Which mineral fibre board for each space? Accessible suspended ceilings 60×60

Solutions & Applications · Mineral Fibre Suspended Ceilings

The accessible suspended ceiling is the only structural element that is designed in reverse: not from the desired level upwards, but from the deepest point downwards. Anyone who first sets the height and then looks at what needs to fit will have to redefine it. The mineral fibre board is the final element — and is selected based on the use of the space, not on the sample.

What is a mineral fibre board?

A board made of biodegradable mineral fibre with inorganic additives and a binder, usually 15 or 19 mm thick, in dimensions of 600×600 or 1200×600. Its porous structure absorbs sound, its mass limits sound transmission to adjacent spaces, and its composition gives it an A2-s1,d0 reaction to fire — effectively non-combustible, with minimal smoke and no flaming droplets.

The slab rests freely on a metal framework and can be lifted by hand. This is its advantage over any enclosed ceiling: access to electrical and mechanical installations at any point, without the need for cutting, repair or painting.

The nine components of the system

No.	Item	Role & key considerations
1	Ceiling plug	Transfers the entire load to the slab — the type is selected based on the sub-base, not out of habit
2	Suspension strut	It defines the level; the length is derived from the depth of the plenum
3	Suspension bracket	Quick link for levelling without cutting the string
4	Perimeter L-bracket	It supports the end slabs — it does not bear the framework
5	Main Guide T	It bears the load; the secondary 120 and 60 cm elements interlock vertically
6	Mineral fibre board	Selected according to the intended use of the space — acoustics, hygiene, humidity, aesthetics
7	Sprinkler system	Head centred on the slab, flexible spiral, cover rosette
8	LED panel light fitting	60×60 fixed directly to the framework; heavy light fittings require independent suspension
9	Air-conditioning system	Openings in the partitions, connection via flexible air ducts

Board edge: Board or Tegular

The same slab is available with different edges, and the edge changes the appearance of the entire roof.

Akmi	How it fits	Result
Board	Flat edge, on the guide rail	The grid is clearly visible — an economical, classic look
Tegular 24	Stepped edge extending below a T-24 guide	The slab ‘protrudes’ and the framework appears to recede
Tegular 15	The same principle applies to the T-15 pocket guide	The finest grid line — a more architectural appearance

The edge must correspond to the framework: a Tegular 15 board on a 24 mm guide does not sit correctly. The selection is made simultaneously, not sequentially.

The figures we are comparing

• Sound absorption (αw / NRC) — how much sound the panel absorbs within the same space. Ranging from 0.15 for smooth panels to 0.90 for acoustic panels.
• Sound reduction (Dn,f,w / CAC in dB) — the amount of sound that passes through the partition, via the plenum, into the adjacent space. Measured in offices with enclosed rooms.
• Moisture resistance (RH) — the relative humidity limit at which the board does not bend. A board that does not meet the specification ‘sags’ in a swimming pool or preparation room.
• Light reflectance — 85–88 per cent on white panels. Each unit reduces the amount of artificial lighting required for the space.

The first two factors often work at cross-purposes: a porous slab that absorbs a great deal allows sound to pass through, whilst a dense slab that blocks sound absorbs less. That is why the right slab depends on what is causing the problem — reverberation within the space or speech from the neighbouring room.

Selecting slabs by application

Slab	Key features	Where it fits
AMF THERMATEX® Feinstratos 15 mm	NRC 0.15 · 34 dB · 85 per cent reflectance	Shops, corridors, industrial premises — smooth, cost-effective
ARMSTRONG SAHARA 15 mm	NRC 0.55 · 34 dB · reflectance 85% · Board, Tegular 24/15	Offices, educational premises
AMF THERMATEX® Feinfresko	NRC 0.60 · classic textured finish	Offices, retail
ADAGIO Acoustic+ 19 mm	NRC 0.70 · 39 dB · reflectance 88 per cent	Offices with enclosed rooms — where sound insulation matters
OWA Constellation	NRC up to 0.80 · up to 35 dB · 95% RH · 88% reflection	Offices, education, reception areas
Knauf ECOMIN Alpha 15	NRC 0.90 · up to 100 per cent RH	Open-plan offices, non-air-conditioned spaces
AMF THERMATEX® Alpha Colour Black	NRC 0.90 · black smooth finish	Cinemas, restaurants, studios
AMF THERMATEX® Aquatec 19 mm	NRC 0.90 · up to 100 per cent RH · reflectance 88 per cent	Swimming pools, changing rooms, kitchens, wet areas
MEDIGUARD Plain	Antimicrobial · resistance to disinfectants · 88% reflectance	Hospitals, laboratories, food preparation areas
HERADESIGN® Fine 15 mm	Wood wool · impact resistance	Gyms, schools — an alternative where mineral fibre cannot withstand impact
RAW CONCRETE OWA	NRC up to 0.70 · exposed concrete finish	Industrial design, catering, retail

Installation procedure

• Laser marking: the finished level is marked across the entire surface and the L-shaped corner beading is fitted to the walls.
• Installation: drilling the roof, metal plugs and dowels. Levelling is carried out using washers, not by cutting the dowels.
• Framework: the main T-profiles are suspended, whilst the secondary 120 and 60 cm profiles are fixed vertically, forming a 60×60 cm grid.
• M&E integration: sprinklers with flexible spiral hoses and rosettes, light fittings on the framework, air conditioning vents in the recesses.
• Tile laying: to be carried out last, once work generating dust and moisture has been completed; at the corners, tiles are cut with a tile cutter so that they fit snugly into the perimeter corner.

The perimeter corner is not a support

It is the mistake that goes unnoticed until it becomes apparent. The L-bracket supports the edge of the slab — it was not designed to bear the load of the framework. When the final opening near the wall is left without a lintel, the main stud rests on the angle bracket, the angle gradually bends and the perimeter of the ceiling ‘sags’ visibly in relation to the rest of the ceiling.

The rule: fix it in place and close to the perimeter, at the distance specified by the system — not just inside the grid.

Heavy-duty lighting and equipment

The 60×60 framework is dimensioned to support the weight of slabs and lightweight panels. Spotlights, large light fittings, loudspeakers, screens and large-diameter vents are suspended independently of the concrete slab. A load ‘suspended’ from the guide deforms the grid, causing the openings to lose their square shape — and the slabs no longer sit correctly.

Seismic behaviour

A factor that is rarely discussed in Greek projects, yet is the most relevant. A frame suspended solely by vertical studs may sway horizontally during an earthquake. The consequences are predictable:

• Slabs projecting from the formwork — in a public area, this is a safety issue.
• Stress on sprinkler heads where they penetrate the slab, with a risk of leakage.
• The perimeter comes away from the L-corner as the battens move.

The solution involves lateral ties within a defined grid and adequate perimeter reinforcement. In public buildings — schools, hospitals, retail premises, and assembly spaces — it is advisable to stipulate this as a requirement in the design rather than leaving it to the installer.

Mineral Fibre Boards

Acoustics, Wet Rooms & Sanitary Facilities

Structure & Categories

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