STC4 rack)

4. Storage (HHS) — Ceiling Around 12.2 m

ESFR options

CMSA alternatives

5. Storage (HHS) — Above 12.2 m (13.7, 15.2 and 16.8 m)

At these heights only pendent ESFR (K400/K480) and dry CMSA (K480) remain available; aisle width and deflector clearance become the critical constraints.

6. Special Commodities: Rubber Tyres and Roll Paper

7. Combined Ceiling and In-Rack Design

Where the ceiling-only limit is exceeded, in-rack sprinklers are added. The in-rack hydraulic calculation is based on the 8 most remote heads at a minimum of 230 L/min, and the water supply duration is at least 60 minutes (Cl. 6.6.2). The ceiling side:

Frequently Asked Questions

Are ESFR sprinklers prohibited in high hazard storage under EN 12845-2?

No - the opposite is true. ESFR and CMSA were developed for high hazard storage (HHS1 to HHS5) and EN 12845-2 protects those classes with them. The prohibition in Clause 6.2 applies to non-storage high hazard process occupancies (FH3, FH4, FH5). The clause is even titled Protection of non-storage occupancies. You protect the warehouse with ESFR or CMSA; you cannot protect the production area with them, where CMDA or deluge is required.

What ESFR options are available for HHS1-HHS3 at a 7.6 m ceiling?

From the Table 7 ceiling-only design with 12 sprinklers: K200 at 3.4 bar, K240 at 2.4 bar, K320 at 1.7 bar or K360 at 1.0 bar pendent; upright K200 at 3.4 bar or K240 at 2.4 bar. Using the special-condition route in Table 10 the count can drop to 9 sprinklers: K200 at 2.4 bar, K240 at 1.7 bar, K320 at 1.4 bar, K360 at 1.4 bar. Fewer sprinklers means a smaller pump and a smaller tank.

Which designs apply at a 12.2 m ceiling?

For HHS1-HHS3, ESFR ceiling-only gives K240 at 12 sprinklers and 3.6 bar, K320 at 12 and 2.8 bar, or K360 at 12 and 1.7 bar (Table 7). The special-condition route gives K320 at 9 and 3.5 bar or K360 at 9 and 2.8 bar (Table 10). On the CMSA side, wet K360 pendent at 15 sprinklers and 1.6 bar, or dry K360 upright at 24 sprinklers and 1.0 bar with 25 second water delivery (Tables 15 and 18). For HHS4 and HHS5 the pressures increase.

How are very tall warehouses above 12.2 m protected?

With ESFR ceiling-only: at 13.7 m, K320 or K360 at 12 sprinklers and 2.8 bar; at 15.2 m, K400 at 12 and 2.8 bar or K480 at 12 and 3.8 bar with a minimum 1.8 m aisle; at 16.8 m, K400 at 12 and 5.5 bar with a 2.4 m aisle, or K480 at 12 and 3.8 bar (Table 7). Alternatives are the Table 11 special design reducing to 9 or 10 sprinklers, or dry CMSA systems from Tables 18 and 21 using K480 upright at 15 to 16 sprinklers and 3.4 to 3.5 bar with 20 second water delivery.

ESFR is wet only and CMSA can be wet or dry - how do I choose?

ESFR may only be used on a wet pipe system, since even a dry pendent ESFR is served from a wet system. If the warehouse is unheated and freezing is a risk so a dry system is genuinely required, you move to CMSA. On dry CMSA the water delivery time and the increased operating sprinkler count both come into play, and the heads must be 141 degrees C nominal on terminal tree pipework, with gridded and looped arrangements prohibited under Clause 6.7.2.

What are the water supply duration and roof slope limits?

For ESFR and CMSA the water supply duration is generally at least 90 minutes; it can reduce to 60 minutes for combined ceiling and in-rack designs, and certain special dry CMSA designs require 120 minutes (Table 21). The maximum roof or ceiling slope is 10 degrees; beyond that you need a flat suspended ceiling, an in-rack combination, or a move to CMDA. Interpolation and extrapolation within the tables are also prohibited.

When are in-rack sprinklers required?

When the ceiling-only design exceeds its commodity or height limit. For example, up to 13.7 m in open-frame racks with commodities up to HHS4, a K200 or larger pendent ceiling ESFR is supplemented by a single level of wet in-rack sprinklers in the longitudinal flue. The in-rack hydraulic calculation uses the 8 most remote heads at a minimum of 230 L/min, and the water supply duration is at least 60 minutes (Clause 6.6.2 and Table 12).

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