61 secrets to inspecting concealed works

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61 secrets to the inspection of concealed works. Concealed works generally refer to elements such as foundations, electrical wiring, and water and heating pipelines that need to be covered or concealed. Since, after being concealed, any quality issues related to concealed works would necessitate re-covering and concealing them again, resulting in significant losses such as rework, inspections of concealed works are routinely conducted to ensure project quality and successful completion. Process for the acceptance of concealed works: (1) Before starting work on concealed works, the project team is responsible for inspecting the materials to be used. The inspection includes checking the material certification provided by the manufacturer, conducting visual inspections, performing sample tests, and obtaining re-inspection reports from the project team. Construction can only proceed once all inspection results are satisfactory. (2) The construction of concealed work shall be carried out under the supervision of supervisors, the project chief engineer, and full-time quality inspectors. For important foundations such as cast-in-place pile foundations, the design unit must be present. The construction of concealed work must be carried out strictly in accordance with regulations, standards, and operation instructions. (3) After the construction of the concealed work is completed, the construction supervisor must conduct a self-inspection to ensure it is satisfactory; thereafter, a construction record shall be filled out. The team leader, quality inspector, technician, and inspector shall sign to confirm that everything is in order, followed by the on-site supervisor’s signature to confirm approval. (4) After the construction team conducts the inspection and confirms it is satisfactory, the person in charge of the construction team shall sign the \"Hidden Works Acceptance Certificate\" and submit it to the project department for further inspection. (5) The project department conducts random inspections of concealed works and checks the construction records; once they are found to be satisfactory, a signature is placed on the \"Concealed Works Acceptance Certificate,\" which is then submitted to the engineering supervision department of the supervision company for inspection. (6) The supervision company conducts on-site random inspections of concealed works, checks the construction records and material quality certification documents, and issues a signature on the \"Concealed Works Acceptance Visa Form\" after confirming their compliance. Contents of acceptance for concealed works – Pile foundation works: (1) Records of setting out and positioning of the pile foundation axis and reference piles, as well as verification records. (2) Pile driving (pressing) construction records, cast-in-place pile construction records. (3) Splicing of precast piles, drilling and hole cleaning of cast-in-place piles, fabrication, lowering of rebar cages, and concrete pouring. (4) Records of inspection for pile position axis deviation and elevation (if the elevation of the pile top is the same as that of the construction site, it should be carried out after the completion of pile foundation construction). Foundation works (1) Axis: The construction unit shall submit a construction survey submission form (application form), along with a verification form for the construction survey and setting out. (2) Excavation (including design elevation, hidden beaches, geology, foundation trench width, length, slope formation, and slope gradient): The construction unit shall fill in the foundation inspection record. (3) Bedding layer (including elevation, length, thickness, width, and concrete strength grade). (4) Reinforcement for the bottom slab (including type, specification, quantity, lap length, stirrup spacing, cover thickness, and quantity and location of embedded parts). (5) Concrete (including cross-sectional dimensions, elevation, presence of honeycombing, pitting, exposed rebar, and concrete strength grade): Concrete pouring order, concrete mix design sheet. (6) Foundation wall (including elevation, base dimension, and masonry mortar strength): Mortar gradation sheet. (7) Reinforcement for the moisture barrier (including quantity, specifications, type, and lap length). (8) Installation of suspended slabs (including floor slab type, gap between lower slabs, overhang length, rigid leveling, and flexible bedding) ； Number, specification, and length of the anchor bars for the suspended slab). Main structure (1) Axis and setting out (for each floor). (2) Rebar for columns, beams, stairs, and slabs (including quantity, specifications, type, lap length, welding condition, cover thickness, stirrup spacing, embedded parts, etc., once per floor), along with records of on-site inspections. (3) Reinforcement for cantilevered parts such as canopies, balconies, and air conditioning slabs (once per floor); records of inspections and on-site supervision. (4) Concrete (including surface quality, strength grade, per layer per application), inspection and on-site supervision records. (5) Wall masonry (including the quantity, specifications, and placement of reinforcement bars connecting columns to walls), mortar mix design sheet. (6) Reinforcement for roof water tanks (including quantity, specifications, type, and lap length), along with records of on-site inspections. (7) Reinforcement for the parapet cap (including quantity and specifications). Building decoration and finishing works (1) Plastering work: Reinforcement measures when the plaster thickness is 35 mm or more ； Strengthening measures at the joints of different material matrices. (2) Door and window works: embedded parts and anchors ； Anti-corrosion and filling treatment for concealed areas. (3) Ceiling installation: fire and corrosion protection treatment for wooden joists ； Embedded parts or tie bars ； Hanging rod installation ； Keel installation ； Fill material settings. (4) Light partition wall project: fire and corrosion protection treatment of wooden studs, embedded components or tie rods, installation of studs, and application of filling materials. (5) Cladding (brick) works: embedded parts (post-installed embedded parts), connection joints, waterproof layer. (6) Curtain wall project: embedded parts (or post-installed embedded parts), connection joints of components, construction joints at expansion joints and wall corners, curtain wall lightning protection systems ； Fire protection structure for curtain walls. (7) Detail work: embedded parts (or post-installed embedded parts), and the connection joints between guardrails and embedded parts. (8) Floor and ground works: Each structural layer must undergo acceptance for concealed works ； Treatment of deformation joints. Roofing work (1) Substrate for membrane and coating waterproof layers. (2) Areas requiring sealing and waterproofing treatment. (3) Details such as gutters, eaves drains, flashing, and expansion joints. (4) Lap width of rolled or coated waterproof layers and additional layers. (5) A separation layer between the rigid protective layer and the membrane or coating waterproofing layer. Circuit Engineering (1): Whether the various materials used meet the design requirements, and whether the distance between strong-current and weak-current conduits is more than 500 mm. (2) Whether the wire tube is fixed and whether its connections are secure. (3) All wires within the conduit must have no joints or kinks; if any are present, they must be replaced. (4) Check whether there are any connectors in the television cable; if so, verify whether a distributor is used at those connectors. (5) Is the dark box installed properly and at the required height? (6) Have the construction workers marked the areas where the conduit is to be laid? Note whether the position of the dark box, the direction of the cable tube, and the location of the cable connectors are appropriate. Waterway engineering: (1) Check whether the layout of the water pipes is reasonable, whether the locations of the various outlets correspond to those of the connections in the sanitary fixtures, and whether there are too many bends and joints. (2) Check whether there are any kinks in the hose, and whether the connection length is greater than 1 meter (the connection length of the hose should be kept as short as possible). (3) Check all connections for any leaks. (4) Check whether a shut-off valve is installed at the hose (to prevent it from being impossible to replace in case the water pipe cracks). (5) The inspection of the下水 involves using a drainage method. (6) Are all joints, valves, and pipe connections tightly sealed with no leakage? (7) Water pipes shall not be installed near power sources, and the distance between water pipes and gas pipes should be no less than 500 mm. Waterproofing work: (1) Fill the room with water, ensuring that the lowest point of the water surface is not lower than 20 mm. Be sure to mark the height of the water surface; after 48 hours, check whether there are any significant changes in this height. At the same time, go to the corresponding location downstairs to check whether there is any water leakage from the ceiling of the room. (2) If the above phenomena do not occur, the waterproofing work can be considered to have passed the inspection ； Conversely, if the above phenomena are observed, the waterproofing work can be considered unsatisfactory; it must be redone in its entirety and re-inspected. (3) For the acceptance of lightweight and strong waterproofing works, a water spraying test should be employed: a water hose is used to spray water continuously from top to bottom on the wall that has been coated with waterproof material for 3 minutes. After 4 hours, it is checked whether any leakage occurs on the other side of the wall; if no leakage is observed, the waterproofing work on the wall can be considered successful. Key points for the inspection of concealed works: Foundation and substructure (1) Before carrying out foundation reinforcement, and after the excavation of foundation pits and trenches is completed, it is necessary to inspect and evaluate the soil quality and bearing capacity of these areas. Relevant responsible persons and technical staff from the surveying, design, quality supervision, supervision, construction, and project owner parties were present to determine whether the soil quality and bearing capacity meet the requirements, based on the structural drawings at the construction phase as outlined in the foundation plan and general structural specifications, as well as the geotechnical investigation report from the detailed survey phase. (2) The contents of the acceptance for foundation and substructure works include unsupported earthwork, supported earthwork, foundation and substructure treatment, pile foundations, underground waterproofing, concrete foundations, masonry foundations, reinforced concrete, steel structures, etc. Before the foundation pouring, a quality supervision agency, as well as the design and construction units, should be invited to conduct on-site inspections and acceptance. Inspect and accept the construction quality after the foundation reinforcement treatment. (3) Acceptance of foundation works. Before backfilling the foundation trench, inspect and accept the quality, construction, and dimensional deviations of the foundation work. Main structure: (1) During the acceptance of works such as steel reinforcement, it must be ensured that prior to pouring concrete, and before applying the roof protective layer, backfilling the basement trenches, or caulking the exterior wall panels, the quantity, dimensional deviations, construction requirements, and protective layer thickness of the steel reinforcement frameworks, pipelines, components, and embedded parts are inspected and accepted. (2) Before the block masonry work begins, the structural works must have been approved by the relevant authorities. Before beginning the actual construction, a model unit should first be built on a standard floor, including structural columns, window sill caps, lintels, etc., all of which must be constructed in accordance with the design requirements and relevant specifications ； Construction can proceed only after it has been approved by the supervision unit; at the same time, it is necessary to ensure that the construction workers have received proper technical instructions, with clear guidelines regarding the construction procedures and quality acceptance standards. Building decoration works: (1) Wall cracks and the appearance of floor slabs are key concerns for property owners upon taking possession of their homes; they must be addressed seriously. Generally, the main focus is on checking whether there are stress-induced cracks in load-bearing walls and floor slabs ； Is there a significant color difference in the wall color? (2) The quality of the surface of doors and windows directly affects the decorative appearance of the entire wall after installation. The visual inspection of doors and windows includes checking for cracks on the surface, any deformation, and the condition of the window seals. (3) For the visual inspection of the ground surface, first, from a distance of 2 meters, visually check whether the color of the surface is uniform, and whether there are any color differences or scratches. Examine the brick surface for any abnormal contaminants such as cement or paint. Then, use both eyes and hands to check for cracks, fissures, or damage on the surface. Building roof: (1) The height of the waterproofing lap shall be no less than 25 cm. An additional waterproof layer shall be applied around pipe roots; metal clamps shall be used for securing the waterproofing edges, and sealant shall be applied to the upper edges. (2) The height of the pipes on the roof should be no less than 1.8 m. The smoke and wind hood cover is sloped at 2%. Mechanical and Electrical Engineering: (1) During the acceptance of water supply and drainage projects, the main materials, finished products, semi-finished products, accessories, appliances, and equipment used must come with Chinese-language certificates of quality compliance, and their specifications, models, and performance test reports must meet the **technical standards or design requirements ； Upon arrival, all materials are inspected for their variety, specifications, and appearance; the packaging must be in good condition, with no scratches or damage caused by external forces on its surface ； The main instruments and equipment come with complete installation and usage manuals. (2) Check the low-voltage distribution box to see if the wiring is clearly organized and if the functions of each module are well defined. When laying circuits, if the horizontal distance between low-voltage systems and high-voltage systems, or between different low-voltage systems, is too small, it can easily lead to signal interference in the future. During acceptance, make sure to check whether the distance between the wire tubes meets the specified requirements. (3) Lightning protection project work mainly includes the welding of pile foundations, the continuous welding of rebar leads leading down from columns, as well as the installation of equipotential rings, lightning protection meshes, lightning rods, and lightning arresters. To improve the construction quality of lightning protection projects, it is necessary to enhance the construction quality of lightning protection devices to ensure that the quality of such projects meets the required standards.