Waterproofing for indoor applications - Part 4: Waterproofing with mastic asphalt or asphalt mastic
1Key Takeaways
This standard provides guidelines for the application of waterproofing in indoor environments. It specifically addresses the use of bituminous mastics or asphalt mastics for waterproofing purposes. The document outlines the requirements and procedures necessary to ensure effective and durable waterproofing solutions. I…
2Expert Interpretation
This in-depth analysis of the German standard DIN 18534-4:2025 covers the technical requirements, construction specifications, material selection, and maintenance strategies for indoor cast bitumen and bitumen mastic waterproofing systems. It is applicable to indoor floor waterproofing projects with a maximum hydrostatic pressure of 10 cm.
Overview and Technical Evolution of DIN 18534-4:2025 Standard
The German industrial standard DIN 18534-4:2025-10, "Waterproofing of Indoor Spaces—Part 4: Waterproofing with Pitch or Bituminous Mastic," was published in October 2025, officially replacing the July 2017 version. This standard belongs to the DIN 18534 series of indoor waterproofing standards, specifically regulating indoor floor waterproofing projects using pitched bitumen and bituminous mastic as the main waterproofing materials. The new standard maintains continuity in technical content, mainly through editorial revisions, and moves the original Section 4.2 regarding the requirements for waterproofing substrates to Section 6, making the standard structure clearer and more reasonable.
From a historical perspective, German indoor waterproofing standards have undergone a process of integration from fragmentation to a systematic approach.
Early standards such as DIN 4031, DIN 4117, DIN 4122, and DIN 18195 addressed different waterproofing materials and construction methods. With technological advancements and accumulated engineering experience, the DIN Standardization Committee's Building Specialty Committee (NABau) gradually integrated these standards to form the current systematic DIN 18534 series. This integration not only improved the standard's harmonization but also provided a more complete technical framework for engineering design, construction, and quality control.
Scope and Core Requirements of the Standard
According to Chapter 1 of the standard, DIN 18534-4 applies to the planning, construction, and maintenance of waterproofing for indoor floors using cast bitumen or bitumen mastic, with a waterproofing capability against a hydrostatic pressure of up to 10 cm.
This standard must be used in conjunction with DIN 18534-1 "Waterproofing of interior spaces – Part 1: Requirements, planning and basic principles of construction", which provides general technical requirements for interior waterproofing works. Regarding the requirements for the waterproofing substrate, Chapter 6 of the standard specifies the substrate types applicable to cast bitumen or bitumen mastic waterproofing: Concrete conforming to DIN EN 206; Cement mortar leveling layer conforming to DIN 18560 series standards; Insulation layer applicable only to composite waterproofing structures of cast bitumen and bitumen welded rolls (must meet DIN 18560-2 requirements). The substrate surface must be kept dry. During construction, the surface temperature of the substrate must be at least 3K higher than the dew point temperature of the surrounding air to prevent condensation from forming a water-retaining film under the waterproof layer.
Technical Requirements and Selection Criteria for Waterproofing Materials
Main Waterproofing Materials
Chapter 7 of the standard details the technical requirements for various waterproofing materials:
| Material Category | Standard Basis | Key Performance Requirements | Application Scenarios |
|---|---|---|---|
| Pouring Asphalt Leveling Mortar | DIN EN 13813 | Flowability, Density, Water Resistance | Single-Layer Pouring Asphalt Waterproofing, Composite Waterproofing Top Layer |
| Asphalt Mastic | DIN EN 12970 | Adhesion, Flexibility, Aging Resistance | Single-layer mastic waterproofing, composite waterproofing underlayer |
| Polymer modified bitumen welding membrane | DIN/TS 20000-203 | Including polyester nonwoven reinforcement layer, welding performance | Composite waterproofing underlayer, detail treatment |
Detail Treatment Materials
For detail treatment such as corners and pipe penetrations, the standard requires the use of the following materials:
- Bitumen or polymer modified bitumen membrane: conforming to the types specified in Table 1, including specifications such as G 200 S4 and PV 200 S5 Liquid plastics (FLK): Single-component or multi-component synthetic resins based on polymethyl methacrylate (PMMA) or polyurethane resin (PUR) must meet the 9 performance requirements in Table 2, including anti-slip properties, fire resistance, alkali resistance, crack bridging ability (≥2.0mm), water resistance, and bond strength (≥0.5N/mm²). Reinforcing layer: A minimum area mass of 110g/m² must be included in the ETA or abP certification. All liquid plastic materials must undergo suitability verification through the European Technical Assessment (ETA) based on EAD 030350-00-0402 or the General Building Supervision Test Certificate (abP) issued by the German Building Technology Institute (DIBt).
- Expected Water Pressure: For areas that may generate high hydrostatic pressure (such as basement interior walls), construction system 4 should be given priority
- Base Crack Condition: For base layers with active cracks or expected to develop cracks, a system with stronger crack bridging ability should be selected
- Construction Conditions: Consider the impact of site temperature, humidity, and ventilation conditions on material performance.
- Economy: Under the premise of meeting performance requirements, comprehensively consider material costs and construction costs.
- Pouring Asphalt System: A isolation layer must be set, usually using coarse glass fiber felt with a unit area mass of 60-100g/m².
- Asphalt Mastic System: An isolation layer or asphalt primer can be selected. An isolation layer must be set when water may seep from the back during construction.
- Roll Composite System: Concrete or cement mortar substrates need to be primed. For W2-I and W3-I grades, epoxy resin sealant must be used.
- Asphalt Pouring Construction: Manual construction with a scraper can be used; for large-area construction, machinery can be used. When construction is interrupted, cold edges must be indirectly heated and seamlessly connected using hot materials.
- Asphalt mastic application: Manual application. When interrupted, the material must be spread over a 300mm width to approximately 5mm thickness, overlapping upon resumption of construction.
- Roll material application: Must be hot-melt welded according to DIN 18534-2. Full adhesion is required on concrete substrates; on insulation layers, it must be laid on top of the isolation layer and the joints welded.
- Corner treatment: All systems must be applied with a single layer overlapping 100mm according to DIN 18534-2 before pouring asphalt or mastic.
- Pipe Penetration: Use materials specified in standards 7.2 and 7.3c, apply a single layer with a 100mm overlap, and form a grouting joint.
- Expansion Joint Waterproofing: Install suitable joint profiles, and use 300mm wide polymer-modified bitumen welded rolls or liquid plastic at the joints.
- Grouting Joint Treatment: A grouting joint must be formed between the waterproofing material and the finishing material, and filled with materials such as bitumen grout, plastic sealant, bitumen or polymer-modified bitumen, bitumen sealant tape, etc.
- Crack Repair: Pouring bitumen or Composite System Repair: For polymer-modified asphalt welded roll and cast asphalt composite systems, cracks ≤2mm wide can also be repaired with suitable reactive resins. Anchoring treatment can be performed in the crack area if necessary.
- Regular Inspection: It is recommended to establish a regular inspection system, focusing on detailed treatment areas, joints, and areas that may generate stress.
- Compatibility: The repair material must be compatible with the original waterproofing material to avoid adverse reactions.
- Workability: Consider on-site construction conditions and select materials suitable for manual operation.
- Durability: The durability of the repair material should not be lower than that of the original waterproofing system.
- Environmental friendliness: Prioritize environmentally friendly materials with low volatility and low odor.
- Waterproofing Rating Determination: Accurately assess the water action rating and crack rating of the project, and select a suitable waterproofing construction system.
- Material Selection: Select certified and qualified materials according to the characteristics of the project, ensuring that the material performance meets the standard requirements.
- Detailed Design: Design all detailed treatment schemes in advance, including key areas such as corners, pipe penetrations, and joints.
- Construction Plan: Develop a detailed construction plan, including base treatment, material preparation, construction sequence, and quality control points.
- Base layer acceptance: The base layer must be inspected before construction to ensure it meets requirements such as dryness, flatness, and cleanliness.
- Material inspection: All incoming materials must be inspected to ensure they meet standard requirements and design specifications.
- Process monitoring: Key construction procedures must be monitored throughout the entire process, especially detail treatment and joint construction.
- Finished product protection: Appropriate protective measures should be taken after construction to prevent mechanical damage to the waterproof layer.
- Structural Optimization: Unifying the requirements for the base layer into Chapter 6 improves the standard's logic and usability.
- Technical Continuity: Maintaining the continuity of technical requirements facilitates understanding and application by engineers and construction personnel.
- International Harmonization: Maintaining harmony with the European standards system promotes international exchange of technology and materials.
- Quality Improvement: Clear technical requirements and comprehensive quality control measures help improve the quality of waterproofing projects.
Technical Comparison of Four Waterproofing Construction Systems
Chapter 8.2 of the standard clarifies the correspondence between the four waterproofing construction systems and the **water action level (W0-I to W3-I)** and **crack level (R1-I to R3-I)** through Table 3:
| Construction System Number | Waterproofing Construction | Applicable Water Action Level | Applicable Crack Level | Minimum Thickness Requirement | Key Construction Points |
|---|---|---|---|---|---|
| 1 | Single-Layer Cast Asphalt | W0-I | R1-I to R2-I | 25-40mm (single layer) | Isolation layer required, fine aggregate sprinkled on surface |
| 2 | Single layer asphalt mastic | W0-I | — | 7-15mm (average 10mm) | Isolation layer or asphalt primer optional |
| 3 | Asphalt mastic + cast asphalt composite | W0-I to W1-I | No isolation layer: R1-I With isolation layer: R1-I to R2-I | Mastic 7-15mm + asphalt ≥25mm | The mastic layer must be complete and continuous |
| 4 | Polymer-modified bitumen welded roll + cast bitumen composite | W0-I to W3-I | R1-I to R3-I | Roll + bitumen ≥25mm | Highest requirements for base treatment |
Structure System Selection Strategy
In practical engineering applications, a suitable waterproofing construction system should be selected based on the following factors:
Key Technical Points of Construction Process
Substrate Treatment Requirements
Different waterproofing structures have different requirements for substrate treatment:
Construction Operation Specifications
The standard sets forth detailed requirements for construction operations:
Detail treatment techniques
Detail treatment is crucial for waterproofing projects. Standards specify uniform technical requirements:
Maintenance and Repair Technical Requirements
Chapter 13 of the standard specifies the maintenance requirements for the waterproofing system. In addition to following the general provisions of DIN 18534-1, it also puts forward specific requirements for the properties of bitumen materials:
Principles for Selecting Repair Materials
The following factors should be considered when selecting repair materials:
Standard Implementation Recommendations and Engineering Application Cases
Design Phase Considerations
During the design phase, engineers should focus on the following aspects:
Key Points of Construction Quality Control
A strict quality control system should be established during construction:
Case Study Analysis
Case Study: Waterproofing Project for Underground Parking Lot
In a certain underground parking lot project, the ground may be subjected to a hydrostatic pressure of up to 8 cm, and there are minor cracks in the concrete base layer.
The design employs a polymer-modified bitumen welded membrane + cast-in-place bitumen composite waterproofing structure (System 4) for the following reasons: The water action level is W2-I, requiring a high waterproofing level. The base layer crack level is R2-I, requiring good crack bridging ability. The composite system provides double waterproofing protection, resulting in higher reliability. During construction, the concrete base layer is first sealed with epoxy resin, then the polymer-modified bitumen welded membrane is laid, and finally a 30mm thick cast-in-place bitumen layer is poured. Detail treatment uses a 300mm wide liquid plastic reinforcement. After completion, a 24-hour water tightness test showed no leakage, indicating excellent waterproofing performance.
Technical Impact of Standard Updates
Although DIN 18534-4:2025 is mainly an editorial revision, it still has a positive impact on engineering practice:
Future Development Trends and Technological Prospects
With the development of building technology and the emergence of new materials, indoor asphalt waterproofing technology is also constantly progressing:
- Material Innovation: Develop environmentally friendly, high-performance modified bitumen materials to improve the durability and workability of waterproofing systems. Construction Technology Improvement: Promote mechanized construction techniques to improve construction efficiency and quality stability. Testing Technology Development: Apply non-destructive testing techniques to achieve rapid quality assessment of waterproofing systems. Standardization Improvement: Further improve the standard system to cover more application scenarios and new materials. DIN 18534-4:2025, as the authoritative standard for indoor bitumen waterproofing technology in Germany, provides comprehensive technical guidance for engineering design, construction, and quality control. By deeply understanding and correctly applying this standard, the quality and reliability of indoor waterproofing projects can be effectively improved, extending the service life of buildings and reducing maintenance costs.