Introduction to the Method of Exposed-Frame Suspended Ceilings

What is an exposed-grid ceiling?

Everyone is accustomed to calling it that, but why is it named this way? As the name suggests, it refers to a suspended ceiling system in which the framing members are left exposed. This type of ceiling falls under the category of panel ceilings—as opposed to solid‑board ceilings—where the finish panels rest within the framework, and the exposed framing, together with the finish panels, serves as a decorative element, creating the overall aesthetic. From a construction standpoint, exposed‑frame ceilings are classified as prefabricated systems.

Next, we will outline the installation procedure for exposed‑grid ceiling systems: mark and position the ceiling elevation lines; install suspension rods; mount the UC‑type main runners; install the T‑type runners (exposed); attach the edge runners; and finally, install the ceiling panels.

Next, we will detail the installation process. The first step—“opening up the space”—is layout and positioning: based on the design elevation, mark the finished ceiling plane on the wall; on the structural ceiling, lay out the locations for the main keels and suspension hangers. Pay attention to the following dimensions: main‑keel spacing ≤ 1.2 m, hanger spacing ≤ 1.2 m, distance from hanger to the end of the main keel ≤ 300 mm, and distance from hanger to the side wall ≤ 150 mm.

Step 2: Install the suspension rods. Secure them to the structural ceiling using expansion bolts, and select hot-dip galvanized full-threaded rods with a diameter of φ8 mm or greater. When the rod length is ≥1.5 m, an additional reverse support must be provided.

Additional suspension rods shall be provided at locations such as luminaires, air diffusers, and access panels. Heavy luminaires, ceiling fans, and other heavy equipment weighing more than 3 kg that are installed on the suspended ceiling framework must be fitted with separate hangers connected to the structural ceiling.

Step 3: Install the main keels. Here, the main keels refer to UC‑type light steel keels. The main keels shall be suspended from the suspension rods. The spacing between main keels should be between 0.9 and 1.2 m, typically taken as 1 m. For non‑accessible ceilings, UC50 keels are generally suitable. The main keels must be cambered, with a camber height of 1/200 to 1/300 of the room’s shorter span. Splicing of the main keels shall be done by butt jointing, and the butt joints of adjacent keels must be staggered. After installation, the main keels should be roughly leveled. For ceilings with spans exceeding 15 m, an additional large keel shall be installed every 15 m along the main keels, securely connected vertically to the main keels. If there is a complexly shaped ceiling, the decorative sections shall be framed with angle steel or flat steel welded into a rigid structure, which must be firmly attached to the structural ceiling surface.

Step 4: Install the exposed T‑profile ceiling grid. The T‑grid typically consists of main T‑sections and cross T‑sections, with main T‑sections measuring 3 m in length and cross T‑sections ranging from 0.3 to 0.6 m (selected according to panel dimensions). Materials may include powder‑coated steel or aluminum alloy. The main T‑section is often referred to as the “main runner,” while the cross T‑section is called the “secondary runner”; care should be taken to distinguish these terms, as they are frequently confused. The main T‑section is installed perpendicular to the light‑steel main runners and secured using specialized hangers, with a typical spacing of three hangers per meter. The cross T‑section connects to the main T‑section at a right angle; its ends are usually equipped with locking tabs, which must be properly aligned and firmly engaged with the main T‑section. Overall flatness deviation shall not exceed 2 mm per 2 m.

Step 5: Install the edge furring. The edge furring should be installed according to the chalk line markings, with L‑shaped or W‑shaped baked‑on‑paint galvanized light steel strips secured to the side walls using self‑tapping screws along the horizontal chalk lines on the wall surface.

Step six: With the project nearing completion, we move on to the final stage—installing the finish panels. These decorative panels, commonly referred to as ceiling tiles, typically include mineral wool, fiberglass, and rock wool acoustic panels, calcium silicate boards, and decorative gypsum boards (such as high‑crystal and silicon‑crystal boards), among others. The panels are placed within the enclosed framework formed by the T‑shaped main and secondary furring channels, ensuring that the arrows on the back of each panel point in the same direction during installation. Ceiling panel dimensions are generally determined by the design layout and manufactured as finished products in the factory; however, on‑site trimming is still unavoidable. For flat panels, this is usually straightforward, but for stepped‑ceiling designs, creating precise edge chamfers on rigid inorganic panels—particularly decorative gypsum boards and calcium silicate boards—can be quite challenging.

In addition to the usual scenarios where we can anchor suspension rods to the top of a structure, there is another situation that is rather unique: in many public buildings today, corridors often have such a dense network of overhead services that they simply lack the structural conditions necessary for installing suspension‑rod anchors. How can this be addressed?

In most corridors, the walls on both sides are solid; in such cases, a double-sided fixing method can be employed. Along the corridor walls, use expansion bolts to secure continuous L‑shaped angle brackets (50×50×5 mm) as load‑bearing supports. Then, overlap and fasten both ends of the light‑steel main studs onto these angle‑bracket supports, and proceed with the installation of the T‑shaped primary and secondary studs as described in Step 4 above.

Of course, in addition to securing the points on both sides, you can also use clamps or hoop‑type fixtures to fasten the lifting points; however, we will not elaborate on this here.

As the primary form of prefabricated suspended ceilings, exposed‑grid ceilings offer short installation times, cost‑effectiveness, and ready‑to‑use convenience. With a wide variety of finish panel materials available, they can meet diverse functional requirements—such as fire resistance, sound absorption, moisture protection, and decorative appeal—making them the optimal solution for commercial ceiling applications under current conditions.