Description
The 100 mm thickness sits mid-range in the Frontrock Super family, and it is the board most UK contractors reach for when an elevation has to be non-combustible before it has to be anything else. It belongs to the wider mineral wool insulation range at Renders World, supplied three slabs to a 1.8 m² pack.
Where This Stone Wool Board Fits on a UK Facade
Rockwool Super 100mm mineral slab is a stone wool ETICS board declaring 0.036 W/mK thermal conductivity to EN 12667 and a declared thermal resistance of 2.75 m²K/W, fixed behind render on solid-wall and framed UK elevations.
That declared resistance is the number a designer needs, and it is worth taking from the declaration rather than calculating it. Dividing 0.100 m by 0.036 W/mK returns 2.78, but the manufacturer declares 2.75 m²K/W at this thickness — a rounding difference that only matters when a calculation sits close to a target, which is exactly when people check.
- Solid-wall retrofit: a vapour-open layer over Victorian and Edwardian brick, with a water vapour diffusion resistance factor of μ = 1 to EN 12086.
- Framed construction behind a render carrier: a non-combustible insulation layer where the fire strategy sets the material before the U-value does.
- Exposed and wind-driven-rain elevations: long-term water absorption declared at ≤ 3.0 kg/m² to EN 12087.
Why Specifiers Choose a Dual-Density Stone Wool Slab
- Euroclass A1 to EN 13501-1: declared for the slab itself under DoP RW-CEE-DoP-0237/BCM/23/w1 — the highest reaction-to-fire class, and one that does not change with age or weathering.
- Declared compressive stress of 20 kPa: CS(10)20 to EN 826, so the board holds its thickness under fixing plates and base coat rather than dishing behind the render.
- Tensile strength of 10 kPa perpendicular to the faces: TR10 to EN 1607, the property that governs pull-off resistance once adhesive and fixings are both working.
- Vapour-open at μ = 1: effectively the resistance of still air, so an insulated solid wall keeps drying outward through a wet UK winter.
- Tight thickness tolerance at class T5: to EN 823, which keeps the board faces flush across a run and saves base-coat material at joints.
Declared Performance — Thermal, Fire and Moisture
| Property | Declared value | Standard |
|---|---|---|
| Thermal conductivity λD | 0.036 W/mK | EN 12667 |
| Thermal resistance RD at 100 mm | 2.75 m²K/W | EN 13162 |
| Reaction to fire | Euroclass A1 | EN 13501-1 |
| Compressive stress at 10% deformation | 20 kPa | EN 826 |
| Tensile strength perpendicular to faces | 10 kPa | EN 1607 |
| Water vapour diffusion resistance factor | μ = 1 | EN 12086 |
| Short-term water absorption | ≤ 1.0 kg/m² | EN 1609 |
| Long-term water absorption | ≤ 3.0 kg/m² | EN 12087 |
| Thickness tolerance | Class T5 | EN 823 |
| Dimensional stability | DS(70,-); DS(70,90) | EN 1604 |
Two entries on the declaration are blank by design, and both are useful to know before a specification is written. Sound absorption and point load carry no declared performance, so an acoustic figure for a finished wall comes from project testing rather than from this board. A wall U-value works the same way: it is a property of the whole build-up, never of a board, and the U-value calculation method for wall insulation thickness sets out how the layers are added.
How to Install the Slab Behind a Render System
Stone wool is fitted, not poured, and the sequence below is the one that keeps a 100 mm board flat enough for a thin-coat finish to sit over it.
- Set the base track level and work upward from it, so the first course carries the geometry for every course above.
- Bond with a wool-compatible adhesive. Use Roker U grey adhesive for wool and EPS, which is formulated for stone wool fibres; general-purpose board adhesives from the EPS adhesives basecoats shelf are matched to polystyrene.
- Butt the slabs tightly in a broken-bond pattern and keep joints closed — open joints are the only place a continuous insulation layer loses its continuity.
- Fix mechanically with plates from the insulation fixing accessories range, to the fixing schedule issued for the project.
- Reinforce and render once fixings are flush, embedding mesh fully in the base coat.
Fixing count and plug length are set by a project wind-load calculation and the system holder's schedule, not by a rule of thumb — Renders World supplies the plate and plug range to match whichever schedule the designer issues.
Thickness Options Across the Range
| Thickness | Declared RD | Pack | When to choose it |
|---|---|---|---|
| 80 mm slab | 2.20 m²K/W | 3 slabs, 1.8 m² | Where reveal depth or projection limits the build-up |
| 100 mm | 2.75 m²K/W | 3 slabs, 1.8 m² | The general-purpose retrofit thickness |
| 120 mm slab | 3.30 m²K/W | 3 slabs, 1.8 m² | Deeper retrofit targets on solid walls |
| 160 mm slab | 4.40 m²K/W | 2 slabs, 1.2 m² | Low-energy work where depth is available |
Note the pack break at 160 mm: coverage drops to 1.2 m², so a price comparison across thicknesses is only fair once it is put on a per-square-metre basis.
Ordering — Pack Size, Price and Matched Components
Rockwool Super 100mm mineral slab is sold by the pack of three at £45.00 per 1.8 m² pack as displayed in August 2026. On the pack coverage above that works out at £45.00 ÷ 1.8 m² = £25.00 per m² for the insulation layer alone, before adhesive, fixings, mesh and finish.
- Order in pack multiples: coverage steps in 1.8 m², so a 60 m² elevation lands on 34 packs once an allowance for cuts at reveals and returns is added.
- Pallet quantity: 16 packs per pallet, covering 28.8 m² — the figure to give a scaffold-loading calculation.
- Pack weight: 16.2 kg, comfortably a one-person lift up a scaffold ladder.
Is This the Right Slab for Your Project?
- Choose it where a non-combustible A1 insulation layer is required and 100 mm of depth is available on the elevation.
- Step down to the 80 mm Super slab at 2.20 m²K/W where window reveals or a boundary limit the projection.
- Step up to the 120 mm Super slab at 3.30 m²K/W when the calculation asks for more.
- Weighing wool against polystyrene? The mineral wool and polystyrene comparison sets out where each material earns its place, and the facade fire requirements briefing covers where the choice is made for you.
- Period masonry: the solid-wall Victorian retrofit guide and the condensation risk guide cover the moisture side of the decision.
FAQ — Coverage, Compatibility and Compliance
How much does one pack cover?
Three slabs at 1000 × 600 mm give 1.8 m² laid flat. Add an allowance for cuts at reveals, returns and parapets before converting an elevation area into a pack count.
Which adhesive suits stone wool?
A wool-compatible cementitious adhesive is the requirement, because stone wool fibres bond differently from a closed-cell board face. Roker U grey is the product held for this range at Renders World.
Does the A1 class apply to the finished wall?
Euroclass A1 to EN 13501-1 is declared for the slab under its Declaration of Performance. A completed external wall is a build-up of several materials, so its performance is assessed as a system by the building designer under current Approved Document B guidance.
Why is the declared R-value 2.75 rather than 2.78?
The declaration publishes a rounded value per thickness, and that published figure is the one a compliance calculation should carry. Dividing thickness by lambda gives a slightly different answer and is not the declared property.
Can the slabs be left exposed on site?
Short-term water absorption is declared at ≤ 1.0 kg/m², which covers incidental wetting during installation. Keeping packs under cover until they go on the wall is still the practice worth following, since dry boards handle and cut better overhead.
Is an acoustic improvement figure available?
Sound absorption is declared as NPD — no declared performance — for this slab, so any acoustic benefit on a finished facade is established by testing the completed build-up rather than quoted from the board.
Technical Documentation