EN 12845 Annex D — Installation Zoning Rules

Dividing a sprinkler installation into zones is not just a design convenience. It determines whether an alarm can be located, whether testing is practical, whether a section can be isolated — and whether the insurer will accept the system. Poor zoning starts with the ten minutes lost searching after a "system activated" alarm.

In a seven-storey office building, a sprinkler alarm sounded because of a small leak on the fourth floor. The system had been designed as a single zone, so the alarm simply read "Building — General". The fire service searched floor by floor for 22 minutes. The insurer's report recorded that there was no zone separation, that every floor sat in one zone, and that the alarm was not identifiable. Renewal was made conditional on zone separation with a flow alarm on each floor, retrofitted within four months — at many times what it would have cost to do at design stage.

Annex D — basic zoning rules

Maximum zone area

Hazard class	Max. zone area	Max. sprinklers per zone
LH	10 000 m²	500
OH	12 000 m²	1000
HHP	9000 m²	1000
HHS	9000 m²	1000

Zone separation by floor

• At least one zone per floor
• Exception: a small plant level under the roof (≤ 200 m²) may be combined with the main floor
• Basements and below-ground floors: a separate zone, because the fire spread path differs
• Atria: a separate zone regardless of how many floors they cross, treated like a fire compartment

Aligning zones with fire compartments

Where possible, a sprinkler zone boundary should coincide with a structural fire compartment boundary (an REI 60 or 90 wall). When it does:

• Even if fire crosses a compartment, sprinkler zones do not open simultaneously
• The hydraulic design area can be optimised to cover a single compartment
• When a zone is shut down for testing, compartment protection is preserved

The zone valve set

The standard set for each zone:

• Stop valve (butterfly or OS&Y, supervised)
• Water flow alarm (vane- or sail-type switch)
• Pressure switch (optional but common)
• Drain valve, DN50 minimum
• Inspector test connection
• A label reading "Zone Z-X Stop Valve — DO NOT CLOSE"

The zone valve need not sit with the control valve set; a separate set is installed at each zone take-off from the riser. Access has to be planned, with a fixed ladder or platform.

Zoning a multi-storey building

Building height	Typical zone arrangement	Risk management
1–3 storeys	One zone per floor	Standard
4–7 storeys	One or two zones per floor; two on large floors	Annex D plus Annex E (high-rise)
8–15 storeys	Two zones per floor (north-south or east-west)	Annex E mandatory
Above 15 storeys	Two to four zones per floor, with a pressure zone every seven or eight floors	Annex E plus a separate pump set

Field error — zone boundary in the wrong place

At a textile warehouse, zone boundaries had been drawn on the structural column grid at 8 m, while the internal fire compartment wall stood at 12 m. When a small fire started in the production area, two zones opened simultaneously, the hydraulic capacity fell short, pressure dropped, and the later sprinklers received insufficient water. The design assumed a 260 m² operating area; the reality was 480 m². The Annex D principle that a zone equals a fire compartment had been skipped. The boundaries were later moved to the walls and an extra alarm valve set installed. Zoning design should not begin before the building plan has settled.

The flow alarm zone map

The alarm panel must present zones clearly:

• A graphic map for each zone (floor plan plus sprinkler network)
• Zone names matching the block plan signage, for example "Z3 — Floor 4 East"
• A time stamp on the flow alarm, recording first activation
• The fire service panel near the main entrance, with a visual zone map

One riser, several zones

A single riser can serve several floor zones, with a zone valve set at each tee take-off. The riser is sized not for the simultaneous demand of every zone but for the hydraulic design requirement of a single operating area — which is why risers are typically DN150 to DN200.

Zone testing sequence

Zones are tested in sequence during the monthly and quarterly routines:

• While one zone is under test, the others must remain in service
• The stop valve of the zone under test is not closed; the alarm test connection is used instead
• Flow alarm, pressure switch and panel signal are verified separately for each zone
• All zones are tested under full flow annually

Comparison with NFPA 13

NFPA 13 requires a separate control valve for every floor, matching EN 12845 exactly. The NFPA limit is 1000 sprinklers per system for light and ordinary hazard, with a 100 000 ft² (about 9290 m²) area limit — close to the 9000 m² EN 12845 limit for HHP and HHS. NFPA's single-floor rule is stricter, whereas Annex D allows an exception for a small plant level. On the NFPA side a flow alarm is mandatory for every zone under NFPA 72. The two standards run parallel on zoning philosophy.

Link to Turkish regulation

BYKHY inspections check alarm zoning. Sprinkler and fire detection zones must appear on the same map, and in a multi-zone building the fire detection panel and the sprinkler flow alarm panel should share a room or be integrated. Where the building exceeds 21.5 m in height, the high-rise provisions add further zone restrictions — a separate riser and zone for every seven floors or pressure zone — applied together with Annex E.

Quick check list

• At least one zone per floor, two on large floors.
• Maximum zone area matches the hazard class.
• Zone boundaries coincide with fire compartment walls.
• Each zone has a stop valve, flow alarm, drain and test connection.
• Labelling matches the block plan.
• The alarm panel shows a graphic zone map.
• Basements, atria and roof plant levels assessed as separate zones.
• Zone valve access guaranteed by a platform or ladder.

Frequently Asked Questions

What is the maximum zone area?

10 000 m² for light hazard, 12 000 m² for ordinary hazard and 9000 m² for high hazard, with a maximum of 1000 sprinklers per zone (500 for LH).

Should a zone boundary follow the fire compartment?

Yes, wherever possible. When zone and compartment coincide, the design operating area covers a single compartment and testing does not compromise compartment protection.

What does a zone valve set contain?

A supervised stop valve, a water flow alarm, usually a pressure switch, a DN50 drain valve, an inspector test connection, and clear labelling matching the block plan.

Can a single riser feed several zones?

Yes — with a zone valve set at each tee. The riser is sized for one operating area, not for every zone simultaneously, which is why DN150–200 is typical.

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