Expansion joints are deliberate gaps that allow a structure to move without damage under temperature changes, settlement and seismic loads. When the waterproofing detail is not designed correctly, however, these gaps become the weakest point of the building. Running as continuous lines through the concrete, expansion joints are where water ingress occurs most often — in basement retaining walls, above parking decks, on terraces and where building blocks meet. Standard waterproofing membranes cannot withstand the constant movement at these points for long, which is why expansion joint waterproofing must be treated as a separate engineering detail in its own right.
Success in sealing a movement joint starts with the right analysis, before the right material. The joint width, the expected movement capacity, the direction of water pressure, whether the joint carries traffic and its compatibility with the existing waterproofing system all directly determine whether a tape, sealant or injection system should be used. A poorly chosen system starts letting water in again after a few seasonal temperature cycles, and the cost of repair then far exceeds that of the original application.
EREL Yalitim, built on its founding team's more than 20 years of industry experience, installs expansion joint waterproofing across Istanbul from its base in Esenyurt, with an engineering-driven technical evaluation approach. We apply certified products from leading global manufacturers, working turnkey to a written technical specification prepared for each project — a clear, documented process valued by international property owners and B2B contractors alike. Our aim is not to close the joint once, but to build a verifiable detail that reliably follows the movement of the structure for many years.
Where Is Expansion Joint Waterproofing Needed?
Expansion joints are typically found where two building blocks meet, at regular intervals in long structures, and at the interfaces between masses that settle differently. Every expansion joint in contact with water requires its own waterproofing detail in the project. Below-grade wall and foundation joints in particular are the hardest areas to reach once the building is in use, so getting the right system in place during construction is critical.
In existing buildings, the picture usually starts with a complaint: water dripping from the parking garage ceiling, damp tracking along a joint line on a basement wall, rainwater leaking into the floor below at a terrace junction. In most cases the common source of these symptoms is a worn, detached or entirely missing expansion joint seal. Movement joints in the following locations are exposed to water loads and should be addressed as a priority.
- Foundation and basement wall expansion joints (below grade, under water pressure)
- Slabs above parking garages and joint lines inside parking decks
- Roof and terrace expansion joints and parapet junctions
- Vertical expansion joints between adjoining building blocks
- Movement joints in water tanks, treatment structures and swimming pools
- Joints in retaining walls and civil engineering structures
Expansion Joint Tape Systems and Design Options
The backbone of modern expansion joint waterproofing is highly elastic TPE- and FPO-based joint tape. The tape is bonded to both sides of the joint with epoxy resin, and the overlaps are hot-air welded to form a continuous, unbroken line. Leading global manufacturers' dedicated expansion-joint tape systems accommodate joint movement safely thanks to their high elongation capacity and perform both on the positive side and under pressurised water.
Not every joint needs a tape. In joints with low movement and no water pressure, polyurethane or hybrid sealant systems combined with a backer rod offer a fast, economical solution. On parking decks open to vehicle traffic, combined details are preferred, pairing mechanical expansion joint profiles with a waterproofing tape. System selection must weigh joint width, expected movement, water pressure and floor traffic together — a decision that cannot be made from a catalogue without a site survey.
- TPE/FPO expansion joint tape with epoxy bonding: the primary solution for joints under water pressure and with high movement capacity
- Polyurethane and hybrid sealants with backer rod: an economical option for low-movement, non-pressurised joints
- Injection-backed systems: for actively leaking joints accessible only from the negative side
- Mechanical expansion joint profiles: combined with waterproofing tape on trafficked deck joints
- Hydrophilic profiles that swell on contact with water: a complementary safeguard in newly built foundation joints
Fixing a Leaking Expansion Joint in an Existing Building
In a building in use, a leaking expansion joint is usually a wider problem than it appears, because water travels along the joint line: the point where the drip shows and the point where water enters the structure are often not the same. Before any repair, the full length of the joint is therefore inspected and, where necessary, a controlled water test is run to locate the source. Local patches applied without finding the source simply push the water out again a few metres further along.
Where the positive side — the side the water comes from — is accessible, the most durable fix is to open the joint and re-seal it with a new expansion joint tape. For below-grade joints where excavation is not possible, the joint is treated from the negative side with polyurethane injection resins and acrylic gels: the resin expands on contact with water and forms an elastic, watertight fill inside the joint cavity. Where required, injection and tape systems are combined to provide two-stage security.
Engineer-Supervised Expansion Joint Waterproofing: The EREL Difference
Expansion joint waterproofing is not solved by picking a material from a product catalogue; it takes an engineering eye that reads how the joint behaves and details the solution accordingly. At EREL Yalitim, every project is handled under the technical supervision of our engineering team. During the survey the joint is measured and its movement and water load assessed; the system, materials and detail drawings are then fixed in a written technical specification. The works are executed to that specification and checked stage by stage.
Our track record on corporate projects is the outcome of this approach: we completed the water tank waterproofing at a major airport project with a certified crystalline system, and installed thousands of square metres of membrane across industrial and residential projects. At this scale, expansion joints and joint details are the most critical part of the system — and the same care carries over to residential-scale projects. We work turnkey with certified global products from our solution partners.
Our Application Process
- 1
Site Survey and Joint Analysis
The joint width, movement capacity, direction of water pressure and condition of the existing waterproofing are inspected on site; for active leaks, a controlled water test pinpoints the source.
- 2
System Selection and Technical Specification
The choice between tape, sealant, injection or a combined system is made; materials, detail drawings and application method are set out in a written technical specification submitted with the quotation.
- 3
Surface Preparation
Joint edges are cleared of old filler, loose concrete and dirt; surfaces to receive epoxy bonding are ground back to a sound, dry substrate, and damaged edges are reprofiled with repair mortar.
- 4
Joint Filling and Backing Profile
A backer rod of the appropriate diameter is placed in the joint cavity; where needed, a hydrophilic profile or injection hose detail is added to the system.
- 5
Expansion Joint Tape Installation
The TPE/FPO tape is bonded to both sides of the joint with epoxy resin in an omega loop that allows for joint movement; overlaps are hot-air welded, and corners and intersections are resolved with prefabricated pieces.
- 6
Inspection, Testing and Handover
Tape adhesion and weld seams are checked; a water test is carried out where the detail allows, protective layers are completed and the work is handed over verified against the specification.
Frequently Asked Questions
How is expansion joint waterproofing priced?
The price depends on the total length and width of the joint, the system to be used (tape, sealant, injection or combined) and the extent of surface preparation, so no reliable figure can be given without a survey. We carry out free site surveys across Istanbul and provide a written, itemised quotation showing the proposed system and the cost line by line.
How is a leaking expansion joint fixed?
The true source of the leak is located first; because water can travel along the joint, the dripping point can be misleading. If the positive side is accessible, the joint is opened and a new expansion joint tape is installed; if excavation is not possible, the joint is permanently treated from the negative side by injecting polyurethane resin or acrylic gel.
Is filling an expansion joint with sealant enough?
Only for joints with low movement and no water pressure. In a joint under pressurised water or with significant movement, the sealant debonds from the substrate after a few thermal cycles and the leak returns. Such joints call for an elastic expansion joint tape or an injection-backed system; the right choice is determined by the analysis carried out during the survey.
Can expansion joints be sealed from inside the building, without excavation?
Yes. For below-grade foundation and wall joints, polyurethane injection resin or acrylic gel is pumped into the joint line through ports opened from the inside. The material expands on contact with water, filling the joint cavity elastically and stopping water penetration without any excavation.
How durable is expansion joint tape?
TPE and FPO tapes are engineered products made for long-term performance under constant joint movement and water contact. What determines their service life on site is workmanship as much as material: with correct surface preparation, proper bonding and welded overlaps executed to specification, the tape reliably follows the joint's movement for many years.
How long does the work take, and can the building stay in use?
The duration depends on joint length, system type and the extent of surface preparation. Because the work is confined to the joint line, most of the parking garage, basement and common areas can remain in use during application. After the survey we set out the work programme day by day and confirm it in writing.