Wall dry hanging stone construction technology standard

[Students' Questions] What is the wall construction technology for dry-hanging stone?

[Answer] A. Working Conditions

1. The structure must be inspected and approved, with all pre-inspection procedures completed. All water, electrical, ventilation, and equipment installations should be finalized before starting the work.

2. The slate should be prepared according to the design specifications, including type, quality, physical and mechanical properties, and quantity. The surface of each stone should be protected on all six sides.

3. The exterior doors and windows must be installed and pass inspection to meet required quality standards.

4. Essential materials such as stainless steel anchors, structural adhesives, sealants, caulking guns, foam strips, and hand tools should be fully prepared.

5. Technical briefings should be conducted for the workers to emphasize safety, technical measures, quality standards, and protection of finished products.

6. A trial model should be made first. After internal quality checks, it should be reviewed by the client and designer. Only after approval can large-scale construction begin.

B. Construction Process

1. Stone Inspection: A dedicated person should manage the incoming stone. Each piece must be carefully checked against the design specifications and material list. If there are significant color mismatches, they should be separated and returned to the manufacturer.

2. Scaffolding Setup: Steel pipe scaffolding should be erected with a minimum clearance of 500mm from the wall. The horizontal crossbars should be at least 300mm away from the wall. The framework should be securely anchored to the main structure, with full planks laid and safety nets installed outside.

3. Layout and Measurement: Use a plumb line or theodolite to measure vertical alignment from top to bottom for walls, columns, and door/window openings. Consider the thickness of the stone and the spacing between the stone and the structure (typically 60–80 mm). Mark horizontal lines on the wall based on the stone’s height (usually 6–10 mm). Ensure even distribution of errors.

4. Drilling and Grooving: Before installation, measure the exact position of each stone. For concrete or brick walls, drill a hole 80–100 mm from the center of the slab, about 20–25 mm deep, then drill a 8–10 mm diameter hole where the stone will be placed. Insert one end of the stainless steel expansion bolt into the hole and secure the anchor. For reinforced concrete columns, avoid drilling near steel reinforcement. Accurately mark the drilling positions and install the bolts accordingly.

5. Installing the Bottom Slab: Place the bottom slab according to the position of the stainless steel anchors on the wall. Align the slab holes with the anchor pins and use the rectangular bolt hole. Adjust for flatness and squareness. Pull lines to check alignment and secure the slab with the anchor, filling the hole with structural adhesive.

6. Installing Upper Slabs: Apply structural adhesive into the bolt hole of the next row, wipe off excess, then place the slab using the same method. Check the installation quality and fix it according to design requirements. For hard-to-reach areas, fix the sides in the same way.

7. Sealing and Caulking: After the stone is fixed, clean the surface and remove dust from the gaps. Insert 8–10 mm diameter foam strips into the gap, leaving a 5–6 mm deep seam. Apply a 10–15 mm wide plastic tape on both sides of the seam to prevent sealant from staining the stone. Then apply the sealant using a caulk gun. If the sealant gets on the stone, clean it immediately. Finally, remove the tape, clean the stone surface, and polish it until it meets quality standards. Remove the scaffold once done.

C. Construction Method

1. Stone Preparation: Select and classify stones using colorimetric methods. Stones installed on the same side should have consistent color. Number the stones according to the design drawings and block order.

2. Base Layer Preparation: Clean the prefabricated stone surface. Perform structural layout, mark vertical and horizontal lines, and pop up installation position and block lines according to the design.

3. Hanging Lines: Before installing the stone, use a theodolite to strike vertical control lines on both sides of the large corner. It’s best to set the line 20 cm away from the corner to ensure accurate vertical hanging lines and smooth installation.

4. Support Bracket Installation: Place the pre-arranged support on the upper slab according to the upper line. Ensure the brackets are firmly connected and aligned. Lay a 50 mm thick wooden board in the direction of the supports, ensuring the top and bottom of the stone are level.

5. Fixing Iron Parts: Secure angle steel and flat steel plates with stainless steel bolts as per design. Adjust the flat steel plate so that its small hole aligns with the stone’s insertion hole. Tighten with a wrench.

6. Bottom Slab Installation: Place the bottom panel on the corner of the connecting iron pieces.

7. Adjustment and Fixing: After temporary fixation, adjust the level. If the surface is uneven, place a double-strand copper wire mat on the flat steel plate at the bottom of the board. Adjust verticality and the gap between the stainless steel connectors on the top of the panel until it is straight.

8. Top Panel Installation: In addition to general installation requirements, the last layer of the top panel should be installed and adjusted. Place a 20 mm thick wooden strip in the gap between the structure and the stone, flat over 250 mm. Set the lifting point on the connecting iron piece and use aluminum wire to hang the wooden strip. Fill the gap between the stone and the wall with packing to prevent grout leakage.

9. Cleaning the Stone Surface: Remove anti-stain strips from marble and granite surfaces and wipe the stone with cotton thread.

D. Finished Product Protection

1. Arrange the construction sequence scientifically. Water, electricity, heating, ventilation, and equipment installation should be completed in advance to avoid damaging or polluting the external stone cladding.

2. Clean the sealant, dust, adhesive, oil stains, fingerprints, and water debris left on the door frame, glass, and metal veneer promptly. Apply protective film to prevent pollution and rust.

3. Avoid collisions with dry-hung stone finishes during disassembly or loading.

4. After finishing, protect the corners of easily damaged parts with wooden boards. Prevent painting or other works from damaging the stone surface.

5. Do not pour garbage, sludge, or waste onto the outdoor area until the brushing agent is fully dry.

6. Assign someone to monitor the finished stone cladding to prevent vandalism like scribbling on the surface.

7. Construction Precautions

7.1. Color Consistency: To prevent color variation, select and test stones carefully before installation.

7.2. Uneven Lines and Joints: To ensure straight lines and uniform joints, check the actual size of the structure against the design. Make precise segments and frequently pull horizontal and vertical lines for adjustments.

7.3. During dry-hanging, only use marble glue temporarily. Once in place, reinforce with AB glue.

E. Quality Standards

(1) Main Control Items

1. Materials used in the stone wall project, including type, specification, performance, and grade, must comply with design requirements and current national standards.

2. The shape, facade, color, gloss, and pattern of the stone wall should meet the design specifications.

3. The number, depth, position, and size of holes and grooves in the stone must match the design. The connection nodes at the corners should also meet the design and technical standards.

(2) General Items

1. The stone wall surface should be smooth, clean, and free of pollution, cracks, or defects. The color and pattern should be consistent, with no obvious color differences or scratches.

2. The joints should be straight and evenly spaced. The edge of the stone should be neat, and the embossed lines should be consistent in thickness. The cut edges of the stone should be precise and well-matched.

3. The allowable deviation of stone cladding installation must follow the provisions of Table 8.2.9 in the “Code for the Acceptance of Quality of Building Decoration Engineering.”

This content has been compiled based on common questions raised by students in real-world scenarios. It is provided for reference only. If you find any issues, please communicate and correct them promptly.

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