{"title":"Negative-Side Waterproofing","description":"\u003cdiv class=\"tldr-box\" style=\"background:#f0f4f8;border-left:4px solid #2c5282;padding:16px;margin-bottom:24px;\"\u003e\n\u003cstrong\u003eNegative-side waterproofing\u003c\/strong\u003e means the water pushes through the substrate from the outside, and the waterproofing is applied from the interior to resist that pressure. Unlike positive-side waterproofing (e.g. bathrooms, water tanks), negative-side waterproofing is a \u003cstrong\u003eremedial measure\u003c\/strong\u003e for situations where exterior access is impossible — it is not a replacement for proper external waterproofing. Where the leak source can be addressed from outside, that should always be the priority.\n\u003c\/div\u003e\n\n\u003ch2\u003eCommon scenarios in Hong Kong\u003c\/h2\u003e\n\n\u003ch3\u003e1. Old buildings and \"three-nil buildings\"\u003c\/h3\u003e\n\u003cp\u003eHong Kong has a large stock of aging walk-up buildings (唐樓) that commonly face the following obstacles to exterior waterproofing repair:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eFragmented ownership, no management body\u003c\/strong\u003e — in buildings without an Incorporated Owners' Corporation, residents' organisation or property management company (commonly known as \"three-nil buildings\" \/ 三無大廈), it is impossible to obtain unanimous owner consent for exterior wall repairs\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eProhibitive scaffolding cost\u003c\/strong\u003e — exterior scaffolding on old buildings is expensive, and narrow rear lanes or unauthorised structures often make erection physically impossible\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eStructural aging risk\u003c\/strong\u003e — older buildings may already suffer from concrete spalling or structural deterioration, making large-scale exterior works high-risk\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eIn these situations, negative-side waterproofing applied from the interior is a remedial option that allows the property owner to actively manage water ingress.\u003c\/p\u003e\n\n\u003ch3\u003e2. Public housing and newly completed developments under warranty\u003c\/h3\u003e\n\u003cp\u003eIn Hong Kong public housing and newly completed private developments, the building exterior is managed and maintained by the Housing Authority (房屋署) or the developer during the defects liability period (保養期). Interior renovation contractors and residents cannot carry out any waterproofing works on the exterior. When interior water ingress occurs but the exterior cannot be addressed due to jurisdictional restrictions, negative-side waterproofing from the interior serves as a \u003cstrong\u003etemporary protective measure\u003c\/strong\u003e — controlling water damage to the interior finishes while awaiting official repair by the responsible authority.\u003c\/p\u003e\n\u003cp\u003e⚠️ Before commencing work, confirm compliance with the building's Deed of Mutual Covenant and relevant regulations, and report the seepage case to the management office or responsible authority.\u003c\/p\u003e\n\n\u003ch3\u003e3. Slope retaining walls and basements\u003c\/h3\u003e\n\u003cp\u003eHong Kong is built on hills, and a large number of residential and commercial buildings have basements, carparks or lower-level spaces backed directly against slopes or earth. The exterior face of the retaining wall is in direct contact with soil and groundwater, making excavation and exterior waterproofing physically impossible. When groundwater seeps through concrete cracks or pores into the interior, negative-side waterproofing is the only viable treatment. This is the most typical and straightforward technical application of negative-side waterproofing.\u003c\/p\u003e\n\n\u003ch3\u003e4. Modular Integrated Construction (MiC)\u003c\/h3\u003e\n\u003cp\u003eAs Modular Integrated Construction (組裝合成建築法) becomes more common in Hong Kong — adopted in some public housing and transitional housing projects — its modular structure may present exterior-access constraints for future maintenance. When seepage occurs at module joints or the exterior envelope, traditional exterior repair methods can be significantly more difficult. Negative-side waterproofing may serve as one of the interior remedial options for such buildings, though the actual approach depends on the specific structure and cause of seepage — consultation with relevant professionals is recommended.\u003c\/p\u003e\n\n\u003ch2\u003eSelection guide\u003c\/h2\u003e\n\u003cp\u003eNegative-side waterproofing products fall into the following categories:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eEpoxy-modified cementitious mortars\u003c\/strong\u003e (e.g. \u003ca href=\"\/en\/products\/西卡sikagard-720-epocem-批蕩砂漿\"\u003eSikagard 720 EpoCem\u003c\/a\u003e) — trowel-applied; epoxy resin penetrates concrete pores for chemical bonding while the cement component hydrates to form the waterproofing body; excellent adhesion to damp concrete\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003ePolymer-modified cementitious coatings\u003c\/strong\u003e (e.g. \u003ca href=\"\/en\/products\/spec-cw100\"\u003eSPEC CW100\u003c\/a\u003e, \u003ca href=\"\/en\/products\/fosroc-nitocote-cm210\"\u003eFosroc CM210\u003c\/a\u003e, \u003ca href=\"\/en\/products\/偉伯-weber-weberdry-elastic-slurry-高柔防水塗料\"\u003eWeber Elastic Slurry\u003c\/a\u003e) — applied by brush, roller or trowel; good flexibility and crack-bridging ability\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eWater-based epoxy membranes\u003c\/strong\u003e (e.g. \u003ca href=\"\/en\/products\/ardex-wpm-300-hydrepoxy-300-20l\"\u003eArdex WPM 300\u003c\/a\u003e) — applied by brush or roller to form a thin waterproof film; solvent-free, safe for enclosed spaces, applies to damp and green concrete\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eProducts differ in application method, suitable substrates and pressure resistance. The choice depends on site conditions and project design — refer to each product's Technical Data Sheet (TDS) or consult Wah Hing.\u003c\/p\u003e\n\n\u003ch2\u003eRelated waterproofing methods\u003c\/h2\u003e\n\u003cp\u003eNegative-side waterproofing forms a continuous waterproof coating over the concrete surface. Where seepage is concentrated at individual cracks or joints, it can be combined with \u003ca href=\"\/en\/collections\/打針防水-灌漿止漏\"\u003e\u003cstrong\u003echemical injection (grouting)\u003c\/strong\u003e\u003c\/a\u003e for localised crack sealing. The two methods address different types of seepage and can be used individually or in combination depending on site conditions.\u003c\/p\u003e\n\u003ch2\u003eImportant note\u003c\/h2\u003e\n\u003cp\u003eNegative-side waterproofing is a \u003cstrong\u003eremedial measure\u003c\/strong\u003e and not a replacement for proper positive-side exterior waterproofing. Water pressure may be diverted rather than fully eliminated, and the root cause — failed external waterproofing — remains. This method is only recommended where exterior access is genuinely impossible. If the structure shows severe cracking or settlement, a structural assessment by relevant professionals should be carried out first.\u003c\/p\u003e\n\n\u003cp\u003eMost products typically in stock; individual items welcome to enquire.\u003c\/p\u003e","products":[{"product_id":"fosroc-nitocote-cm210","title":"Fosroc Nitocote CM210","description":"\u003cdiv class=\"tldr-box\" style=\"background:#f0f4f8;border-left:4px solid #2c5282;padding:16px;margin-bottom:24px\"\u003e\u003cstrong\u003eTL;DR:\u003c\/strong\u003e\u003cp\u003eNitocote CM210 is a two-component elastomeric cementitious waterproof coating by Fosroc. Approved by the UK Drinking Water Inspectorate (DWI) (per manufacturer), it withstands high positive and negative water pressure and maintains excellent crack-bridging performance even after prolonged immersion.\u003c\/p\u003e\u003c\/div\u003e\u003ch2\u003eProduct Overview\u003c\/h2\u003e\u003cp\u003eNitocote CM210 is a two-component polymer-modified elastomeric cementitious coating supplied in pre-packaged form. It is mixed on-site with a slow-speed drill and paddle, then applied to form an elastomeric impermeable membrane. Available in grey and white, the product is designed for waterproofing water-retaining and water-excluding structures such as potable water tanks, reservoirs, canals, and culverts. It can be applied to concrete, brick, and blockwork substrates and maintains excellent crack accommodation even after long-term water immersion — a condition many cementitious coatings cannot satisfy.\u003c\/p\u003e\u003ch2\u003eKey Features\u003c\/h2\u003e\u003cul\u003e\u003cli\u003e\u003cstrong\u003ePotable water approved\u003c\/strong\u003e — Approved by the UK Drinking Water Inspectorate (DWI) (per manufacturer)\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eHigh water pressure resistance\u003c\/strong\u003e — Withstands high positive and negative hydrostatic pressures\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eCrack bridging after immersion\u003c\/strong\u003e — Maintains excellent crack accommodation after prolonged water immersion\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eStrong adhesion\u003c\/strong\u003e — Excellent bond to concrete and masonry substrates\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eDamp surface application\u003c\/strong\u003e — Can be applied directly to green or damp concrete\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eChemical barrier\u003c\/strong\u003e — Effective barrier to sulphates and chlorides\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eVersatile application\u003c\/strong\u003e — Suitable for brush, roller, trowel, or spray application\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eAmple working time\u003c\/strong\u003e — Sufficient working life after mixing\u003c\/li\u003e\u003c\/ul\u003e\u003ch2\u003eApplications\u003c\/h2\u003e\u003cul\u003e\u003cli\u003ePotable water tanks (rooftop and underground)\u003c\/li\u003e\u003cli\u003eReservoirs and water storage facilities\u003c\/li\u003e\u003cli\u003eCanals and culverts\u003c\/li\u003e\u003cli\u003eBasements and underground structures (resists negative water pressure)\u003c\/li\u003e\u003cli\u003eConcrete, brick, and blockwork structures\u003c\/li\u003e\u003cli\u003eWater-retaining structures requiring long-term immersion resistance\u003c\/li\u003e\u003c\/ul\u003e\u003ch2\u003ePackaging\u003c\/h2\u003e\u003cp\u003e23KG per set (18kg powder component + 5kg liquid polymer). Available in grey and white.\u003c\/p\u003e\u003ch2\u003eImportant Notes\u003c\/h2\u003e\u003cul\u003e\u003cli\u003eNot suitable for application in low-temperature conditions\u003c\/li\u003e\u003cli\u003eProtect from rainfall and running water during application and initial curing\u003c\/li\u003e\u003cli\u003eNot recommended for external surfaces where aesthetic appearance is critical, as curing conditions may cause colour variations\u003c\/li\u003e\u003cli\u003eLiquid component must not be frozen during storage\u003c\/li\u003e\u003cli\u003eShelf life is six months in unopened packs\u003c\/li\u003e\u003cli\u003eStrict adherence to mixing instructions is essential — inadequate mixing may compromise performance\u003c\/li\u003e\u003cli\u003eFor detailed application methods, coverage rates, and technical parameters, please refer to the official product data sheet\u003c\/li\u003e\u003c\/ul\u003e\u003ch2\u003eFAQ\u003c\/h2\u003e\u003ch3\u003eHow do I choose between CM210 and Brushbond for potable water tanks?\u003c\/h3\u003e\u003cp\u003eBoth are approved for potable water contact (per manufacturer). CM210 resists both positive and negative water pressure with higher elasticity, making it ideal for underground tanks subject to external water pressure. Brushbond offers better breathability, making it more suitable for rooftop water tanks where moisture vapour permeability is needed.\u003c\/p\u003e\u003ch3\u003eCan CM210 be used for basement waterproofing?\u003c\/h3\u003e\u003cp\u003eYes, it is well suited for this application. CM210 resists negative water pressure (groundwater pushing from outside through the structure), making it an ideal choice for basement and underground waterproofing. It can be applied directly to damp concrete surfaces without waiting for the substrate to dry completely.\u003c\/p\u003e","brand":"Fosroc 富斯樂","offers":[{"title":"Default Title","offer_id":42397801971862,"sku":"","price":1.0,"currency_code":"HKD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0594\/9027\/1382\/files\/Nitocote_CM210.png?v=1776659385"},{"product_id":"偉伯-weber-weberdry-elastic-slurry-高柔防水塗料","title":"Weber Weberdry Elastic Slurry Waterproofing Coating","description":"\u003cdiv class=\"tldr-box\" style=\"background:#f0f4f8;border-left:4px solid #2c5282;padding:16px;margin-bottom:24px\"\u003e\u003cstrong\u003eOverview:\u003c\/strong\u003e\u003cp\u003eWeber Weberdry Elastic Slurry is a two-component latex modified cementitious waterproofing coating with medium elastomeric properties. Suitable for both positive and negative waterproofing in tunnels, basements, water tanks, swimming pools and bathrooms. Pre-packed kit ensures accurate mixing proportions. Non-toxic and environmentally friendly with a rough surface finish that enhances tile adhesion.\u003c\/p\u003e\u003c\/div\u003e\u003ch3\u003eProduct Features\u003c\/h3\u003e\u003cul\u003e\u003cli\u003e\u003cstrong\u003eTwo-component elastic formula\u003c\/strong\u003e — pre-packed powder plus latex kit with fixed mixing ratio for consistent quality\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003ePositive and negative waterproofing\u003c\/strong\u003e — suitable for both water-facing and non-water-facing applications\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eMedium elasticity\u003c\/strong\u003e — accommodates substrate movement from shrinkage, vibration or thermal changes\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eAnti-carbonation protection\u003c\/strong\u003e — prevents concrete carbonation to extend structural life\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eRough surface for tiling\u003c\/strong\u003e — textured finish enhances subsequent tile adhesion\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eNon-toxic eco-friendly\u003c\/strong\u003e — safe formulation suitable for potable water structures\u003c\/li\u003e\u003c\/ul\u003e\u003ch3\u003eApplications\u003c\/h3\u003e\u003cul\u003e\u003cli\u003eBathroom and kitchen wet area waterproofing\u003c\/li\u003e\u003cli\u003eSwimming pool waterproofing\u003c\/li\u003e\u003cli\u003eBasement and underground structure waterproofing\u003c\/li\u003e\u003cli\u003eTunnel waterproofing works\u003c\/li\u003e\u003cli\u003eWater tank and reservoir waterproofing\u003c\/li\u003e\u003cli\u003eExternal wall and interior wall\/floor waterproofing\u003c\/li\u003e\u003c\/ul\u003e\u003ch3\u003ePackaging\u003c\/h3\u003e\u003cp\u003ePlease refer to the product TDS or contact Wah Hing for details.\u003c\/p\u003e\u003ch3\u003eImportant Notes\u003c\/h3\u003e\u003cul\u003e\u003cli\u003eFor detailed application methods, coverage rates and technical parameters, please refer to the official product data sheet\u003c\/li\u003e\u003cli\u003ePour liquid first, then gradually add powder and mix thoroughly with electric mixer\u003c\/li\u003e\u003cli\u003eSubstrate must be pre-dampened to saturated surface dry (SSD) condition\u003c\/li\u003e\u003cli\u003eShelf life 12 months unopened; store in dry conditions\u003c\/li\u003e\u003c\/ul\u003e","brand":"Weber 偉伯","offers":[{"title":"Default Title","offer_id":43648810123414,"sku":"","price":1.0,"currency_code":"HKD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0594\/9027\/1382\/files\/357-B25WBZHK-19R03weberdryelasticslurry_png.webp?v=1716033429"},{"product_id":"spec-cw100","title":"SPEC CW100","description":"\u003cdiv class=\"tldr-box\" style=\"background:#f0f4f8;border-left:4px solid #2c5282;padding:16px;margin-bottom:24px;\"\u003e\u003cstrong\u003eOverview:\u003c\/strong\u003e\u003cp\u003eSpECtite CW100 is a two-component polymer-modified cementitious waterproof coating, applied by trowel, brush or spray to form a flexible waterproof barrier. It handles both positive and negative water pressure and has crack-bridging capability. Approved for contact with potable (drinking) water, suitable for water tanks, reservoirs, swimming pools and general building waterproofing.\u003c\/p\u003e\u003c\/div\u003e\u003ch2\u003eApplications\u003c\/h2\u003e\u003cul\u003e\u003cli\u003e\u003cstrong\u003ePositive and negative water pressure\u003c\/strong\u003e — can be applied from either the water-facing or the dry side; suitable for basements, retaining walls and other negative-pressure situations, as well as bathrooms, kitchens and terraces on the positive side\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003ePotable water facilities\u003c\/strong\u003e — water tanks, reservoirs and cisterns (meets potable-water contact standards)\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eSwimming pools and water features\u003c\/strong\u003e\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eGeneral building waterproofing\u003c\/strong\u003e — new and existing structures\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eStone backing\u003c\/strong\u003e — applied behind marble and granite to prevent water ingress and surface staining\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eBrackish and seawater channels\u003c\/strong\u003e — resistant to salt water and mild chemicals\u003c\/li\u003e\u003c\/ul\u003e\u003ch2\u003eKey features\u003c\/h2\u003e\u003cul\u003e\u003cli\u003eHandles both positive and negative water pressure\u003c\/li\u003e\u003cli\u003eGood crack-bridging capability\u003c\/li\u003e\u003cli\u003eStrong bond to concrete and masonry substrates\u003c\/li\u003e\u003cli\u003eApproved for potable-water contact\u003c\/li\u003e\u003cli\u003eExcellent weathering resistance, maintains performance after prolonged immersion\u003c\/li\u003e\u003cli\u003eCan be applied by trowel, brush or spray\u003c\/li\u003e\u003c\/ul\u003e\u003ch2\u003eFAQ\u003c\/h2\u003e\u003cp\u003e\u003cstrong\u003eCan CW100 be used for negative-side waterproofing?\u003c\/strong\u003e\u003cbr\u003eYes. CW100 handles both positive and negative water pressure, making it suitable for basements, underground carparks, retaining walls and other locations where exterior waterproofing is not possible.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is the difference between CW100 and Sika 107?\u003c\/strong\u003e\u003cbr\u003eBoth are cementitious waterproofing coatings, but CW100 handles both positive and negative water pressure and is approved for potable-water contact; \u003ca href=\"\/en\/products\/sika-西卡-sika®top-seal-107-hk\"\u003eSikaTop Seal 107\u003c\/a\u003e is primarily for positive-pressure applications (bathrooms, kitchens, etc.). The choice depends on the project requirements.\u003c\/p\u003e\u003cp\u003eMost products typically in stock. For detailed technical data and application method, refer to the product Technical Data Sheet (TDS), or WhatsApp Wah Hing.\u003c\/p\u003e","brand":"SPEC","offers":[{"title":"Default Title","offer_id":43686347210902,"sku":"","price":1.0,"currency_code":"HKD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0594\/9027\/1382\/files\/SPECCW100_e7b971e6-8010-4a50-beb3-c61ae37c2f13.png?v=1754554311"},{"product_id":"西卡sikagard-720-epocem-批蕩砂漿","title":"Sika Sikagard 720 EpoCem","description":"\u003cdiv class=\"tldr-box\" style=\"background:#f0f4f8;border-left:4px solid #2c5282;padding:16px;margin-bottom:24px;\"\u003e\u003cstrong\u003eOverview:\u003c\/strong\u003e\u003cp\u003eSikagard®-720 EpoCem is Sika's three-component epoxy-modified cementitious mortar, combining the chemical resistance and high bond strength of epoxy resin with the breathability of cement mortar. It bonds excellently to both dry and damp concrete and is used for concrete pore sealing and levelling, as a temporary moisture barrier, and for negative-side waterproofing — applied from the interior when exterior access is impossible (e.g. basements, retaining walls, lift pits). Solvent-free, suitable for interior and exterior use.\u003c\/p\u003e\u003c\/div\u003e\n\u003ch2\u003eKey features\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eEpoxy-modified cementitious formulation\u003c\/strong\u003e — epoxy resin penetrates concrete pores for chemical bonding while the cement component undergoes hydration, providing a dual bonding mechanism\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eExcellent adhesion to dry or damp concrete\u003c\/strong\u003e — can be applied directly to damp substrates (substrate must be moist but free of standing water)\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eImpervious to liquids, permeable to water vapour\u003c\/strong\u003e — blocks liquid water while allowing the substrate to breathe\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eGood thixotropy\u003c\/strong\u003e — suitable for vertical and overhead surfaces without sagging\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eThree-component pre-dosed packaging\u003c\/strong\u003e — Part A (resin) + Part B (hardener) + Part C (powder), simple to mix\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eSolvent-free\u003c\/strong\u003e — can be used in enclosed interior spaces, though adequate ventilation should still be maintained\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eFine surface finish\u003c\/strong\u003e — can serve as substrate preparation for subsequent epoxy systems or decorative finishes\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eApplications\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eNegative-side waterproofing\u003c\/strong\u003e — basements, underground carparks, retaining walls, lift pits and other locations where exterior waterproofing is impossible; applied from the interior to resist external water pressure\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003ePore sealing and levelling\u003c\/strong\u003e — filling pores and smoothing concrete and mortar surfaces\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eTemporary moisture barrier\u003c\/strong\u003e — blocking rising damp from the substrate, preparing for subsequent floor coatings or finishes\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eChemically aggressive environments\u003c\/strong\u003e — protective rendering on concrete in sewage treatment plants, chemical facilities, etc.\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eEpoxy system substrate\u003c\/strong\u003e — surface preparation mortar for subsequent Sika epoxy products\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eWhy choose Sikagard 720 EpoCem\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cstrong\u003eSolves the \"no exterior access\" waterproofing problem\u003c\/strong\u003e — when basement or underground walls are surrounded by soil and cannot be excavated, 720 can be applied from the interior for negative-side waterproofing, offering an alternative to traditional chemical injection\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eDual bonding mechanism\u003c\/strong\u003e — epoxy chemical bonding + cement hydration crystallisation gives superior adhesion to damp concrete compared to single-system products\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eBlocks water, allows breathing\u003c\/strong\u003e — impervious to liquid water but permeable to water vapour, preventing the coating from blistering under back-pressure\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eApplication notes\u003c\/h2\u003e\n\u003cp\u003eBefore application, clean the concrete substrate thoroughly (remove loose material, dust and oil), and \u003cstrong\u003edampen the surface to saturated surface-dry (SSD) condition\u003c\/strong\u003e — a bone-dry substrate will draw moisture from the mortar and impair the cement hydration needed for proper bonding. Mix the three components in the correct ratio: first blend Part A + Part B (liquids) thoroughly, then add Part C (powder) and mix with an electric stirrer until homogenous. Ideally use the full pre-dosed set in one batch; if splitting, \u003cstrong\u003eweigh each component with a digital scale to maintain the correct ratio\u003c\/strong\u003e. After application, carry out proper curing — do not allow the coating to dry too quickly.\u003c\/p\u003e\n\u003cp\u003eFor coverage, layer thickness, curing times and primer requirements, refer to the product Technical Data Sheet (TDS).\u003c\/p\u003e\n\u003ch2\u003eWhat is the difference between 720 and 107?\u003c\/h2\u003e\n\u003cp\u003eBoth belong to the Sika waterproofing system but address different water-pressure directions: \u003ca href=\"\/en\/products\/sika-西卡-sika®top-seal-107-hk\"\u003eSikaTop Seal 107\u003c\/a\u003e is for \u003cstrong\u003epositive-side waterproofing\u003c\/strong\u003e (water pushes against the coated face, e.g. bathrooms, kitchens, water tanks), while 720 EpoCem is for \u003cstrong\u003enegative-side\u003c\/strong\u003e situations (water penetrates from behind the substrate, resisted from the interior). Use 107 for bathroom waterproofing; use 720 for basement\/underground waterproofing from the inside.\u003c\/p\u003e\n\u003ch2\u003eFAQ\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eCan Sikagard 720 be applied to damp concrete?\u003c\/strong\u003e\u003cbr\u003eYes. 720 has excellent adhesion to both dry and damp concrete. Before application, dampen the substrate to saturated surface-dry condition, but ensure there is no standing water.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan 720 replace chemical injection (grouting)?\u003c\/strong\u003e\u003cbr\u003eThey work differently: chemical injection targets individual cracks with injected resin, while 720 provides a continuous coating over the concrete surface. Depending on the cause and site conditions, one or both methods may be used — the specific approach should be determined by relevant professionals.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIs 720 suitable for ceiling leaks?\u003c\/strong\u003e\u003cbr\u003e720 is primarily for negative-side waterproofing (water penetrating from behind the substrate). If the source of a ceiling leak can be repaired from above (e.g. fixing waterproofing upstairs or sealing window ingress), it is better to address the source first. Negative-side treatment is a remedial option when the source cannot be reached.\u003c\/p\u003e\n\u003cp\u003eMost products typically in stock. For detailed technical data and application conditions, refer to the product Technical Data Sheet (TDS), or WhatsApp Wah Hing.\u003c\/p\u003e","brand":"Sika 西卡","offers":[{"title":"Default Title","offer_id":46352841965718,"sku":null,"price":1.0,"currency_code":"HKD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0594\/9027\/1382\/files\/sikagard-720-epocem.jpg?v=1776710970"},{"product_id":"ardex-wpm-300-hydrepoxy-300-20l","title":"Ardex WPM 300 水性環氧防水膜 \/ 20L","description":"\u003cdiv class=\"tldr-box\" style=\"background:#f0f4f8;border-left:4px solid #2c5282;padding:16px;margin-bottom:24px;\"\u003e\u003cstrong\u003eOverview:\u003c\/strong\u003e\u003cp\u003eArdex WPM 300 (HydrEpoxy 300) is a two-component water-based epoxy waterproofing membrane that can be applied directly to damp or freshly laid concrete. It withstands both positive and negative water pressure, making it suitable for basements, underground carparks, retaining walls, lift pits, water tanks and reservoirs. Solvent-free and non-flammable, it is safe for use in moisture-sensitive interior environments.\u003c\/p\u003e\u003c\/div\u003e\u003ch2\u003eKey features\u003c\/h2\u003e\u003cul\u003e\u003cli\u003e\u003cstrong\u003eWater-based epoxy\u003c\/strong\u003e — solvent-free, non-flammable, low odour; suitable for poorly ventilated interior spaces\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003ePositive and negative water pressure\u003c\/strong\u003e — can be applied from either the water-facing or the dry side\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eApplies to damp and green concrete\u003c\/strong\u003e — excellent adhesion to damp substrates and freshly cast concrete\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003ePrevents rising damp and efflorescence\u003c\/strong\u003e — acts as a vapour barrier\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eOverpaintable\u003c\/strong\u003e — can be overcoated once cured\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eBroad substrate adhesion\u003c\/strong\u003e — concrete, brick, masonry, stone and timber\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eChemical resistance\u003c\/strong\u003e — passes acid, alkali and UV tests\u003c\/li\u003e\u003c\/ul\u003e\u003ch2\u003eApplications\u003c\/h2\u003e\u003cul\u003e\u003cli\u003e\u003cstrong\u003eNegative-side waterproofing\u003c\/strong\u003e — basements, tunnels, retaining walls, lift pits\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003ePositive-side waterproofing\u003c\/strong\u003e — water tanks, reservoirs, pools\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eDamp-proof membrane\u003c\/strong\u003e — blocks rising damp for subsequent floor coverings\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eGreen-concrete sealing\u003c\/strong\u003e — waterproof barrier on freshly hardened concrete\u003c\/li\u003e\u003c\/ul\u003e\u003ch2\u003eWhy choose Ardex WPM 300\u003c\/h2\u003e\u003cul\u003e\u003cli\u003e\u003cstrong\u003eWater-based = safe\u003c\/strong\u003e — no solvents, non-flammable, low odour in enclosed spaces\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eTwo-way waterproofing\u003c\/strong\u003e — one product for positive and negative pressure\u003c\/li\u003e\u003cli\u003e\u003cstrong\u003eDamp-substrate application\u003c\/strong\u003e — no waiting for the substrate to dry\u003c\/li\u003e\u003c\/ul\u003e\u003ch2\u003eApplication notes\u003c\/h2\u003e\u003cp\u003eSubstrate must be sound and clean. Mix A + B with an electric stirrer. Dampen dry concrete before application. Minimum two coats in alternating directions. Refer to TDS for coverage, thickness and curing.\u003c\/p\u003e\u003ch2\u003eApplication demo video\u003c\/h2\u003e\n\u003cdiv style=\"position:relative;padding-bottom:56.25%;height:0;overflow:hidden;max-width:100%;margin-bottom:24px;\"\u003e\n\u003ciframe src=\"https:\/\/www.youtube.com\/embed\/H4zJh51B_DI\" style=\"position:absolute;top:0;left:0;width:100%;height:100%;border:0;\" allow=\"accelerometer;autoplay;clipboard-write;encrypted-media;gyroscope;picture-in-picture\" allowfullscreen loading=\"lazy\" title=\"Ardex WPM 300 application demo\"\u003e\u003c\/iframe\u003e\n\u003c\/div\u003e\n\u003ch2\u003eFAQ\u003c\/h2\u003e\u003cp\u003e\u003cstrong\u003eCan WPM 300 be used for negative-side waterproofing?\u003c\/strong\u003e\u003cbr\u003eYes. It handles both positive and negative water pressure.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat is the difference between WPM 300 and Sikagard 720?\u003c\/strong\u003e\u003cbr\u003eBoth suit negative-side waterproofing. WPM 300 is a water-based epoxy membrane (brush\/roller); \u003ca href=\"\/en\/products\/西卡sikagard-720-epocem-批蕩砂漿\"\u003e720 EpoCem\u003c\/a\u003e is an epoxy-modified cementitious mortar (trowel-applied). Choice depends on substrate and project design.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCan WPM 300 be used in drinking-water tanks?\u003c\/strong\u003e\u003cbr\u003eYes. Approved under BS 6920 for potable-water contact.\u003c\/p\u003e\u003cp\u003eMost products typically in stock. Refer to the TDS for details, or WhatsApp Wah Hing.\u003c\/p\u003e","brand":"Ardex","offers":[{"title":"20L Kit","offer_id":46535389905046,"sku":null,"price":1.0,"currency_code":"HKD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0594\/9027\/1382\/files\/ardex-wpm-300-water-based-epoxy-waterproofing-membrane-part-a-b.jpg?v=1787066518"}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0594\/9027\/1382\/collections\/negative-side-waterproofing-collection-cover.jpg?v=1787071436","url":"https:\/\/wahhingwp.com\/en\/collections\/%e8%b2%a0%e6%b0%b4%e5%a3%93%e9%98%b2%e6%b0%b4.oembed","provider":"華興建築防水材料有限公司","version":"1.0","type":"link"}