Criterion
-
Construction
-
Flame/smoke integrity
-
Insulation time
-
Typical location
-
Flooring relevance
SOLAS Ratings in Plain English
A-60 vs B-15 Fire Divisions Explained
A-60 and B-15 are SOLAS fire-division classes — ratings for the bulkheads and decks that separate spaces on a ship. The letter defines the construction and how long the division must block flame (A: steel, 60 minutes; B: non-combustible, 30 minutes). The number is how many minutes the unexposed side must stay within the temperature-rise limits.
This short guide decodes the classes, shows where each rating is required on board, and explains what they mean in practice for deck build-ups and flooring — in the language your Class surveyor uses.
60 min
A-class integrity test
30 min
B-class integrity test
139°C
Avg. temperature-rise limit
SOLAS II-2A-0 to A-60B-0 / B-15
Letter is the build. Number is the minutes.
Letter First, Number Second
The Division Classes at a Glance
SOLAS Chapter II-2 defines three division classes. For outfitting and flooring work, A and B are the two you will meet on every drawing.
'A' class — structural
Steel or equivalent, stiffened, prevents smoke and flame for a 60-minute standard fire test. Insulated to A-0, A-15, A-30 or A-60 depending on the required temperature-rise time.
'B' class — non-combustible
Approved non-combustible construction — typically cabin bulkheads, linings and ceilings — holding integrity for a 30-minute test, insulated to B-0 or B-15.
'C' class — material only
Approved non-combustible materials with no integrity or insulation requirement — no fire test time attached. Used where the tables require only non-combustibility.
A-60 vs A-30 vs A-0 vs B-15 vs B-0
Rule of thumb: the letter tells you the construction and integrity time, the number tells you the insulation time — how long the cold side must stay within the temperature-rise limits (139°C average / 180°C at any point for A-class; 139°C average / 225°C at any point for B-class).
A-60
-
Steel or equivalent
-
60 min
-
60 min
-
Decks/bulkheads at machinery, galleys, cargo
-
A-60 floating floor build-ups
A-30 / A-15
-
Steel or equivalent
-
60 min
-
30 / 15 min
-
Intermediate-risk adjacencies per Reg. 9 tables
-
Thinner insulated deck build-ups
A-0
-
Steel or equivalent
-
60 min
-
None (0 min)
-
Low-risk steel boundaries
-
Bare or levelled steel deck + approved covering
B-15 / B-0
-
Approved non-combustible
-
30 min
-
15 / 0 min
-
Cabin bulkheads, corridor linings, ceilings
-
Rarely the deck — a partition rating
Related Reading
Go deeper on the ratings, the certificates and the certified systems themselves.
A-60 floating floor systems↗
The build-up that turns a steel deck into an A-60 division — layer by layer, with the certified GTF Freese systems.
IMO/MED certification↗
FTP Code parts, wheelmark, Module B+D and the documentation package your surveyor expects.
Marine flooring systems↗
The complete deck picture zone by zone — from bare steel to finished floor.
Marine flooring catalogue↗
IMO/MED certified vinyl, carpet, linoleum and deck systems supplied across the EU.
A-60 vs B-15 — Frequently Asked Questions
The questions specifiers ask when the fire plan lands on their desk.
01 What is the difference between A-60 and B-15?
They belong to two different SOLAS division classes. An A-60 division is steel (or equivalent), blocks smoke and flame for a 60-minute standard fire test, and keeps the unexposed side within the temperature-rise limits for the full 60 minutes. A B-15 division is approved non-combustible construction, holds integrity for a 30-minute test, and meets the temperature-rise limit for the first 15 minutes. A-60 is a structural boundary for high-risk adjacencies; B-15 is a lighter partition rating inside accommodation areas.
02 What does the number in A-60 or B-15 mean?
The number is the insulation time in minutes — how long the cold side of the division must stay within the temperature-rise limits during the fire test. A-class comes as A-0, A-15, A-30, A-60; B-class as B-0 and B-15. The letter fixes construction and integrity time; the number fixes insulation performance.
03 Where is A-60 required on a ship?
Wherever the SOLAS II-2 Regulation 9 tables say so for the two space categories either side of the boundary — typically where machinery spaces of category A, galleys or cargo spaces border accommodation, control stations or escape routes. Decks over machinery spaces are the classic case, and the reason A-60 floating floors exist.
04 Is B-15 relevant for flooring?
Rarely for the deck itself — rated decks are normally A-class, because they are structural steel boundaries. B-15 applies mostly to bulkheads and linings between cabins and corridors. For flooring the practical pairing is: A-class for the deck build-up, FTP Code Part 2/Part 5 approvals for the coverings on top.
05 Can a floor covering itself be A-60 rated?
No — A-60 is a property of the whole tested division: steel deck plus the complete build-up. A covering on its own carries IMO FTP Code approvals (Part 2 surface flammability, Part 5 primary deck covering). When a datasheet says a product is “used in A-60 constructions”, it means the product is a named component of a type-approved system — the certificate belongs to the system.
Decoding a Fire Plan for a Real Project?
Trivaro supplies certified A-60 floating floor systems and IMO/MED approved finishes across the EU — and helps you translate the fire plan into a build-up your classification society signs off first time.
Send the drawing, the required divisions and the deck areas — we respond with a certified system per zone and a B2B quotation.
