Analysis and prevention of water seepage in light steel structure color steel plate workshop

1.Steel structure roof form

Steel structure roof, wall and other envelope structure, generally use color steel plate, its thickness is generally 0.3~ 1.0mm, color steel molding plate is galvanized (or aluminum plated zinc) and other pre-coated color steel plate rolling, the surface spray paint layer. For buildings requiring heat preservation, heat insulation and sound insulation, double-layer color steel molding plates can be used, and thermal insulation materials (such as glass wool, rock wool, foam, etc.) can be filled in the middle; The filling material can be filled in the field, or it can be pre-combined with the color steel plate factory (called the color steel sandwich board). As the load-bearing and external protection structure of the top floor of the building, the building roof's enclosure and facade modeling function are crucial to the whole building, and it is the most important part of the light steel structure enclosure system leakage. Its main function is to resist the invasion of wind, rain, snow and solar radiation, and to withstand the weight of the roof and the load of the wind, snow and people on the roof. According to the materials used, the light steel structure roof has many types, such as colored molded steel plate, colored steel plate sandwich plate, colorful linoleum tile, various light roofing panels, GRC panels, metal arch corrugated roofing, composite molded steel plate and so on. Light steel structure roofing and wall materials, mainly use color molding plate or sandwich plate. In the steel structure plant project supervised by the author, the roofing materials are mainly finished glass wool sandwich board or color molded steel plate. Commonly used steel plate specifications are mainly YX173-300-600, YX130-275-550, YX70-200-600, YX38-175-700, YX21-180-900 and other 28 kinds of plate types, in the above specifications of the plate, both 360° rolled edge plate, dark buckle plate lap connection, there are also nail board, Purlins are thin-walled C-type or Z-type steel purlins with light weight, and the roof slope design is generally 1/10 ~ 1/15.

2.Connection of roof panels

Steel structure system building roof panel, there are two kinds of long connection and side connection on the roof. The long connection is mainly lap, that is, the uphill plate is pressed down the slope plate, and the lap is set up with special waterproof sealant and fixed special layering, and the lateral connection method is mainly divided into the following three kinds:

1) The lap joint overlaps the lap edge of the molded steel plate and connects it with various bolts, rivets or self-tapping screws. The connection is divided into two kinds with sealant groove and without sealant groove. The roof screws are exposed and the wave crest is relatively low.

2) The button-type connection fixed support is fixed on the roof purlin with flat head tapping screws, and then the pressure type roof plate is buttoned with the fixed support. The roof is not exposed with screws, but because it is directly connected with purlins with screws, it cannot control the deformation of thermal expansion and cold contraction.

3) Occlused-underbutton-type connection, which is a relatively advanced roof plate connection method, the roof system fixes the roof plate by sliding the bracket, which is conducive to waterproof the roof and maintain the integrity of the roof, and can effectively control the deformation caused by thermal expansion and contraction. The connection form is 180 points. And 360. Two kinds.

3.Water leakage cause analysis

Color steel plate maintenance system itself has a certain strength and stiffness, the material generally does not leak, maintenance system water leakage mainly in the node handling, the quality of the material, the maturity of the system design, completeness, structural structure and installation technology are also directly affect the waterproof effect of the enclosure system. The color steel plate shrinks and deforms due to changes in the environment and temperature, and when the interface and lap connection parts are displaced, the ordinary sealing rubber strip or silicone rubber and the surface of the color plate can not be synchronized and dislodged, resulting in water leakage of the color steel plate roof. The degree of deformation and aging of different light mining plates is not the same in the same time. For the same flange plate, the waterproof performance of the Butler system is much stronger than the imitation of the same template type; The same is the nail board, the installation effect of different construction teams is also very different. The main reasons for roof leakage are as follows.

3.1 Design Factors

1) Technical Regulations for Steel Structure of light housing with portal rigid frame (CECS 102:98) stipulate that the roof slope of light housing with portal rigid frame should be taken from 1/8 to 1/20, and the larger value should be taken in areas with more rain. In the actual design project, the construction unit in order to save money or other reasons, required to minimize the roof slope, the design unit often dead set of regulations, do not consider the actual situation. As a result, the slope of many project roofs is too small, roof rainwater can not be discharged into the gutter in time, and roof water causes roof seepage phenomenon.

2) Designers do not understand the local rainfall, which is also an important factor causing the slow slope design of the roof and the small cross-sectional area of the gutter.

3) The lack of node design, the construction unit chooses the node method at will, the height of the parapet wall at the ridge is not enough, the location of the pipe and the exhaust channel extending out of the roof is not appropriate or the height is not enough, and the construction of the waterproof layer is difficult.

4) Improper selection of plate type, for the hidden buckle and bite type plate type, as long as the site is properly installed, there is generally not much problem. If the plate type connected directly with self-tapping screws is selected, even if the site is treated well, the waterproof glue is also in place, but because the panel has the performance of thermal expansion and cold contraction, there will also be water leakage.

5) The roof hole design is not considered. It is not allowed to cut holes in the construction site, and the hole waterproof should be done.

6) The enclosure part of the color plate is too thin, after a period of use, the outer plate corrosion or deformation under the influence of temperature, the gap between the plates increases.

7) The roof rainwater system does not set overflow measures according to the specifications, and when the intensity of the rainstorm exceeds the drainage capacity of the rainwater system, it will exceed the lap joint and even spread on the roof, resulting in accidents.

8) The number of downspouts is insufficient, and the rain water flows far along the gutter for a long time, resulting in water accumulation; The upper part of the outer panel of the wall is not equipped with L-shaped edge pieces, and there is a hidden water leakage in the inside of the gutter.

9) Color steel flooding accessories design is unreasonable, can not achieve waterproof effect.

10) The specification specifies the component deformation control value, purlin deflection L / 180, roof beam deflection L / 180(type L is the span of the bending component), roof purlin section design is too small, the distance is too large, under the wind load purlin and pressure plate deformation will be too large.

11) It does not fully consider the influence of structural deformation, temperature difference deformation, dry shrinkage deformation, vibration, etc., and the fortification does not meet the needs of base deformation.

3.2 Construction Factors

1) During the construction process, the roof enclosure is not protected, and the roof is trampled at will, which damages the flatness of the roof, and even cracks, insufficient sealant, incorrect position, too many rivets, and no waterproof treatment is carried out.

2) Gutter is not anticorrosive, some construction units in the gutter anticorrosion, just brush anti-rust paint or asphalt paint, after a period of time, the gutter corrosion is serious.

3) Steel structure factory housing panel, due to the large span, the roof plate is overlapped, although polyurethane sealant and 138900 stitching nails are used in the overlap, but the installation is often difficult to meet the design theory standard, resulting in rain leakage.

4) There is no horizontal slope of the gutter, and at least 0.5% slope should be left when making.

5) Sloppy construction of key node parts. The female wall and other root Angle is not made into an arc or too small arc according to the regulations, the end end of the coil is not tightly sealed, the upper iron sheet is deformed, the fixed point is rare and the sealing material is not good, the pipe root hole stretching out of the roof is not strictly blocked, the leveling layer around the pipe is not higher than the nearby leveling layer, and the flooding height of the waterproof layer is not enough. The construction of the insulation layer is rained, the exhaust tank is blocked, and the exhaust hole is set unreasonable, resulting in long-term water immersion of the insulation layer. The rigid roof produces cracks, and the waterproof sealing paste in the divided joint is not firmly bonded to the side wall of the joint, and water permeates.

3.3 Structural factors

1) The load is arbitrarily increased during the use of the house, resulting in the deformation of the roof panel. Especially in the roof purlin will increase the load, purlin deformation, resulting in roof water.

2) Waterproof glue, sealant aging, the use of the project lack of necessary maintenance.

3) The plug is useful for the water leakage caused by the wind, which should not be ignored, it is necessary to ensure that the color steel plate and the roof cover plug are installed in place, the lower part of the plug between the light mining plate and the roof cover plate should be made of silicone sealant, and the steel plug is set at the peak end of the color steel plate at the roof fan.

4) The gap is easy to be affected by temperature when bonding, and the length of the bonding should be fully left.

5) The water should be sparse and not blocked, and the sealant on the inside of the steel plate is generally installed, the more the better.

6) We must pay enough attention to the adverse effects of thermal expansion and cold contraction of the steel structure roof enclosure system, and take reasonable structural measures.

3.4 Material Factors

1) Plastic pipe for rainwater pipe, poor strength, steel structure plant from installation to operation, easy to damage.

2) Because the steel groove is relatively thin, the weld is prone to problems.

3) Not according to the slope of the roof to choose the appropriate light plate plate type and roof color steel plate type, small crest, side lap too little, not conducive to drainage.

4) The enclosure part of the color plate is too thin, after a period of use, the outer plate corrosion or deformation under the influence of temperature, the gap between the plates increases.

5) The quality of the galvanized layer of the press plate substrate is not good, the coating is too thin, resulting in short service life of the press plate and easy corrosion damage.

6) The quality of self-tapping rubber pad is poor and easy to crack, and the glass sealant is easy to aging.

7) The buckle plate is obviously deformed, the board height and spacing of the adjacent two plates are different, and the buckle nail should be waterproof.

4.Measures to prevent leakage

(1) Designers should be strictly in accordance with the specifications of the design, not because of cost savings and arbitrary reduction of design indicators, designers should go to the construction site, combined with the actual situation of the design.

(2) The designer should make a detailed and reasonable node sample according to the actual situation, and can not only draw convenience and blindly apply the nodes on the map. Designers in the design of roof purlins, should be conservative, do not blindly in order to save steel, and reduce the height of the purlin, purlin height is higher, is conducive to leakage.

(3) The roof plate should use a better waterproof performance of the plate type, according to market research statistics, 760 type field composite plate, 475 type color steel plate, 675 type color steel plate, bite 360° at least 180°, almost no leakage phenomenon, although these types of plate installation is more troublesome, but the use effect reflects well.

(4) The choice of roof waterproof materials, should choose the quality of trustworthy manufacturers, due to the material characteristics of metal roof panels, should choose waterproof materials suitable for metal sheet roofing; For example, butyl rubber waterproof sealing adhesive tape with high bonding strength, good followability and excellent weather resistance is used as a supporting waterproof material for metal sheet roofing.

(5) When the project is installed, on-site management should be strengthened to improve the quality of the installation team, and it is best that the steel structure manufacturer has its own construction team or technical backbone and management backbone to curb the power of the contractor.

5.Cause analysis and solution of water leakage in each part

Light steel structure roof slope is generally small, often less than 6%, in the central and southern areas with more rain, the roof leakage phenomenon of this structure is more common, there are large areas of water leakage, lighting Windows and roof ridge combination spots, etc., the cause, the formation of water leakage phenomenon, Most of them are caused by self-tapping screws, color steel plate lashing, roof tile, core rivets, roof roof caused by the deformation of color steel plate and the rainproof glue falling off decorative parts such as lighting Windows.

5.1 Roof screws and fasteners leak

This phenomenon is more common, mainly in double-layer color steel plate and single-layer color steel plate roof. In the construction process, the self-tapping screw force is too heavy, too light, the self-tapping screw deflection, skew, etc., may cause the self-tapping screw rubber gasket deformation, fall off or form a concave, causing the roof drip water leakage, and through the thermal insulation cotton accumulation, the accumulation becomes more, forming a multi-point water leakage. In addition, the position of the self-tapping screw is not correct, and the hole is directly formed under the purlin of the color steel plate is also one of the important reasons for water leakage. This leakage phenomenon may not be obvious in the roof structure of the single-layer color steel plate without insulation system, mainly because the rain is directly dispersed after the leakage of the steel plate and purlin contact, and does not necessarily drip quickly.

5.2 Water leakage at the lap of color steel plate

Horizontal lap joints and vertical lap joints, the color steel plate lap water leakage, if the color steel tile wave is too low or the rainwater volume is not over the tile wave, it is easy to form a large area of water leakage, and it is not easy to find the water leakage point, once it is not easy to repair. Common in curved roof. The main reason is that the lap between the two plates is not tight, the self-tapping screw is not full to form a gap and so on.

5.3 Roof ridge is leaking

In the construction of light steel structure roof, water leakage caused by roof tile is also a more common phenomenon. In the rainy season, especially when the amount of rain is large, the rain splash through the gap between the two color steel plates at the lower part of the ridge tile, forming a large area of leakage. The main reasons for the water leakage in this part are: the crest of the ridge is too high, and the roof cover can not guarantee waterproof; Longitudinal lap does not put mud or silicone, forming a gap and water leakage; Ridge cover plate longitudinal lap with rivet connection, thermal expansion and contraction strength is not enough to pull the rivet, forming water leakage; No plug is laid between the ridge cover plate and the roof plate, or the plug is not placed in a standard and falls off to form water leakage. The solution is to make the ridge cover wider, and the slope to find a larger point; Cement or silicone shall be applied at the joint; Replace the stitching nails; The plug should be matched with the plate type, and the plug should be placed on and off the clay or silica gel. In order to prevent the ridge tile from leaking rain, it is advisable to increase the length of ridge tile flanging, cut the spot of tile wave and glue the joint.

5.4 Roof gas building parts

The main causes of water leakage in this part are: there is no foam plug under the edge of the gas building and the roof, and the longitudinal lap of the edge is not laid with mud or silicone; The outer plate of the roof is not mounted at the junction of the gas building; The opening part of the pillar of the gas building structure has not been waterproof treatment; There are hidden water leakage hazards in the production and installation of the gas tower itself. The solution is: the foam plug should be laid before the edge installation, and the longitudinal lap must be set with mud or the plug fixed with stitching nails; The roof plate must be good before the installation of the gas building; The construction side of the gas building is required to waterproof the opening part after the completion of the gas building structure, and check the installation quality and waterproof performance of the gas building.

5.5 Light plate parts

The waterproofing of the light board is an important part of the maintenance system. The clay laying and waterproof screws in the installation of the light board are the main hidden dangers of roof leakage. The wave crest on both sides of the light board is higher than the roof board. After installation, the seal is too strict or the pressure difference between the inside and outside of the light board, and the capillary water enters the roof from the gap on both sides of the light board. The longitudinal bonding length of the light mining plate is not enough, and the adhesive mud loses viscosity after aging. Longitudinal slime off; There is a rigid lap between the light plate and the color steel plate, and the gap in the middle is not sealed. Roof light plate to prevent water leakage should pay attention to the following aspects: first, the waterproof screw is applied in the upper part of the wave crest; Second, the edge plate at the light plate should be firmly sealed with the light plate, the longitudinal sides of the mud should be widened, and the upper part of the wave crest should be laid to prevent water capillary and water seepage; The third is to control the center distance of the wave crest on both sides, which is consistent with the center distance of the wave crest of the light mining plate, and the height or width of the wave crest of the light mining plate cannot be removed due to installation problems or different dimensions and width, causing hidden dangers in quality; Fourth, the longitudinal lap is generally not less than 300㎜, and the lap is sealed firmly with silicone, and the place where the light plate is overlapped should be sealed with flexible tape.

5.6 Openings on the roof

When opening the hole of the color steel plate roof, it is necessary to consider the appearance and solve the problem of roof waterproof, which should be decided according to the opening form and the model of the color steel roof plate. The main causes of water leakage in this part are: the entrance of the fan is not waterproof according to the design node, and the steel plug is not laid waterproof cement and silicone; The reserved area around the fan entrance is small, the rain is not flowing smoothly, and it is easy to collect water; The wrapping around the hole is not waterproof; No structural parts are added around the inside of the hole, forming a low concave water; There is water blocking phenomenon in waterproof construction, resulting in water accumulation. The solution is: according to the design drawings construction and strict construction procedures, laying mud, silicone; The reserved range around the fan must meet the drainage requirements; The wall and roof must be waterproof immediately after opening holes; After increasing the enclosure opening, purlin or Angle steel structure should be added as far as possible to reduce the enclosure deformation; Waterproof installation must be tight and smooth, so that the water flow is smooth.

5.7 Cornice parts

This part is the main part of the water leakage, the main reasons for water leakage are: the roof plate is installed without foam plug, the roof plate is not down; The length of the outer panel of the wall is insufficient, and the cornice is not waterproof. The solution is: foam plugs should be placed at the same time when the roof outer plate is installed, and the roof outer plate should be lowered by 30 degrees, and the eaves should be added according to the design requirements.

5.8 Gutter area

Lap joint and bridge joint are the two key parts of the water leakage, compared with the reinforced concrete roof, the gutter depth of the steel structure roof is small, and the gutter and the roof have no continuous waterproof structure, and it is difficult to ensure no water leakage when the gutter water. The main causes of water leakage in this part are: there are gaps in the welded joints of the inner gutter, resulting in water seepage; Gutter and rain pipe diameter design is too small, and does not match the slope length of the workshop; No head plate is made at the end of the gutter; The length of the roof outer plate extending into the gutter is insufficient, and the water will pour into the inside of the plant. The solution is: appropriately increase the depth of the gutter, so that the gutter rain does not exceed the lap joint; Do waterproof test after welding of inner gutter joint, if water leakage is found, secondary welding is required; The design diameter of gutter and storm pipe should be determined by calculating the displacement of roof; Install the gutter end head plate; The roof panels shall be constructed according to the design length.

5.9 Awning parts

The main causes of water leakage in this part are: improper treatment of the indirect 151 parts of the awning and the attached room; There is no plug between the awning and the outer wall or it is not extended into the outer wall panel according to the design requirements. The solution is: the indirect 151 of the awning and the attached room must be connected with the edge and waterproof treatment; Under normal circumstances, the awning 151 flooding edge should enter the outer wall panel, in order to facilitate installation and construction, flooding edge can also be directly against the wall panel, but must be placed on the plug, and silicone seal the gap.

5.10 The interface between the plant and the attached room

The main reason for the water leakage in this part is that the construction is unreasonable and the installation of the interface edge does not meet the design requirements. The solution is: the waterproof treatment of the attached room is usually more than 2 times waterproof, the first waterproof edge is cut 20mm ~ 40mm with the concrete interface, and the waterproof sealant is laid after the edge is inserted; When the plant and the attached room interface is installed, only one end can be fixed, the other end must form a free state, and the apricot will cause the heat expansion and cold contraction of the edge to open water leakage.

5.11 Connection between brick wall and light steel roof

This part is easy to form a hidden water leakage, roof panel and cement wall joint water leakage, the main reason is the stress is not synchronized caused by silicone adhesive and bonding surface cracking and water leakage. Solution: Prevent temperature deformation, using two edge connection processing; When connected with the brick wall, the edge should be at a certain Angle and completely sealed; Sealant should be applied before closing the edge.

5.12 Aluminum alloy Windows

Aluminum alloy window and color steel wall and brick wall connection part is one of the waterproof problems, the main reason for the water leakage is: wall purlin and aluminum alloy gap; The seal between the lower opening of the window and the steel structure, the brick wall and the window glass and the profile is not strict; There is a large gap between the windowsill and the table top or there is backwater phenomenon; There is no silicone gel in the installation of 151 flooding edge pieces on the window. The solution is to ensure the flatness of the structural purlin and reduce the gap between the purlin and the aluminum alloy; All gaps at the lower window opening should be completely sealed and silicone glue should be applied; Aluminum alloy and single slot, single slot and glass should be completely sealed treatment; The surface tile outside the brick wall should ensure the fullness of mortar; Urge the civil construction unit to find the slope of the windowsill before painting the windowsill to facilitate drainage; Pre-apply sealant to 151 flooding edge pieces on the window, and do not overlap the steel column.