Watertight Expansion Joints with High-Flexibility EPDM
EPDM profiles and systems for expansion joints guarantee watertightness under cyclic movements of ±75 mm, in roofs, bridges, slabs and facades, maintenance-free for 50+ years.
The Expansion Joint Challenge
Expansion joints are the most critical points in any waterproofing system. They are needed to accommodate structural movements, but each joint is a potential infiltration point. Over 60% of infiltrations in roofs and slabs occur at joints.
- Cyclic thermal movements of ±10-75 mm create fatigue and fracture in rigid sealing materials
- Seismic movements in Lisbon Zone 1.3 can reach 30-50 mm relative displacement between blocks
- Progressive differential settlements in large buildings amplify movements over decades
- Inadequate solutions (silicone, polysulphide) last 10-20 years and lose elasticity over time
The EPDM Solution for Expansion Joints
EPDM profiles and membrane systems for expansion joints are specifically developed to accommodate large-amplitude movements durably. EPDM's intrinsic elasticity — without migrating plasticisers — eliminates fatigue from repeated cycles.
- Pre-moulded EPDM centre-bulb, gland and waterstop profiles for different amplitudes and applications
- Loop membrane method with EPDM for movements up to ±75 mm without additional profile
- On-site vulcanisation for monolithic connections between membrane and joint profile
- Systems tested for 10,000+ movement cycles without permanent compression set degradation
EPDM Benefits
Lasting Watertightness
EPDM maintains watertightness in joints under decades of cyclic movements without losing elasticity. Compression set after 22h at 70°C is below 15% (EN ISO 815-1), unlike polysulphide with compression set of 25-40%.
Factory Pre-Moulded Profiles
Factory pre-vulcanised EPDM centre-bulb, gland and waterstop profiles guarantee perfect geometry and predictable behaviour for each joint type. Moulded corner pieces eliminate vulnerable field welds.
±25% Movement Capacity
EPDM works at ±25% of joint width — the largest capacity of any sealing system. For a 50 mm joint, EPDM accommodates ±12.5 mm. Polysulphide accommodates only ±6.25 mm in the same joint.
No Migrating Plasticisers
EPDM flexibility is intrinsic to the vulcanised rubber network, not dependent on plasticisers. Unlike PVC and neoprene profiles that lose 20-40% of plasticisers in 15-20 years in Portuguese climate.
No Preventive Maintenance
Unlike silicone (replacement at 10-15 years), polysulphide (annual inspection) and PVC (progressive hardening), EPDM requires no preventive maintenance at joints throughout its service life.
Lowest Total Cost over 50 Years
EPDM initial cost exceeds silicone, but the absence of replacements (2-3 silicone interventions in 50 years) results in significantly lower total life-cycle cost.
Technical Specifications
Movement amplitude
±10 mm to ±75 mm (profile dependent)
Working capacity
±25% of joint nominal width
Tested cycle count
> 10,000 cycles without degradation
Compression set (EN ISO 815-1)
< 15% after 22h at 70°C
Service temperature
-45°C to +130°C
Profile elongation at break
≥ 300%
Available profiles
Centre-bulb, gland, waterstop, omega, seismic
Standard
EN 14695 (bridges) / EN 13956 (roofs)
Installation Process
- 1
Movement Analysis
Movement amplitude calculation by thermal analysis (concrete thermal expansion coefficient × length × temperature range) and seismic analysis (Eurocode 8, National Annex). Profile selection for each joint with 2:1 safety factor.
- 2
Edge Preparation
Joint face rectification or blasting. Minimum pull-off resistance 0.5 N/mm². Removal of any existing sealant and incompatible adhesive residues. Compressed air cleaning.
- 3
Primer Application
EPDM primer applied on joint faces and adjacent surfaces with the planned bonding width (minimum 100 mm each side). Strict observation of manufacturer flash-off time — critical for adhesion strength.
- 4
Base Membrane Installation
Main EPDM membrane installation to 50 mm either side of joint. Flat bonding without air bubbles. The central zone over the joint gap is not bonded — reserved for movement.
- 5
Joint Profile or Loop Formation
Pre-moulded EPDM profile bonding over joint (profile method) or loop formation with depth = 2 × maximum extension movement (loop method). Moulded corner pieces at all direction changes.
- 6
Connection Vulcanisation
Cold vulcanisation at connections between membrane and joint profile with specific vulcanising adhesive. EPDM cover strip over full assembly. Reinforcement at joint crossings and corners.
- 7
Testing and Verification
Watertightness test of each joint by flooding (50 mm water layer for 24h) or air pressure. Physical movement simulation — manual opening to maximum design extension. Photographic documentation and 15-year warranty.
Installation Techniques
EPDM Membrane Loop Method (Movements up to ±75 mm)
EPDM membrane bonded on joint edges and folded into a loop centred over the gap, with depth calculated for the design movement. For large-amplitude movements including seismic. Continuous system without different materials.
Vantagens
- Accommodates very large movements including seismic (±40-75 mm)
- Full membrane continuity — no interface between different materials
- Suitable for roofs, bridges and structures in seismic zones A and B
- 8:1 safety factor at maximum extension with EPDM 400% elongation
Desvantagens
- More complex installation than simple profile — requires specialist technician
- Specific mechanical protection needed over the loop in trafficked zones
Pre-Moulded Centre-Bulb Profile (Movements up to ±30 mm)
Extruded EPDM profile with central bulb and anchoring flanges. The bulb acts as material reservoir: opens when the joint dilates, compresses when it closes. Available for joints of 20 to 150 mm.
Vantagens
- Fast and precise installation — factory-controlled geometry
- Laboratory-tested for defined amplitudes and loads
- Moulded corner pieces eliminate vulnerable field connections
- Traffickable versions (gland) for accessible pavement joints
Desvantagens
- Amplitude limited to ±30 mm in standard profile (±40-50 mm in seismic grade)
- Requires pre-formed or mechanically cut anchoring groove in slab
Concrete-Cast Waterstop Profile
EPDM profile cast into concrete during pouring — anchoring flanges are incorporated into each concrete element. Preferred solution for watertightness joints in underground structures, pools and reservoirs.
Vantagens
- Mechanical concrete anchorage — not dependent on surface adhesion
- Maximum hydrostatic pressure resistance in buried joints
- Installation during pouring — no subsequent joint intervention
Desvantagens
- Coordinated installation with concreting — impossible to install subsequently
- Requires precise positioning during formwork to guarantee centring
Comparison with Other Membranes
| Característica | EPDM | Structural silicone | Polysulphide |
|---|---|---|---|
| Seal service life | 50+ years without replacement | 10-15 years | 15-20 years |
| Movement capacity | Up to ±75 mm (loop system) | ±25% of width (max ±25 mm) | ±12.5% of width (max ±12 mm) |
| Compression set at 70°C | < 15% (EN ISO 815-1) | 20-30% | 25-40% |
| Preventive maintenance | None required | Replacement at 10-15 years | Annual inspection and re-profiling |
| De-icing salt resistance | Excellent — inert to NaCl | Good | May suffer chloride attack |
| Life-cycle cost (50 years) | Lowest — no interventions | 3-4 replacements in 50 years | 2-3 replacements in 50 years |
Performance in the Portuguese Climate
Continental Interior (Extreme Thermal Amplitude)
Portuguese interior with cold winters (-5°C to -15°C) and very hot summers (+35°C to +45°C) creates joints with ±20-40 mm movements in 30-metre structures. EPDM accommodates these movements with 8:1 safety factor without fatigue.
Seismic Zones (Lisbon, Setúbal, Algarve)
Expansion joints in seismic zones must accommodate 30-50 mm relative displacement (Eurocode 8). EPDM returns to its nominal dimension after the earthquake — rigid sealants fracture and remain permanently open.
Coastal Zones (Salt and Humidity)
Joints in marine environments subject to salt, sea spray and wetting cycles. EPDM is inert to the saline environment and resists alkaline hydrolysis of concrete (pH 12-13) throughout its service life.
Large-Area Roofs (Industrial Buildings)
Flat roofs exceeding 25-30 metres require expansion joints. In Alentejo and Algarve, the annual surface amplitude of 80-85°C produces 25 mm movement in 30-metre roofs. EPDM sized with ±30% reserve provides adequate margin.
Beiras and Serra da Estrela (Snow and Ice)
Joints in pavements and bridges in snow zones exposed to de-icing salts. EPDM is inert to sodium chloride and calcium chloride. Traffickable gland profiles maintain watertightness even under snow-ploughing vehicle traffic.
Frequently Asked Questions
The centre-bulb profile is an extruded element installed over or in the joint, suitable for movements up to ±30-40 mm. The membrane loop uses the waterproofing membrane itself folded over the joint, suitable for movements up to ±75 mm including seismic. The choice depends on the calculated movement amplitude and project context.
Yes, for joints in roofs, slabs, bridges and underground structures. The process includes complete removal of existing silicone (including adhesive residues), face preparation and installation of the appropriate EPDM system. EPDM has far superior performance to silicone in durability, movement amplitude and seismic behaviour.
The calculation combines: (1) thermal expansion = expansion coefficient × length × temperature range; for concrete with 10×10⁻⁶/°C, in a 30 m slab with 75°C range, movement is 22.5 mm; (2) seismic displacement from structural analysis per Eurocode 8; (3) estimated differential settlement. Membriko performs this calculation and selects the system with a 2:1 safety factor.
Repair by vulcanised EPDM patch over the damage with specific contact adhesive. If the joint profile is damaged, replacement of the damaged section by welding in a new profile with vulcanising adhesive. Repair is generally possible without removing other waterproofing elements.
Yes. For seismic joints in Lisbon Zone 1.3, with potential movements of 30-50 mm combining opening and shear, Membriko specifies the loop system with depth calculated for the design seismic displacement with 2:1 safety factor. EPDM returns to nominal position after the seismic event, unlike sealants that fracture.
EPDM systems are tested for 10,000+ complete opening and closing cycles without measurable degradation. In a building with daily thermal cycles, 10,000 cycles represents over 27 years of daily movements. In structures with less frequent cycles (seasonal), service life expressed in cycles far exceeds 100 years.
Depends on substrate condition. If existing waterproofing is bonded and old sealant has been fully removed, EPDM system can be installed over the prepared substrate. If silicone or incompatible adhesive residues are present, complete removal and surface preparation are mandatory before installation.
EPDM initial cost (profiles or loop system) is typically 2-4 times higher than silicone. However, silicone requires replacement at 10-15 years — 3-4 interventions in 50 years — each with material cost plus labour for removing degraded silicone. In 50-year total cost analysis, EPDM is invariably more economical.
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