What details should be paid attention to during the construction of metal exterior wall panels?

The construction of metal exterior wall panels should focus on three core aspects: "ensuring secure installation, avoiding leakage risks, and ensuring a smooth appearance." Special attention should be paid to details such as base treatment, panel fixing, and sealing and waterproofing to avoid problems such as detachment, leakage, and deformation later. The specific details are divided into three stages: pre-construction, construction, and acceptance.

I. Before construction: Prepare the foundation and eliminate potential problems.

Preparing the base layer and materials in advance lays a stable foundation for subsequent construction and avoids rework due to insufficient preparation.

Grassroots handling details

Check the flatness of the base layer: Use a 2m straightedge to measure the base layer (such as concrete wall surface, light steel keel frame). The maximum gap should not exceed 3mm. If there are protrusions, they need to be ground flat. Depressions should be repaired with cement mortar or special putty to prevent uneven base layer from causing the boards to warp after installation.

Ensure the stability of the base layer: If it is a light steel keel base layer, check the keel spacing (usually no more than 600mm) and the tightness of the bolts. Loose bolts need to be tightened again. If it is a brick wall or concrete wall, the position of the embedded parts needs to be marked in advance to ensure reliable support when fixing the panels later, and to avoid the panels falling off due to the loosening of the base layer.

Clean the substrate surface: Remove dust, oil, and laitance from the substrate. If necessary, rinse with a high-pressure water gun and let it dry to prevent debris from affecting the adhesion between the board and the substrate (such as when using adhesive for fixing).

Details of material and tool preparation

Check the quality of metal sheets: verify that the sheet model, thickness (such as 0.8mm-1.2mm, a common thickness), and surface coating (such as fluorocarbon paint, polyester paint) are consistent with the design. Check whether the edges of the sheet are flat, whether there is any deformation, and whether the coating is peeling off. Unqualified sheets are prohibited from use.

Pre-processing and layout: Cut the panels in advance at the factory or on-site according to the dimensions of the exterior wall, reserve the positions of door and window openings and pipe interfaces, and mark the panel numbers (such as numbering from left to right and from top to bottom) during layout to avoid incorrect installation during construction; a special cutting machine (such as a metal circular saw) should be used for cutting to prevent too many burrs on the cut edges from affecting the splicing and sealing.

Prepare special auxiliary materials: The sealant should be a weather-resistant silicone sealant (avoid using ordinary glass glue, which is prone to aging and cracking), and it should have good compatibility with the metal sheet (perform compatibility testing in advance); the fixing screws should be stainless steel self-tapping screws (avoid using carbon steel screws, which are prone to rust and corrosion), and the length should be more than 15mm longer than the thickness of the sheet plus the thickness of the base layer to ensure a firm fixation.

II. During construction: Control key processes to avoid quality problems.

Install according to the standard procedures, paying close attention to details such as fixing the panels, sealing the joints, and treating openings to ensure structural stability and waterproofing.

Panel installation and fixing details

Control the installation sequence: Start from the bottom of the exterior wall, install from bottom to top and from left to right. After every 3-5 panels are installed, use a level to check the levelness and a plumb bob to check the verticality to avoid overall tilting. The joints of the panels on the same wall must be kept on the same straight line with a deviation of no more than 2mm to ensure a flat appearance.

Screw fixing should be standardized: screws must be driven vertically into the base layer without tilting, and the screw spacing should be controlled between 300mm and 500mm (specifically according to design requirements), and the screws should be no less than 15mm from the edge of the board (to prevent edge cracking); each board should have no less than 4 fixing screws (larger boards require more screws), and after tightening, the screw caps should be flush with the surface of the board, and should not be too loose (easy to loosen) or too tight (deform the board).

Expansion joints should be reserved: Metal sheets are prone to thermal expansion and contraction due to temperature changes. When splicing horizontally and vertically, expansion joints of 5mm-10mm should be reserved to avoid deformation or cracking of the sheets due to temperature changes. The position of the expansion joints should be consistent with the layout drawing and should not be adjusted arbitrarily.

Sealing and waterproofing details

Joint sealing treatment: After cleaning the joint (free from dust and moisture), apply silicone sealant evenly. The width and thickness of the sealant joint must meet the design requirements (usually 10mm-15mm wide and 5mm-8mm thick). The sealant should be applied continuously to avoid air bubbles or gaps in the sealant. The surface of the sealant joint should be smoothed with a special tool to ensure a neat appearance and a tight seal to prevent rainwater from seeping in.

Treatment of door and window openings and pipe joints: At the junction of the board material and the door and window frame and pipes, water-stop tape (such as butyl tape) should be pasted first, and then sealant should be applied to form double waterproofing; additional fixing screws should be added to the board material around the opening (2-3 screws on each side) to prevent deformation of the opening from causing the seal to fail.

Treatment of inside and outside corners: Special corner fittings (such as right-angle metal fittings) should be used at inside and outside corners. The joint between the corner fitting and the board should be sealed with glue to prevent the inside and outside corners from becoming weak points for water leakage. Sufficient space should be reserved for the board at the outside corner to prevent collision damage.

Safety and protection details

High-altitude work protection: Construction workers must fasten safety belts and wear safety helmets. Scaffolding or suspended platforms must be checked for stability. Scaffold boards must be fully laid and fixed. Work is prohibited without protective measures. Construction must be suspended in strong winds (wind force exceeding level 5) or rain to prevent boards from being blown off by the wind or rain from affecting the sealing effect.

Panel protection: Avoid scratching the surface coating of the panels with sharp tools during installation. Installed panels should be covered with a protective film (such as PE protective film) until the project is completed. Handle the panels with care to avoid edge collisions and deformation, which may affect the splicing quality.

III. Post-construction: Thorough inspection and investigation of potential problems.

During acceptance, the focus should be on checking the appearance, sturdiness, and waterproofing to ensure that the construction quality meets the specifications and avoid potential problems later.

Appearance inspection details

Inspect the surface of the board: there should be no obvious scratches, dents, or peeling of the coating; the color should be uniform and consistent with no color difference; the joints of the boards should be flat with a height difference of no more than 1mm; the expansion joints should be accurately positioned; the glue joints should be smooth and straight with no cracks or bubbles.

Check dimensions and location: The installation location of the panels should be consistent with the design drawings. The reserved dimensions of door and window openings and pipe interfaces should not deviate by more than 5mm. The inside and outside corners should be square (measured with a right angle ruler, the deviation should not exceed 2mm).

Details of Firmness and Waterproofing Inspection

Check the fixation: Gently push the board with your hand, and there should be no looseness; check the tightness of the screws, and use a wrench to check that the screws are not loose and the screw caps are not damaged; check the joint between the base layer and the board, and there should be no hollow spots (tap lightly with a small hammer, a crisp sound indicates it is qualified, and a dull sound indicates it is hollow).

Waterproofing test: A water spray test was conducted, in which a high-pressure water gun (0.3MPa) was used to spray water continuously from the top of the exterior wall downwards for 2 hours. Afterwards, the interior walls and base layer were inspected, and there was no water seepage or dampness. Special attention was paid to the joints, door and window openings, and inside and outside corners to ensure that there were no leaks.