POLYSTYRENE EPS GRAFIT 90mm

For UK solid-wall retrofit projects targeting the 0.30 W/m²K Approved Document L threshold without stepping into 100 mm depth, EPS Grafit 90 mm delivers R 2.90 m²K/W at λD 0.031 W/mK — the solid-wall target thickness in the Genderka EPS 031 Fasada Extra Plus range, supplied at 6 boards per pack covering 3 m² for surveyed-elevation procurement.

What EPS Grafit 90 mm Does in a UK EWI System

EPS Grafit 90 mm is a graphite-enhanced polystyrene primary-insulation board certified to EN 13163, delivering R 2.90 m²K/W at λD 0.031 W/mK in a 1000 × 500 mm panel sized as the solid-wall target thickness for UK domestic retrofit programmes. On a typical 215 mm solid brick wall (original U-value around 2.1 W/m²K), 90 mm of graphite EPS brings the assembly to roughly 0.31 to 0.33 W/m²K — within touching distance of the 0.30 W/m²K Approved Document L retrofit elemental target, close enough for most Building Control officers to sign off as compliant under the "technically feasible" provision. 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 precise. Specify 90 mm when the 80 mm result sits too marginally above the compliance line for the project's documentation requirements, but the 100 mm depth would force secondary modifications to reveals, soffits, or rainwater goods that the budget cannot absorb. That balance — extra thermal margin, manageable façade projection — is what earns 90 mm its place as the solid-wall target thickness on grant-funded retrofit schemes.

Why Specifiers Choose EPS Grafit 90 mm for UK Solid Walls

• R 2.90 m²K/W in a 90 mm profile: the additional 0.35 m²K/W over the 80 mm board pulls a typical 215 mm solid brick assembly from roughly 0.35 W/m²K down to 0.31 to 0.33 W/m²K — close enough to the Approved Document L 0.30 W/m²K threshold for sign-off under the "technically feasible" provision.
• Six boards per pack, 3 m² coverage: a precise ordering unit that matches a storey-height strip approximately 1.5 m wide — the right granularity for surveyed-elevation procurement on semi-detached and terraced retrofit work.
• Annual heating energy saving of 5,000 to 6,500 kWh: on a three-bedroom semi-detached with roughly 80 m² of treated wall area, the 84 percent heat-flow reduction translates to meaningful annual bill savings, subject to heating system efficiency and exposure zone.
• Identical mechanical spec across the range: CS70, BS100, and TR100 carry across every Grafit thickness, so the running-bond pattern and 6 to 8 fixings per m² used on adjacent thicknesses transfer directly to the 90 mm layer with no schedule change.
• Preserves most existing window-reveal details: the total 105 to 110 mm system build-up (insulation plus basecoat and render) keeps within tolerance for many standard UK window reveals, avoiding the oversill replacement work that often follows a step up to 100 mm or above.
• Light single-handed handling at scaffold height: at approximately 0.675 kg per board, the 90 mm panel positions cleanly on standard scaffold without hoisting equipment — practical for two-person retrofit crews working at storey-height.
• UK warehouse stock for next-working-day dispatch: the solid-wall target thickness ships in the same consignment as detailing and parapet boards, so main-wall material arrives with the rest of the EWI order rather than as a separate back-order.

Thermal Specifications — λ, R-Value, Reaction to Fire

Property	Value
Declared Thermal Conductivity (λD)	0.031 W/mK
Thermal Resistance (RD) at 90 mm	2.90 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	≈ 113 mm at λ 0.038 W/mK
Solid Brick Wall U-Value (215 mm)	≈ 0.31–0.33 W/m²K with 90 mm overlay

R 2.90 m²K/W places the 90 mm board at the solid-wall compliance target — the thickness where typical 215 mm brickwork comes within touching distance of the 0.30 W/m²K Approved Document L retrofit threshold. On well-pointed standard brickwork at 0.77 W/mK substrate conductivity, the resulting assembly sits in the 0.31 to 0.33 W/m²K band; on better-conducting brickwork or with composite contributions from existing internal finishes, the result can drop to 0.30 W/m²K or below. The U-value calculation guide for wall insulation thickness covers how substrate conductivity feeds into the assembly U-value calculation.

Physical Specifications — Density, Mechanical Strength, Dimensions

Property	Value
Manufacturer	Genderka Sp. z o.o.
Product Range	EPS 031 Fasada Extra Plus
Thickness	90 mm
Board Dimensions	1000 × 500 mm
Coverage per Board	0.50 m²
Boards per Pack	6
Pack Coverage	3.0 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 90 mm Performs Best — Solid Wall, Stone, Grant-Funded Retrofit

The 90 mm board earns its place in four specific scenarios across UK domestic retrofit work. Solid-wall masonry stock from pre-1919 through to 1970s sits at the top of the list: uninsulated 215 mm solid brick walls with original U-values in the 1.6 to 2.1 W/m²K band consistently reach the 0.31 to 0.33 W/m²K assembly band with 90 mm of graphite EPS — close enough to the Approved Document L threshold for compliance acceptance on the majority of retrofit programmes.

Stone-wall properties come next. Random-rubble and dressed-stone walls of 300 to 600 mm thickness with original U-values around 1.3 to 1.6 W/m²K typically reach 0.27 to 0.32 W/m²K with 90 mm of graphite EPS — actually achieving or closely approaching Part L compliance on most stone constructions, since the thicker substrate already contributes to the assembly resistance.

• Solid-wall domestic retrofit (pre-1919 to 1970s): the primary use case — 215 mm brick brought close to 0.30 W/m²K and accepted under the "technically feasible" provision on grant-funded schemes.
• Stone-wall properties: 300 to 600 mm random-rubble and dressed-stone walls reaching or exceeding Part L compliance with 90 mm graphite EPS.
• Cavity-wall over-cladding with definitive compliance: failed or partial cavity assemblies brought comfortably within the 0.30 W/m²K threshold by a continuous external 90 mm layer.
• Parapet and gable-end wrapping on mid-terrace stock: targeted over-insulation at heat-loss hotspots where 90 mm carries enough depth to close thermal bridges while remaining within facade-projection limits.

How EPS Grafit 90 mm Fits Into a Full EWI System

Within the layered build-up, the 90 mm board forms the primary thermal layer between substrate and basecoat. Apply adhesive from the EPS adhesives and basecoats range using the circumferential-and-spot method — at this thickness, aim for at least 40 percent contact area between adhesive and substrate to satisfy wind-load design under BS EN 1991-1-4. Press onto the prepared wall 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. The board retains enough mass to remain stable on the wall during the 24-hour adhesive cure window without propping.

After 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 120 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; the wind-load fixing pattern is detailed in the insulation board fixing pattern and spacing guide.

How EPS Grafit 90 mm Compares to Sibling Thicknesses

Property	80 mm Grafit	90 mm (this board)	100 mm Grafit
Thickness	80 mm	90 mm	100 mm
λD	0.031 W/mK	0.031 W/mK	0.031 W/mK
RD	2.55 m²K/W	2.90 m²K/W	3.20 m²K/W
Solid-Brick U-Value	~ 0.33–0.35 W/m²K	~ 0.31–0.33 W/m²K	~ 0.28–0.30 W/m²K
Boards per Pack	7	6	6
Pack Coverage	3.5 m²	3.0 m²	3.0 m²
Typical Use	Volume domestic retrofit	Solid-wall compliance target	Semi-detached standard spec, Part L pass

The three thicknesses bracket the transition from volume retrofit specification to definitive Part L pass. The 80 mm board sits as the practical default where reveal preservation matters; the 100 mm board crosses the 0.30 W/m²K line on most standard masonry. The 90 mm board occupies the compliance-target position — close enough to the threshold for sign-off under the "technically feasible" provision while keeping façade projection within reach of standard reveal details.

How EPS Grafit 90 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; BS100 bending strength accommodates thermal movement between summer surface temperatures and winter night-time lows without cracking at the joint between adjacent boards. At 90 mm the board carries sufficient mass to remain stable on the wall during the 24-hour adhesive cure window without propping, simplifying the installation sequence on whole-elevation work.

Wind-load design is a primary specification 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 baseline density steps up to 9 to 11 fixings per m² at corner and edge zones — the system designer's wind-load calculation sets the exact pattern for each elevation. The TR100 tensile strength of the board comfortably accommodates the resulting uplift loads in standard UK exposure.

Pro Tips From UK Installers Using EPS Grafit 90 mm

Five habits separate a tight, callback-free 90 mm install from one that drags on the Building Control sign-off. None of them appear on the technical data sheet, and all of them come from the way experienced UK applicators handle the solid-wall compliance-target thickness.

• Dry-stack the base course before adhesive: set the first row of 90 mm boards on the base track without bonding, check level and continuous bearing across the full base course, then commit to adhesive working upward in running-bond. Catches base-track alignment issues before they propagate up the elevation.
• Switch to a fine-tooth handsaw for bulk cutting: at 90 mm the Stanley knife needs multiple passes and tends to leave a ragged edge. A fine-tooth saw produces a clean square edge in one pass, maintaining the butt-joint adhesive contact that matters at this thickness.
• 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 40 percent without chasing it with extra mortar.
• 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 wind-load uplift more efficiently than even-spaced field patterns.
• Fully detail reveals, soffits, and lintels for Building Control: at the compliance-target thickness, the 90 mm main-wall result depends partly on having insulated junctions. Specifying 10 mm at reveals, 20 mm at lintels, and continuous wrapping at soffits supports the "technically feasible" compliance argument when the documented U-value falls in the 0.31 to 0.33 band.

Handling and Storage on Site

The 90 mm board feels solid and rigid in the hand, making it comfortable to carry and position single-handed without flex or droop. Stack 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 or a long-blade hot-wire cutter gives the cleanest edge at this thickness; the hot-wire cutter is the faster option for bulk panel runs when fed at a steady rate.

Certifications and Compliance — EN 13163, Euroclass E, Approved Document L

• 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.
• Part L Solid-Wall Target Contribution: at R 2.90 m²K/W, the 90 mm board forms part of a wall assembly that approaches or meets the 0.30 W/m²K retrofit U-value target set out in Approved Document L (2021 edition, England) on typical 215 mm solid brick constructions, subject to substrate conductivity and complete system build-up.

Is EPS Grafit 90 mm Right for Your Project?

• Specify EPS Grafit 90 mm for solid-wall retrofit targeting Approved Document L compliance on 215 mm brick or thicker stone walls, where the project documentation requires a result close to or at the 0.30 W/m²K threshold.
• Use on grant-funded retrofit schemes such as those supported under current Warm Homes Plan and PAS 2035 frameworks, where documented compliance and reveal-detail preservation both matter to the funding criteria.
• Drop to the 80 mm Grafit board where façade depth is tightly constrained and the 0.33 to 0.36 W/m²K result is acceptable under the "technically feasible" Part L provision.
• Step up to the 100 mm Grafit board for new-build work targeting the 0.26 W/m²K elemental wall U-value or for enhanced SAP ratings requiring documented headroom below 0.30 W/m²K.
• 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

Two boards per square metre at 0.50 m² coverage each — a three-bedroom semi-detached property with around 80 m² of exposed wall area typically requires 27 to 30 packs of 6 boards, including 5 to 10 percent cutting margin around reveals, soffits, and service penetrations. Pair the order with the matching adhesive from the EPS adhesives and basecoats range and the LTX 120 mm fixing plug for mechanical retention on standard masonry. UK warehouse stock supports next-working-day dispatch on full-pack quantities ordered before midday, so the solid-wall material arrives with the rest of the EWI consignment rather than as a separate delivery.

FAQ — EPS Grafit 90 mm Coverage, Compatibility, Installation

How many 90 mm boards do I need per square metre, and how many packs for a semi-detached house?

Each board covers 0.50 m², so 2 boards per m² of wall area are required. A three-bedroom semi-detached property with approximately 80 m² of exposed wall area (after deducting windows and doors) typically needs 27 to 30 packs of 6 boards, allowing 5 to 10 percent for cutting waste around reveals, soffits, and service penetrations. The technical desk can sense-check pack quantities against a surveyed elevation drawing before dispatch.

Does the 90 mm board meet Approved Document L on a 215 mm solid brick wall?

The 90 mm board brings a typical 215 mm solid brick wall to approximately 0.31 to 0.33 W/m²K, depending on substrate conductivity and the complete system build-up. The current Approved Document L retrofit elemental target is 0.30 W/m²K where technically feasible. On well-pointed standard brickwork the result sits marginally above the threshold, but the gap is small enough that most Building Control officers accept the specification as compliant under the "technically feasible" provision — particularly when reveals, soffits, and lintels are fully insulated. For projects requiring a documented pass below 0.30 W/m²K, stepping up to the 100 mm Grafit board closes the remaining margin on most substrates.

How does the 90 mm board perform on stone-wall properties?

Random-rubble and dressed-stone walls of 300 to 600 mm thickness typically have original U-values in the 1.3 to 1.6 W/m²K band — lower than 215 mm solid brick because of the substrate's own thermal contribution. Adding 90 mm of graphite EPS reaches approximately 0.27 to 0.32 W/m²K on most stone constructions, actually meeting or closely approaching the 0.30 W/m²K target depending on mortar conductivity and stone type. For listed and conservation-area properties, confirm planning consent before specifying external insulation on stone elevations.

Which fixing plug length matches the 90 mm board on standard masonry?

The LTX 120 mm polystyrene fixing plug is the correct match for a 90 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, with higher densities at corner and edge zones on exposed elevations.

How does the 90 mm compare to the 80 mm and 100 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 80 mm variant gives R 2.55 m²K/W at 7 boards per pack as the volume retrofit specification where reveal preservation matters, 90 mm gives R 2.90 m²K/W at 6 boards per pack as the solid-wall compliance-target thickness, and the 100 mm variant reaches R 3.20 m²K/W at 6 boards per pack as the standard semi-detached spec delivering documented pass below 0.30 W/m²K on most substrates.

Is the 90 mm board specified for grant-funded retrofit schemes?

The 90 mm graphite EPS thickness is commonly specified on Warm Homes Plan, ECO4, and related grant-funded retrofit programmes where the funding criteria require documented progress against the Approved Document L 0.30 W/m²K target on solid-wall properties. The 0.31 to 0.33 W/m²K result is typically accepted under the "technically feasible" provision, and stepping up to 100 mm where the geometry allows provides documented headroom for schemes that require an explicit numerical pass. Confirm the specific compliance criteria with the appointed PAS 2035 retrofit coordinator before specification.

What fire classification rules apply when specifying 90 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 90 mm TDS, DoP, Certificates

• Genderka EPS 031 Fasada Extra Plus — Declaration of Performance (Wschowa factory, PDF)
• Genderka EPS 031 Fasada Extra Plus — Manufacturer Product Page and Technical Data