Seamless acoustic plaster is a system, not a coating: an acoustical board, a plaster of perlite and recycled cotton, and a sprayed colour coating, installed with no grid, tile or joint. The Styjl Fellert Even Better system reaches NRC 0.95 and absorption class A on a 39 mm board, tested to ASTM C423 and EN ISO 354. That figure belongs to the whole build-up and its mounting, not to the finish, so a Dubai fit-out has to reserve the void before the ceiling is drawn.
What a seamless acoustic plaster ceiling actually is
Seamless acoustic plaster is a system rather than a coating. The one we supply in Dubai is made by Styjl in Sweden: the Fellert Even Better build-up is an acoustical board of recycled fibre adhered or mechanically fixed to the substrate, an acoustic plaster of perlite and recycled cotton sprayed and trowelled at roughly 1.5 to 3 mm wet, and an acoustical coating sprayed in two light passes to carry the colour. Sound passes through the open plaster and coating into the board behind it, and the board does the absorbing. There is no grid, no tile and no visible joint, which is the whole reason an architect reaches for it.
That gives a Dubai lobby or majlis one continuous plane from wall to wall, and the surface is chosen from a range rather than being a single look. The three standard textures are Silk, the smoothest; Sahara, a fine open texture; and Secern, a coarse open texture. Decorative variants add Concrete, New England, Silk Metallic, Marble and Stone. Colour runs from Standard, equal to RAL 9001, through Standard+ with seven predefined RAL colours plus concrete, marble, stone and metallic effects, to Special, which covers any RAL or NCS reference.
The limits are firm and worth writing into the schedule early. It is an interior ceiling and wall system: not an exterior finish, not for wet rooms, not for floors. The acoustical board is fibreglass-based and has to be adhered or mechanically fixed to an approved substrate, so it is specified against a named background rather than applied to whatever the site offers. The finished face is open and comparatively soft, which is the same property that makes it absorb, so it belongs on ceilings and high wall areas rather than at shoulder height in a busy Dubai restaurant. Where other surfaces in the same room need a different answer, the materials page sets out where each finish belongs.
What NRC and class A actually mean
NRC is a single number from ASTM C423, measured on a specimen in a reverberation room. It is the arithmetic average of the sound absorption coefficients at 250, 500, 1,000 and 2,000 Hz, rounded to the nearest 0.05. That is all it is. It carries no information about 125 Hz, where a room's boom lives, or about 4,000 Hz, and it describes a laboratory specimen rather than your ceiling. It is useful for comparing products on a like-for-like basis. It is not a prediction of what a Dubai lobby will sound like.
The European route runs in parallel and the two are not interchangeable. EN ISO 354 governs the measurement; EN ISO 11654 converts the octave-band results into a single weighted figure, alphaW, by fitting a reference curve, then sorts that figure into a class. Class A is alphaW 0.90 to 1.00, class B 0.80 to 0.85, class C 0.60 to 0.75, class D 0.30 to 0.55 and class E 0.15 to 0.25. Class A therefore means a threshold has been crossed, not that one class A product performs like another.
On the Fellert Even Better system the figures separate quickly. Sahara on the 39 mm board reaches NRC 0.95 to ASTM C423, and alphaW 0.95, class A, to EN ISO 354 and EN ISO 11654. Silk reaches NRC 0.90 and class A on the same board, and NRC 0.85 on the 25 mm board. Marble and Stone sit at NRC 0.60 and alphaW 0.55, class D: they buy an appearance with roughly half the absorption. Same family, same thickness, a different acoustic answer, which is why the finish is selected after the acoustician has fixed the absorption area, not before.
The mounting condition is part of the number
Every absorption figure is a figure for a specimen in a mounting, and ASTM E795 defines what those mountings are. Type A is the specimen laid directly against a solid backing with no air space behind it. Type E200 and type E400 hold it 200 mm or 400 mm off the structure. The same product returns different numbers in each, because an air space behind an absorber mainly changes its behaviour at low frequency. A data sheet quoting NRC without stating the mounting is a marketing number, and it should not clear a Dubai submittal.
The Fellert figures above are all type A, which means the acoustical board is fixed to a solid backing: 16 mm plasterboard, concrete or a previously painted substrate. The Straight Up system publishes the full set, and it shows the direction is not fixed. Straight Up 20 mm gives NRC 0.75 at type A, 0.85 at E200 and 0.80 at E400; with the high-NRC backer board it gives 0.95 at type A, 0.90 at E200 and 0.90 at E400. Adding an air space helps in the first case and costs you in the second.
The practical consequence in a Dubai fit-out is a plenum decision rather than an acoustic one. If the number in the specification was measured at E400, the ceiling needs 400 mm of clear air behind it, and in a fit-out that void is already spoken for by chilled-water pipework, fresh-air ducting, containment and sprinkler runs. Settle the mounting with the acoustician and the MEP engineer in the same conversation, before the reflected ceiling plan is issued, rather than discovering at first fix that the tested condition cannot be built.
The build-up and void a Dubai fit-out has to reserve
Start with the depth below the structure. A Fellert Even Better ceiling on 16 mm plasterboard adds a 25 mm or 39 mm acoustical board plus roughly 1.5 to 3 mm of plaster and the coating, so allow around 45 to 60 mm from the ceiling framing to the finished face, before hangers and before any air space the mounting requires. The metal ceiling grid sits at 400 mm centres, built exactly as it would be for 16 mm commercial plasterboard. That is worth knowing at tender stage: this is not a proprietary carrier imported as a separate package, so the framing can be priced and programmed as ordinary ceiling work.
Straight Up runs on a plasterboard suspension grid at 300 mm centres, with boards of 800 by 1,200 mm in the 20 mm system and 600 by 1,200 mm in the 15 mm system. The shallower build-up exists for ceilings where the void will not give up 20 mm, and it carries an honest penalty: without the high-NRC backer board, Straight Up 15 mm has no published type A figure at all, and its absorption is materially lower than the 20 mm system. Specify the backer wherever type A mounting is required.
The accepted substrates are 16 mm gypsum wallboard, the metal ceiling grid constructed for it, concrete and previously painted substrates, and a seamless finish inherits the flatness of whatever sits beneath it. Sequencing matters as much as depth. This is a wet trade near the end of the programme, so first fix has to be complete and tested, the facade closed and the site conditioned. The mixed plaster has a pot life of 12 to 18 hours; the coating dries in 20 to 30 minutes and is fully cured after 24. None of that suits an open slab in a Dubai August.
Coordinating with MEP and lighting when there is no tile to lift
A monolithic ceiling has nothing to lift. Every service that penetrates the plane has to be designed in before the board goes up: sprinkler heads and their cover plates, smoke detectors, speakers, linear slot diffusers and return air paths. Anything above the plane that will need maintenance must be reachable through a designed access panel, or serviced from somewhere else in the void. Access cut later is a repair, and a repair on a seamless ceiling is a decision to accept a patch, so it is worth walking the reflected ceiling plan against the MEP model service by service.
Lighting deserves its own pass. Trimless plaster-in luminaires suit the system, because the fitting is installed before the plaster and the plaster is returned into it. Light reflectance runs up to 93 to ASTM 1477, which makes the ceiling efficient for the indirect and cove schemes common in Dubai hotel and retail interiors. The same reflectance cuts the other way: a wall-washer grazing a hand-applied plane will read every variation in texture. Either keep raking light off the plaster or take the texture as part of the design, and settle it on the mock-up under the project's own fittings.
Then the perimeter. Shadow gaps and movement joints at wall junctions, bulkhead changes and structural movement joints are set out before the ceiling is framed, not negotiated afterwards, because a seamless plane has no joint of its own to hide the movement in. The same applies to the junctions with the rest of the palette, where the ceiling meets a clay plaster wall, a stone reveal or a joinery head. Each of those junctions is easier to resolve on a panel than on a finished ceiling, and each one is a place where two trades have to agree a sequence before either starts.
Reverberation in hard-surfaced Dubai interiors
The reason this question comes up so often in Dubai is the material palette. A typical restaurant, lobby or majlis here is large-format porcelain or stone underfoot, full-height glazing on one or two sides, gypsum walls, glass balustrades and hard joinery. Almost nothing on that list absorbs anything. Reverberation time follows the Sabine relationship, roughly 0.161 times the room volume divided by the total absorption present, so a double-height space needs proportionally more absorbing area than a low one to reach the same result.
That arithmetic is why the suspended tile grid gets specified in the first place: it is the cheapest large absorbing plane available. Where the grid is visually unacceptable, in a double-height lobby, a majlis ceiling, an auditorium soffit or a restaurant with exposed structure, seamless plaster keeps the plane and keeps the absorption. The order of work still matters. The acoustician sets the target reverberation time and the absorption area needed to reach it; the finish is then chosen to deliver that area. Choosing the finish first and hoping it covers the target is the common failure.
It is also worth being blunt about what absorption does not do. NRC and alphaW describe sound removed from the room a surface faces. Neither says anything about sound travelling from one room to the next, which is transmission, and is governed by the partition, how it meets the slab, and the flanking path over the ceiling through a shared void. The measure for that ceiling path is ceiling attenuation class to ASTM E1414, and Styjl publishes CAC 51 for the Straight Up 15 mm system. Where two meeting rooms share a plenum, the answer is a plenum barrier or a partition taken to the soffit, not a higher NRC.
Repair, restoration, and the coating that must not be rolled
Because the surface is applied by hand rather than manufactured as a unit, a damaged area is cut back and re-plastered by the same trade instead of a tile being swapped out. The match is the whole question, and it is a question about texture and colour under the project's own lighting, which is why the approved panel is retained on site and the batch recorded against the room. Keeping spare plaster and coating from the same batch is worth the storage for the same reason: a repair made from a later batch is a colour risk that nobody notices until the light rakes across it.
The coating is also the restoration route. Fellert Even Better Acoustical Coating is water-based and sprayed with an air-mix gun, a Kremlin 30:25 or equivalent, in two light passes. Applied that way it does not reduce the absorption of the ceiling beneath it, whether that ceiling is new or an existing acoustic ceiling being brought back rather than stripped out. Coverage is roughly 120 m² per pail over Silk, 100 m² over Sahara and 80 m² over Secern, drying in 20 to 30 minutes and curing fully in 24 hours.
That permission is method-specific, and the failure mode follows directly from it. Roller and brush application sits outside the manufacturer's method, and applied outside the method the coating can reduce the absorption of the ceiling under it. In practice the risk is not the installer. It is a maintenance contractor two years after handover rolling ordinary emulsion across the ceiling during a refresh: the acoustic design is undone in an afternoon and nothing about the room looks different. Write the restriction into the operation and maintenance manual and put it on the handover drawing.
The test data to demand, and the documents a Dubai ceiling needs
Ask for the test report rather than the headline. It should name the testing laboratory and the standard, ASTM C423 with the ASTM E795 mounting stated, or EN ISO 354 rated to EN ISO 11654, and give the octave-band absorption coefficients from 125 Hz to 4,000 Hz rather than the averaged figure alone. It should describe the exact build-up tested: board thickness, plaster and finish. Reaction to fire should be classified against that same build-up, because the classification depends on it — Straight Up is rated B s1d0 or A2 s1d0 to EN 13823 and Class A to ASTM E84 depending on the set-up. The data sheets and certificates we hold sit on the specify page.
A Dubai job then asks for a second folder alongside the acoustic one. Al Sa'fat, Dubai Municipality's green building system, sets a minimum of Silver Sa'fa and so brings emissions and material origin onto the ceiling schedule next to the absorption figures; how Al Sa'fat reads a finishes package covers that ground. For this system the relevant lines are specific: the Even Better acoustical plaster carries 40 per cent recycled content and the board 60 per cent, Straight Up 15 mm runs up to 92 per cent recycled by weight and is built to be demounted and re-used rather than demolished, and VOC emissions are tested to CDPH/EHLB Standard Method v1.2-2017. A ceiling contributes evidence to a submittal; it does not satisfy one. Issuer, scope and expiry for every document are listed on our credentials register.
Then the ceiling itself. A sample settles the colour; only a panel sprayed on the real soffit, by the applicator who will spray the rest of it, settles the texture, and that panel is what the finished plane is judged against — signed off from the floor under the project's own fittings, never from a rendering. Earth Layers is the exclusive Middle East dealer for Styjl, and the roughly 200 artisanal applicators who trowel and spray this work sit on our own sponsorship and payroll rather than hired in per package, so material, panel and finished ceiling all come from one company. Bring us the reflected ceiling plan, the acoustician's report and the void you actually have: send the drawings, or reach us by WhatsApp on +971 50 136 0506. Sample panels travel to your office or to site, and a mock-up on the ceiling itself settles the finish - ask for one.