Protected Retaining Walls with EPDM Membrane
Waterproof and protect retaining and support walls against moisture, sulphates and carbonation with long-lasting EPDM — the only solution combining hydrostatic pressure resistance, crack-bridging elongation, and durability in permanent contact with wet soil.
The Retaining Wall Challenge
Retaining and support walls are exposed to lateral soil pressure, infiltration water, sulphates and expansion-retraction cycles. Moisture through walls causes aesthetic and structural problems that, by the time they become visible, already require expensive remediation.
- Efflorescence and moisture stains on non-waterproofed concrete and masonry walls
- Soil sulphates progressively attack mortar and wall concrete, causing structural deterioration
- Hydrostatic pressure during rainy periods can destabilise walls without adequate drainage
- Construction joints opening through differential shrinkage create preferential water infiltration paths
- Walls in garden zones suffer additional pressure from tree and shrub roots
- Late remediation of walls with corroded reinforcement costs 5 to 12 times more than preventive waterproofing
The EPDM Solution for Retaining Walls
EPDM membrane installed on the soil face protects the wall from moisture and soil chemical aggressiveness. With ≥ 400% elongation, the membrane bridges structural cracks and joints without failure. Tested at 60 kPa (EN 1928), it covers the vast majority of residential and commercial retaining wall situations in Portugal.
- Impermeable barrier on soil face protecting wall from moisture, sulphates and humic acids
- 400% elongation that bridges construction joints and cracks without compromising watertightness
- Compatible with geocomposite drainage board for complete hydrostatic pressure relief
- Chemical resistance to pH 3-12 — inert to all soil types found in Portugal
EPDM Benefits
Soil Aggressive Resistance
Physical barrier completely isolating wall from sulphates, chlorides and humic acids. EPDM is chemically inert to all Portuguese soil environments — granite, clay, limestone or alluvium — without degradation over 50+ years.
Complete Moisture Control
Eliminates moisture stains, efflorescence and limescale on the visible wall face. EPDM membrane does not absorb water or undergo hydrolysis — water absorption is below 1% by mass even after decades of immersion.
Complete System with Drainage
The EPDM + geocomposite drainage board + French drain system is the standard for retaining walls in high-rainfall zones. Drainage reduces hydrostatic loading from several metres of water head to less than 0.5 m.
Construction Joint and Crack Bridging
The base-stem construction joint is the critical point in cantilever walls. EPDM with ≥ 400% elongation bridges 15-20 mm openings with a safety factor of ≥ 2.5 — unlike bitumen systems that crack at these points.
Investment Protection
Retaining walls have high construction costs. EPDM protection ensures the investment lasts 50+ years without structural deterioration. Repairs to corroded reinforcement cost 5 to 12 times more than preventive waterproofing.
Root Resistance and FLL Compatibility
1.5 mm EPDM with FLL certification suitable for garden-zone walls with nearby vegetation. The three-dimensional carbon-carbon bond network of vulcanised rubber cannot be penetrated by root tips.
Technical Specifications
Thickness (residential/agricultural)
1.5 mm (EN 1849-2)
Thickness (commercial/infrastructure)
2.0 mm (EN 1849-2)
Tensile strength
≥ 9 N/mm² (EN 12311-2)
Elongation at break
≥ 400% (EN 12311-2)
Hydrostatic watertightness
Pass at 60 kPa — 6 m water head (EN 1928)
Tear resistance
≥ 10 N/mm (EN 12310-2)
Chemical resistance (pH)
Excellent — pH 3 to 12, sulphates, chlorides, humic acids
Product standard
EN 13956 / EN 13967
Installation Process
- 1
Geotechnical Assessment and Diagnosis
Free technical site visit. Assessment of wall type and condition (gravity, cantilever, urban sheet pile), groundwater indicators, crack and efflorescence identification. Review of project documentation where available.
- 2
Waterproofing Design
EPDM thickness selection (1.5 or 2.0 mm), drainage system type (geocomposite, granular or combined), singular point details (joints, corners, penetrations, anchors) and cut plan to minimise field seams.
- 3
Surface Preparation
Cleaning and degreasing of wall face, removal of efflorescence and flaking paint. Crack repair with flexible repair mortar — active cracks with expansive polyurethane. Grinding of sharp edges and protrusions above 5 mm.
- 4
EPDM Membrane Installation
Full adhesion with water-based neoprene adhesive. Installation from base to coping. Internal and external corners with pre-moulded EPDM accessories. Seams with minimum 50 mm overlap and QuickSeam tape. Individual testing of each seam.
- 5
Integrated Drainage System
Geocomposite drainage board installation over EPDM, covering the full retained face from base drain to coping. Retention profile at top to prevent soil fines entry. Connection to perimeter French drain pipe with outfall to inspection chamber.
- 6
Singular Points and Coping Termination
Treatment of all pipe penetrations, anchor heads and expansion joints with pre-moulded EPDM accessories or flanged mechanical compression sleeves. Coping termination with metal termination bar sealed with polyurethane sealant.
- 7
Inspection, Backfill and Warranty
Systematic visual inspection and electrical spark testing at seams and singular points. Photographic as-built record. Backfill in 300 mm compacted lifts without heavy plant within 2 m of wall face for first three lifts. Issue of 20-year warranty.
Installation Techniques
EPDM + Geocomposite Drainage Board (Standard)
Standard method for retaining walls in wet zones. EPDM waterproofs the wall and the geocomposite drainage board over it relieves hydrostatic pressure, directing water to the base French drain. Membriko supplies the complete system — membrane, drainage board, drain pipe and warranty.
Vantagens
- Dual function: waterproofing + hydrostatic pressure relief
- Reduces hydrostatic loading from metres of water head to less than 0.5 m
- Complete system for any soil type, including expansive clays
- Geocomposite mechanically protects membrane during backfilling
Desvantagens
- Two-layer installation — slightly more expensive than simple solution
- Requires functional base drain for evacuation of captured water
Direct Bonded EPDM (Shallow-Buried Walls)
For garden or support walls with minimal buried depth and no significant hydrostatic pressure, EPDM bonded directly to concrete or masonry without drainage board. Suitable for walls up to 1 m of soil depth in zones with good natural drainage.
Vantagens
- Faster and more economical installation for simple projects
- Suitable for garden walls and agricultural terracing up to 1 m of soil
- No base drain required in permeable soils
Desvantagens
- Not suitable for walls with significant hydrostatic pressure
- Requires good natural soil drainage — not suitable for clays
External System for Cantilever Walls and Sheet Pile Walls
For reinforced concrete cantilever walls and urban sheet pile walls. EPDM 2.0 mm in full adhesion with penetration sleeves at anchor heads. High-capacity geocomposite for urban soils with artesian pressure conditions.
Vantagens
- Positive-side system — blocks water before it reaches structural concrete
- Pre-moulded EPDM sleeves at anchor heads ensure system continuity
- Specified for walls in Seismic Zone A with dynamic pressure increments
Desvantagens
- Requires exterior access for installation — not applicable adjacent to buildings
- Greater complexity at anchor penetrations in sheet pile walls
Comparison with Other Membranes
| Característica | EPDM | SBS modified bitumen | HDPE geomembrane | Cementitious crystalline |
|---|---|---|---|---|
| Service life | 50+ years | 15-25 years | 30-50 years | 20-30 years (if crack-free) |
| Elongation at break (joint bridging) | ≥ 400% | 30-150% | 12-18% (yield strain) | 0% (rigid) |
| Sulphate resistance | Excellent — inert pH 3-12 | Moderate | Good | Limited in acid soils |
| Compatibility with irregular masonry | Excellent — conforms to surface | Good | Limited — requires regular surface | Not suitable for masonry |
| Installation method | Cold adhesive — no fire risk | Torch — fire risk in confined spaces | Thermal welding — controlled conditions | Brush/spray on clean concrete only |
| 30-year cost index | 100 | 175 (repairs and replacement) | 120 | 160 (crack remediation) |
Performance in the Portuguese Climate
Humid North (Minho, Trás-os-Montes)
High rainfall creates permanent hydrostatic pressure on retaining walls. Granitic soils with abrasive sand require geocomposite drainage board with verified puncture resistance (minimum 1.5 kN per EN ISO 12236). EPDM + drainage board system is mandatory in these zones.
Alentejo and Ribatejo (Expansive Clays)
Vertisol clay soils swell significantly when saturated and shrink when dry. This cycle imposes additional movements on retaining walls that rigid systems cannot accommodate. EPDM at ≥ 400% elongation is the only solution that bridges joints without cracking.
Algarve (Limestone, Karst and Seismic Zone A)
The Algarve has the highest seismic hazard on Portuguese territory (Seismic Zone A, EC8). Dynamic earth pressure increments during seismic events can reach 30-50% above static values. Membriko specifies 2.0 mm EPDM for all walls above 2 m height in the Algarve.
Lisbon and Porto (Urban Environment, Fill Soils)
Cities built on Tagus and Douro alluvium with high water tables — sometimes artesian in the lowest zones. Membriko specifies 2.0 mm EPDM in full adhesion, high-capacity geocomposite (minimum 1 l/s·m) and reinforced detail at all construction joints.
Coastal Zones (Marine Environment)
Salt and chlorides from marine environments attack unprotected concrete. EPDM as exterior barrier completely isolates concrete from the corrosive environment — chemically inert to sodium chloride and the saline coastal environment.
Frequently Asked Questions
For walls with construction joints, movement potential or masonry substrates, EPDM is technically superior in every relevant category. The ≥ 400% elongation of EPDM (compared to 30-150% for SBS bitumen) is decisive when wall joints open under thermal and moisture cycling. Cold adhesive installation eliminates fire risk in confined spaces. The 50+ year service life compares favourably with 15-25 years for bituminous systems.
Yes, whenever the wall is subject to hydrostatic pressure. Drainage is the first line of defence — a wall with correctly installed geocomposite drainage board can reduce hydrostatic loading from several metres of water head to less than 0.5 m. Membriko specifies and installs the drainage system as an integrated part of the waterproofing package.
The membrane is not a structural element — it is a hydraulic barrier. Earth pressure is resisted by the wall structure. The EPDM membrane resists hydrostatic water pressure up to 60 kPa (equivalent to a 6 m water head, per EN 1928) and bridges structural cracks and joints through its ≥ 400% elongation capacity.
Yes. EPDM is ideal for remediation of cracked or deteriorated retaining walls. Cracks are filled with flexible repair mortar before membrane application. If new cracks develop at the same location after waterproofing, the EPDM accommodates the movement without tearing — unlike rigid cementitious or aged bituminous systems that crack again at the same point.
Yes. EPDM's ≥ 400% elongation and cold-adhesive installation method allow the membrane to conform to irregular stone masonry surfaces. Protrusions above 10 mm are ground flush or mortared in; sharp edges are rounded; the membrane is pressed into surface depressions during adhesive application. This adaptability is not available with rigid HDPE or cementitious systems.
Membriko specifies 1.5 mm for residential and agricultural retaining walls up to 3 m height. For commercial structures, walls above 3 m, walls in seismic zone A (southern Portugal) and walls subject to a water table more than 3 m above foundation level, the specification is 2.0 mm. For hydrostatic pressure heads above 6 m, a specific engineering analysis is conducted.
Localised damage at the exposed coping zone is repaired with EPDM patch and QuickSeam tape without excavation. For damage to the buried membrane, repair requires localised excavation of the backfill to access the membrane. Membriko supplies an emergency repair kit with every completed project.
Membriko issues a 20-year installation warranty on all retaining wall waterproofing work. This warranty supplements the manufacturer's product warranty and the 5-year statutory defects liability period under the Portuguese Civil Code (Art. 1225). The warranty certificate is delivered with a photographic as-built record and an installation report.
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