Roof waterproofing
Waterproofing project is an important project in house construction. The quality of the project is related to the service life of the building and will also directly affect people's production activities and life. proceed normally. According to statistics, there are several reasons for roof leakage: materials account for 20% to 22%, design accounts for 18% to 26%, construction accounts for 45% to 48%, and management and maintenance account for 6% to 15%. At present, there are many new materials for roof waterproofing, but the membrane waterproof layer still occupies an important position. Therefore, this article focuses on the construction of roof membrane waterproofing.
1. The following work should be done before the waterproof construction of roofing membranes
(1) Technical preparations before construction
Before the construction of the roof project, The construction unit should organize technical management personnel to review the roof project drawings, understand the detailed structure and relevant technical requirements in the construction drawings, and prepare the construction plan or technical measures for the roof project based on the actual conditions of the project. This avoids defects and rework after construction. At the same time, the project is carried out in a planned manner according to the construction organization to prevent omissions, confusion, and inversions from affecting the quality of the project.
With the construction organization in place, the next step is for the construction leader to make a technical briefing to the team. The content includes: construction parts, construction sequence, construction technology, structural levels, node fortification methods, reinforced parts and practices, project quality standards, technical measures to ensure quality, protection measures for finished products and safety precautions.
(2) Requirements for construction personnel and construction procedures
The waterproofing of roofing projects must be carried out by a professional waterproofing team or waterproofing workers. Units without qualification certificates and non-waterproofing majors are strictly prohibited. When teams or non-waterproof workers carry out waterproofing construction on roof projects, the construction unit or supervision company should carefully check the employment certificates of the construction personnel. During construction, the construction unit should conduct quality self-inspection, self-inspection, and self-correction according to the construction process and level and keep construction records. The supervision unit should do the acceptance work of each step. Only after the acceptance is passed, the next process or level can be carried out. .
(3) Quality requirements for waterproof materials
The waterproof materials used in roofing projects should have material quality certification documents and be certified by the designated quality inspection department to ensure that their quality complies with the " Roofing Engineering Technical Specifications" (GB50207-94) or relevant national standards. After the waterproof materials enter the construction site, they should be accompanied by a factory inspection report and factory certificate, and the production date, batch number, specifications, and name should be noted. The construction unit shall take samples for re-inspection in accordance with regulations. Sampling and re-inspection shall strictly follow the witnessed sampling and delivery system. Under the witness of representatives of the construction unit or supervision unit personnel, construction personnel shall take samples on site and send them to the laboratory for testing. After passing the re-inspection and submitting the re-inspection test report, it can be used in waterproofing projects. It is strictly prohibited to use unqualified waterproof materials in the project. Once unqualified materials are discovered, all unqualified materials should be evacuated from the construction site immediately.
2. Key points of roof waterproofing construction
(1) Environmental requirements for construction
In order to ensure the quality of construction operations and membrane paving, it is advisable to operate at +50C Construction at temperatures of ~+350C; polymer modified asphalt and polymer waterproofing membranes are not suitable for construction below negative temperatures. Hot-melt paving membranes can be constructed at temperatures above -100C. This membrane is resistant to low temperatures , not easily frozen under negative temperatures. It is not suitable to operate in the open air in rain, snow, frost, fog, excessive atmospheric humidity, or windy weather, otherwise corresponding technical measures should be taken.
(2) Requirements for roof drainage slope
The drainage slope of flat roofs is 2% to 3%. When the slope is less than or equal to 2%, materials should be used to find the slope; When the slope is greater than 3%, structural slope finding should be used. The longitudinal slope of gutters and eaves shall not be less than 1%, and the drop at the bottom of the ditch shall not exceed 200mm. The slope within a diameter of 500mm around the water drop opening should not be less than 5%.
(3) Treatment of gaps and cracks in the roof base layer
The base layer is made of prefabricated concrete slabs. When the width of the gap between the slabs is less than 20mm, use fine stone concrete for filling. The particle size of the stone shall not be greater than 10mm, and its strength grade shall not be less than C20. Expanding cement or concrete mixed with expansion agent shall be used as much as possible to fill the joints; when the width of the gap between the boards is greater than 40mm, the joints shall be installed inside the joints. 1ф6 steel bars or steel bars configured according to design requirements. After pouring the slab joint concrete, it should be covered in time and watered and cured for 7 days. Construction can only continue when the concrete strength grade reaches C15. Prevent the grouting concrete from prematurely bearing the influence of construction loads and ensure the bonding strength between panels.
When the base layer is cast-in-situ reinforced concrete, and there are cracks in the slab, you should first use a chisel to cut the cracks into 15-20mm wide and deep eight-shaped grooves, and then remove the gravel. Blow the groove clean and fill the cracks with caulking paste in two or three times. The interval between each time must be 15 minutes. After filling the cracks, use a roller to flatten it.
(4) Requirements for roof leveling layer
The leveling layer is the base layer for paving the waterproof membrane, which provides a flat, dense, strong and bondable layer for the waterproof membrane. structural basis. Therefore, the leveling layer of the rolled material should be solid and should not have protruding sharp corners, pits or surface sand. When inspected with a 2-meter-long ruler, the gap between the ruler and the surface of the leveling layer should not exceed 5mm. , the gaps are only allowed to change gently, and there must be no more than one per meter length.
The corners formed by the adjacent surfaces of the leveling layer should be made into arcs or obtuse angles.
When the base layer is solid concrete, use cement mortar leveling layer with a thickness of 20mm, a cement to mortar ratio of 1:2.5 to 1:3 (volume ratio), and a cement grade of not less than 42.5. The leveling layer must also be provided with grating joints and filled with sealing materials. This can avoid or reduce cracking of the leveling layer, so that when the structure deforms or the temperature difference deforms, the waterproof layer will not form cracks, leading to leakage. The seam width is 20mm, and the longitudinal and transverse spacing of the lattice seams is not greater than 6m. The lattice seams are located at the support ends of the roof panels, at the intersection of the waterproof layer and the protruding roof components at the corners of the roof, and at the intersection of the waterproof layer and the parapet. wait. And it should be aligned with the end seam of the board, even and straight. When constructing the cement mortar leveling layer, first clean up the debris on the roof and floor and sprinkle water to moisten it. When laying mortar, follow the procedure from far to near and from high to low. Pave continuously in each grid once. Control the slope according to the design. Use a scraper with a length of more than 2m to scrape it flat. After the mortar has slightly absorbed water, Use a trowel to compact and smooth it. After 12 hours, cover it with a straw bag and water it for maintenance. Detailed nodes such as structures and pipe roots on the protruding roof should be made of arcs, truncated cones or square truncated cones, and made of fine stone concrete to avoid cracking of the roll material at the node locations and facilitate solid adhesion.
1． Water drop mouth: made within 500mm of the surrounding area, with a slope of ≥5% and smooth.
2. The roots of the parapet, roof flue and staircase are made into arcs with a radius of 80mm and are made of fine stone concrete.
3． Extend around the root of the roof pipe and use fine stone concrete to make a square frustum. The bottom surface of the frustum is 300mm wide and 60mm high, and is smooth and polished.
(5) Base treatment agent
In order to strengthen the bonding force between the waterproof membrane and the base layer and ensure the integrity, it is pre-painted on the base layer before the construction of the waterproof layer. of paint. Commonly used base treatment agents include cold base oil and primer (base treatment agent) matched with various polymer-modified asphalt membranes and synthetic polymer membranes. The selection should be compatible with the material of the membrane to avoid rolling. The material is corroded or incompatible with poor bonding.
Before spraying and applying cold base oil and base treatment agent, check the dryness of the leveling layer and clean it. Then use a brush to treat the nodes, periphery, corners and other parts of the roof first, and finally spray it on a large area. ,brush. The spray and brush should be thin and even, and should not leak white spots or be too thick or peeling. Apply cold base oil 1 to 2 days before paving, and apply the base treatment agent about 4 days after it dries before paving the membrane.
(6) Paving of roll materials
1. The laying direction of the roll material. The laying direction of the membrane should be determined according to the slope of the roof and whether there is vibration on the roof. When the roof slope is less than 3%, the membrane should be laid parallel to the roof ridge; when the roof slope is 3% to 15%, the membrane can be laid parallel or perpendicular to the roof ridge; when the roof slope is greater than 15% or subject to vibration, the asphalt roll The materials should be laid perpendicular to the roof ridge, and other materials can be laid parallel or perpendicular to the roof ridge according to the actual situation. Laying is carried out layer by layer from the eaves to the ridge. All types of membranes should be overlapped at the top and bottom. The overlapping positions of multi-layer membranes should be staggered. The upper and lower membranes should not be laid vertically.
2. The order in which the rolls are applied. When constructing the waterproof layer, the nodes, additional layers and areas where roof drainage is concentrated (such as the connection between the roof and the water outlet, cornices, gutters, gutters, roof corners, plate end seams, etc.) should be processed first, and then the Work upwards at the lowest elevation of the roof. When paving gutter and eaves rolled materials, it is advisable to follow the direction of the gutter and eaves to reduce overlap.
When paving multi-span roofs and roofs with high and low spans, they should be carried out in the order of high first, then low, first far, then near.
3． Coil overlap method and width. The overlapping method is used for paving the rolls, and the overlap joints of the upper and lower layers and the two adjacent rolls should be staggered. The lap joints parallel to the roof ridge should overlap in the direction of water flow; the lap joints perpendicular to the roof ridge should overlap smoothly in the prevailing wind direction. Each layer of rolled materials laid in stacks should be overlapped at the junction between the gutter and the roof, and the overlapping joints should be staggered; the joints should be left on the side of the roof or gutter, not at the bottom of the ditch.
On arched roofs with a slope exceeding 25% and on slopes under skylights, short-side overlaps should be avoided as much as possible. When short-side overlaps are necessary, measures should be taken at the overlap to prevent the roll from sliding down. .
(7) Details of waterproofing membrane
The base layer at the intersection of flashing water and roof should be made into an obtuse angle (>1350) or arc (R=50~100mm), and the waterproof layer The roll-up height to the vertical surface should not be less than 250mm, usually 300mm; the closing of the roll should be tight to prevent water seepage at the closing. The waterproof cornice of the roll can be divided into free falling water, external overhanging eaves, and gutter inside the parapet. Its structural diagram is shown in the figure below.
(8) Protection of roof waterproofing membrane
After the waterproofing membrane is laid, it must be well protected to avoid affecting the waterproofing effect. Spread 300mm × 300mm expanded perlite insulation blocks on the waterproof layer, and then add a 3cm thick cement mortar protective layer on top of it. Steel wire mesh is laid inside this layer. The protective layer is set with dividing seams, and the seams are filled with sealing materials. , better protect the waterproof layer.
3. Precautions
In order to block the influence of water vapor from indoors and cause the roof waterproofing layer to bulge, in general structure, exhaust pipes are often installed in the insulation layer of the roof. Make a vapor barrier layer on the air channel and above it (such as one layer of oil paper, one layer of felt and two layers of oil, or one layer of cloth and two glue, etc.) to block the upward penetration of water vapor.
The spacing between exhaust ducts should be 6 meters vertically and horizontally, and should not be blocked. They should be connected to the exhaust holes connected to the atmosphere. Before construction of the drainage roof waterproof layer, check whether the exhaust ducts are blocked, and clean and clear them.
It is not very difficult to make a good waterproof layer of roofing membranes. As long as we follow the construction process of roofing membrane waterproofing, implement it layer by layer, strictly control it, and do every step of the work carefully according to the specifications, we will be able to It can prevent roof leakage caused by construction