Roof Renovation: EPDM Over Existing — No Demolition
Revitalise ageing roofs without the disruption and cost of full demolition. EPDM installs over most existing systems with a new 20-year guarantee — the smartest solution for Portugal's vast existing building stock.
The Ageing Roof Challenge in Portugal
Portugal has a building stock of over 800,000 buildings constructed between 1950 and 1990, many with flat roof waterproofing systems that have long exceeded their service life. These oxidised and cracked bituminous systems are now the leading cause of infiltration in office, commercial, collective residential and industrial buildings. The traditional approach of full demolition and reconstruction is expensive, slow, produces large quantities of construction waste and seriously disrupts building occupants for weeks.
- Oxidised and cracked bitumen on 20+ year roofs allows infiltration at multiple simultaneous points
- Full demolition of existing system costs 2-3x more than over-installing EPDM
- Demolition works disrupt occupied or commercial buildings for weeks with noise, dust and odours
- Demolition rubble has significant environmental, transport and disposal costs
- Repeated infiltrations degrade interiors, damage ceilings, walls, equipment and reduce property value
- Localised bitumen repairs have service lives of only 2-5 years, creating a cycle of recurring costs
The EPDM Solution for Roof Renovation
In most cases, EPDM can be installed directly over the existing waterproofing system, whether APP or SBS bitumen, PVC, in-situ applied polyurethane or bituminous felt. This "over-roofing" approach eliminates the need for demolition, reduces costs by 30-50%, accelerates the work from weeks to days and minimises disruption to occupants. The result is a roof with a new 50+ year service life and a new 20-year warranty — without the trauma of demolition works.
- Installation over existing system in bitumen, PVC, polyurethane or felt with compatibility primer
- Free technical diagnosis identifies if partial demolition is needed in problem areas
- New 20-year warranty issued on the complete renovated system
- Minimal disruption to occupants — cold works, no torch, no dust, no strong odours
- Construction waste reduction of 80-90% compared with full demolition
- Eligible for urban rehabilitation fiscal incentives in Portugal (Art. 71 of CIRS)
EPDM Benefits
Proven 30-50% Savings
Over-installing EPDM on an existing system typically costs 30-50% less than full demolition and reconstruction with a new equivalent system. On a 500 m² roof, savings can be €15,000-€40,000. These savings often allow additional improvements (thermal insulation, new drainage system) that full demolition alternatives would not permit within budget.
Works 2-3x Faster
Without a demolition phase, EPDM installation over existing is 2-3x faster. 500 m² roofs that would take 2-3 weeks of demolition plus new system installation are ready in 3-5 days. This time reduction is especially critical for hotels, hospitals, shopping centres and offices where each day of works represents operational losses.
Most Sustainable Renovation Solution
Near-total elimination of demolition rubble (80-90% less waste), reduction of new material consumption and lower embodied carbon footprint. For companies with ESG objectives or LiderA/SBTool PT certifications, EPDM renovation without demolition is the lowest environmental impact roof rehabilitation solution available. Contributes to LEED credits in rehabilitation projects.
Full New 20-Year Warranty
Renovation with EPDM comes with a new 20-year warranty on system watertightness — regardless of the condition of the old system below. This warranty is issued by Membriko and covers both material and installation, providing the owner with full legal and financial security over the new investment.
Minimal Disruption to Occupants
Cold installation, no torch, no strong odours, no demolition noise or dust. Ideal for renovations in hotels and resorts (that cannot close), hospitals, schools, shopping centres or occupied residential condominiums. Works are sequenced by zones to always maintain safe access to the roof and building.
Complete Technical Diagnosis Included
Before any work, Membriko carries out a complete and free technical diagnosis of the existing roof: thermography for humidity detection, problem zone mapping, existing system analysis, and detailed report with renovation method recommendation. This professional diagnosis — which would cost €500-€2,000 in other contexts — is included in our process at no extra cost.
Technical Specifications
EPDM thickness for renovation
1.2 mm / 1.5 mm
Compatibility over APP/SBS bitumen
Yes — with specific primer
Compatibility over PVC
Yes — verify chemical compatibility
Compatibility over felt
Yes — if structurally sound
Service temperature
-45°C to +130°C
Additional system thickness
1.2-1.5 mm (minimal addition)
Additional structural load
1.5-2.0 kg/m²
Wind uplift resistance
≥ 1,500 N/m² (bonded)
New warranty issued
20 years on watertightness
Product standard
EN 13956
Installation Process
- 1
Detailed Technical Diagnosis
Complete inspection of existing roof: mapping of active and potential infiltrations, substrate humidity testing by electrical resistivity, systematic photographic survey, identification of existing system (bitumen type, thickness, number of layers) and adhesion assessment by pull-off testing. For complex cases, infrared thermography for hidden moisture location.
- 2
Selective Repair of Old System
Based on diagnosis, selective repair of problem areas: cutting and removing areas with delamination, trapped moisture blisters or structural failures. Filling larger cracks with hot bitumen or polysulphide mastic. Forced drying of wet zones if necessary. In severe cases or with significant retained moisture, selective demolition of affected areas.
- 3
Flashings, Drains and Joint Preparation
Replacement or repair of degraded drains before new membrane. Grinding down prominent flashings that would prevent good EPDM conforming. Preparation of all expansion joints with new profiles if necessary. Checking and cleaning perimeter drainage channels.
- 4
Cleaning and Compatibility Primer
Complete cleaning of existing surface: sweeping, vacuuming dust, removing loose granules. Application of compatibility primer specific to the type of existing membrane: solvent-based primer for oxidised bitumen, special primer for aged PVC. Primer prepares the surface chemically and physically for EPDM adhesion.
- 5
EPDM Installation over Existing System
Installation of new EPDM membrane in maximum possible sheet sizes (minimising seams). Full bonding with neoprene contact adhesive or mechanical fixing at perimeter zones. Careful treatment of all singular points: parapet flashings, wall flashings, drains, penetrations, expansion joints — each detail with pre-formed or field-cut-and-bonded EPDM accessories.
- 6
Rigorous Quality Control
Visual and tactile inspection of entire installed surface. Pull-off adhesion testing at sampled points (minimum 1 test per 100 m²). Watertightness testing by flooding of low zones or by electronic detection (high voltage spark testing) for weak point location. Verification of all singular details before approval.
- 7
New Warranty Issue and Documentation
Complete documentation of renovation carried out: before and after photographic report, specifications of materials applied, quality test results. Issue of new 20-year warranty certificate on watertightness of renovated system. Delivery of recommended preventive maintenance plan to maximise service life.
Installation Techniques
EPDM Fully Bonded over Bituminous System
The most common flat roof renovation method in Portugal. After technical diagnosis, selective repair and compatibility primer, EPDM is fully bonded with neoprene adhesive over the existing bituminous membrane (APP, SBS or oxidised). Applicable when the bituminous system is structurally sound, without widespread delamination or retained moisture.
Vantagens
- Eliminates demolition — 30-50% savings over full replacement
- Immediate new impermeability over old system without transition risk
- Compatible with APP, SBS or oxidised bitumen — the most common in Portugal
- Minimal works time — 500 m² roof in 3-4 days
Desvantagens
- Requires structurally sound bituminous system without widespread delamination
- Trapped moisture between layers can compromise adhesion and create future blistering
- Rigorous technical diagnosis mandatory — do not apply without prior inspection
EPDM with Selective Demolition of Problem Areas
For roofs with severe localised problems — areas with significant moisture accumulation, severe delamination or compromised structural substrate — the strategy combines selective demolition of problem areas (typically 10-30% of total area) with EPDM over-installation in the remainder. Result combines overall economy with maximum quality.
Vantagens
- Eliminates hidden localised problems that compromise pure over-installation
- Cost and disruption far lower than full demolition
- Quality result equivalent to full replacement but at 40-60% of the cost
- Much simpler and more economical waste management
Desvantagens
- More time-consuming than direct over-installation (typical: 4-7 days for 500 m²)
- Intermediate cost between over-installation and full demolition
- Requires precise technical diagnosis to delimit areas for demolition
Mechanically Fixed EPDM with Additional Insulation
For roofs requiring simultaneous waterproofing renovation and energy performance improvement, a new rigid thermal insulation layer (PIR or EPS) is mechanically fixed to the substrate, with EPDM bonded over this new insulation layer. Eliminates old system without demolition and adds insulation.
Vantagens
- Double improvement: new waterproofing + new thermal insulation in one process
- Meets RECS minimum insulation thickness requirements for rehabilitation
- Improves building energy certificate (may rise 1-2 energy ratings)
- Good solution when old system does not offer sufficient adhesion
Desvantagens
- Higher cost than direct over-installation
- Adds significant thickness and weight — structural check required
- More time-consuming — typically 5-8 days for 500 m²
Comparison with Other Membranes
| Característica | EPDM | Full demolition + new APP bitumen | Localised bitumen repair | Full demolition + new PVC | Liquid polyurethane over existing |
|---|---|---|---|---|---|
| Renovation cost (500 m²) | Low — €15-25/m² (over existing) | High — €35-55/m² | Very low — but repeats every 2-5 years | High — €30-50/m² | Medium — €20-35/m² |
| Project duration (500 m²) | 3-5 days | 2-3 weeks | 1-2 days — but repeats cyclically | 1-2 weeks | 3-7 days + curing |
| New guaranteed service life | 50+ years (20-year warranty) | 15-20 years | 2-5 years | 25-30 years | 10-15 years |
| Building disruption | Minimal — no torch, no dust | High — noise, dust, bitumen odours | Low — but recurring | Moderate — no torch but demolition | Moderate — solvents and odours |
| Construction waste generated | Minimal — < 1 kg/m² | Very high — 15-25 kg/m² | Low | High — 10-20 kg/m² | Low |
| Eligibility for rehabilitation incentives | Yes — Art. 71 CIRS, municipal PDM | Yes, but lower ESG impact | Limited — minor intervention | Yes, but lower ESG impact | Yes, applicable |
Performance in the Portuguese Climate
All Portugal — 1950-1990 Building Stock
Portugal has a massive stock of buildings with roofs built between 1950 and 1990 using oxidised bitumen or first-generation APP/SBS systems. The vast majority of these systems are beyond service life and need urgent renovation. EPDM over-installation is the most cost-effective solution for this widespread problem affecting hundreds of thousands of buildings across the country.
South and Atlantic Coast (Accelerated UV Degradation)
High solar irradiation in the south (Alentejo, Algarve) and western coast degrades bituminous systems faster than in the north. Roofs installed 15 years ago in Faro or Évora may already show cracking and delamination that in Porto only appears at 20-25 years. EPDM renovation in these areas should be planned earlier, but is equally effective.
Industrial and Urban Commercial Zones
Atmospheric pollution from industrial and urban centres (SO₂, ozone, acid particles) chemically attacks bituminous systems, accelerating oxidation and embrittlement. EPDM installed over these degraded roofs is chemically resistant to all these pollutants, offering superior protection and full 50+ year service life even in aggressive environments.
North and Interior (Rainfall and Snow)
In the humid north and interior mountain ranges, infiltration is the primary problem of ageing roofs. Cracked bituminous systems allow continuous water ingress causing cumulative damage to structures, ceilings, walls and insulation. EPDM renovation definitively resolves the problem and protects the accumulated investment in the building.
High-Occupancy Service Buildings
Hotels, hospitals, health centres, schools and shopping centres cannot sustain the disruption of weeks of demolition works. EPDM over-installation, executed in 3-5 days in rotating zones, allows the building to remain in full operation throughout renovation — a decisive factor for facilities managers who cannot close the service.
Frequently Asked Questions
Yes, when correctly executed with complete prior technical diagnosis, selective repair of problem areas and adequate compatibility primer. Our 20-year warranty explicitly covers renovations over bituminous systems — our confidence in the solution is based on hundreds of similar installations successfully completed in Portugal. The technical diagnosis is key to identifying the (few) situations where partial demolition is necessary.
Clear warning signs: moisture stains on the building interior after rain, visible blisters or cracks in the existing membrane, membrane edges lifting or disintegrating, loose granules on granule-surfaced bitumen roofs, or a system over 15-20 years old without documented maintenance. Our free inspection with technical report determines the exact condition and most appropriate solution.
Yes, but requires careful coordination. For ballasted systems, panels are temporarily moved by sections (renovation is done in 50-100 m² zones at a time). For anchored systems, renovation requires more coordination with the solar installer. In both cases, we always maintain part of the roof accessible and operational. We have carried out this type of renovation on photovoltaic warehouses with 500+ installed panels.
A 1.5 mm EPDM membrane adds only 1.5-2.0 kg/m² to the structure — less than a person walking on the roof. This is negligible for any normal structure. For older buildings with 1950s-1970s concrete structures, we always verify structural capacity as part of the technical diagnosis. In 99% of cases there is no issue.
Technically yes — EPDM can be installed in selected areas with seams to existing systems. However, from a warranty and works efficiency perspective, we recommend renovating the complete roof in one intervention. Partial renovations create interfaces between systems of different ages that are future vulnerability points.
1.2 mm EPDM supports occasional maintenance pedestrian traffic (predefined paths). For roofs with frequent pedestrian traffic (technical terraces, technical green roofs), we recommend 1.5 mm EPDM with protection walkways. For public-access walkable roofs, the system must include heavy protection (decking or floating slab).
Existing wall flashings are inspected and, if in good condition, EPDM is bonded over them with specific primer and adhesive. If flashings are degraded, they are replaced, or EPDM runs directly up the wall with a mechanical fixing bar at the top and edge sealing with butyl tape. We leave no vulnerable transition — this is one of the technical points that most distinguishes professional renovation from amateur work.
For renovation over existing bituminous system without traffic, 1.2 mm is the standard thickness. For roofs with occasional pedestrian traffic or an irregular old system that may create pressure points, 1.5 mm offers greater safety margin. For renovations over old PVC that may have plasticiser migration, we always recommend 1.5 mm with a separator between systems.
Ready to Get Started?
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