Dry, Protected Basements with EPDM Membrane
Convert your damp basement into a functional, dry space with the EPDM waterproofing system — the definitive solution for below-ground floors, resistant to hydrostatic pressure and radon.
The Damp Basement Challenge
Damp basements are common in Portugal, especially in buildings constructed before 2000 with deficient waterproofing. Failure manifests silently — moisture corroding reinforcement, deteriorating installations and feeding mould — and when repair becomes urgent, the cost is 5-15 times the original waterproofing.
- Silent infiltrations corrode concrete reinforcement for years before visible manifestation — progressive structural damage
- Persistent basement moisture creates health-harmful mould — radon gas in at-risk geological zones is the second cause of lung cancer
- Temporary repairs (waterproof paints, injections) fail in 2-5 years creating expense cycles without definitive solution
- Wet or unusable basement represents property devaluation of €20,000-€50,000+ depending on size
The EPDM Solution for Basements
EPDM membrane creates a continuous impermeable envelope (tanking) around the entire underground structure. Approved at 200 kPa (20 m water column) per EN 1928, it offers a safety factor of 5-20 times for standard basements at 3-5 m depth.
- EPDM tanking system with full continuity — no seam at the slab/wall junction (the highest-risk point)
- Approved at 200 kPa EN 1928 Method A — 5-20× safety factor for typical Portuguese basements
- Simultaneous water and radon protection — recognised by Portugal's DGS as effective barrier (BRE 211, EN 13829)
- Pre-applied system for new construction or internal tanking for rehabilitation without exterior excavation
EPDM Benefits
Definitive Solution (50+ Years)
Unlike paints (2-5 years) and injections (5-15 years) that progressively fail, EPDM approved at 200 kPa (EN 1928) is a structural solution with documented 50+ year service life. An engineering decision made once, correctly.
Radon Gas Protection
EPDM is recognised by Portugal's DGS and the UK BRE as an effective radon retention barrier. In at-risk zones in Portugal (Beira Interior, Trás-os-Montes, Serra da Estrela), the membrane reduces Rn-222 entry to levels below the 300 Bq/m³ action level (Portaria 353-A/2013).
Reusable Basement for Habitation
A completely watertight basement can be transformed into habitable space, garage, office or technical area. Return on investment — €20,000-€50,000+ property value increase — far exceeds the waterproofing cost.
Structural Repair Costs Avoided
The cost of structural repair for a basement with corroded reinforcement is 5-15 times the original waterproofing cost. The economic case for quality waterproofing is irrefutable: investing correctly in waterproofing is always cheaper than repairing structural damage.
Health and Indoor Air Quality
Elimination of moisture and mould significantly improves indoor air quality throughout the building. In geological radon risk zones (Central and Northern Portugal), EPDM membrane is the recommended mitigation system — radon is the second cause of lung cancer in Europe (IARC/WHO).
No Exterior Excavation for Rehabilitation
The internal tanking system (mechanically anchored EPDM) is installed without excavating around the building — fully interior work. The external system (post-applied) is installed during construction or when exterior face access is available.
Technical Specifications
Thickness
1.5 mm (standard basements) / 2.0 mm (high pressure or critical)
Hydrostatic watertightness
Approved at 200 kPa (EN 1928 Method A — 20 m water column)
Elongation at break
≥ 400% (accommodates seismic crack opening of 50+ mm)
Soil sulphate resistance
Classes EA1-EA4 (EN 206) — excellent
Radon retention
Per BRE 211 / EN 13829 / DGS Portugal
pH range
4 to 12 — resistant to concrete alkaline environment
Service temperature
-50°C to +130°C
Product standard
EN 13967 (CE marking for underground applications)
Installation Process
- 1
Full Diagnosis
Assessment of infiltration extent and location. Cause identification (water table, surface runoff, condensation). Moisture measurement in walls and slab. In radon risk zones, Rn-222 concentration measurement (Portaria 353-A/2013).
- 2
Active Infiltration Treatment
Stopping active water flow with rapid-set hydraulic mortar — prerequisite before membrane installation. Polyurethane injection into cracks with active flow. Without stopping active flow, membrane installation is not possible.
- 3
Surface Preparation
Removal of unstable coatings, efflorescence and salts. Levelling of irregular surfaces. 45° chamfering of corners and filling of protrusions. Minimum pull-off resistance of 0.5 N/mm².
- 4
Sub-Slab Drainage System (Radon)
In radon risk zones, installation of drainage geocomposite under the slab with passive ventilation risers connected to exterior or roof. Sub-slab depressurisation prevents Rn-222 entry even in case of localised membrane damage.
- 5
EPDM Membrane Installation
Pre-applied system (new construction): EPDM fixed to excavation support before concrete. Post-applied system (accessible exterior): EPDM fully bonded to exterior concrete face. Internal tanking (rehabilitation): EPDM mechanically anchored to interior of walls and slab, with continuous slab/wall transition pieces without seam at the critical corner.
- 6
Singular Points and Full Continuity
Slab/wall junction with full continuity — membrane folds from horizontal to vertical without seam at the highest-risk angle. Pipe and cable penetrations with pre-fabricated EPDM sleeves. No mastic or silicone as primary sealant at any point.
- 7
Interior Finishes and Warranty
Application of interior finishes over EPDM (plaster, insulation, plasterboard) for quality finish. Delivery of dossier with as-built plan, photographic documentation, test results and 20-year warranty.
Installation Techniques
Pre-Applied / Blind-Side System (New Construction)
For new construction with inaccessible exterior face after construction (bored pile walls, sheet piles, top-down construction), EPDM fixed to excavation support before concrete. Structural concrete bonds directly to membrane inner face through bonding geotextile — no longitudinal migration pathway.
Vantagens
- Completely eliminates sub-membrane water migration pathway between membrane and concrete
- Applicable when exterior face is not accessible after construction
- Positive system — water blocked before contacting structural concrete
- Ideal for Lisbon (alluvial ground) and Porto (fractured granite with concentrated drainage)
Desvantagens
- Only applicable during construction phase, not in rehabilitation
- Requires rigorous coordination with formwork and concreting phasing
Post-Applied External System (Accessible Exterior)
For basements where the exterior face is accessible during construction or with feasible excavation, EPDM fully bonded to the exterior concrete face before backfilling. Maximum-effectiveness positive system — water blocked before contacting concrete.
Vantagens
- Maximum effectiveness — positive system, no water contacts concrete
- No interior space loss
- Most durable system for high hydrostatic pressures (>5 m water column)
- Compatible with exterior drainage geocomposite for pressure relief
Desvantagens
- Requires exterior access — perimeter excavation
- Not applicable in terraced basements or with adjacent buildings
Internal Tanking (Rehabilitation Without Excavation)
For rehabilitation of existing basements with infiltrations without exterior face access, EPDM mechanically anchored to the interior of walls and slab. Creates air cavity draining any infiltrations to perimeter channel. Fully interior solution.
Vantagens
- Fully interior work — no excavation, minimal disruption
- Applicable to terraced basements or with adjacent buildings
- Perimeter drainage channel as complementary safety system
- Compatible with radon — ventilation riser installation integrated
Desvantagens
- Negative system — does not prevent water contacting concrete; manages entry
- Slight interior space reduction from air cavity (30-50 mm per wall)
Comparison with Other Membranes
| Característica | EPDM | Interior waterproof paint | Epoxy resin injection |
|---|---|---|---|
| Durability and service life | 50+ years without re-intervention | 2-5 years — fails under hydrostatic pressure | 5-15 years — plugs existing cracks only |
| Hydrostatic pressure effectiveness | Approved at 200 kPa (EN 1928) | None — lifts under hydrostatic pressure | Manages water entry (does not stop) |
| Radon gas protection | Effective — BRE 211 / EN 13829 / DGS | No effectiveness for radon | Limited — not a gas barrier |
| Seismic movement accommodation | 400% elongation — seismic cracking up to 50+ mm | Zero — brittle failure at seismic cracks | Limited — seasonal desiccation risk |
| Soil sulphate resistance | Excellent — Classes EA1-EA4 EN 206 | Moderate — saponification risk | Ion exchange risk in calcareous soils |
| Life-cycle cost (50 years) | Lowest — no replacements | 5-8 re-applications in 50 years | Electricity consumption + pump replacement |
Performance in the Portuguese Climate
Lisbon and Tagus Valley (Alluvial Ground and High Water Table)
Basements in central Lisbon, Chiado, Almada waterfront and Setúbal have water table at 1-3 m depth in alluvial ground. EPDM approved at 200 kPa (20 m water column) provides 5-10× safety factor over the typical 20-30 kPa design pressures at these locations.
Beira Interior and Trás-os-Montes (Radon)
Portugal's uraniferous granite interior has the highest radon concentrations in continental Europe. EPDM recognised by DGS as a radon retention barrier (BRE 211, EN 13829) is mandatory in basements in these regions — combined with passive sub-slab depressurisation.
Porto and North (Fractured Granite)
Porto and northern Portugal's weathered granite has moderate water table but fractures that conduct water in concentrated flows. EPDM accommodates sudden flow increases at fracture fronts without the localised pressure compromising the membrane — unlike rigid systems.
Coastal Zones (Chlorides and Saline Intrusion)
Basements in coastal zones (Algarve, Alentejo coast, estuaries) face additional saline intrusion and chloride risk. EPDM is completely inert to salt water and chloride solutions — protecting concrete from attack in tidal or brackish water table environments.
Alentejo and Southern Interior (Expansive Clays)
Basements founded on Alentejo expansive clay soils face seasonal differential settlement risk (clays expand in wet winter and shrink in dry summer). EPDM 400% elongation accommodates these movements without failure — cementitious systems would crack.
Frequently Asked Questions
Yes. The mechanical anchoring system of the internal tanking is designed to resist the specific hydrostatic pressure of each case. EPDM is approved at 200 kPa (20 m water column) per EN 1928 Method A — for a standard basement at 3-5 m depth, the safety factor is 5-20 times.
The pre-applied (blind-side) system is installed over the excavation support before concrete in new construction — the concrete bonds directly to the membrane. Internal tanking is installed inside the existing basement without excavating — it creates an air cavity between EPDM and wall draining to a perimeter channel. The pre-applied system is more effective; internal tanking is the solution when exterior access is unavailable.
Yes. EPDM is recognised by Portugal's DGS and the UK BRE (BRE 211) as an effective radon retention barrier for new construction and rehabilitation. For highest-risk locations (Beira Interior, Trás-os-Montes), Membriko specifies the EPDM membrane combined with a passive sub-slab depressurisation system (geocomposite + ventilation risers), per DGS guidelines and Portaria 353-A/2013.
The slab-to-wall junction is the highest-risk point in any basement waterproofing. Membriko resolves this with full continuity: the EPDM membrane from the slab folds vertically on the wall with minimum 300 mm width, without a seam at the transition angle. Pre-formed EPDM fillet pieces are bonded at the interior corner to eliminate tensile stress. A single membrane without transverse seam at the highest-risk point.
A 50-100 m² basement typically takes 5-10 days of interior work, including preparation, stopping active infiltrations and membrane installation. Without exterior excavation, disruption is minimal. In new construction with pre-applied system, coordination with the main contractor occurs before concreting begins.
Yes. EPDM has excellent resistance to sulphates (Exposure Classes EA1-EA4 per EN 206), chlorides, organic acids and petroleum hydrocarbons. For sites with identified contamination (former landfills, fuel stations, industrial zones), Membriko performs chemical compatibility assessment based on the site characterisation report.
Repair by EPDM patch of the same thickness and formulation, bonded with QuickPrime primer and 150 mm QuickSeam tape over the damaged zone, with minimum 75 mm overlap in all directions over clean dry membrane. For damage in zones under concrete or backfill, Membriko performs electric leak detection (ELD) diagnosis before defining the repair strategy.
Yes. EPDM 400% elongation accommodates movements of 50+ mm and seismic crack openings of several millimetres — with a safety factor far exceeding any rigid system. For underground structures in Lisbon (Seismic Zone 1.3) and Algarve, Membriko can confirm documentally that the membrane's deformation capacity is compatible with the drift values calculated by the structural engineer per Eurocode 8.
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