Description
Polystyrene EPS Grafit 90mm is the graphite façade board Renders World keeps for solid-wall work where 80mm leaves too little thermal margin and 100mm starts to crowd the window reveals. The declared figure to specify against is a thermal resistance of 2.80 m²K/W at this thickness.
What the 90mm Graphite Board Does in a Rendered Wall
Polystyrene EPS Grafit 90mm installs as the thermal layer of a rendered external wall, declared to EN 13163:2012+A1:2015 at a thermal resistance of 2.80 m²K/W, which is the figure a U-value calculation takes. The board belongs to the graphite EPS insulation boards range held by Renders World, where the thickness ladder runs from reveal strips up to deep-retrofit depths.
At 90mm the board occupies a useful middle position on solid masonry: more declared resistance than the 80mm board, less projection than a 100mm layer, and the same bonding and fixing sequence either way. That makes it a straightforward substitution when a surveyed elevation shows the reveals will take 90mm and no more.
The manufacturer's data sheet lists where this board type is intended to work, and it is wider than main-wall insulation alone:
- walls in bonded render systems (ETICS), which is the main façade use;
- walls behind cladding with a ventilated air gap;
- reveals and lintels, where the 0.5 m² board size cuts down easily;
- soffits insulated from below within a render system;
- ring beams and reinforced concrete slabs as permanent shuttering under render.
Why Specifiers Choose This Thickness
Six things decide the specification once the elevation survey is in, and all of them read off the declaration rather than off a brochure.
- Declared resistance of 2.80 m²K/W at 90mm, taken from the declared table rather than from thickness divided by lambda, so the number that reaches a wall U-value calculation is the one on the declaration of performance.
- Declared λD 0.032 W/mK across every thickness in the range, so stepping up or down the ladder changes the declared resistance and nothing else in the specification.
- Reaction to fire class E, declared for the board. That is a board property; the performance of a finished rendered wall is a system matter, covered in the graphite EPS and mineral wool comparison.
- Tight geometry tolerances — thickness ±1 mm, squareness ±2 mm/m, flatness ±5 mm — which is what lets butt joints close up cleanly across a whole elevation.
- Dimensional stability of ≤2% under the specified temperature and humidity condition, worth knowing on a steel-grey board that sits on a sunny gable.
- A documented adhesive rule: only products dedicated to grey graphite boards, which keeps the choice inside the EPS adhesives basecoats range rather than open to any bagged mortar on the van.
Declared Performance — Resistance, Lambda, Fire and Tolerances
Everything in this table comes from the Genderka EPS 032 Fasada Extra data sheet and its declaration of performance, both fetched this session. Scope is stated alongside each value, because a figure without its scope cannot be specified against.
| Property | Declared value | Scope of the declaration |
|---|---|---|
| Harmonised standard | EN 13163:2012+A1:2015 | EPS 032 Fasada Extra, all thicknesses |
| Thermal conductivity λD | 0.032 W/mK | EPS 032 Fasada Extra, all thicknesses |
| Thermal resistance RD at 90 mm | 2.80 m²K/W | Declared table, 90 mm row |
| Bending strength | ≥ 75 kPa | EPS 032 Fasada Extra |
| Tensile strength, perpendicular to faces | ≥ 80 kPa | EPS 032 Fasada Extra |
| Compressive stress at 10% deformation | Not declared (NPD) | Declaration of performance, Table 1 |
| Reaction to fire | Class E | The board, not a wall build-up |
| Thickness tolerance | ± 1 mm | EPS 032 Fasada Extra |
| Squareness / flatness | ± 2 mm/m / ± 5 mm | EPS 032 Fasada Extra |
| Dimensional stability, 70 °C condition | ≤ 2% | EPS 032 Fasada Extra |
| Board format | 1000 × 500 mm | This product listing |
The absent line is worth naming: compressive strength is declared NPD on this declaration, so no kPa figure appears above. Where a plinth, a paved perimeter or a loaded zone needs a declared compressive figure, that calls for a board declared for it rather than a façade board pressed into the role.
Two Genderka Declarations — What to Specify Against
Two documents are in circulation for the grey Genderka façade board, and they do not declare the same numbers. The EPS 032 Fasada Extra sheet and declaration give 0.032 W/mK, 2.80 m²K/W at 90 mm, bending ≥75 kPa and tensile ≥80 kPa. The EPS 031 Fasada Extra Plus declaration, issued for the Wschowa plant, gives 0.031 W/mK, 2.90 m²K/W at 90 mm and 100 kPa for both strength classes.
This page publishes the stricter of the two and names both, which is the safe way round for a calculation that has to survive Building Control. The purchasing instruction is simple: specify against 0.032 W/mK and 2.80 m²K/W, and ask the Renders World desk to confirm the range name and production plant printed on the delivery paperwork before a U-value is signed off. Where the paperwork comes back as Fasada Extra Plus, the calculation gains a small margin rather than losing one.
Why No Wall U-value Appears on This Page
A U-value belongs to a whole build-up — substrate, adhesive, board, reinforced layer and render — and not to a board, so none is stated here. The declared resistance above is the board's contribution to that sum, and the method for assembling the rest sits in the EWI layer-by-layer build-up guide. Energy efficiency requirements themselves are set by Approved Document L, Volume 1: Dwellings, now published in a 2026 edition alongside the earlier editions that still apply to older work.
How to Install the 90mm Board — Bonding, Plugging, Reinforced Layer
The sequence below follows the manufacturer's installation section, and the timings in it are the ones that shape a day's programme rather than the ones that pad a data sheet.
- Abrade the bonding face. The sheet recommends sanding the board surface immediately before bonding to raise adhesion of the mortar — quick work with a rasp, and it also lifts the smooth factory skin that graphite bead leaves behind.
- Bond with a dedicated grey-board product. Permitted types are cement-based adhesives, polyurethane foam adhesives and water-dispersion bitumen compounds intended for graphite boards, each used to its own data sheet.
- Leave at least 24 hours before mechanical fixing. Plugging comes no earlier than a day after bonding, so it is worth planning as an overnight break rather than an afternoon job.
- Plug to the system designer's pattern. Plug counts and layout come from the system figure, not from a rule of thumb — the fixing pattern and spacing guide sets out how that is arrived at, and the hardware sits in the insulation fixing accessories range. Plug length is read from the manufacturer's own table, which the plug length method explains.
- Build the reinforced layer. Basecoat with alkali-resistant rendering mesh embedded in it follows the fixing stage, and it is the layer the render finish then keys into.
Two site habits keep the declared performance intact. Keep organic solvents and their vapours away from the boards in storage and on the scaffold, and keep the steel-grey faces out of direct sunlight both briefly and over time — the sheet is unconditional about that, and opaque scaffold sheeting does the job while it is up anyway.
Choosing Between the 80mm, 90mm and 100mm Graphite Boards
All three sit in the same declared table, so they differ by declared resistance and by how much they project from the wall. Nothing else in the specification moves.
| Board | Declared resistance | Where it earns its place |
|---|---|---|
| 80mm graphite EPS board | 2.50 m²K/W | Tight reveals, sills and soffit returns that cannot lose depth |
| 90mm (this board) | 2.80 m²K/W | Solid masonry where the survey shows a little more depth is available |
| 100mm graphite EPS board | 3.10 m²K/W | Elevations with room to project, and deeper retrofit targets |
Because the declared step from 80mm to 90mm is 0.30 m²K/W and from 90mm to 100mm another 0.30 m²K/W, the choice is usually settled by reveal depth and sill projection rather than by thermal ambition. Where the reveals will take it, the deeper board is the cheaper way to buy resistance; where they will not, the 90mm board keeps the existing details working.
Is the 90mm Board the Right Call for Your Project?
Four checks settle it before the order goes in.
- Fit 90mm where the reveal and sill survey allows the depth and the calculation needs more than the 80mm board's declared 2.50 m²K/W contributes.
- Confirm the target with the calculation, not the thickness. New-build targets are covered in the Future Homes Standard 2026 guide; retrofit work follows Approved Document L and the project's own assessment.
- Check the funding route early where the work is grant-supported, since scheme paperwork often fixes the specification — the EWI grant funding guide covers what the schemes ask for.
- Take the non-combustible route where the fire strategy calls for it. This board is declared class E; the comparison of graphite EPS against stone wool sets out where a slab is the better specification.
How to Order the 90mm Board — Price, Stock and Delivery
The listing shows £6.70 as displayed in August 2026, and the board is in stock at the same date. What the listing does not state is the selling unit, so a per-square-metre figure is not published here; confirm with Renders World whether that price covers one 1000 × 500 mm board or a pack, and the quantity arithmetic follows immediately from the answer.
- Delivery is arranged after the order, because dimensions and weight vary too much for an automatic quote — the customer service team costs the cheapest method and confirms it.
- Parcels up to 25 kg move on next-working-day courier; pallets up to 1200 kg go next working day, or two business days on the economy option.
- All deliveries are curbside and pallets are shrink-wrapped rather than weatherproofed, so plan somewhere dry to move the boards to on arrival.
FAQ — Quantities, Compatibility and Compliance
How many boards cover a square metre, and how many for an 80 m² elevation?
At 1000 × 500 mm, one board covers 1.000 m × 0.500 m = 0.50 m², so 1 m² ÷ 0.50 m² = 2 boards per m². An 80 m² elevation therefore needs 80 ÷ 0.50 = 160 boards before cutting allowance, and the allowance itself is best set from the surveyed elevation, since reveals, soffits and service penetrations differ so much between houses.
Which adhesives can be used with a grey graphite board?
The data sheet permits cement-based adhesives, polyurethane foam adhesives and water-dispersion bitumen compounds, in each case products dedicated to graphite (grey) boards, applied to their own manufacturer's instructions. It also asks for the board face to be abraded immediately before bonding, which is the detail most often skipped on graphite work.
How does the 90mm differ from the 80mm and 100mm boards?
Only in declared thermal resistance and depth: 2.50 m²K/W at 80mm, 2.80 m²K/W at 90mm and 3.10 m²K/W at 100mm, all at the same declared 0.032 W/mK and the same declared strength classes. The bonding, plugging and reinforced-layer sequence is identical, so a change of thickness does not change the method statement.
How long after bonding can the boards be plugged?
Mechanical fixing follows no earlier than 24 hours after the boards are bonded, and the reinforced layer comes after that. Two conditions run throughout: no contact with organic solvents or their vapours, and no direct sunlight on the grey faces, short-term or long-term, in storage or on the wall.
What fire class does the board carry?
Reaction to fire is declared as class E for the board under EN 13163:2012+A1:2015. That class describes the board and not a finished wall, because a rendered build-up is assessed as a system with its own evidence; where a project needs non-combustible insulation, the stone wool comparison is the place to start.
Why does this page state 0.032 W/mK when another sheet says 0.031?
Two Genderka declarations cover grey façade board — Fasada Extra at 0.032 W/mK and Fasada Extra Plus at 0.031 W/mK — and this page publishes the stricter figure so that no calculation is built on the more generous one. Confirm the range and plant named on your paperwork at order, and the calculation can be tightened afterwards if the Plus declaration applies.
Technical Documentation for the Grey Graphite Board
- Genderka EPS 032 Fasada Extra — technical data sheet (PDF)
- Genderka EPS 032 Fasada Extra — declaration of performance, Bydgoszcz plant (PDF)
- Genderka EPS 031 Fasada Extra Plus — declaration of performance, Wschowa plant (PDF), the divergent range document
Declarations are issued per production plant, so the number that belongs on a compliance file is the one for the plant that supplied the delivery. Confirm it at order and it can be filed with the calculation.