Polystyrene EPS Grafit 100 mm — Graphite Insulation Board for Semi-Detached Houses, λ 0.031 W/mK

Genderka EPS 031 Fasada Extra Plus 100 mm is a graphite-enhanced expanded polystyrene insulation board delivering a declared thermal conductivity of λD 0.031 W/mK and thermal resistance of R 3.20 m²K/W — the standard specification for semi-detached house retrofit and the thickness at which typical UK masonry walls meet or exceed the 0.30 W/m²K Approved Document L retrofit U-value target. Each board measures 1000 × 500 mm and is supplied in packs of 6 boards covering 3.0 m², sized for efficient ordering against surveyed wall areas on domestic and light-commercial properties. Browse the full selection of graphite EPS insulation boards to match every zone of your façade build-up to the right thickness.

Certified to EN 13163:2012+A1:2015 with the classification string T1-L2-W2-Sb2-P5-BS100-DS(N)2-DS(70,-)2-TR100, this board shares the same graphite bead technology and mechanical properties as every variant in the Genderka EPS 031 Fasada Extra Plus family. At 100 mm the board crosses the compliance line — where 80 mm and 90 mm bring solid-wall assemblies close to the Part L retrofit target, 100 mm delivers a clear pass on most standard 215 mm brick constructions, achieving approximately 0.27–0.30 W/m²K depending on brick conductivity and mortar type. For context on how evolving UK energy standards influence insulation thickness choices across the building envelope, see the Future Homes Standard 2026 and its insulation requirements.

Key Benefits and Performance Advantages

Clear Part L Compliance on Standard Masonry

• R 3.20 m²K/W — The Compliance Thickness: On a typical 215 mm solid brick wall, 100 mm of graphite EPS brings the assembly U-value to approximately 0.27–0.30 W/m²K, clearing the Approved Document L retrofit target of 0.30 W/m²K and approaching the 0.26 W/m²K new-build elemental threshold. This is the thickness that gives Building Control sign-off confidence on the majority of semi-detached and terraced properties across England and Wales.
• Graphite-Enhanced λ 0.031 W/mK: Integrated graphite particles reflect infrared radiation within each cell, delivering approximately 20 % better insulation than standard white EPS of the same thickness. A 100 mm graphite board matches the thermal performance of roughly 125 mm of white EPS, saving 25 mm of build-up depth on every square metre of wall.

The Go-To Thickness for Semi-Detached Retrofit

• Addresses the UK's Largest Housing Type: Semi-detached properties make up approximately 26 % of England's housing stock. Most feature solid or unfilled cavity walls with original U-values of 1.6–2.1 W/m²K. Specifying 100 mm of graphite EPS provides a standardised, repeatable insulation specification that surveyors, energy assessors, and contractors can apply across entire streets and estates with confidence.
• Balanced Depth and Performance: At 100 mm the total system build-up (insulation + basecoat + render) reaches approximately 115–120 mm from the original wall face — deep enough to deliver compliance yet manageable enough to maintain window-reveal proportions and avoid extensive oversill or rainwater-goods modifications on most standard semi-detached façades.

Handles and Cuts Cleanly on Site

• Bending Strength BS100 (≥ 100 kPa): Each board resists flexing during handling and positioning at scaffold height, maintaining its shape when carried flat or leant temporarily against the wall face between adhesive application and mechanical fixing.
• Tensile Strength TR100 (≥ 100 kPa): Adhesive bonds securely to the graphite-EPS surface, providing a reliable hold that withstands wind-load deflection across all UK exposure zones when supplemented by mechanical fixings at the recommended density.

Compact Packs Matched to Domestic Wall Areas

• 6 Boards per Pack (3.0 m²): Each pack covers a storey-height strip approximately 1.5 m wide — a practical ordering unit that minimises surplus material on site. At 15 kg/m³ density each board weighs approximately 0.75 kg, keeping single-handed positioning straightforward on scaffold platforms without hoisting equipment.

Drops Straight Into Standard EWI Build-Ups

• Compatible With All Standard EWI Adhesives and Finishes: Bond this board using cement-based or polyurethane foam adhesives from the EPS adhesives and basecoats range, then complete with basecoat, mesh, and render following the same build-up sequence as other primary insulation thicknesses. Where the specification requires mechanical retention, pair with the appropriate fixing plug from the insulation fixing accessories range.

Technical Specifications

Physical Properties

Property	Value
Manufacturer	Genderka Sp. z o.o.
Product Range	EPS 031 Fasada Extra Plus
Thickness	100 mm
Board Dimensions	1000 mm × 500 mm
Coverage per Board	0.50 m²
Boards per Pack	6
Pack Coverage	3.0 m²
Density	15 kg/m³
Colour	Steel grey (graphite)
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)
Reaction to Fire	Class E (EN 13501-1)
Standard	EN 13163:2012+A1:2015

Thermal Performance

Property	Value
Declared Thermal Conductivity (λD)	0.031 W/mK
Thermal Resistance (RD) at 100 mm	3.20 m²K/W
Classification String	EPS EN 13163 T1-L2-W2-Sb2-P5-BS100-DS(N)2-DS(70,-)2-TR100

Best Use Scenarios

Ideal Applications

• Semi-Detached House Retrofit: The primary use case for this thickness. A standard semi-detached property with 215 mm solid brick walls achieves approximately 0.27–0.30 W/m²K when wrapped with 100 mm of graphite EPS — meeting or exceeding the Approved Document L retrofit target and providing a specification that energy assessors, local authority grant schemes, and Building Control officers recognise as a proven compliance pathway.
• Terraced and End-Terrace Properties: Mid-terrace homes with a single exposed elevation and end-terrace properties with two exposed elevations both benefit from 100 mm as a standardised primary thickness, simplifying material ordering and installation sequencing across multi-property retrofit programmes.
• Cavity-Wall Over-Cladding for Full Compliance: Properties with failed or partial cavity fill that need a definitive pass below 0.30 W/m²K benefit from 100 mm of external graphite EPS, which creates a continuous high-performance envelope independent of the cavity condition and delivers compliance headroom on virtually all UK masonry wall types.
• Local Authority and Social Housing Programmes: The 100 mm specification aligns with the insulation thickness commonly adopted in Warm Homes Plan, ECO4, and social housing retrofit programmes, where a standardised, auditable, and Building-Control-compliant thickness simplifies procurement, surveying, and post-installation inspection across large property portfolios.

When an Alternative Fits Better

• Depth-Constrained Façades: Where window reveals, rainwater goods, or boundary proximity limit total build-up, the 90 mm Grafit board at R 2.90 m²K/W achieves near-compliance within a slimmer 90 mm profile — accepted by many Building Control officers under the "technically feasible" provision.
• Deep Renovation or Passive House Targets: For projects targeting U-values well below 0.26 W/m²K or aiming for Passive House certification, the 150 mm Grafit board at R 4.80 m²K/W provides the additional thermal resistance needed to reach these enhanced performance thresholds on standard masonry constructions.
• High-Rise or Non-Combustible Requirements: Where Euroclass A1 fire rating is mandated, the mineral wool insulation range provides non-combustible slabs compliant with Building Safety Act façade requirements for buildings above 18 metres.

System Integration

The 100 mm graphite EPS board forms the thermal core of a standard EWI build-up on semi-detached, terraced, and cavity over-cladding projects. Apply adhesive from the adhesives and basecoats collection to the back face using the circumferential-and-spot method — aim for a minimum 40 % contact area between the adhesive and the substrate to satisfy wind-load design requirements under BS EN 1991-1-4. Press firmly onto the prepared wall surface in a running-bond pattern, offsetting vertical joints by at least 200 mm from row to row and ensuring tight butt joints with no gaps exceeding 2 mm.

After a minimum of 24 hours' adhesive curing, secure each board with 6–8 mechanical fixings per m² from the fixing accessories range. The matching plug for this thickness is the LTX 140 mm polystyrene fixing plug, which provides the correct embedment depth into standard masonry substrates for a 100 mm board with adhesive layer. Once fixed, rasp or sand the outer face to create an adhesion key, then apply the reinforcing basecoat with embedded Atlas 150 g/m² fibreglass mesh for long-term crack resistance. The complete layer-by-layer build-up sequence — from substrate preparation through to the decorative render finish — is detailed in the EWI system build-up layers guide.

Comparison Table — Genderka EPS Grafit Range

Property	90 mm Grafit	100 mm Grafit (This Board)	150 mm Grafit
Thickness	90 mm	100 mm	150 mm
λD	0.031 W/mK	0.031 W/mK	0.031 W/mK
RD	2.90 m²K/W	3.20 m²K/W	4.80 m²K/W
Approx. Wall U-Value (215 mm solid brick)	0.31–0.33 W/m²K	0.27–0.30 W/m²K	0.19–0.21 W/m²K
Pack Coverage	3.0 m²	3.0 m²	2.0 m²
Boards per Pack	6	6	4
Typical Use	Solid wall target thickness	Semi-detached standard spec	Part L 2025 compliance target

UK Climate Performance Context

On a typical UK semi-detached property with 215 mm solid brick walls (original U-value around 2.1 W/m²K), adding 100 mm of graphite EPS with λ 0.031 W/mK reduces the wall U-value to approximately 0.27–0.30 W/m²K — a reduction of over 85 % in heat flow through the wall and a clear pass against the Approved Document L retrofit target of 0.30 W/m²K. For a three-bedroom semi-detached home with roughly 80 m² of exposed wall area, this translates to an estimated annual heating energy saving of 5,500–7,000 kWh, depending on heating system efficiency and exposure zone. In SAP calculations, this improvement can shift the property from EPC band D or E into band C or upper C, supporting grant eligibility thresholds, mortgage green-deal products, and resale value. The 100 mm thickness is widely recognised across the UK retrofit industry as the standard semi-detached specification — a proven depth that balances compliance, cost, and practical build-up limits on the country's most common housing type.

Trade Insight: Handling and Storage

At 100 mm the boards are solid, rigid, and comfortable to carry single-handed — the thickness that most installers consider the ideal balance between rigidity and weight. Store packs flat on a level surface and under opaque sheeting; the steel-grey graphite surface absorbs solar radiation quickly, and even a few hours of direct summer sun can soften the outer bead layer, weakening the adhesion key for basecoat application. When cutting boards to size, a fine-tooth handsaw gives the cleanest edge; a hot-wire cutter works well for batch-cutting consistent widths around reveals and soffits. For best adhesive coverage, rasp the bonding face lightly before application — the factory skin on graphite EPS is smoother than white EPS and benefits from mechanical keying to achieve the target 40 % contact area. One practical tip for multi-property programmes: set up a cutting station at ground level with a jig for the most common reveal and soffit widths, and pre-cut the entire allocation for each property before starting the fix. This speeds up scaffold work significantly across repetitive semi-detached elevations and reduces on-platform waste.

Certifications and Compliance

• EN 13163:2012+A1:2015: Harmonised European standard for factory-made expanded polystyrene products used in buildings, covering declared thermal conductivity, dimensional tolerances, and mechanical strength properties.
• Reaction to Fire — Euroclass E: Suitable for use within EWI systems on buildings up to 18 m in height when combined with approved fire-barrier detailing at each floor level, in accordance with Approved Document B and Building Safety Act guidance.
• CE Marking and DoP: Each production batch carries a Declaration of Performance referencing the specific Genderka factory of origin (Bydgoszcz, Ostrów Mazowiecka, Oświęcim, Brzeziny, or Wschowa), supporting full traceability for Building Control inspections.
• Part L Compliance: At R 3.20 m²K/W, the 100 mm board forms part of a wall assembly that meets the 0.30 W/m²K retrofit U-value target and approaches the 0.26 W/m²K new-build elemental target set out in Approved Document L (2021 edition, England) on typical 215 mm solid brick constructions.

Technical Disclaimer

All thermal values stated are declared (λD, RD) per EN 13163 and manufacturer technical data sheet (Genderka karta techniczna nr W31FEP, July 2024). Actual installed U-values depend on wall construction, adhesive coverage, fixing thermal bridging, and the complete EWI system build-up. Always verify system-level U-value calculations with a competent energy assessor or building control body before specifying. Specifications are subject to manufacturer update; confirm current data at point of order.

Summary

The Genderka EPS Grafit 100 mm board delivers λ 0.031 W/mK and R 3.20 m²K/W — the standard semi-detached specification that brings typical UK masonry walls to approximately 0.27–0.30 W/m²K, clearing the Approved Document L retrofit target with confidence. Each pack of 6 boards covers 3.0 m², sized for efficient ordering against surveyed elevations on domestic and multi-property programmes. Where façade depth is constrained, the 90 mm Grafit board delivers R 2.90 m²K/W within a slimmer profile. For deep renovation or Passive House targets, the 150 mm Grafit board steps up to R 4.80 m²K/W — delivering U-values of 0.19–0.21 W/m²K on standard masonry constructions.

Frequently Asked Questions

How many 100 mm boards are in a pack, and how many packs do I need for a typical semi-detached house?

Each pack contains 6 boards covering 3.0 m². A three-bedroom semi-detached property with approximately 80 m² of exposed wall area (after deducting windows and doors) requires roughly 27–30 packs, including 5–10 % for cutting waste around reveals, soffits, and service penetrations. Ordering against a measured survey ensures accurate quantities and minimises surplus material on site.

What is the environmental benefit of upgrading a semi-detached house with 100 mm of graphite EPS?

Graphite EPS is fully recyclable through specialist polystyrene recovery programmes, and off-cuts generated on site can be returned for granulation and re-expansion into new products. The primary environmental benefit is operational: reducing the wall U-value from approximately 2.1 W/m²K to 0.27–0.30 W/m²K cuts annual heating energy demand by an estimated 5,500–7,000 kWh on a typical semi-detached property. Over a 25-year installed lifespan, this translates to a substantial cumulative CO₂ reduction — with the embodied energy of manufacture typically paid back within the first two heating seasons.

Does the 100 mm board achieve Part L compliance on a standard 215 mm solid brick wall?

On a typical 215 mm solid brick wall with standard conductivity (0.77 W/mK), 100 mm of graphite EPS brings the assembly U-value to approximately 0.27–0.30 W/m²K. The Approved Document L retrofit target is 0.30 W/m²K where technically feasible, and the new-build elemental target is 0.26 W/m²K. In practice, the 100 mm board delivers a clear pass against the retrofit target on most standard masonry constructions and comes within reach of the new-build threshold — particularly when the specification includes fully insulated reveals, soffits, and lintels that improve the overall psi-values at junctions.

What fixing plug length pairs with the 100 mm board on standard masonry?

The LTX 140 mm polystyrene fixing plug is the correct match for a 100 mm board on standard masonry substrates, providing approximately 30–40 mm of embedment beyond the board thickness and adhesive layer. Install 6–8 fixings per m² in the pattern recommended for the project's wind-load zone, positioning fixings at board junctions and in the field area for even load distribution across the façade.