When did the regulation take effect?
Turkey's Building Waterproofing Regulation came into force on 1 June 2018. For structures permitted after that date, waterproofing is no longer optional in areas directly exposed to water, it is an obligation. According to IZODER figures, buildings covered by the mandatory waterproofing requirement account for only 5 to 5.5 percent of Turkey's total building stock. In other words, the vast majority of existing buildings stand without this protection.
What does it say about foundations?
The regulation covers every surface of the structure in contact with the ground. Below the foundation slab, the outer face of retaining walls, the basement floor and all levels bearing on soil fall within its scope. The system to be applied is determined by the groundwater level and whether the water is under pressure. A single membrane layer may be sufficient for non-pressurised water, while a double membrane layer combined with a drainage system is required where the water table sits above foundation level.
Drainage does not replace waterproofing, it completes it
A common mistake is treating drainage and waterproofing as interchangeable solutions. Drainage relieves the pressure of water reaching the structure and carries it away. Waterproofing stops the remaining moisture from entering the building. Without one, the other is incomplete. The combination of drainage board, filter geotextile and perforated pipe removes the hydrostatic load on the membrane and extends the life of the waterproofing.
What should existing buildings do?
The regulation does not apply retroactively. However, in buildings constructed before 2018, waterproofing is usually either absent altogether or limited to a single bituminous sheet. Basement damp, salt efflorescence on retaining walls and reinforcement corrosion are widespread in these buildings. Where external excavation is possible, external drainage and membrane are applied. Where excavation is not possible, crystalline waterproofing or polyurethane injection is applied from the inside.
The link with earthquakes
Waterproofing is not a comfort issue. Moisture reaching reinforcing steel causes corrosion, the steel cross section is reduced, and the load bearing capacity of the structure during an earthquake drops. IZODER defines correct and complete waterproofing as part of protecting buildings against earthquakes. In first degree seismic zones such as Sakarya, Kocaeli and Istanbul, this connection becomes even more critical.
What to watch during application
- The groundwater level in the geotechnical survey report must always be read
- The selected membrane must be certified under TS EN 13967
- Detail points, meaning corners, pipe penetrations and joints, must be resolved separately
- The waterproofing layer must be covered with a protection board before backfilling
- A water test must be carried out after application