Ceilings & suspended ceilings

Closed plasterboard suspended ceiling: framework, panelling, recessed lighting and Q1–Q4

Last updated: 15 October 2026

A comprehensive guide to flat roofs: from the framework and boarding to Q4 for recessed lighting. It highlights where issues with flatness, fire resistance and

The system at a glance

Solutions & Applications · Plasterboard Ceilings

Curves, changes in level, recessed lighting and domes do not arise from the plasterboard — they arise from the framework. The plasterboard follows; whatever shape can be constructed from metal can also be clad. There is one trade-off for a seamless surface: access to the services from above is only possible where we have provided for it.

When to use a closed roof

A closed plasterboard ceiling is chosen when the surface area takes precedence over accessibility: in residential properties, hotel rooms, reception areas and wherever the architect wishes to create a specific form — flat surfaces, curves, light lines. It is also chosen when the ceiling needs to provide fire resistance or sound insulation to the floor above, something that suspended ceiling panels struggle to achieve.

Where electrical and mechanical installations require frequent maintenance across the entire area — offices, service corridors — the correct solution is an accessible suspended ceiling. Most projects combine both.

Three families of roofing systems

Type	What it offers	Where is it going?
Continuous plasterboard	Uniform painted surface, freedom of form, fire resistance	Residential properties, hotels, and spaces with architectural requirements
Perforated acoustic panels	Sound absorption with a uniform appearance	Halls, catering facilities, open-plan offices
Detachable on grid	Full access to the vacancy	Areas with dense networks

The three do not compete — they coexist within the same project. A hotel has a continuous ceiling in the rooms, a perforated ceiling in the lobby and a demountable ceiling in the service corridors.

Which plasterboard for the ceiling?

Plank	When to use it
Type A	Dry spaces with no specific requirements — the basis for homes and offices
Type H2 — moisture-resistant	Bathrooms, kitchens, areas subject to periodic damp
Type DF — fire-rated	Ceilings requiring fire resistance, in a certified configuration
DFH2 — moisture- and fire-resistant	Damp and fire together — boiler rooms, catering kitchens
ULTRA BOARD 15 mm — DFIR	Higher requirements for strength and fire resistance
SILENTBOARD 12.5 mm	Sound insulation to the floor above or against noise from noisy activities
CLEANEO® AKUSTIK	Sound absorption within the space, with a uniform appearance

Fire-rated boarding alone does not make for a fire-rated ceiling. Fire resistance is attributed to the entire assembly — board, number of layers, framework, battens, insulation — and is valid only as tested.

The framework: single or double configuration

It is the first construction decision and determines everything — openings, levelness, load and cost.

	Single layout	Dual configuration
Structure	A stack of CD-ROMs, suspended directly	Load-bearing beams and, perpendicular to these, secondary beams
Height consumed	Smaller	Larger — two layers of profile
Flatness	This depends directly on the accuracy of the suspensions	Better — the second layer corrects
Opening & load	Limited	Larger — double cladding, insulation, lighting fittings
Standard	Small spaces, low head	Large surfaces, EI-rated systems, acoustic ceilings

The components and what each one entails

Accessory	Role	What determines the choice
Post immediately P	Secures the guide to the slab at a low height	Available space — the setting is restricted to its own range
Post with a screw	Large gaps, adjustable	Clearance height and levelling requirements
Quick link / butterfly	Adjustment without cutting	Speed and accuracy in levelling
Cross-reference	Connects load-bearing elements to secondary guides	It bears the load — it cannot be replaced by a makeshift solution
Guide rail extension	Profile continuation over long lengths	The joints are offset between adjacent guides
UD Perimeter Guide	Supports the roof against the masonry	It is not a load-bearing element — the support extends close to the perimeter
Anchor plug	Transfers the load to the slab	The substrate: concrete, composite, aerated concrete, old concrete
Soundproofing tape	Interrupts the vibration bridge around the perimeter	Essential for any acoustic requirement

ARGYNET Note

The roof structure is a load-bearing element, not a secondary structure. It is suspended from the slab and continuously bears the weight of the system — battens, insulation, light fittings, vents — with the loads concentrated at a few anchor points.

Two rules that are systematically breached. Firstly: the spacing of hangers and guides is determined by the load — the number of layers of plasterboard, the thickness and density of the insulation, and any additional fittings — and, in a certified EI system, form part of the test. They are not reduced.

Secondly: components from different systems must not be mixed. The suspensions, connectors and profiles have been designed and tested as a complete system; an ‘equivalent’ component from another manufacturer invalidates the construction documentation.

And the rule that applies everywhere: spotlights, speakers, screens and large vents are suspended independently of the concrete slab — never from the framework.

Fasteners, joints and expansion joints

Orientation: the boards are screwed perpendicular to the battens supporting them, with alternating transverse joints — never a cross joint of four boards.
Screws: sharp plasterboard screws, with the head sitting slightly below the surface without tearing the paper. Screws are spaced more closely together on the ceiling than on the wall, as the board is suspended.
Double cladding: the joints in the second layer are offset relative to those in the first.
Expansion joints: on large surfaces — typically over 15 m — and always above the building’s expansion joints. A roof without a joint will crack of its own accord at the point where a joint would have been.
Perimeter: on ceilings requiring sound insulation or movement, the junction with the walls must be made using an elastic seal or a shadow joint — not a rigid connection.

Curves, planes and concealed lighting

Freedom of form arises from a combination of three techniques:

Profile curvature: specially shaped or notched profiles form arcs and waves. The radius achieved depends on the profile and the pitch of the notches.
Bending timber: for small radii, thinner timbers are used in two layers instead of a single thick one — each bends more easily and the assembly results in the same thickness. For very small radii, bending is achieved by wetting and controlled drying.
Level changes: these are constructed as independent ‘boxes’ with their own framework, supported by the floor slab — not suspended from the ceiling of the adjacent level.

ARGYNET Note

Concealed lighting is scraped light — and scraped light reveals everything. It is the reason why the same construction appears flawless in one project and problematic in the next.

A beam travelling almost parallel to the surface reveals every undulation in the framework, every trace of a trowel and every joint that has not been fully smoothed — imperfections that would never be visible under diffused lighting.

In practice: where recessed lighting or large openings with side lighting are specified, the required surface quality is raised by one grade. This work is invoiced; it does not arise automatically simply because the drawing showed a lighting line.

Surface quality: Q1 to Q4

The Q scale, established by the German plaster industry, defines how much skimming work is required after fixing. This must be stated in the quotation — otherwise, everyone will interpret ‘ready for painting’ differently.

Level	What’s included	When is it sufficient?
Q1	Filling of joints and screw heads	Surfaces that are not visible or are covered with tiles
Q2	Q1 + second pass for a smooth transition between joint and board	Standard matt finish, diffused lighting
Q3	Q2 + a thin layer of filler across the entire surface of the joint and beyond it	Subtle paint finishes, more sophisticated lighting
Q4	Complete coverage across the entire surface	Glossy paints, concealed lighting and diffused light

Perforated acoustic ceilings

Perforated plasterboard provides sound absorption whilst maintaining the uniform appearance of a continuous ceiling — in contrast to loose-laid panels, where the battens are visible.

The perforation rate determines the water vapour permeability: a larger open area means a higher αw value. The pattern of the holes is both an acoustic and an aesthetic choice.
The acoustic fabric on the rear side is part of the system — without it, the required performance cannot be achieved.
Drilling reduces the strength of the board: the stud spacing is closer together than with standard plasterboard.
Insulation behind the slab increases absorption — the air gap and the fibrous material work in conjunction with the holes.

Access hatches

In a closed roof, the access hatch is not an accessory — it is the only access point to the services. It is designed in conjunction with the electrical and mechanical systems: beneath valves, junction boxes, air-conditioning units, distribution boxes and fire barriers. The access panel must be large enough to accommodate a hand and a tool, and in a ceiling with an EI rating, it must be of the same class as the ceiling.

Seismic behaviour

In the event of an earthquake, the roof must maintain its structural integrity — not only for its own sake, but for the people beneath it. A frame suspended solely by vertical hangers may oscillate horizontally; the consequences are the falling of sections, stress on sprinkler heads and detachment of the perimeter.

The key requirements are lateral bracing and a suitable type of suspension. In schools, hospitals, commercial premises and public gathering spaces, it is worth including this as a design requirement.

Design series

Roof type by zone — continuous, perforated or detachable; usually all three are found in the same building.
Clearance height from services, not from the desired level — and maintenance clearance.
Performance requirements: EI, sound insulation to the floor above, sound absorption within the room, thermal insulation.
Board per area — A, H2, DF, SILENTBOARD, perforated.
Framework layout and steps, based on the total load.
Lighting: positions, type and — crucially — whether there is diffused light that raises the quality to Q4.
Heavy loads: independent suspensions, designed in conjunction with the M&E systems.
Access hatches in areas requiring maintenance.