Concealed works generally refer to works that need to be covered or concealed, such as foundations, electrical conduits, water supply and heating pipelines. Since concealed works, once concealed, if quality problems occur, need to be re-covered and concealed, causing significant losses such as rework, concealed works acceptance is often conducted to ensure project quality and smooth completion. The following summarizes 61 key points for concealed works acceptance. Spot on!

Concealed Works Acceptance Process

(1) Before the commencement of concealed works, the project department shall be responsible for inspecting the materials used, including: material certificates provided by the manufacturer, appearance inspection, sampling tests, and re-inspection reports conducted by the project department. Construction can only proceed after all inspection results are qualified.

(2) The construction of concealed processes shall be carried out under the supervision of supervision personnel, the project chief engineer, and full-time quality inspectors. For important foundations such as bored pile foundations, the design unit must be present. The construction of concealed processes shall be carried out strictly in accordance with regulations, specifications, and work instructions.

(3) After the construction of concealed processes is completed, the construction supervisor must conduct self-inspection and fill in the construction record. After confirmation by the team leader, quality inspector, technician, and inspector, they shall sign. Then, the on-site supervisor shall confirm and sign.

(4) After the construction team's inspection is qualified, the construction supervisor of the construction team shall sign the "Concealed Works Acceptance Certificate" and submit it to the project department for inspection.

(5) The project department shall conduct random inspections of concealed works, check construction records, and after confirming qualification, sign the "Concealed Works Acceptance Certificate" and submit it to the engineering supervision department of the supervision company for inspection.

(6) The supervision company shall conduct on-site random inspections of concealed works, check construction records and material quality certification documents, and after confirming qualification, sign the "Concealed Works Acceptance Certificate".

Concealed Works Acceptance Content

➤ Pile Foundation Engineering

(1) Pile foundation axis and sample pile setting-out positioning and re-inspection records.

(2) Driving (pressing) pile construction records, cast-in-place pile formation construction records.

(3) Precast pile splicing, cast-in-place pile drilling, hole cleaning, reinforcement cage fabrication, lifting and installation, and concrete pouring.

(4) Pile position axis deviation and elevation acceptance records (if the pile top elevation is the same as the site elevation, it should be carried out after the completion of pile foundation construction).

➤ Foundation Engineering

(1) Axis: The construction unit fills in the construction measurement inspection application form (inspection application form), attached with the construction measurement setting-out re-inspection sheet.

(2) Excavation (including design elevation, hidden ponds, geology, foundation trench width, length, slope release, slope): The construction unit fills in the foundation trench inspection record.

(3) Cushion layer (including elevation, length, thickness, width, concrete strength grade).

(4) Bottom slab reinforcement (including variety, specification, quantity, lap length, stirrup spacing, protective layer thickness, number and position of embedded parts).

(5) Concrete (including section size, elevation, whether there are honeycombs, pitted surfaces, exposed reinforcement, concrete strength grade): Concrete pouring permit, concrete mix proportion sheet.

(6) Foundation wall (including elevation, footing dimensions, masonry mortar strength): Mortar mix proportion sheet.

(7) Damp-proof layer reinforcement (including quantity, specification, variety, lap length).

(8) Overhead slab installation (including floor slab model, gap between bottom slabs, bearing length, hard leveling, soft seating mortar; number, specification, length of anchor bars for overhead slabs).

➤ Main Structure Engineering

(1) Axis and setting-out (each floor).

(2) Reinforcement of columns, beams, stairs, slabs (including quantity, specification, variety, lap length, welding condition, protective layer thickness, stirrup spacing, embedded parts, etc., once per floor), patrol and stand-by records.

(3) Reinforcement of cantilever parts such as canopies, balconies, air-conditioning boards (once per floor), patrol and stand-by records.

(4) Concrete (including surface quality, strength grade, once per floor), patrol and stand-by records.

(5) Wall masonry (including quantity, specification, and installation of tie bars between columns and walls), mortar mix proportion sheet.

(6) Roof water tank reinforcement (including quantity, specification, variety, lap length), patrol and stand-by records.

(7) Parapet coping reinforcement (including quantity, specification).

➤ Building Decoration Engineering

(1) Plastering engineering: Reinforcement measures when plastering thickness is greater than or equal to 35mm; reinforcement measures at the junction of different material substrates.

(2) Doors and windows engineering: Embedded parts and anchors; anti-corrosion and filling treatment of concealed parts.

(3) Suspended ceiling engineering: Fireproof and anti-corrosion treatment of wooden keels; embedded parts or tie bars; suspension rod installation; keel installation; filling material installation.

(4) Lightweight partition wall engineering: Fireproof and anti-corrosion treatment of wooden keels, embedded parts or tie bars, keel installation, filling material installation.

(5) Decorative panel (brick) engineering: Embedded parts (post-embedded parts), connection nodes, waterproof layer.

(6) Curtain wall engineering: Embedded parts (or post-embedded parts), component connection nodes, structural nodes at deformation joints and wall corners, curtain wall lightning protection devices; curtain wall fireproof structure.

(7) Detail engineering: Embedded parts (or post-embedded parts), connection nodes between guardrails and embedded parts.

(8) Floor engineering: All structural layers must be subject to concealed works acceptance; treatment of deformation joints.

➤ Roof Engineering

(1) Base layer of rolled material and coating waterproof layers.

(2) Sealed waterproof treatment parts.

(3) Detail practices such as gutters, eaves gutters, flashing, and deformation joints.

(4) Lap width and additional layers of rolled material and coating waterproof layers.

(5) Isolation layer between rigid protective layer and rolled material or coating waterproof layer.

➤ Electrical Engineering

(1) Whether various materials used meet design requirements, and whether the spacing between strong and weak current conduits is more than 500mm.

(2) Whether the conduits are fixed and the conduit connections are firm.

(3) All lines must be inside conduits, without joints or kinks; if any, they must be replaced.

(4) Whether there are joints in the TV cable; if so, check whether a splitter is used at the joint.

(5) Whether the junction boxes are installed squarely and at the required height.

(6) Whether the construction personnel have marked the positions of conduits, and whether the junction box positions, conduit routes, and line joint positions are reasonable.

➤ Waterway Engineering

(1) Check whether the water pipe route is reasonable, whether the positions of each water outlet correspond to the interfaces of sanitary fixtures, and whether there are excessive bends and joints.

(2) Check whether the flexible hose has sharp bends, and whether the connection distance is greater than 1m (the connection distance of the flexible hose should be as short as possible).

(3) Check whether there is leakage at all connections.

(4) Check whether a stop valve is installed at the flexible hose (to prevent inability to replace after the water pipe cracks).

(5) The inspection of the drain is carried out by the drainage method.

(6) Whether all joints, valves, and pipe connections are tightly connected without leakage.

(7) Water pipes must not be installed close to power sources; the spacing between water pipes and gas pipes should be no less than 500mm.

➤ Waterproof Engineering

(1) Store water in the room; the lowest water surface must not be lower than 20mm. Mark the water surface height, observe after 48 hours whether the water surface height has changed significantly, and check whether there is water seepage on the ceiling of the room below at the same position.

(2) If the above phenomena do not occur, the waterproof engineering acceptance can be considered qualified; otherwise, if the above phenomena are found, the waterproof engineering is considered unqualified, and it must be completely redone and re-accepted.

(3) For the acceptance of lightweight wall waterproof engineering, the water spray test should be used: use a water pipe to spray water continuously from top to bottom on the wall with waterproof coating for 3 minutes, and observe after 4 hours whether there is seepage on the other side of the wall. If no seepage occurs, the wall waterproof construction acceptance can be considered qualified.

Key Points for Concealed Works Acceptance

➤ Foundation and Base

(1) Before foundation reinforcement treatment, after the foundation pit and trench are excavated and leveled, the soil quality and bearing capacity shall be inspected and accepted. Responsible personnel and technicians from survey, design, quality supervision, supervision, construction, and construction parties shall be present. Based on the foundation plan and the structural drawings of the construction drawing stage in the general structural description, as well as the geotechnical investigation report of the detailed investigation stage, determine whether the soil quality and bearing capacity meet the requirements.

(2) The acceptance content of foundation and base engineering includes unsupported earthwork, supported earthwork, foundation and base treatment, pile foundation, underground waterproofing, concrete foundation, masonry foundation, steel-reinforced (pipe) concrete, steel structure, etc. Before foundation pouring, the quality supervision agency, design unit, and construction unit shall be invited to conduct on-site inspection and acceptance. Inspect and accept the construction quality after foundation reinforcement treatment.

(3) Acceptance of foundation engineering. Before backfilling the foundation trench, inspect and accept the quality, structure, and dimensional deviations of the foundation engineering.

➤ Main Structure

(1) For the acceptance of reinforcement and other works, ensure that before concrete, before covering the roof protective layer, backfilling the basement foundation trench, and pointing the external wall panels, the quantity, dimensional deviations, structural requirements, and protective layer thickness of the reinforcement skeleton, pipelines, components, embedded parts, etc. are accepted.

(2) Before block masonry construction, the structural engineering has been accepted by the relevant units. Before formal masonry, a sample room shall first be built on the standard floor, including structural columns, window sill copings, lintels, etc., constructed according to design and specification requirements; construction can proceed only after acceptance by the supervision unit, and ensure that technical disclosure has been completed for the construction personnel, clarifying the construction process and quality acceptance standards.

➤ Building Decoration Engineering

(1) Wall cracks and floor slab appearance are the focus of attention when owners take over the building and must be taken seriously. Generally, focus on checking whether there are stress cracks in load-bearing walls and floor slabs; whether there is serious color difference in the wall color.

(2) The quality of the door and window surface directly affects the decorative effect of the entire wall after installation. The appearance inspection of doors and windows includes checking whether there are cracks on the surface, whether there is deformation, and the installation of window rubber.

(3) For the ground appearance inspection, first, at a distance of 2m, visually inspect whether the ground color is uniform, whether there is color difference and scratches, and check whether there is abnormal pollution on the brick surface, such as cement, paint, etc. Then, visually and manually check whether the surface has cracks, fissures, or damage.

➤ Building Roof

(1) The height of waterproofing upturn shall not be less than 25cm; additional waterproofing layer shall be applied at the pipe root; the waterproofing termination shall use metal hoops, and sealant shall be applied at the upper opening.

(2) The height of pipes on accessible roofs shall not be less than 1.8m. The smoke vent cap cover plate shall be sloped at 2%.

➤ Mechanical and Electrical Engineering

(1) During the acceptance of water supply and drainage engineering, the main materials, finished products, semi-finished products, accessories, appliances, and equipment used must have Chinese quality qualification certificates, and the specifications, models, and performance test reports must comply with national technical standards or design requirements; all materials shall be inspected for variety, specification, and appearance upon entering the site, and the packaging shall be intact, with no scratches or external impact damage on the surface; main appliances and equipment shall have complete installation and operation manuals.

(2) Check the weak current box to see whether the line distribution is clear and whether the functional modules are relatively clear. When laying circuits, if the horizontal spacing between weak current and strong current, or between weak current and weak current, is too small, it is easy to cause signal interference in the future. During acceptance, pay attention to checking whether the conduit distance meets the regulations.

(3) Lightning protection engineering projects mainly include welding of pile foundations, full-length welding of column reinforcement down-conductors, and installation of equalizing rings, lightning protection nets, lightning rods, and lightning arresters. In order to improve the construction quality of lightning protection engineering projects, the construction quality of lightning protection devices should be strengthened to ensure that the lightning protection engineering quality is qualified.