Description
For UK projects where wall U-value needs to drop without committing to full main-wall thickness, EPS Grafit 50 mm delivers R 1.60 m²K/W at λD 0.031 W/mK as the first standalone primary-insulation thickness in the Genderka EPS 031 Fasada Extra Plus range — 12 boards per pack covering 6 m² of parapet, secondary-overlay, and depth-constrained façade work.
What EPS Grafit 50 mm Does in a UK EWI System
EPS Grafit 50 mm is a graphite-enhanced polystyrene primary-insulation board certified to EN 13163, delivering R 1.60 m²K/W at λD 0.031 W/mK in a 1000 × 500 mm panel that marks the transition from junction-detailing to standalone wall insulation within a UK external wall insulation build-up. On a typical 215 mm solid brick wall, 50 mm of graphite EPS brings the assembly U-value down to roughly 0.48 to 0.52 W/m²K — a reduction of more than 75 percent on the original U-value, falling short of the 0.30 W/m²K Approved Document L retrofit target on its own but delivering most of the gain on parapets, secondary overlays, and depth-constrained zones where thicker boards cannot fit. The board belongs to the wider graphite EPS insulation range, which covers every façade zone from reveal strips through to Passive House main-wall thicknesses.
The role is specific. Specify 50 mm where boundary proximity, planning conditions, or existing architectural features restrict total build-up depth, or as a secondary overlay over partial cavity insulation that no longer performs. On those projects the board delivers a measurable EPC shift — typically band E into band D or band D towards band C — while keeping the elevation projection inside the constraints that ruled out a thicker primary specification.
Why Specifiers Choose EPS Grafit 50 mm for UK Depth-Constrained Walls
- R 1.60 m²K/W in a 50 mm profile: over one and a half units of thermal resistance — the first thickness in the range that carries genuine standalone main-wall duty rather than detailing or composite roles, and a clean step up from the 30 mm board's R 0.95 m²K/W.
- Twelve boards per pack, 6 m² of targeted coverage: one pack matches a typical parapet run, a gable triangle, or one storey of a narrow flank wall — practical procurement for the zones where 50 mm earns its place rather than for whole-elevation main-wall work.
- Identical mechanical spec across the range: CS70, BS100, and TR100 carry over from every Grafit thickness, so the adhesive bed pattern and 6 to 8 fixings per m² used on the main wall transfer directly to the 50 mm zone with no schedule change.
- Heating-energy saving of 3,000 to 4,500 kWh per year: on a three-bedroom semi-detached with roughly 80 m² of exposed wall area treated at 50 mm, the reduction in fabric heat loss translates to meaningful annual bills saved, subject to heating system efficiency and exposure zone.
- Lightweight handling on framed structures: at approximately 0.375 kg per board, the 50 mm panel imposes minimal dead load on timber-frame and steel-frame cladding rails, making it a practical thermal core for direct-applied façade systems.
- UK warehouse stock for next-working-day dispatch: the 50 mm thickness ships in the same consignment as detailing thicknesses and thicker primary boards, so parapet and secondary-layer material arrives with the rest of the EWI order.
- Full DoP traceability for compliance audits: each batch carries a factory-specific Declaration of Performance referencing Bydgoszcz, Ostrów Mazowiecka, Oświęcim, Brzeziny, or Wschowa — supporting Building Control sign-off and PAS 2035 retrofit audits.
Thermal Specifications — λ, R-Value, Reaction to Fire
| Property | Value |
|---|---|
| Declared Thermal Conductivity (λD) | 0.031 W/mK |
| Thermal Resistance (RD) at 50 mm | 1.60 m²K/W |
| Reaction to Fire (EN 13501-1) | Euroclass E |
| Classification String (EN 13163) | T1-L2-W2-Sb2-P5-BS100-DS(N)2-DS(70,-)2-TR100 |
| Equivalent White EPS Thickness | ≈ 62 mm at λ 0.038 W/mK |
| Solid Brick Wall U-Value (215 mm) | ≈ 0.48–0.52 W/m²K with 50 mm overlay |
R 1.60 m²K/W places the 50 mm board in genuine primary-insulation territory rather than junction-detailing territory, where the contribution flows through the assembly U-value rather than through the psi-value at a single junction. On a 215 mm solid brick wall the resulting U-value sits in the 0.48 to 0.52 W/m²K band — a substantial gain but short of the 0.30 W/m²K Approved Document L retrofit elemental target, which is why 50 mm reads as a parapet, secondary-overlay, and depth-constrained thickness rather than a default main-wall specification. The U-value calculation guide for wall insulation thickness covers how each insulation layer feeds into the dwelling fabric calculation.
Physical Specifications — Density, Mechanical Strength, Dimensions
| Property | Value |
|---|---|
| Manufacturer | Genderka Sp. z o.o. |
| Product Range | EPS 031 Fasada Extra Plus |
| Thickness | 50 mm |
| Board Dimensions | 1000 × 500 mm |
| Coverage per Board | 0.50 m² |
| Boards per Pack | 12 |
| Pack Coverage | 6.0 m² |
| Density | 15 kg/m³ |
| Compressive Strength (CS) | ≥ 70 kPa |
| Bending Strength (BS) | ≥ 100 kPa (BS100) |
| Tensile Strength (TR) | ≥ 100 kPa (TR100) |
| Dimensional Stability — Normal | ± 0.2 % (DS(N)2) |
| Dimensional Stability — 70 °C | ≤ 2 % (DS(70,-)2) |
| Colour | Steel grey (graphite) |
| Standard | EN 13163:2012+A1:2015 |
Where EPS Grafit 50 mm Performs Best — Parapets, Secondary Layers, Tight Geometry
The 50 mm board earns its place in four specific zones of a UK EWI build-up, all of them defined by the gap between detailing thicknesses and full main-wall primary insulation. Parapet and roof-edge upstands top the list: where the main wall insulation terminates at the roofline, the parapet itself becomes a continuous thermal bridge running the full length of the dwelling. Wrapping the parapet with 50 mm of graphite EPS brings that junction below the BR 443 default psi-values and protects the SAP improvement delivered by the main wall insulation below.
Secondary overlays come next. On properties with ageing or incomplete cavity-wall insulation that still underperforms, a continuous external 50 mm graphite EPS layer eliminates residual cold bridges between existing cavity batts and creates a uniform thermal envelope across the entire façade. The composite assembly — partial cavity plus external 50 mm — can reach U-values in the 0.18 to 0.25 W/m²K band on the right substrate, bringing the wall within or close to current compliance thresholds without the depth of a full external retrofit.
- Parapet and upstand wrapping: closing the thermal bridge at the roof edge where main wall insulation terminates.
- Secondary overlay on partial cavity fill: eliminating residual bridges between existing cavity batts on a continuous external layer.
- Depth-constrained primary insulation: standalone main-wall duty where boundary proximity, planning conditions, or architectural features rule out thicker boards.
- Lightweight timber-frame and steel-frame cladding: thermal core for rendered rain-screen and direct-applied façade systems on new-build framed construction.
How EPS Grafit 50 mm Fits Into a Full EWI System
Within the layered build-up, the 50 mm board installs as a primary insulation layer either on bare substrate or laminated over existing wall finishes. Apply adhesive from the EPS adhesives and basecoats range using the circumferential-and-spot method — at 50 mm and above, this pattern is the standard adhesive route, aiming for at least 40 percent contact area between adhesive and substrate to satisfy wind-load design under BS EN 1991-1-4. Press the board firmly onto the prepared wall surface in a running-bond pattern, offsetting vertical joints by at least 200 mm row to row with tight butt joints and no gaps exceeding 2 mm.
After a minimum 24 hours of adhesive cure, secure each board with 6 to 8 mechanical fixings per m² from the fixing accessories range. The matching plug at this thickness is the LTX 90 mm polystyrene fixing plug, which delivers 25 to 30 mm of embedment beyond the board and adhesive layer into standard masonry. Once fixed, rasp the outer face to create a basecoat key, then embed alkali-resistant fibreglass mesh in fresh basecoat. The full layer-by-layer sequence is covered in the complete EWI system build-up and layers explained guide, and the wind-load fixing pattern is detailed in the insulation board fixing pattern and spacing guide.
How EPS Grafit 50 mm Compares to Sibling Thicknesses
| Property | 30 mm Grafit | 50 mm (this board) | 80 mm Grafit |
|---|---|---|---|
| Thickness | 30 mm | 50 mm | 80 mm |
| λD | 0.031 W/mK | 0.031 W/mK | 0.031 W/mK |
| RD | 0.95 m²K/W | 1.60 m²K/W | 2.55 m²K/W |
| Boards per Pack | 20 | 12 | 7 |
| Pack Coverage | 10.0 m² | 6.0 m² | 3.5 m² |
| Solid-Brick U-Value | ~ 0.65 W/m²K | ~ 0.50 W/m²K | ~ 0.34 W/m²K |
| Typical Use | Lintel, soffit, composite top-up | Parapet, secondary overlay, depth-constrained primary | Standard domestic retrofit main wall |
The three thicknesses bracket the transition from cost-effective entry through to mainstream retrofit specification. The 30 mm board sits clearly in junction and composite-layer territory; the 80 mm board is the volume domestic retrofit thickness for the main wall on most semi-detached UK stock. The 50 mm board is the bridge between them — a genuine primary thickness that earns its place specifically where the geometry rules out 80 mm and above.
How EPS Grafit 50 mm Performs in UK Weather — Moisture, Frost, Wind
The board's W2 water absorption classification and DS(70,-)2 dimensional stability hold declared performance through UK seasonal cycling. The closed-cell graphite EPS matrix absorbs negligible bulk moisture; the BS100 bending strength accommodates thermal movement between summer surface temperatures and winter night-time lows without cracking at the joint with adjacent boards or at the base track. At 50 mm the board carries enough mass to remain stable on the wall during the 24-hour adhesive cure window, reducing the propping discipline needed on thinner detailing boards.
Wind-load performance becomes a real design consideration at this thickness. On exposed elevations in BS EN 1991-1-4 wind zones 4 and 5, the 6 to 8 fixings per m² density may step up to 9 to 11 fixings per m² in corner and edge zones — the system designer's wind-load calculation sets the exact pattern. The TR100 tensile strength of the board itself comfortably accommodates the resulting uplift loads.
Pro Tips From UK Installers Using EPS Grafit 50 mm
Five habits separate a tight, callback-free 50 mm install from one that develops adhesion issues at the second-year inspection. None of them appear on the technical data sheet, and all of them come from the way experienced UK applicators handle the first true primary-thickness board in the range.
- Dry-stack the base course before adhesive: set the first row of 50 mm boards on the base track without bonding, check for level and continuous bearing, then commit to adhesive working upward in a running-bond pattern. Saves repositioning freshly bonded boards.
- Rasp the bonding face lightly: the factory skin on graphite EPS is smoother than white EPS. A quick mechanical key with an EPS rasp lifts the adhesive contact area cleanly above the 40 percent minimum without chasing it with extra mortar.
- Fine-tooth handsaw for clean edges: at 50 mm a fine-tooth saw produces a cleaner edge in one pass than a Stanley knife, which needs a second scoring pass at this depth and tends to leave a ragged face that compromises butt-joint adhesion.
- Plug pattern follows board joints first: position the first fixing at the cross-joint between four boards, then the field-area fixings in the running-bond rhythm. Concentrating plugs at joints carries the wind-load uplift more efficiently than even-spaced field patterns.
- Stagger the parapet wrap from the wall course: when wrapping a parapet with 50 mm, offset the parapet board joints from the main-wall board joints by at least 250 mm. Continuous joints at the roof-edge corner are the single most common cracking initiation point on parapet installations.
Handling and Storage on Site
The 50 mm board feels noticeably more rigid than the thinner detailing variants, so packs stack neatly without distortion and lift cleanly from pallet to platform. Keep packs flat on a level surface and under opaque sheeting, both to prevent UV softening of the graphite finish and to keep boards at ambient temperature for predictable adhesive open-time. Lift packs by the strapping or by supporting the long edges rather than the short ends to avoid creasing the outer boards in transit. A fine-tooth handsaw remains the cleanest cutting tool at this thickness; a hot-wire cutter works for repetitive panel runs when fed at a steady rate.
Certifications and Compliance — EN 13163, Euroclass E, BS EN 1991-1-4
- EN 13163:2012+A1:2015: the harmonised European standard for factory-made expanded polystyrene in buildings, covering declared thermal conductivity, dimensional tolerances, mechanical strength, and water absorption.
- Reaction to Fire — Euroclass E: typically suitable for use within EWI systems on residential buildings below 18 metres, where the project fire strategy permits Euroclass E with approved fire-barrier detailing under current Approved Document B guidance.
- CE Marking and Declaration of Performance: each production batch carries a DoP referencing the specific Genderka factory of origin (Bydgoszcz, Ostrów Mazowiecka, Oświęcim, Brzeziny, or Wschowa), supporting full traceability for Building Control inspections and PAS 2035 retrofit audits.
- Wind-Load Design Under BS EN 1991-1-4: the 6 to 8 fixings per m² baseline density is set by the project wind-load calculation, with higher densities applied at corner and edge zones in exposed locations under current UK practice.
Is EPS Grafit 50 mm Right for Your Project?
- Specify EPS Grafit 50 mm for parapet wrapping and roof-edge upstands where the main wall insulation needs a continuous extension over the parapet to close the thermal bridge at the roofline.
- Use as a secondary overlay over partial cavity insulation where the existing assembly underperforms and a continuous 50 mm external layer eliminates residual cold bridges between cavity batts.
- Drop to the 30 mm Grafit board for lintel, soffit, and composite top-up duty where depth is constrained below 50 mm and standalone primary-layer performance is not required.
- Step up to the 80 mm Grafit board for standard domestic retrofit on the main wall area — the UK's most popular thickness for solid-wall and cavity over-cladding projects, with U-value performance in the 0.34 to 0.37 W/m²K band on standard brickwork.
- Switch to mineral wool slabs where the project fire strategy requires non-combustible A1-rated insulation across the whole build-up, typically on residential buildings above 18 metres.
- Confirm thickness against the dwelling target using the Future Homes Standard 2026 insulation requirements guide for new-build work and Approved Document L for retrofit programmes.
Declared thermal values (λD, RD) are stated per EN 13163 and the Genderka manufacturer technical data sheet. Actual installed U-values depend on wall construction, adhesive coverage, fixing thermal bridging, and the complete EWI system build-up. Verify system-level U-value calculations with a competent energy assessor or Building Control before specification.
What to Order Next — Pack Sizes, Lead Times, Compatible Components
One pack of 12 boards covers 6 m² of parapet, secondary-overlay, or targeted primary insulation — typically one to two packs match a parapet run or single elevation zone on a semi-detached property. Pair the order with the matching adhesive from the EPS adhesives and basecoats range and the LTX 90 mm fixing plug for mechanical retention on standard masonry substrates. UK warehouse stock supports next-working-day dispatch on full-pack quantities ordered before midday, so the 50 mm material arrives with the rest of the EWI consignment rather than as a separate delivery.
FAQ — EPS Grafit 50 mm Coverage, Compatibility, Installation
How many 50 mm boards are in a pack, and what area does one pack cover?
Each pack contains 12 boards, each measuring 1000 × 500 mm, giving a total pack coverage of 6.0 m². For a typical parapet run (8 to 12 linear metres at 300 to 600 mm height) on a semi-detached property, one to two packs provide full coverage with a 5 to 10 percent allowance for cutting waste around corners, services, and non-standard geometries.
Which fixing plug length matches the 50 mm board?
The LTX 90 mm polystyrene fixing plug is the correct match for a 50 mm board on standard masonry substrates, providing approximately 25 to 30 mm of embedment beyond the board thickness and adhesive layer — within the minimum embedment band most UK wind-load calculations work to. Install 6 to 8 fixings per m² in the pattern set by the project wind-load zone, positioning fixings at board cross-joints first and then in the field area for even load distribution.
Can the 50 mm board meet Part L wall U-value targets on its own?
On a standard 215 mm solid brick wall, 50 mm of graphite EPS brings the assembly U-value to approximately 0.48 to 0.52 W/m²K. The current Approved Document L elemental target for retrofit walls is 0.30 W/m²K where technically feasible, so 50 mm alone does not meet the target on most solid-wall constructions. The 50 mm board performs at its best as a parapet layer, secondary overlay, or depth-constrained primary specification — for full Part L compliance on the main wall area, thicknesses of 80 mm and above deliver the R-values needed to meet the target on typical UK masonry substrates.
How does the 50 mm board work as a secondary overlay on existing cavity insulation?
On properties with ageing or incomplete cavity-wall insulation, an external 50 mm graphite EPS overlay eliminates residual cold bridges between existing cavity batts and creates a continuous insulated envelope. The composite U-value depends on the existing cavity assembly: a partially insulated cavity at around 0.55 W/m²K combined with external 50 mm can approach the 0.18 to 0.25 W/m²K band, bringing the wall within or close to current compliance thresholds without the depth of a full external retrofit.
How does the 50 mm compare to the 30 mm and 80 mm Grafit variants?
All three share λD 0.031 W/mK and identical mechanical properties (CS70, BS100, TR100). The difference is R-value and the application band: the 30 mm variant gives R 0.95 m²K/W at 20 boards per pack as the cost-effective entry thickness for lintels and composite top-ups, 50 mm gives R 1.60 m²K/W at 12 boards per pack as the first standalone primary thickness for parapets and depth-constrained zones, and the 80 mm variant reaches R 2.55 m²K/W at 7 boards per pack as the UK's volume domestic retrofit specification for main-wall work.
Is the 50 mm board suitable for timber-frame and steel-frame cladding systems?
At approximately 0.375 kg per board the 50 mm panel imposes minimal dead load on lightweight structural frames, making it a practical thermal core for rendered rain-screen and direct-applied façade systems on new-build framed construction. Detailing must allow for vapour-open performance of the wall assembly behind the insulation — confirm the breather-membrane and airtightness layer specification with the system designer before bonding boards to a framed substrate.
What fire classification rules apply when specifying 50 mm graphite EPS in the UK?
The board carries a Euroclass E reaction-to-fire classification under EN 13501-1 and is typically suitable for residential buildings below 18 metres, where the project fire strategy permits Euroclass E with approved fire-barrier detailing in accordance with current Approved Document B guidance. For taller buildings or higher-risk façades where the fire strategy requires non-combustible A1-rated insulation, mineral wool replaces EPS across the build-up. Confirm classification with the designer and Building Control at design stage to avoid substitutions on site.
Technical Documentation — EPS Grafit 50 mm TDS, DoP, Certificates