Restec Flexitec 2020 is a multi-surface fibreglass resin system that sits in a category of its own - combining the structural toughness of traditional GRP with the overlay versatility of liquid roofing.
Having already waterproofed hundreds of thousands of square metres on commercial and residential projects across the UK, it's building a strong following among contractors who need a fast, dependable system that works across almost any existing roof surface. Here are the questions we're most commonly asked.
What is Restec Flexitec 2020?
Flexitec 2020 is a flexible hybrid polyester resin system manufactured by Restec, cured with a specialised peroxide catalyst and reinforced with 225g/m² fibreglass chopped strand mat (CSM) to form a tough, seamless, fully waterproofed membrane. It is designed for use by professional installers on both new OSB3 deck applications and overlay refurbishment of virtually any existing roofing substrate.
Unlike standard GRP systems, Restec Flexitec 2020 uses a single resin for both the base coat and the topcoat - there is no separate basecoat/topcoat product to stock, and no separate pigment required, as the resin is self-coloured in dark grey or light grey as standard. This simplifies ordering, reduces on-site stock, and eliminates the possibility of mismatched products.
It is ETA-certified (ETA-24/0069) and achieves a BRoof(T4) fire classification - the highest available under UK regulations for external roofing - and installations by trained installers are supported by Restec's 20 Year Materials Guarantee.
What Makes Flexitec 2020 Different from Standard GRP Systems?
Standard fibreglass GRP systems are rigid, which makes them prone to cracking with structural movement, and they typically cannot be applied over an existing membrane without stripping back to the deck. Flexitec 2020 is engineered differently in several important ways.
Flexible polyester resin. The hybrid resin formulation provides excellent crack resistance and tolerates the structural movement that causes conventional GRP systems to fail - making it genuinely suitable for overlay applications on roofs that would otherwise need to be stripped.
Multi-surface adhesion. Flexitec bonds to felt, asphalt, concrete, GRP, PVC single-ply, OSB3 TG4, and metal details - often without the need to remove and re-board. This makes it one of the most versatile overlay systems available.
Single resin, two purposes. The same drum of Flexitec 2020 is used for both the reinforced base coat and the unreinforced topcoat. No basecoat/topcoat split, no separate pigment pots.
Rain resistant once consolidated. Once the fibreglass CSM reinforcement is wetted through and consolidated, the membrane will continue to cure even if it rains - a significant practical advantage over many resin systems where an unexpected shower can ruin an application.
Over-coatable without grinding. Unlike traditional GRP, Flexitec can be repaired or over-coated at a later date without the need to grind down the existing surface, making future maintenance and repair straightforward.
Rapid walk-on time. The system is walk-on ready in 30–60 minutes depending on conditions, making it suitable for occupied properties and projects where disruption needs to be minimised.
What Surfaces Can Flexitec 2020 Be Applied To?
Flexitec 2020 can be applied to almost any common roofing substrate, making it one of the broadest-compatibility systems available. Key surfaces and their primer requirements are as follows.
Felt (sanded/smooth or mineral): Flexitec Primer is recommended. Badly damaged or decayed felt must be replaced, blisters star-cut and re-bonded, and loose sand brushed off before coating.
Asphalt: Flexitec Primer is recommended. Blow holes should be smoothed or repaired with a suitable compound, and large cracks made good before application.
GRP: No primer required. Aged and weathered GRP with a sound topcoat does not need mechanical abrasion, but GRP with a topcoat less than 12 months old will require abrading at the edges. All GRP surfaces must be thoroughly scrubbed with clean acetone prior to coating. Note that existing GRP trims must always be waterproofed with reinforced Flexitec resin - not simply painted.
Concrete and screed: Flexitec Primer is essential, not just recommended. Smooth concrete should be lightly abraded to remove laitance. Newly laid concrete must cure for at least 28 days before application.
PVC single-ply: Adhesion tests are required before proceeding. Where tests are passed, Restec SP Primer or standard Flexitec Primer is used depending on results.
Metal (detailing only): Restec Metal Detailing Primer or Twin-Pack Epoxy Metal Primer required. Flexitec is suitable for metal detailing work and small areas - it is not recommended for coating large areas of metal, particularly where significant joint movement may occur.
OSB3 TG4 (new deck): Flexitec Primer is applied by brush to all board joints before the main system. Tongue-and-groove joints receive stripe priming; square-edge board joints require additional local reinforcement with primer and taping mat.
Important: The substrate must always be visibly dry, with a moisture content not exceeding 20% w.m.e. as measured by a Protimeter moisture meter. Gas torches and standard electric driers must not be used for drying - they can damage the substrate and create a fire hazard.
How Long Does Flexitec 2020 Last?
Installations by trained and approved Restec installers are supported by a 20 Year Materials Guarantee. The system achieves ETA-24/0069 European Technical Assessment certification and BRoof(T4) fire classification, and is manufactured to ISO 9001 and ISO 14001 standards.
The long-term performance of the system is underpinned by the fully reinforced 225g/m² CSM laminate, the flexible polyester resin formulation that accommodates structural movement, and the seamless monolithic membrane that eliminates joint failure. The system is also over-coatable without grinding, meaning future maintenance and repair is straightforward without requiring a full re-application.
How Is Flexitec 2020 Applied?
Flexitec 2020 is a two-coat system applied over a prepared, primed substrate.
- Prepare the substrate - clean, dry, and structurally sound. Moisture content must not exceed 20% w.m.e. Repair all defects, treat any moss or fungal growth with fungicidal wash, and powerwash to remove residues.
- Prime where required - apply Flexitec Primer (or the appropriate specialist primer for the substrate) at 4–6m²/litre. Allow to cure for 30–60 minutes before overcoating. Do not leave primed surfaces uncoated for more than 7 days without re-priming.
- Tape all joints and details - all trim joints, upstands, outlets, penetrations, OSB square-edge board joints, and any dissimilar substrate junctions must be locally reinforced with Restec Taping Mat wetted into Flexitec Resin before the main application begins.
- Mix the first coat - add Powder Hardener at the correct rate for conditions (2% at 18-30°C; 3% at 11-17°C; 4% at 5 -10°C). Mix no more than 10kg at a time and test pot life before starting full application.
- Apply the first coat - apply approximately two-thirds of the calculated resin quantity by roller onto the surface. Roll out the 225g/m² fibreglass CSM, ensuring a 50mm overlap between strips with feathered edge over straight edge. Work the CSM fibres into the resin, then apply the remaining one-third over the top. Consolidate with the roller until the matting appears "swirly" with no straight fibres visible and a closed, pinhole-free surface is achieved. Allow 30-60 minutes before walking on.
- Apply the second coat - once the first coat is cured, apply unreinforced Flexitec Resin at a minimum of 0.5 litres/m² (0.7kg/m²) by roller, ensuring even and uniform thickness. Check for pinholes and rectify. The second coat must be applied within 7 days of the first; if more than 7 days have elapsed, clean the surface with acetone first.
Anti-slip finishes: For terraces, balconies, and walkways requiring a non-slip surface, Restec RESGRIP Anti-Slip Coating or broadcast aggregate can be applied over the completed system.
What Is the Powder Hardener and How Does It Work?
Powder Hardener is the catalyst that initiates the curing of the Flexitec resin. The addition rate is adjusted based on ambient temperature to control pot life and cure time - more hardener in cold conditions to accelerate curing, less in warm conditions to extend working time.
The standard addition rates for Flexitec Resin are as follows:
| Temperature | Hardener Rate |
|---|---|
| 18–30°C | 2% |
| 11–17°C | 3% |
| 5–10°C | 4% |
| 1–10°C (with Winter Accelerator) | 5% typical |
Never use less than 2.5% or more than 5% - outside this range, full cured properties will not be achieved. Hardener is measured in heaped scoops using the scoop provided: 2 scoops per litre at 2%; 3 scoops per litre at 3%; 4 scoops per litre at 4%. Do not catalyse more than 10kg of resin at a time.
For very cold conditions (1-10°C), Flexitec 2020 Winter Accelerator can be used to normalise pot life and curing. For hot summer conditions, Restec Summer Inhibitors are available to extend pot life and working time.
Can Flexitec 2020 Be Applied in Cold or Wet Weather?
Cold weather: The standard system can be applied in temperatures as low as 5°C for both air and deck temperature. With the addition of Flexitec Winter Accelerator, this drops to 1°C - making Flexitec one of the few GRP systems genuinely usable through a UK winter. Store resin at around 15°C for 24-48 hours before use on cold days to ensure optimum performance.
Rain resistance: Once the fibreglass CSM reinforcement has been fully consolidated with resin, the membrane is highly resistant to rainfall and will cure through even if it rains. This is a significant advantage over many competing systems. However, application must not begin in wet conditions or if rain is imminent, and the substrate must be dry before any product is applied.
Hot weather: Apply in temperatures up to 30°C. For best results, apply in cool overcast conditions and avoid direct sunlight where possible, as high temperatures shorten pot life. Summer Inhibitors are available to extend working time in hot conditions.
What Coverage Rates and Quantities Do I Need?
Coverage varies with substrate roughness and porosity. The following rates are for the standard two-coat 20-year system using 225g/m² fibreglass CSM. Always add a 10% wastage allowance to calculated quantities.
Flexitec Resin - first coat (reinforced):
| Substrate | 1st Coat Coverage |
|---|---|
| Asphalt (smooth) | 0.85 litres/m² (1.2 kg/m²) |
| Asphalt (medium) | 1.0 litres/m² (1.4 kg/m²) |
| Asphalt (rough/de-chipped) | 1.4 litres/m² (2.0 kg/m²) |
| Concrete / screed | 1.0 litres/m² (1.4 kg/m²) |
| Felt (sanded/smooth) | 0.85 litres/m² (1.2 kg/m²) |
| Felt (mineral) | 1.15 litres/m² (1.6 kg/m²) |
| GRP | 0.85 litres/m² (1.2 kg/m²) |
| OSB3 TG4 | 0.85 litres/m² (1.2 kg/m²) |
| PVC single-ply | 0.85 litres/m² (1.2 kg/m²) |
| Restec SA Carrier Layer | 0.85 litres/m² (1.2 kg/m²) |
Flexitec Resin — second coat (unreinforced): 0.5 litres/m² (0.7 kg/m²) across all surfaces.
Flexitec Primer: 4–6m²/litre depending on surface roughness.
As a rough guide for a 20-year system on smooth surfaces: 10m² requires approximately 19kg of resin; 20m² requires approximately 38kg; 50m² requires approximately 95kg.
What Are the Key Technical Properties?
Liquid resin properties:
| Property | Value |
|---|---|
| Viscosity at 25°C (6 RPM) | 6,200 MPas |
| Viscosity at 25°C (60 RPM) | 2,000 MPas |
| Thixotropic index | 3.1 |
| Gel time (25°C, 3.75% hardener) | 18 minutes |
| Specific gravity | 1.1 |
| Flash point | 32°C |
| Shelf life (unopened, stored below 25°C) | 12 months from delivery |
Cured resin properties:
| Property | Test Method | Unreinforced | Reinforced (1×225g/m² CSM) |
|---|---|---|---|
| Tensile strength | ISO 527 | 5 MPa | 27 MPa |
| Tensile modulus | ISO 527 | 22 MPa | 1,370 MPa |
| Elongation at break | ISO 527 | 22% | 2% |
| Shore D hardness | ASTM D2240 | 40 | 60 |
What Certifications Does Flexitec 2020 Hold?
- ETA-24/0069 - European Technical Assessment certifying essential performance characteristics
- BRoof(T4) - the highest fire classification for external flat roofing under UK regulations; also achieves BS 476-3 F.AA rating
- ISO 9001 - quality management standard
- ISO 14001 - environmental management standard
- 20 Year Materials Guarantee - available for installations by trained Restec-approved contractors
For full compliance, installations should conform to BS6229 (Code of Practice for flat roofs with continuously supported coverings) and BS5250 (Control of Condensation in Buildings). Local Authority Building Control should be consulted where required.
What Project Types Is Flexitec 2020 Suitable For?
Flexitec 2020 is suitable across a wide range of domestic and commercial roofing applications.
- Flat roof overlay refurbishment -over felt, asphalt, concrete, GRP, PVC single-ply, and existing liquid coatings without stripping back to the deck (where substrate is sound and dry)
- New OSB3 TG4 timber deck roofs - new-build or replacement decks, with or without Restec SA Carrier Layer
- Warm roof build-ups - over tissue-faced PIR insulation using the Restec SA Carrier Layer system
- Cold roof designs - in compliance with BS6229:2018, though warm roof designs are recommended wherever possible
- Balconies, terraces, and walkways - with RESGRIP or broadcast aggregate anti-slip finish
- Dormers and pitched roof abutments - using flat sheet trims and appropriate detailing
- Complex roof details - upstands, penetrations, outlets, rooflights, and irregular geometries, using Restec Taping Mat for local reinforcement
Note: Flexitec 2020 is not for consumer use and should only be installed by trained professionals. For large roofs (over 50m² or in excess of 10m in length) on new timber decks, expansion trims or the Restec SA Carrier Layer will be required.
Ready to order Flexitec 2020 for your next project? You can buy Restec Flexitec 2020 Multi-Surface GRP Resin here at All Flat Roofing Supplies, available in 10kg and 20kg drums in dark grey or light grey.
