Technical solutions for roof leakage, ground cracking, and safety inspection points

#Service case ·2026-06-04 17:55:05

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1. Implementation plan for improving leakage prevention of metal roofing

The metal roof is a non-accessible roof, so the frequency of access should be minimized to reduce the number of subsequent maintenance tasks. Without affecting the cost, the roof slope should be increased as much as possible. The number of holes on the roof should be minimized. The roof panel type should be 360° seamed to form a unified roof. The supports should be sliding bearings, which can effectively solve the leakage caused by thermal expansion and contraction of the roof panels due to temperature changes.

Common roof leakage locations and prevention measures are as follows:

1. Ridge part:

The main causes of water leakage at this location are: the ridge crest is too high, making it impossible for the ridge cover to ensure waterproofing; the longitudinal overlap does not incorporate silicone, resulting in gaps that lead to leakage; the longitudinal overlap of the ridge cover is connected using rivets, which may break due to insufficient strength during thermal expansion and contraction, leading to leakage; and no plugs are placed between the ridge cover and the roof panel, or the plugs are not placed properly and fall off, resulting in leakage.

Preventive measures: Apply sealant longitudinally on the ridge in an overlapping manner, and cover it with three coats of paint and one layer of cloth. Lay a plug between the ridge cover and the roof panel, and increase the width of the ridge cover.

2. Daylighting band location: (1) The shape of the daylighting panel does not match the shape of the roof panel. After installation, the lap joint is not sealed tightly, forming gaps that allow water to enter the interior of the roof and cause leakage. The longitudinal lap length of the daylighting panel is insufficient, and no waterproof sealing strip is installed. The daylighting panel and the color steel plate are rigidly lapped together, and the gap between them is not sealed.

Preventive measures: When purchasing skylights, it is essential to ensure that the shape of the skylight matches the shape of the roof panel. The skylight should have metal edges that mechanically engage with the roof panel in a 360° manner, creating a unified roof surface. The longitudinal overlap length between skylights or between the skylight and the roof profiled steel sheet should be 200-250mm, and two strips of full-length butyl waterproof tape should be applied.

(2) Leakage caused by screw construction at the skylight panel: The main reason is that the difference in linear expansion coefficients between the skylight panel and the purlin causes temperature stress at the screw fixation point of the skylight panel to exceed the shear stress of the panel, resulting in damage and leakage. Preventive measures: Before fixing the skylight panel, pilot holes must be drilled, with the hole diameter being 6-9mm larger than the diameter of the fixing screw, to accommodate thermal expansion and contraction.

(3) Improper design. For example, if the skylight does not start from the ridge, it will be difficult to handle the waterproofing of the upper part of the skylight, leading to leakage. Preventive measures: Change the skylight to start from the ridge, and it is best to extend it all the way to the cornice.

(4) For insulated roofs, the skylight strip should be designed as a double-layer structure. Sealing and vapor barrier treatment must be implemented between each layer of skylight panels, as well as between the skylight panels and the purlins and roof panels. 3. Roof opening areas: The main causes of water leakage in these areas are: failure to conduct waterproof treatment according to the design nodes during opening, failure to apply waterproof mastic and silicone around the steel plugs; the reserved area around the opening is too small, which impedes the flow of rainwater and leads to water accumulation; the edge overlap around the opening is not waterproofed; no structural components are added around the interior of the opening, resulting in low-lying areas that can accumulate water; and waterproof construction may cause water blockage, leading to water accumulation.

Preventive and Control Measures: Construction shall be carried out according to the design drawings and strictly adhere to the construction procedures, with the application of mastic and silicone; the reserved area around the openings must meet drainage requirements; waterproofing treatment must be carried out immediately after drilling holes on walls and roofs; for additional enclosure openings, it is recommended to add purlins or angle steel structures to minimize enclosure deformation; the waterproof construction and installation must be tight and smooth to ensure smooth water flow.

4. Gable eave area: The main reason for water leakage in this area is that the roof external panels were installed without foam plugs, and the roof external panels were not pulled down; the length of the wall external panels is insufficient, and no waterproof edge was added at the eave area.

Preventive measures: During the installation of the roof outer panel, foam plugs should be placed simultaneously, and the roof outer panel should be bent downwards by 30 degrees; additional edge trimming should be added at the cornice according to design requirements.

5. Leakage occurs at the gutter, and the causes are as follows: (1) The ends of the roof panels are not sealed or not sealed tightly enough, and the length of the roof panels extending into the gutter is not long enough, causing water to flow backwards. If the length of the roof panels extending into the gutter is too long, it can cause water to flow back up. Preventive measures: The length of the roof panels extending into the gutter should be constructed according to the design, and the ends of the panels should be angled downwards by 30°; the underside of the roof panels should be continuously sealed, and it is recommended to use rubber plugs that match the shape of the panels; (2) There are gaps in the joints during welding of the gutter, causing slow seepage; Preventive measures: After welding, waterproof tests should be conducted on the weld seams of the gutter joints. If water seepage is found, secondary welding should be performed to ensure the quality of the connection; (3) The design of the gutter and downpipe does not match the catchment area of the roof; the diameters of the gutter and rainwater pipes are designed too small; Preventive measures: The cross-sectional sizes of the gutter and rainwater pipes should be determined based on the roof drainage capacity, and the gutter should be made as deep and wide as possible; 6. Analysis of the causes of water accumulation in the gutter: The water outlet or connection points of the gutter may be elevated due to welding deformation, resulting in a small amount of water accumulation after rain, which affects the service life of the gutter.

Preventive measures: Minimize the number of joints, extend the gutter as much as possible, add brackets to the gutter, and enhance its flatness. At the gutter's water outlet, after cutting, use machinery to fold down along the perimeter, and then proceed with welding.

7. Water leakage occurs at the flashing of the parapet, gable, or at the transition between the high and low spans. The cause of the leakage is: the flashing board rolls up and is not properly sealed at the contact point with the wall, resulting in leakage; the overlapping width between the flashing board and the roof panel is insufficient, and it is not overlapped at a wave crest, but at a wave trough, leading to the backflow of rainwater and snowmelt.

Preventive measures: The flashing board should be rolled up at least 250mm, and it should overlap the roof panel by at least one corrugated peak. At the corrugated peak, use self-tapping screws (or use rivets between purlins and profiled steel sheets). Apply a continuous length of sealing tape between the flashing board and the roof panel. The flashing board should have a 2% slope from the wall base outwards.

8. Roof ventilator area: The main cause of water leakage in this area is the absence of foam plugs at the lower edge of the junction between the ventilator and the roof, and the lack of cement or silicone applied to the longitudinal overlap of the edge; the outer roof panel is not attached at the junction with the ventilator; no waterproof treatment is applied to the holes in the structural pillars of the ventilator; and there are potential water leakage hazards in the manufacturing and installation of the ventilator itself.

Solution: Before installing the edge, foam plugs should be laid. For longitudinal overlaps, clay or plugs must be set and fixed with staples. Before installing the air building, the roof panels must be turned up. The air building construction party is required to perform waterproof treatment on the opening parts after the air building structure is completed. The installation quality and waterproofness of the air building should be inspected.

9. Roof gutter cleaning: Roof gutters are prone to being blocked by debris such as leaves and dust, especially at the siphon mouth, which can prevent rainwater from draining out and cause water to flow back into the factory building from the roof panels. Our company provides free cleaning of roof gutter debris for all construction projects for a period of 3 years.

II. Implementation Plan for Improving Ground Subsidence and Cracking 1. Settlement cracks Settlement cracks are usually continuous, narrow at the bottom and wide at the top. The common cause is that the backfill around the independent foundation, under the connecting beam, at the entrance, etc., is not constructed strictly according to the construction specifications.

Preventive measures: (1) Before backfilling, the debris such as garbage in the foundation pit bottom must be cleaned up; (2) Check whether the moisture content of the backfill meets the standard and is within the control range. The optimal moisture content is such that it forms a ball when held in the hand and spreads out when dropped on the ground. For backfill with high moisture content, measures such as scarifying and drying can be taken for remediation. However, if the moisture content is low, measures such as pre-watering can be taken for remediation.

(3) It is necessary to spread the material in layers, with each layer having a virtual thickness of no more than 250mm. Additionally, when backfilling, due to the narrow operating space around the foundation, mechanical assistance and manual compaction are required to ensure that the compaction coefficient of the backfill reaches 97%.

2. Shrinkage cracks (1) The impact of materials on concrete cracks manifests in the following aspects: First, the greater the amount of cement used, the greater the shrinkage, which then leads to cracks. Second, the higher the strength grade of cement, the smaller the fineness, the greater the hydration heat, the greater the shrinkage, and the more prone to cracking. Third, the smaller the particle size of coarse aggregate, the poorer the stability of the skeleton volume, the greater the concrete shrinkage, and the more prone to cracking. Fourth, the higher the silt content in coarse and fine aggregates, the greater the shrinkage, which can lead to cracking. Fifth, improper selection and dosage of admixtures can increase shrinkage, leading to cracking. Sixth, the requirements for impurity content in aggregates vary for different construction sites. Seventh, excessive concrete slump can easily cause segregation, cracking, and strength reduction. In summary, the performance of concrete materials plays a decisive role in crack control.

Preventive measures: 1. Choose enterprises with strong technical capabilities, large scale, high integrity, and good reputation; 2. For basic parts, the requirements for aggregate impurities are relatively low, while for flooring parts, the requirements for aggregate impurities are relatively strict, such as wood chips and grass roots, which must be sorted out.

(2) Cracks caused by improper vibration techniques. During concrete construction, if the local vibration is insufficient, phenomena such as loose structure, honeycombing, and pitted surface may occur. Over-vibration can lead to coarse aggregate subsidence and surface water seepage, which can easily cause plastic cracks and shrinkage cracks on the surface.

Preventive measures: 1. Select skilled and experienced vibrating operators. 2. Technical and quality assurance personnel should stand by to provide timely guidance in case of any issues.

(3) Cracks caused by improper pouring time: Temperature, humidity, cold, and heat can directly affect the quality of the ground concrete project. Improper selection of pouring time can lead to premature setting or insufficient strength of the concrete, directly affecting the compaction and finishing of the ground, resulting in cracks.

Preventive measures: If construction is carried out in high-temperature environments during summer, it is advisable to pour during the day and finish troweling at night when the temperature is lower. If construction is to be done in winter, pouring can be done at night and finishing troweling during the day when the temperature is higher (around noon).

(4) The untimely cutting of concrete floor joints, insufficient cutting depth, and improper cutting position and area are among the more common and significant reasons for crack formation. Cutting too early may result in damage such as chipped edges and missing corners due to insufficient cement concrete strength to meet the cutting strength requirements; cutting too late may prevent timely release of temperature stress, leading to crack formation.

Preventive measures: After the concrete ground work is completed, cutting should be carried out within 48 hours (provided that the cutting joints do not chip the edges, the earlier the better). The depth of the cutting joints should be 1/3 of the ground thickness. The spacing between cutting joints should not exceed 6 meters, and cutting joints are required around column foundations, equipment foundations, and at doorways.

(5) Cracks caused by insufficient curing: After the concrete is poured, early-age shrinkage cracks are prone to occur if it is not cured in a timely manner. Additionally, insufficient curing time of concrete can also lead to insufficient strength, which in turn can cause cracks.

Preventive and control measures: 1. Natural curing should commence before the final set of concrete, typically within 8 to 12 hours after concrete pouring. 2. Curing measures and duration: The curing measures involve covering with thin film or cotton felt followed by watering for curing, with a curing duration of no less than 7 days (excluding winter).

(6) Construction cracks caused by premature application of load During the construction of a project, in order to use the structure ahead of schedule, the owner's vehicles prematurely apply construction loads that exceed the concrete's bearing capacity when the concrete's strength does not meet the requirements for loading, resulting in cracks that cannot heal.

Preventive measures: The general contracting unit shall provide a timeline for the road to be ready for traffic.

(7) The addition of anti-cracking steel mesh on the ground in processing workshops and road surfaces helps prevent the occurrence and development of concrete cracks, reducing surface cracking by approximately 90%. Common specifications include 5*5cm and 10*10cm, with wire diameters ranging from 4-6mm. 3. Safety Inspection Points 1. High-strength Bolt Inspection: Mechanical vibration can cause bolt screws to back out, affecting usage and structural safety. Our company provides free high-strength bolt inspections for all contracted projects every three years, with inspections conducted once a year. During inspections, bolts are recorded using different colored markers.

2. Electrical equipment spot inspection: (see the figure below for details)