Commonly used metal furring channel plasterboard ceiling technology

Today, let's approach from three aspects to discuss the most basic and commonly used light steel keel plasterboard ceiling technology:

1. Main components and basic structure

2. Construction technology of light steel keel plasterboard ceiling

3. Key control points and main areas of focus

**01. Main Components and Basic Structure**

To understand all the details of a material or technology, one must thoroughly understand everything about it, especially its composition.

1. Main Components

The light steel keel plasterboard ceiling is mainly divided into six major components based on the materials mainly used in construction: hangers, main keel (load-bearing keel), secondary keel, transverse support keel, matching hanging fittings and bolts, and plasterboard, etc.

2. Basic Structure

Using the light steel keel as the supporting structural framework, with plasterboard and latex paint as the decorative materials, in actual projects, more than 90% of the decoration projects adopt this method.

**02. Construction Process**

During construction, the main steps for the light steel keel plasterboard ceiling are:

Preparation – Measurement and marking – Installation of hangers and main keel – Installation of secondary keel and transverse support keel – Concealed acceptance of ceiling internal electrical and mechanical systems and keel – Installation of plasterboard.

1. Preparation

Complete the design drawings and processing preparation of construction materials in advance.

At the construction site, in addition to the necessary materials, equipment, personnel, and other conditions, it is also necessary to ensure that the scaffolding has been accepted, the use of electric tools is within the specified working hours, and the mechanical noise meets environmental protection requirements.

2. Measurement and Marking

According to the construction drawing elevation, mark the ceiling level line on the walls and columns with ink lines, and draw the position of the hangers on the ceiling. Ensure that the distance between hangers is between 900-1200mm, the first row of hangers is less than 300mm from the wall, and the hangers along the direction of the main keel are in a straight line, while also considering the position of the lamps to prevent conflicts with the hangers.

3. Installation of Hangers and Main Keel

Drill holes, install expansion bolts and hangers; the general ceiling uses hot-dip galvanized full-thread hangers with a diameter of Φ8.

Install the hanging fittings on the main keel according to the spacing of the hangers in the length direction of the main keel, and install the hanging fittings in an alternating direction (to eliminate the eccentric force when the keel is hung, resulting in better rigidity).

The spacing for installing the main keel should be 900-1200mm, and it should be installed parallel to the long direction of the room, with an arch, and the overhanging section should be ≤300mm; otherwise, additional hangers should be added.

Adjust the keel to the correct position according to the elevation control line. After the main keel, hanging fittings, and hangers are installed, adjust them to be straight and level for the entire room.

When adjusting the main keel of a large area ceiling, pay attention to the middle part of the ceiling, which should be slightly arched, with the arch height generally being ≥1/200-1/300 of the short span of the room.

4. Installation of Secondary Keel and Transverse Support Keel

Install the secondary keel and transverse support keel in sequence, with the spacing of the secondary keel generally being 400mm, and the transverse support keel 600mm. The hanging fittings for the secondary keel also need to be installed in an alternating direction to eliminate deformation due to force.

Edge keel fixing

The edge keel can be made of L (U) shaped galvanized light steel bars, which can be fixed with nail guns on concrete walls and columns, with the nail gun spacing ≤ the spacing of the ceiling keel.

When fixing, high-strength cement nails are generally used, with the nail spacing ≤ 500mm.

If the base material has low strength and poor clamping force, corresponding measures should be taken, such as using expansion bolts or increasing the length of the nails.

5. Concealed acceptance of ceiling internal electrical and mechanical systems and keel

After the installation of water and electricity, water testing, and pressure testing are completed, a concealed inspection should be carried out, and only after passing the inspection can the next step of construction be entered.

6. Installation of plasterboard

The installation of plasterboard starts from the middle of the ceiling along the direction of the main keel, with the long edge of the plasterboard consistent with the direction of the main keel, extending to both sides.

Galvanized self-tapping screws are used to fix the panel, and the installation should be from the middle to the edges of the board, with the screw spacing controlled between 150-200mm. The screw cap should be sunk 0.5-1.0mm into the board without breaking through the paper surface, and anti-rust paint should be applied on the cap, with the nail distance from the edge of the board 10-15mm.

7. Acceptance and tidying up

After the installation is completed, an acceptance work should be carried out for the entire project to ensure that the ceiling construction complies with the design requirements and construction standards, and to ensure safety, stability, and tightness. After passing the acceptance, clean and tidy up the construction site.

8. Matters needing attention

a. The on-site temperature and humidity environment should meet the construction requirements of this technology to ensure construction quality.

b. The ceiling elevation, size, arching, and modeling should comply with the design requirements, with vertical hangers, no looseness in the hanging fittings and connectors, and load tests on the hangers when necessary. The keel hanger should not be used in common with the equipment hanger.

c. Check and adjust the leveling, the arch height should be 1/200 of the short span, and the structural connections should be solid.

d. The position of equipment such as lamps, smoke detectors, sprinkler heads, and air outlets on the plasterboard should be reasonable and aesthetically pleasing, with a tight and seamless connection to the decoration surface.

**03. Key Control Points and Main Area Practices**

In addition to the main considerations during the construction process mentioned above, corresponding operations need to be carried out according to the main situations when installing according to the design requirements and construction drawings:

1. **About Stepped Ceilings**

a. For stepped ceilings or light groove ceilings, the general approach is to start with the shaped areas, then proceed to the larger ceiling areas, installing the upper keel before the lower keel in sequence.

b. For stepped heights less than 300mm, fine woodworking board can be used as the stepped keel; for heights greater than 300mm, it is recommended to use secondary keels to reduce deformation.

The light steel secondary keel in the light groove area should extend to the bottom of the groove to enhance the rigidity of the keel in this area.

2. **About Installing Expansion Joints**

When the ceiling length is greater than 12m, or when encountering structural expansion joints, expansion joints are required for the plasterboard ceiling.

3. **Curtain Box Construction**

In a previous dop design article titled "This is the Correct Way to Design a Curtain Box" (click for details), there is a specific explanation of how to construct a curtain box. During construction, the main thing to control is the load-bearing capacity of the fixed curtain track, and a fine woodworking board must be added above the track to secure it.

4. **About Inspection Hatches**

For areas with inspection hatches or light embedded lamp reserved openings, add light steel secondary keels around the perimeter. It is recommended to use finished GRG materials or plaster products for inspection hatches.

For light ceiling-mounted lamps, a fine woodworking board can be reserved at the top; heavy lamps (>8KG) are strictly prohibited from being directly installed on the ceiling keel and must be reserved on the structural floor slab.

5. **About Anti-support Setting/Transfer Layer**

According to the provisions of Article 6.1.11 of the "Code for Acceptance of Construction Quality of Building Decoration and Decoration Engineering," when the length of the ceiling hanger is between 1.5m and 3.0m, anti-support should be set according to the specifications.

When installing double-layer plasterboard, the seams of the base board and the surface board should be staggered and should not be joined on the same keel.

When the internal space of the ceiling is 3000mm or more, or when the vertical length of the anti-support is 1500mm or more, a transfer layer should be set.

Note: When the hanger encounters equipment, it should be adjusted and added. When the ceiling area is large and the layout of the ceiling equipment is complex, it is not recommended to use anti-support.

6. **About Ceiling Modeling**

Ceiling modeling generally uses a wooden base layer such as a fine woodworking board.

The splicing of the fine woodworking board adopts a glue-on "燕尾" (this term does not have a direct English equivalent, it refers to a type of joint), which is made on the ground, and after the surface is treated with fire prevention, it is hung and installed.

Modeling requires separate hangers to be installed and the spacing should be appropriately reduced. If the model is heavy, angle steel should be used as the hanger, and the hanger should be fixed to the model with iron parts and counter-sunk bolts.

7. **Attention to Ceiling Corner Areas**

For the sealing board of corner areas of the ceiling, to prevent cracking, a one-piece L-shaped plasterboard should be used instead of piecing together two plasterboards.

The better the overall rigidity of the light steel keel plasterboard ceiling, the lower the probability of cracking and deformation occurring later.

When selecting the model of the light steel keel, on the premise of the cost being basically reasonable, try to choose keels with larger specifications, reduce the spacing of the keels appropriately (in accordance with the modulus), and strengthen the rigidity of the keels at corners, openings, and other parts, which can effectively improve the overall rigidity of the ceiling.